Mission firsts.

Other spacecraft, notably "Galileo" and "NEAR Shoemaker" (both launched by NASA), had visited asteroids before, but the "Hayabusa" mission was the first attempt to return an asteroid sample to Earth for analysis.  In addition, "Hayabusa" was the first spacecraft designed to deliberately land on an asteroid and then take off again ("NEAR Shoemaker" made a controlled descent to the surface of 433 Eros in 2000, but it was not designed as a lander and was eventually deactivated after it arrived). Technically, "Hayabusa" was not designed to "land"; it simply touches the surface with its sample capturing device and then moves away. However, it was the first craft designed from the outset to make physical contact with the surface of an asteroid. Junichiro Kawaguchi of the Institute of Space and Astronautical Science was appointed to be the leader of the mission.  Despite its designer's intention of a momentary contact, "Hayabusa" did land and sit on the asteroid surface for about 30 minutes (see timeline below).

Mission profile.

The "Hayabusa" spacecraft was launched on 9 May 2003 at 04:29:25 UTC on an M-V rocket from the Uchinoura Space Center (still called Kagoshima Space Center at that time). Following launch, the spacecraft's name was changed from the original MUSES-C to "Hayabusa", the Japanese word for falcon. The spacecraft's xenon ion engines (four separate units), operating near-continuously for two years, slowly moved "Hayabusa" toward a September 2005 rendezvous with Itokawa. As it arrived, the spacecraft did not go into orbit around the asteroid, but remained in a station-keeping heliocentric orbit close by. "Hayabusa" surveyed the asteroid surface from a distance of about 20 km (13.7 mi), (the "gate position"). After this the spacecraft moved closer to the surface (the "home position"), and then approached the asteroid for a series of soft landings and for the collection of samples at a safe site. Autonomous optical navigation was employed extensively during this period because the long communication delay prohibits Earth-based real-time commanding. At the second "Hayabusa" touched down with its deployable collection horn, the spacecraft was programmed to fire tiny projectiles at the surface and then collect the resulting spray. Some tiny specks were collected by the spacecraft for analysis back on Earth.  After a few months in proximity to the asteroid, the spacecraft was scheduled to fire its engines to begin its cruise back to Earth. This maneuver was delayed due to problems with attitude control (orientation) and the thrusters of the craft. Once it was on its return trajectory, the re-entry capsule was released from the main spacecraft three hours before reentry, and the capsule coasted on a ballistic trajectory, re-entering the Earth's atmosphere at 13:51, 13 June 2010 UTC. It is estimated that the capsule experienced peak deceleration of about 25 G and heating rates approximately 30 times those experienced by the Apollo spacecraft. It landed via parachute near Woomera, Australia.  In relation to the mission profile, JAXA defined the following success criteria and corresponding scores for major milestones in the mission prior to the launch of the "Hayabusa" spacecraft. As it shows, the "Hayabusa" spacecraft is a platform for testing new technology and the primary objective of the "Hayabusa" project is the world's first implementation of microwave discharge ion engines. Hence 'operation of ion engines for more than 1000 hours' is an achievement that gives a full score of 100 points, and the rest of the milestones are a series of world's first-time experiments built on it.

MINERVA mini-lander.

"Hayabusa" carried a tiny mini-lander (weighing only, and approximately tall by in diameter) named ""MINERVA"" (short for "MI"cro-"N"ano "E"xperimental "R"obot "V"ehicle for the "A"steroid).  The MINERVA has an on-board microcomputer. Its main CPU microprocessor is Hitachi's SH-3, clocked at 10MHz, adopted for its low power consumption, performance efficiency and reliability. The computer's memory includes 2MB RAM, 512KB ROM, and 2MB Flash ROM.  An error during deployment resulted in the craft's failure.  This solar-powered vehicle was designed to take advantage of Itokawa's very low gravity by using an internal flywheel assembly to hop across the surface of the asteroid, relaying images from its cameras to "Hayabusa" whenever the two spacecraft were in sight of one another.  MINERVA was deployed on 12 November 2005. The lander release command was sent from Earth, but before the command could arrive, "Hayabusa"<nowiki>'</nowiki>s altimeter measured its distance from Itokawa to be and thus started an automatic altitude keeping sequence. As a result, when the MINERVA release command arrived, MINERVA was released while the probe was ascending and at a higher altitude than intended, so that it escaped Itokawa's gravitational pull and tumbled into space.  Had it been successful, MINERVA would have been the first hopping space rover. The Soviet mission "Phobos 2" also encountered a malfunction while attempting to deploy a hopping rover.

Scientific and engineering importance of the mission.

Scientists' current understanding of asteroids depends greatly on meteorite samples, but it is very difficult to match up meteorite samples with the exact asteroids from which they came. "Hayabusa" will help solve this problem by bringing back pristine samples from a specific, well-characterized asteroid. "Hayabusa" bridged the gap between ground observation data of asteroids and laboratory analysis of meteorite and cosmic dust collections. Also comparing the data from the onboard instruments of the "Hayabusa" with the data from the "NEAR Shoemaker" mission will put the knowledge on a wider level.  The "Hayabusa" mission has a very deep engineering importance for JAXA, too. It allowed JAXA to further test its technologies in the fields of ion engines, autonomous and optical navigation, deep space communication, and close movement on objects with low gravity among others. Second, since it was the first-ever preplanned soft contact with the surface of an asteroid (the "NEAR Shoemaker" landing on 433 Eros was not preplanned) it has enormous influence on further asteroid missions.

Changes in mission plan.

The "Hayabusa" mission profile was modified several times, both before and after launch.

Mission timeline.

Up to the launch.

The asteroid exploration mission by the Institute of Space and Astronautical Science (ISAS) originated in 1986–1987 when the scientists investigated the feasibility of a sample return mission to Anteros and concluded that the technology was not yet developed. Between 1987 and 1994, joint ISAS / NASA group studied several missions: an asteroid rendezvous mission later became NEAR, and a comet sample return mission later became Stardust.  In 1995, ISAS selected the asteroid sampling as an engineering demonstration mission, MUSES-C, Nereus as the first choice of target, 1989 ML as the secondary choice, and MUSES-C project started in fiscal year 1996. In early development phase, Nereus was considered out of reach and 1989 ML became the primary target. July 2000 failure of M-V forced a delay in the launch from July 2002 to November/December, putting both Nereus and 1989 ML out of reach. As a result, the target asteroid was changed to. In 2002, launch was postponed from December 2002 to May 2003 to recheck O-rings of reaction control system since one of it was found using different material than specification. On 9 May, 2003 04:29:25 UTC, MUSES-C was launched by M-V rocket, and the probe was named ""Hayabusa"".

Cruising.

Ion thruster checkout started on 27 May 2003. Full power operation started on 25 June.  Asteroids are named by their discoverer. ISAS asked LINEAR, the discoverer of, to offer the name after Hideo Itokawa, and on 6 August, Minor Planet Circular reported that the target asteroid was named "Itokawa".  In October 2003, ISAS and two other national aerospace agencies were merged to form JAXA.  On 31 March 2004, ion thruster operation was stopped to prepare for the Earth swing-by. Last maneuver operation before swing-by on 12 May. On 19 May, "Hayabusa" performed Earth swing-by. On 27 May, ion thruster operation was started again.  On 18 February 2005, "Hayabusa" passed aphelion at 1.7 AU. On 31 July, the X-axis reaction wheel failed. On 14 August, "Hayabusa"<nowiki>'</nowiki>s first image of Itokawa was released. The picture was taken by the star tracker and shows a point of light, believed to be the asteroid, moving across the starfield. Other images were taken from 22 to 24 August. On 28 August, "Hayabusa" was switched over from the ion engines to the bi-propellant thrusters for orbital maneuvering. From 4 September, "Hayabusa"<nowiki>'</nowiki>s cameras were able to confirm Itokawa's elongated shape. From 11 September, individual hills were discerned on the asteroid. On 12 September, "Hayabusa" was from Itokawa and JAXA scientists announced that "Hayabusa" had officially "arrived".

In proximity of Itokawa.

On 15 September 2005, a 'colour' image of the asteroid was released (which is, however, grey in colouring). On 4 October, JAXA announced that the spacecraft had successfully moved to its 'Home Position' 7 km from Itokawa. Closeup pictures were released. It was also announced that the spacecraft's second reaction wheel, governing the Y-axis, had failed, and that the craft was now being pointed by its rotation thrusters. On 3 November, "Hayabusa" took station 3.0 km from Itokawa. It then began its descent, planned to include delivery of a target marker, and release of the Minerva minilander. The descent went well initially, and navigation images with wide-angle cameras were obtained. However, at 01:50 UTC ( JST) on 4 November, it was announced that due to a detection of an anomalous signal at the Go/NoGo decision, the descent, including release of Minerva and the target marker had been canceled. The project manager, Junichiro Kawaguchi, explained that the optical navigation system was not tracking the asteroid very well, probably caused by the complex shape of Itokawa. A delay of a few days was required to evaluate the situation and reschedule.  On 7 November, "Hayabusa" was 7.5 km from Itokawa. On 9 November, "Hayabusa" performed a descent to to test the landing navigation and the laser altimeter. After that, "Hayabusa" backed off to a higher position, then descended again to and released one of the target markers into space to test the craft's ability to track it (this was confirmed). From analysis of the closeup images, the Woomera Desert site (Point B) was found to be too rocky to be suitable for landing. The Muses Sea site (Point A) was selected as the landing site, for both first and, if possible, second landings.  On 12 November, "Hayabusa" closed in to from the asteroid's surface. MINERVA was released but due to an error failed to reach the surface. On 19 November, "Hayabusa" landed on the asteroid. There was considerable confusion during and after the maneuver about precisely what had happened, because the high-gain antenna of the probe could not be used during final phase of touch-down, as well as the blackout during handover of ground station antenna from DSN to Usuda station. It was initially reported that "Hayabusa" had stopped at approximately 10 meters from the surface, hovering for 30 minutes for unknown reasons. Ground control sent a command to abort and ascend, and by the time the communication was regained, the probe had moved 100 km away from the asteroid. The probe had entered into a safe mode, slowly spinning to stabilize attitude control. However, after regaining control and communication with the probe, the data from the landing attempt were downloaded and analyzed, and on 23 November, JAXA announced that the probe had indeed landed on the asteroid's surface. Unfortunately, the sampling sequence was not triggered since a sensor detected an obstacle during descent; the probe tried to abort the landing, but since its orientation was not appropriate for ascent, it chose instead a safe descent mode. This mode did not permit a sample to be taken, but there is a high probability that some dust may have whirled up into the sampling horn when it touched the asteroid, so the sample canister currently attached to the sampling horn was sealed.  On 25 November, a second touchdown attempt was performed. It was initially thought that this time, the sampling device was activated; however, later analysis decided that this was probably another failure and that no pellets were fired. Due to a leak in the thruster system, the probe was put in a "safe hold mode".  On 27 November, the probe experienced a power outage when trying to reorient the spacecraft, probably due to a fuel leakage. On 30 November, JAXA announced that control and communication with "Hayabusa" had been restored, but a problem remained with the craft's reaction control system, perhaps involving a frozen pipe. Mission control was working to resolve the problem before the craft's upcoming launch window for return to Earth. On 2 December, an attitude (orientation) correction was attempted, but the thruster did not generate enough force. On 3 December, the probe's Z-axis was found to be 20 to 30 degrees from the Sun direction and increasing. On 4 December, as an emergency measure, xenon propellant from the ion engines was blown to correct the spin, and it was confirmed successful. On 5 December, attitude control was corrected enough to regain communication through the medium gain antenna. Telemetry was obtained and analyzed. As the result of telemetry analysis, it was found that there was a strong possibility that the sampler projectile had not penetrated when it landed on 25 November. Due to the power outage, the telemetry log data was faulty. On 6 December, "Hayabusa" was 550 km from Itokawa. JAXA held a press conference about the situation so far.  On 8 December, a sudden orientation change was observed, and communication with "Hayabusa" was lost. It was thought likely that the turbulence was caused by evaporation of 8 or 10cc of leaked fuel. This forced a wait of a month or two for "Hayabusa" to stabilize by conversion of precession to pure rotation, after which the rotation axis needed to be directed toward the Sun and Earth within a specific angular range. The probability of achieving this was estimated at 60% by December 2006, 70% by spring 2007.

Recovery and return to Earth.

On 7 March 2006, JAXA announced that communication with "Hayabusa" had been recovered in the following stages: On 23 January, the beacon signal from the probe was detected. On 26 January, the probe responded to commands from ground control by changing the beacon signal. On 6 February, an ejection of xenon propellant was commanded for attitude control to improve communication. The spin axis change rate was about two degrees per day. On 25 February, telemetry data was obtained through the low-gain antenna. On 4 March, telemetry data was obtained through the medium-gain antenna. On 6 March, "Hayabusa"'s position was established at about 13,000 km ahead of Itokawa in its orbit with a relative speed of per second.  On 1 June, "Hayabusa" project manager Junichiro Kawaguchi reported that they confirmed two out of four ion engines were working normally, which would have been sufficient for the return journey. On 30 January 2007, Jaxa reported that 7 out of 11 batteries were working and the return capsule was sealed. On 25 April, JAXA reported that "Hayabusa" started the return journey. On 29 August, it was announced that Ion Engine C onboard Hayabusa, in addition to B and D, had been successfully re-ignited. On 29 October, JAXA reported that the first phase of trajectory maneuver operation had finished and the spacecraft was now put in a spin-stabilized state. On 4 February 2009, JAXA reported success in reignition of the ion engines and starting the second phase of the trajectory correction maneuver to return to Earth. On 4 November 2009, the ion engine D automatically stopped working due to an anomaly from degradation.  On 19 November 2009, JAXA announced that they managed to combine the ion generator of ion engine B and the neutralizer of ion engine A. It was suboptimal but expected to be sufficient to generate the necessary delta-v. Out of delta-v necessary to return to the Earth, about had been performed already, and about were still necessary. On 5 March 2010, "Hayabusa" was on a trajectory that would have passed within the lunar orbit. Ion engine operation was suspended to measure the precise trajectory in preparation to perform Trajectory Correction Maneuver 1 to the Earth-rim trajectory. On 27 March, 06:17 UTC, "Hayabusa" was on a trajectory which would pass 20,000 km from Earth center, completing the orbit transfer operation from Itokawa to Earth. By 6 April, the first stage of Trajectory Correction Maneuver (TCM-0) which led to a rough Earth rim trajectory was completed. It was planned to be 60 days until reentry. By 4 May, the probe completed its TCM-1 maneuver to align precisely to the Earth rim trajectory. On 22 May, TCM-2 started, continued for about 92.5 hours, and finished on 26 May. It was followed by TCM-3 from 3 through 5 June to change the trajectory from the Earth rim to Woomera, South Australia, TCM-4 was performed on 9 June for about 2.5 hours for a precision descent to Woomera Prohibited Area.  The reentry capsule was released at 10:51 UTC on 13 June.

Reentry and capsule retrieval.

The reentry capsule and the spacecraft reentered Earth's atmosphere on 13 June 2010 at 13:51 UTC (23:21 local). The heat-shielded capsule made a parachute landing in the South Australian outback while the spacecraft broke up and incinerated in a large fireball.  An international team of scientists observed the 12.2 km/s entry of the capsule from 11.9 km (39,000 ft) on board NASA's DC-8 airborne laboratory, using a wide array of imaging and spectrographic cameras to measure the physical conditions during atmospheric reentry in a mission led by NASA's Ames Research Center, with Peter Jenniskens of the SETI Institute as the project scientist.  Since the reaction control system no longer functioned, the space probe re-entered the Earth's atmosphere similar to the approach of an asteroid along with the sample re-entry capsule, and, as mission scientists expected, the majority of the spacecraft disintegrated upon entry. The return capsule was predicted to land in a by area in the Woomera Prohibited Area, South Australia. Four ground teams surrounded this area and located the re-entry capsule by optical observation and a radio beacon. Then a team on board a helicopter was dispatched. They located the capsule and recorded its position with GPS. The capsule was successfully retrieved at 07:08 UTC (16:38 local) of 14 June 2010. The two parts of the heat shield, which were jettisoned during the descent, were also found. After confirming that the explosive devices used for parachute deployment were safe the capsule was packed inside a double layer of plastic bags filled with pure nitrogen gas to reduce the risk of contamination. The soil at the landing site was also sampled for reference in case of contamination. Then the capsule was put inside a cargo container which had air suspension to keep the capsule below 1.5 G shock during transportation. The capsule and its heat shield parts were transported to Japan by a chartered plane and arrived at the curation facility at the JAXA/ISAS Sagamihara campus on 18 June.  A Tokyo Metropolitan Government adviser and former lieutenant general, Toshiyuki Shikata, claimed that part of the rationale for the reentry and landing part of the mission was to demonstrate "that Japan's ballistic missile capability is credible."

Scientific study of samples.

Before the capsule was extracted from the protecting plastic bag, it was inspected using X-ray CT to determine its condition. Then the sample canister was extracted from the reentry capsule. The surface of the canister was cleaned using pure nitrogen gas and carbon dioxide; it was then placed in the canister opening device. The internal pressure of the canister was determined by a slight deformation of the canister as the pressure of the environment nitrogen gas in the clean chamber was varied. The nitrogen gas pressure was then adjusted to match the internal canister pressure to prevent the escape of any gas from the sample upon the opening of the canister.

Confirmation of asteroid particles.

On 16 November 2010, JAXA confirmed that most of the particles found in one of two compartments inside the "Hayabusa" sample return capsule came from Itokawa, as no full sample collection had been made. Only dust which been kicked up by "Hayabusa" accidentally landing on the asteroid and then drifted into the open collector had been captured. Analysis with a scanning electron microscope identified about 1,500 grains of rocky particles, according to the JAXA press release. After further studying the analysis results and comparison of mineral compositions, most of them were judged to be of extraterrestrial origin, and definitely from the asteroid Itokawa.  According to Japanese scientists, the composition of "Hayabusa"<nowiki>'</nowiki>s samples was more similar to meteorites than known rocks from Earth. Their size is mostly less than 10 micrometers. The material matches chemical maps of Itokawa from "Hayabusa"'s remote sensing instruments. The researchers found concentrations of olivine and pyroxene in the "Hayabusa" samples.  Further study of the samples had to wait until 2011 because researchers were still developing special handling procedures to avoid contaminating the particles during the next phase of research.  In 2013 JAXA announced that 1500 extraterrestrial grains had been recovered, comprising the minerals olivine, pyroxene, plagioclase and iron sulfide. The grains were about 10 micrometers in size. JAXA performed detailed analyses of the samples by splitting particles and examining their crystal structure at SPring-8.

Results.

The 26 August 2011 issue of "Science" devoted six articles to findings based on dust collected by "Hayabusa". Scientists' analysis of the dust from Itokawa suggested that it had probably originally been part of a larger asteroid. Dust collected from the asteroid surface was believed to have been exposed there for about eight million years.  Dust from Itokawa was found to be "identical to material that makes up meteorites." Itokawa is an S-type asteroid whose composition matches that of an LL chondrite.

In popular culture.

In Japan, rival film companies announced the production of three different feature length theatrical films based on the story of "Hayabusa", one of which, "", starred Ken Watanabe.  The Lego construction toy company released a model of "Hayabusa" through their Cuusoo website.  Many references to "Hayabusa" appear in the Japanese series "Kamen Rider Fourze", a space-themed tokusatsu series.  A music video titled "Hayabusa", named after the unmanned spacecraft was made using the Vocaloid Hatsune Miku. The music and lyrics were composed by SHO.  Following the sample return in 2010, Hayabusa-tan (はやぶさたん), an anthropomorphised figure in anime style, was released by the company Aoshima.  "Hayabusa" also appears as a playable character in.

External links.

"Hayabusa", formerly known as MUSES-C for Mu Space Engineering Spacecraft C, was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, "Hayabusa" studied the asteroid's shape, spin, topography, colour, composition, density, and history. In November 2005, it landed on the asteroid and collected samples in the form of tiny grains of asteroidal material, which were returned to Earth aboard the spacecraft on 13 June 2010.

隼鸟号(日文:,开发名称为第20号科学卫星MUSES-C)偶尔也被译为游隼号、猎鹰号或隼鹰号,或是非正式的被称为隼鸟1号,是日本宇宙航空研究开发机构的小行星探测计划。这项计划的主要目的是将隼鸟号探测器送往小行星25143(25143 Itokawa,丝川小行星),采集小行星样本并将采集到的样本送回地球。


History.

In the early 1980s, most home computers manufactured in Japan such as the NEC PC-6001 and PC-8000 series, Fujitsu's FM-7 and FM-8, and Hitachi's Basic Master featured a variant of the Microsoft BASIC interpreter integrated into their on-board ROMs. The hardware design of these computers and the various dialects of their BASICs were incompatible. Other Japanese consumer electronics firms such as Panasonic, Canon, Casio, Yamaha, Pioneer, and Sanyo were searching for ways to enter the new home computer market.  Nishi proposed MSX as an attempt to create a single industry standard for home computers. Inspired by the success of VHS as a standard for video cassette recorders, many Japanese electronic manufacturers along with GoldStar, Philips and Spectravideo built and promoted MSX computers. Any piece of hardware or software with the MSX logo on it was compatible with MSX products of other manufacturers. In particular, the expansion cartridge form and function were part of the standard; any MSX expansion or game cartridge would work in any MSX computer.  Nishi's standard was built around the Spectravideo SV-328 computer. The standard consisted primarily of several off-the-shelf parts; the main CPU was a 3.58 MHz Zilog Z80, the Texas Instruments TMS9918 graphics chip with 16 KB of dedicated VRAM, the sound and partial I/O support was provided by the AY-3-8910 chip manufactured by General Instrument (GI), and an Intel 8255 Programmable Peripheral Interface chip was used for the parallel I/O such as the keyboard. This was a choice of components that was shared by many other home computers and games consoles of the period, such as the ColecoVision home computer (an emulator was later available with which MSX systems could run some of its software), and the Sega SG-1000 video game system. To reduce overall system cost, many MSX models used a custom IC known as "MSX-Engine", which integrated glue logic, 8255 PPI, YM2149 compatible soundchip and more, sometimes even the Z80 CPU. However, almost all MSX systems used a professional keyboard instead of a chiclet keyboard, driving the price up compared to the original SV-328. Consequently, these components alongside Microsoft's MSX BASIC made the MSX a competitive, though somewhat expensive, home computer package.

Debut.

On 27 June 1983, the MSX was formally announced during a press conference, and a slew of big Japanese firms declared their plans to introduce machines. The Japanese companies avoided the intensely competitive U.S. home computer market, which was in the throes of a Commodore-led price war. Only Spectravideo and Yamaha briefly marketed MSX machines in the U.S. Spectravideo's MSX enjoyed very little success, and Yamaha's CX5M model, built to interface with various types of MIDI equipment, was billed more as a digital music tool than a standard personal computer.

Adoption.

During the 1980s, Europe became the largest computer games market in the world, and the extremely popular Commodore 64 and Sinclair ZX Spectrum computers dominated. By the time the MSX was launched in Europe, several more popular 8-bit home computers had also arrived, and it was far too late to capture the extremely crowded European 8-bit computer market.

Technical issues.

A problem for some game developers was that addressing video RAM on the MSX-1 computers is slow compared to systems with direct access to the video memory. This, and the fact that the completely different features the MSX-1's video chip (using the MSX Video access method) had to compensate for the slower video access were not efficiently used while porting (mostly Spectrum) software, made the MSX-1 appear slower when running ported games.  Some minor compatibility issues also plagued ported Spectrum games. For example, the Toshiba HX-10 machine was unable to read certain key combinations at the same time, preventing the Spectrum "standard" of "Q, A, O, P steering", whereas machines by other manufacturers worked fine. Later (ported) games tended to use the MSX-1 joystick port or used MSX's official arrow keys and space bar, or offered the option to choose other keys with which to control the program, solving the problem.  A larger problem was that the designers of the MSX standard bank switching protocol did not prescribe to hardware manufacturers in which banks the cartridges and, more importantly, the RAM should be found. Moreover, the MSX's BIOS did not provide this information either, thus requiring programmers to implement complex routines to "find" these resources. Often programmers assumed that the RAM and cartridges would be available at a "default" bank switch location; in reality some systems had their RAM or cartridge slot(s) not at the "default" location, but at another bank switch location (i.e. Toshiba HX-20). In those cases programs failed to run because they only "saw" 32 KB of the available memory, instead of the full 64 KB that almost all MSX-1 machines offered. All other mainstream MSX-1 machines offered at least the full 64 KB of RAM, with a very few exceptions, such as some early Phillips MSX-1 models (the VG8000 offered 16 KB of RAM and the VG8010, 32 KB) or the Casio PV-7, a low budget MSX targeted for playing games, which has only 8 KB.

Evolution.

MSX spawned four generations: MSX (1983), MSX2 (1985), MSX2+ (1988), and MSX TurboR (1990). The first three were 8-bit computers based on the Z80 microprocessor, while the MSX TurboR was based on a custom 16-bit R800 microprocessor developed by ASCII Corporation. By the time the MSX TurboR standard was announced in 1990, only Panasonic was manufacturing MSX computers. Its initial model FS-A1ST met with moderate success, but the upgraded model FS-A1GT introduced in 1991 sold poorly due to its high retail cost of 99800 yen. Production of the TurboR ended in 1993 when Panasonic decided to focus on the release of 3DO.  The MSX3 was scheduled for market in 1990. Delays in the development of its VDP—then named V9978 on the pre-release spec sheets—caused Yamaha to miss its time to market deadline. In its place, an improved MSX2+ was released as the MSX TurboR; features of the new R800 processor such as DMA and 24-bit addressing were disabled. The VDP was eventually delivered two years after its planned deadline, by which time the market had moved on. In an attempt to reduce its financial loss, Yamaha stripped nearly all V9958 compatibility and marketed the resulting V9990 E-VDP III as a video-chipset for PC VGA graphic cards, with moderate success. Sony also employed the V7040 RGB encoder chip on many other products. MSX-FAN Magazine also mentions the impressive power of the V9990, being able to compete with much more expensive hardware such as Sharp's X68000.

Impact.

In Japan, South Korea, Argentina, and Brazil, MSX was the paramount home computer system of the 1980s. It was also quite popular in continental Europe, especially in the Netherlands and Spain. In the UK on the other hand, its most popular and affordable model is the Toshiba HX-10P and it is the only MSX computer to be commonly seen available around in the entire nation while France and Italy enjoyed very moderate success. While the Philips VG-8020 computer had much impact in the Netherlands, Spain, Italy and Belgium. In France, the Canon V-20 was the most affordable, but it didn't have as much success or impact like the Amstrad CPC and the Thomson TO7/MO5 series of computers did. Classrooms full of networked Yamaha MSX were used for teaching informatics in schools in some Arab countries, the Soviet Union, and Cuba, where they were wildly popular in all government education schools and centers. However, because MSX never took off in the U.S., Canada, Mexico, China, Taiwan, Hong Kong, Denmark, Singapore, Malaysia, the Philippines, Indonesia, the Czech Republic, Hungary, Poland, Serbia, Bulgaria, Romania, South Africa, India and Portugal, it never became the worldwide standard that its makers had envisioned. Before MSX's lack of success in these markets became apparent, US manufacturer Commodore Business Machines overhauled its product line in the early 1980s and introduced models such as the Plus/4 and Commodore 16 that were intended to better compete with the features of MSX computers.  As the Cuban government moved to modernize their studies of computer systems in 1985, Higher Pedagogical Institutes and some schools of Pre-University Education were supplied with Toshiba and Panasonic MSX systems with resident MSX Basic language, popularly known as "Intelligent keyboards". Once they proved useful, the Minister of Education continued the process installing similar systems throughout all Secondary (Junior High) centers and finalized it in Elementary schools, adult education institutions and newly nationwide formed “Computer and Electronic Youth Clubs” in 1987. Forming the Computer Clubs allowed the Cuban government to interest and educate the common citizen in computer subjects, since selling these systems, or any other personal private computer, to the public, was banned. (see: Censorship in Cuba )  In the 1980s, Sakhr (صخر) Computers (Developed by Al Alamiah, a Kuwaiti company), started the production of the first Arabic version of MSX computers. They started producing a Yamaha AX100 and a few other models, including MSX2 and MSX2+. The most popular and affordable model within Arab States of the Persian Gulf was the Sakhr MSX AX170. They were also the first to Arabise BASIC and the MSX LOGO.  Al-Alamiah produced other common models, including AX100, AX123, AX150, AX170, AH200, AX200, AX230, AX235, AX250, AX330, AX350-I, AX350-II, AX355, AX370, AX500, AX550, AX660, and AX990. The only MSX console with a Famicom game slot in the MSX computer is AX330. The user can switch between MSX and Famicom modes by pressing a button on the back of the computer. The other variants, which are compatible with the Sega Mega Drive, are the AX660 and AX990. Sega Master System PAL cartridges are playable with AX660, and AX990 if both the TV Game Computer Cartridge Converter and Master System Converter are attached at the same time, connecting the Sega Master System cartridge to the game inlet in the computer. Attaching only the Master System Converter to play Sega Master Cartridges on the AX660, or AX990 is not possible because of the inlet depth and the physical shape of the Master System Converter that prevent the converter from being attached correctly to the AX660 and AX990 computers.  Many MSX computers were used during the 1980s in the former Eastern Bloc countries as a tool for subtitling pirated films on VHS, or Betamax cassettes. The MSX computers were used for their simplicity and ability to display prepared titles in real time as superimposed text on mastering tapes.  The MSX arrived in Argentina in late 1984. The most popular model was the Talent MSX DPC-200, based on the Daewoo MSX DPC-200. Other models were the Spectravideo (SVI) 728 and the SVI X ́Press, with a 3.5" built-in drive. Later on came the Toshiba and smaller numbers of Gradiente models from Brazil. In late 1987, Talent presented the MSX2 TPC-310 ́Turbo ́ in the Argentine market. ́Turbo ́ was just a name, not referring to MSX2+, also based on Daewoo design. The MSX was as highly successful a computer in Argentina as was the Commodore 64, thanks to its use in education at the national level. The MSX-Logo language was widely used in schools. MSXII+ never made it to the market in Argentina and MSX production ceased in 1990.  In total, 9 million MSX computers were sold in Japan, making it relatively popular but still not the global standard it was intended to be. In comparison with rival 8-bit computers, the Commodore 64 sold 17 million units worldwide in its lifetime, the Apple II sold 6 million units, the ZX Spectrum over 5 million units, the Atari 8-bit sold at least 4 million units, the Amstrad CPC sold 3 million units, and the Tandy TRS-80 Model 1 sold 250,000 units.  A Sony MSX2 machine was launched into space on board of a Russian MIR spacecraft. One professional broadcast video workstation was based on Sony HitBit HB-F900 MSX2 computer.

Similar systems.

The system MSX most closely resembled was the Spectravideo SV-328 home computer (Spectravideo even claimed to be "MSX compatible" in advertisements before the actual launch of MSX systems, but it was in fact not completely compatible with it). This led to a new and short-lived kind of software cracking: "converting". Since the MSX games were unplayable on the SV-328 computer, SV-328 crackers developed a method of modifying the (MSX) games to make them work on the SV-328. In most cases this included downloading the MSX BIOS to the SV-328 from tape or floppy disk. Spectravideo later launched the SVI-728 which completely adhered to the MSX standard.  The Sega SG-1000, the Memotech MTX and the ColecoVision all have many similarities with the MSX1 standard, but none are really compatible with it. Porting games between those systems is somewhat easy. It was also very common to port games from the ZX Spectrum to the MSX, since both have the same CPU, the Spectrum 128 had the same soundchip, and the ZX Spectrum's graphic mode could be easily emulated on the MSX's screen-2 mode.

Localization.

By default MSX machines have a hardcoded character set and keyboard scan code handling algorithm. While MSX has full application software compatibility at the firmware (BIOS) level, due to minor hardware differences, replacement of the BIOS with another from different PC may render incorrect scan code translations and thus incorrect behaviour of the keyboard subsystem for the application software.  In 2011 AGE Labs introduced Language Pack firmware, aiming to make each model support several localizations. By default installed into GR8BIT instead of the Kanji-ROM, it allows changing the character set and keyboard layout of the machine at startup. This allowed changing between Japanese, Russian, International and Portuguese locales, and the ability to change locales during machine operation using newly introduced BASIC command LANG. Selected locale setting is stored into the unused RTC NVRAM memory space.

Games.

Several popular video game franchises were established on the MSX:  Others received various installments on the MSX, including several titles unique to the system or largely reworked versions of games on other formats:

Manufacturers.

Note *: Clones or Unlicensed equipment.

Legacy.

2001 Revival.

In 2001, Kazuhiko Nishi initiated a 'MSX Revival' around an official MSX emulator called MSXPLAYer. This is the only official MSX emulator as all MSX copyrights are maintained by the MSX Association. In 2004, a Dutch company Bazix announced they had become the representatives of MSX Association in Europe, being the English contact for any questions regarding the MSX trademarks, copyrights, and licensing. On October 17, 2006, Bazix launched WOOMB.Net, a website selling MSX games in English and other languages, with a selection of 14 games. In Japan, game sales began earlier, through Project EGG. "WOOMB.Net" was the English counterpart of this and other Japanese services offered by D4 Enterprise, which also announced in August 2006 the launch of a new MSX2 compatible system called the "one chip-MSX", a system based on an Altera Cyclone EP1C12Q240C8 FPGA. The one chip-MSX" is similar in concept to the C-One, a Commodore 64 clone also built on the basis of a single FPGA chip. The new MSX system is housed in a box made out of transparent blue plastic, and can be used with a standard monitor (or TV) and a PC keyboard. It has two MSX cartridge slots and supports the audio extensions MSX-MUSIC and SCC+. A SD/MMC-flashcard can be used as an external storage medium, emulating a disk drive and can be used to boot MSX-DOS. Due to its VHDL programmable hardware, it is possible to give the device new hardware extensions simply by running a reconfiguration program under MSX-DOS. The "one chip-MSX" also has two USB connectors that can be used after adding some supporting VHDL code.  On June 7, 2008, the MSX Resource Center Foundation reported that the MSX trademark had moved from "MSX Association" to the "MSX Licensing Corporation", referring to a Benelux trademark register page of MSX, which names the "MSX Licensing Corporation" as entitled entity till 28-10-2013. At that time, the website of the "MSX Licensing Corporation" that they linked to as source, had a text saying 'We are planning to revitalize MSX, the innovative computer platform.' on it. However, the website was later changed to contain only the logo of "ITNY & Partners", and a link to "ITNY & Partners"' English and Japanese websites and has no mention of the MSX Licensing Corporation at all. On, Bazix reported on their website's front page that they are no longer the representative of MSX Association, due to being unable to achieve their goals of ""bringing about the commercial MSX Revival beyond the Japanese borders"" and ""the transfer of the MSX trademark from MSX Association to MSX Licensing Corporation"" and ""no outlook on any progress in the Western One Chip MSX project any time soon"". As a result of this, "WOOMB.Net" is taken offline as well, with its website redirecting to the Bazix website, until ""a solution free of MSX Association's contributions has been completed"". According to their post, they will cooperate with D4 Enterprise and the MSX Licensing Corporation ""in one or more retro gaming related projects"".  On July 4, 2008, MSX Association's European contact website, which states to be the ""only official contact place for MSX Association in Europe"", reports that the MSX trademark and copyright has been under the MSX Licensing Corporation holding ever since 1983. It explains that MSX Association, chaired by Dr. Kazuhiko Nishi is the operational division of MSX Licensing Corporation which manages the trademarks, logo and copyrights for MSX. According to the same article, D4 Enterprise ""refuse to pay royalties to MSX Association for the use of ESE Artists' Factory's work in 1chipMSX and the software licenses in Project Egg"", thus they deal with Kazuhiko Nishi 'directly' through the MSX Licensing Corporation. The article mentions as well the "ESE MSX System 3", on which the "1chipMSX" (also known as "One Chip MSX" or "OCM") is based.  On July 5, 2008, the MSX Association's Europe website posted an announcement reporting that D4 Enterprise was selling the "1chipMSX" illegally. In the same post it is stated that "Bazix" no longer is their representative in Europe, due to "Bazix" cutting off their relationship.

2011 Revival.

In 2011, AGE Labs announced the launch of a MSX kit called GR8BIT - the do-it-yourself computer for learning purposes, which was licensed by the MSX Licensing Corporation. The kit is priced at $499 and includes all necessary components to assemble a working MSX2 compatible computer, except for an ATX chassis, power supply, floppy drive, hard disk, PS/2 keyboard and monitor. It also comes with assembly and operational manuals and a supplement compiled from vendor and community support (from the "GR8BIT Engineering Community").

2014 Revival.

Some of the Korean forum members who made Zemmix Neo created a new version of MSX called Mini IQ3000 Cutie, which has similar features to the IQ-2000 (MSX2. Made in Korea. Daewoo Electronics ) It is based on 1ChipMSX but has some special features like 'Scan Line Generator' and 'Multi Language Support'. The scan line generator generates scan lines to show the MSX screen with better quality. It supports 2 languages at the same time. Normally it shows Korean font and working as Korean version of MSX but when pressing the 'del' key while booting, it changes to Japanese mode. Even though the default mode is Korean, the default font allocation table is Japanese, as it shows Japanese characters when executing Japanese version software.

Peripherals.

Keyboard.

The keyboard is a functionally separate unit which could be connected by non-multiplexed and multiplexed interfaces. Multiplexed keyboard units feature additional data direction line, allowing sending scan line number to the keyboard using same data lines used for return scan code, decreasing overall number of wires between keyboard and machine. Non-multiplexed interface is usually used for internal keyboards (and some external keyboards, like Panasonic CF-3300); multiplexed interface is used for external keyboards (e.g. in Yamaha YIS805 model).  The keyboard is organized as a matrix with maximum 11 input lines and 8 output lines, accounting for maximum 88 keys (including all control, numerical and alphanumerical keys). Each scan line is regularly queried to identify the state of the keys on the line; query speed is identified by the system interrupt frequency. Such organization allows system to sense state of each key, not exhibiting notorious problem with 8042 microcontroller-based keyboards when pressing several keys simultaneously (usually more than 3) generates wrong input characters, or renders inability to sense the press of more keys.  Due to the keyboard scan being controlled by the system interrupts, one of the troubleshooting hints when an MSX machine does not display any image (assuming power is present) is to press the CAPS key to see if the respective LED toggles. If it does not toggle, the system is likely suffering a more serious problem than just lack of image on the screen (i.e. the problem with video cable or video display interface in overall).  In 2009 Kamil Karimov designed the adapter board to connect PS/2 keyboard to the multiplexed MSX keyboard interface. The firmware embedded into its ATTiny chip was tailored for Daewoo CPC machines.  In 2011 AGE Labs embedded a PS/2 keyboard controller unit, based on Microchip microcontroller, into its GR8BIT do-it-yourself machine. Its firmware is developed to directly convert PS/2 scan codes to the MSX keyboard scan codes. Thus it is fully transparent to the applications, allowing use of the controller unit with different MSX-compatible machines and for different localization setups.

Cartridges.

MSX standard requires at least 1 cartridge slot, most MSX models have 2. These slots are interchangeable, so "in most cases" it makes no difference in which slot a cartridge is inserted. The physical connector is a 50 pin (2 x 25 contacts), standard 2.54 mm (0.1 inch) pitch edge connector. Using these cartridge slots, a wide variety of peripherals could be connected.  Regular game cartridges are about the size of an audio cassette (so-called "Konami size"). Despite their higher cost, this was a popular format due to its reliability and ease of use.  Around 1985, Hudson Soft released the credit card-sized Bee Card, which was meant as a cheaper and more convenient alternative to ROM cartridges. But it was a commercial failure, and very few titles were released on the format.  Source files for development of the MSX cartridges are available from AGE Labs for EAGLE.

Floppy disk drives.

MSX systems generally did not have a built-in disk drive, so games were published mainly on cartridge and cassette tape. Sony created a battery backed RAM cartridge the HBI-55 "data cartridge" for some computers in their "Hit-Bit" line of MSX systems, that could be used to store programs or data as an alternative to cassette tapes.  Floppy disk drives were available for MSX however, in the form of a cartridge containing the disk interface electronics and a BIOS extension ROM (the floppy disk drive interface), connected to an external case with the drive. In South-America, many of these systems used a floppy disk drive, but in Europe, drives were more popular. In Japan, some MSX1 systems included a built-in 3.5" disk drive, like the Panasonic (previously named Matsushita) CF-3000. In Europe, a range of Philips MSX2 systems NMS 8230, 8235, 8245, 8250 and above featured either 360 or 720 Kb 3.5" floppy drives.  In 1985, the MSX2 was released, and these systems often (but not always) included a built-in 3.5" disk drive too. Consequently the popular media for games and other software shifted to floppy disks.  The MSX-DOS disk operating system had internal software mechanisms much like CP/M (so CP/M software could be ported reasonably easily), but had a file system compatible with MS-DOS. Its user commands were also similar to early MS-DOS versions. In this way, Microsoft could promote MSX for home use while promoting MS-DOS based personal computers in office environments.  The MSX 3.5" floppy disks are directly compatible with MS-DOS (although some details like file undeletion and boot sector code were different). Like MS-DOS 1, MSX disks (formatted) under MSX-DOS 1 have no support for subdirectories.  In September 2012, AGE Labs extended the standard by including support for 1.44Mb 3.5” format. The 1.44Mb diskette size goes in two configurations: Standard (1 sector per cluster, 9 FAT sectors), and Compatible (4 sectors per cluster, 3 FAT sectors).

Emulation.

MSX computers are emulated on many platforms today. Early MSX emulators were often based on the code of the pioneer fMSX, a portable MSX emulator by Marat Fayzullin. Many emulators removed Fayzullin's Z80 emulation code entirely in later versions to avoid legal problems, as at the time fMSX wasn't free software. Somewhat later fMSX source code became free to use for non-profit use; however a license was still required for commercial use. On December 31, 2013, the Windows version of fMSX 3.7 was released, free for anyone to use.  The official MSX emulator MSXPLAYer is produced by the MSX Association, of which the inventor of the MSX standard, Kazuhiko Nishi, is the president.  As of version 0.146.u, MESS currently supports 90 percent of all MSX Versions.

Virtual Console.

In February 2007, Nintendo of Japan announced that MSX games will be available for the Wii's Virtual Console emulator. It was confirmed that the games would cost 700 Wii Points and will become available from the middle of 2007. It also became available for the Wii U on December 25, 2013. Ultimately 13 games, mainly Konami titles, for the Wii plus 1 for the Wii U were released for the service in Japan only.

MSX is a standardized home computer architecture, announced by Microsoft and ASCII on June 16, 1983. It was conceived and marketed by Kazuhiko Nishi, then vice-president at Microsoft and director at ASCII Corporation. Nishi conceived the project as an attempt to create unified standards among various home computing system manufacturers of the period, in the same fashion as the VHS standard for home video tape machines.

MSX是一个标准化的家用计算机体系结构,最早由微软于1983年6月16日提出,并由后来的微软日本副总裁与ASCII主管西和彦构思。有人说这是由微软领导,试图在标准硬件制造商建立统一标准的项目 。


Etymology.

The English word "hostage" derives from French "ostage", modern "otage", from Late Latin "obsidaticum" (Medieval Latin "ostaticum, ostagium"), the state of being an "obses" (plural "obsides"), "hostage", from Latin "obsideō" ("I haunt/frequent/blockade/besiege"), but an etymological connection was later supposed with Latin "hostis" ("stranger," later "enemy").

Historical practices.

This long history of political and military use indicates that political authorities or generals would legally agree to hand over one or usually several hostages in the custody of the other side, as guarantee of good faith in the observance of obligations. These obligations would be in the form of signing of a peace treaty, in the hands of the victor, or even exchange hostages as mutual assurance in cases such as an armistice. Major powers, such as Ancient Rome and the British who had colonial vassals, would especially receive many such political hostages, often offspring of the elite, even princes or princesses who were generally treated according to their rank and put to a subtle long-term use where they would be given an elitist education or possibly even a religious conversion. This would eventually influence them culturally and open the way for an amicable political line if they ascended to power after release. This caused the element "gīsl" = "hostage" in many old Germanic personal names, and thus in placenames derived from personal names, for example Isleworth in west London (UK) from Old English "Gīslheres wyrð" (= "enclosure belonging to [a man called] Gīslhere"). The practice of taking hostages is very ancient, and has been used constantly in negotiations with conquered nations, and in cases such as surrenders, armistices and the like, where the two belligerents depended for its proper carrying out on each other's good faith. The Romans were accustomed to take the sons of tributary princes and educate them at Rome, thus holding a security for the continued loyalty of the conquered nation and also instilling a possible future ruler with ideas of Roman civilization. The practice was also commonplace in the Imperial Chinese tributary system, especially between the Han and Tang dynasties.  The practice continued through the early Middle Ages. The Irish High King Niall of the Nine Hostages got his epithet "Noígiallach" because, by taking nine petty kings hostage, he had subjected nine other principalities to his power.  This practice was also adopted in the early period of the British occupation of India, and by France in her relations with the Arab tribes in North Africa. The position of a hostage was that of a prisoner of war, to be retained till the negotiations or treaty obligations were carried out, and liable to punishment (in ancient times), and even to death, in case of treachery or refusal to fulfil the promises made.  The practice of taking hostages as security for the carrying out of a treaty between civilized states is now obsolete. The last occasion was at the Treaty of Aix-la-Chapelle (1748), ending the War of the Austrian Succession, when two British peers, Henry Bowes Howard, 11th Earl of Suffolk, and Charles, 9th Baron Cathcart, were sent to France as hostages for the restitution of Cape Breton to France.  In France, after the revolution of Prairial (June 18, 1799), the so-called law of hostages was passed, to meet the royalist insurrection in La Vendée. Relatives of émigrés were taken from disturbed districts and imprisoned, and were liable to execution at any attempt to escape. Sequestration of their property and deportation from France followed on the murder of a republican, four to every such murder, with heavy fines on the whole body of hostages. The law only resulted in an increase in the insurrection. Napoleon in 1796 had used similar measures to deal with the insurrection in Lombardy.  In later times the practice of official war hostages may be said to be confined to either securing the payment of enforced contributions or requisitions in an occupied territory and the obedience to regulations the occupying army may think fit to issue; or as a precautionary measure, to prevent illegitimate acts of war or violence by persons not members of the recognized military forces of the enemy. During the Franco-Prussian War of 1870, the Germans took as hostages the prominent people or officials from towns or districts when making requisitions and also when foraging, and it was a general practice for the mayor and adjoint of a town which failed to pay a fine imposed upon it to be seized as hostages and retained till the money was paid. Another case where hostages have been taken in modern warfare has been the subject of much discussion. In 1870 the Germans found it necessary to take special measures to put a stop to train-wrecking by "Francs-tireurs" - i.e. "parties in occupied territory not belonging to the recognized armed forces of the enemy", which was considered an illegitimate act of war. Prominent citizens were placed on the engine of the train so that it might be understood that in every accident caused by the hostility of the inhabitants their compatriots will be the first to suffer. The measure seems to have been effective. In 1900 during the Second Boer War, by a proclamation issued at Pretoria (June 19), Lord Roberts adopted the plan for a similar reason, but shortly afterwards (July 29) it was abandoned.  The Germans also, between the surrender of a town and its final occupation, took hostages as security against outbreaks of violence by the inhabitants.  Most writers on international law have regarded this method of preventing such acts of hostility as unjustifiable, on the ground that the persons taken as hostages are not the persons responsible for the act; that, as by the usage of war hostages are to be treated strictly as prisoners of war, such an exposure to danger is transgressing the rights of a belligerent; and as useless, for the mere temporary removal of important citizens till the end of a war cannot be a deterrent unless their mere removal deprives the combatants of persons necessary to the continuance of the acts aimed at. On the other hand, it has been urged that the acts, the prevention of which is aimed at, are not legitimate acts on the part of the armed forces of the enemy, but illegitimate acts by private persons, who, if caught, could be quite lawfully punished, and that a precautionary and preventive measure is more reasonable than reprisals. It may be noticed, however, that the hostages would suffer should the acts aimed at be performed by the authorized belligerent forces of the enemy.  Article 50 of the 1907 Hague Convention on Land Warfare provides that: "No general penalty, pecuniary or otherwise, can be inflicted on the population on account of the acts of individuals for which it cannot be regarded as collectively responsible." The regulations, however do not allude to the practice of taking hostage.  In May 1871, at the close of the Paris Commune, took place the massacre of the so-called hostages. Strictly they were not hostages, for they had not been handed over or seized as security for the performance of any undertaking or as a preventive measure, but merely in retaliation for the death of their leaders E. V. Duval and Gustave Flourens. It was an act of maniacal despair, on the defeat at Mont Valrien on the 4 April and the entry of the army into Paris on the 21 May. Among the many victims who were shot in batches the most noticeable were Georges Darboy, archbishop of Paris, the Abbé Deguery, curé of the Madeleine, and the president of the Court of Cassation, Louis Bernard Bonjean.

Legal hostage-taking.

Taking hostages is today considered a crime or an act of terrorism; the use of the word in this sense of abductee became current only in the 1970s. The criminal activity is known as kidnapping. An acute situation where hostages are kept in a building or a vehicle that has been taken over by armed terrorists or common criminals is often called a hostage crisis.  Common Article 3 of the 1949 Geneva Conventions states that the taking of hostages during an internal conflict is a war crime and shall remain prohibited at any time and in any place whatsoever. In international conflicts, Articles 34 and 147 of the Fourth Geneva Convention state that using civilians as hostages is a grave breach of the Convention. These conventions are supplemented by Article 75(2)(c) of Additional Protocol I in international conflicts and Article 4(2)(c) of Additional Protocol II in internal conflicts.  The International Convention against the Taking of Hostages—which prohibits hostage-taking and mandates the punishment of hostage-takers—was adopted by the United Nations General Assembly in 1979. The treaty came into force in 1983 and has been ratified by all but 24 of the member states of the United Nations.  Hostage-taking is still often politically motivated or intended to raise a ransom or to enforce an exchange against other hostages or even condemned convicts. However, in some countries hostage-taking for profit has become an "industry", ransom often being the only demand.

Hostage-taking in the United States.

Hostage Taking Act.

The United States makes hostage-taking a federal criminal offense pursuant to. Generally, the Act applies to conduct occurring within the territory of the United States. However, under Subsection B, an offender may be indicted under the Act even if the hostage-taking occurred outside the territory of the United States if the "offender or the person seized or detained is a national of the United States; the offender is found in the United States; or the governmental organization sought to be compelled is the Government of the United States." These provisions are consistent with the fundamental principles of international criminal law, specifically active nationality principle, universal principle, and the effects principle, respectively.

18 USC 1203: Hostage Taking Act.

Title 18 of the United States Code criminalizes hostage-taking under "18 USC 1203: Hostage Taking Act", which reads: The Hostage Taking Act is a subsection of the International Convention Against the Taking of Hostages. It became enforceable in the United States January 6, 1985.

Other use.

In old Germanic peoples the word for "hostage" ("gīsl" and similar) sometimes occurred as part of a man's name: "Ēadgils", "Cynegils", "Gīslheard", "Gīslbeorht", etc.; sometimes when a man from one nation was hostage in another nation, his position as hostage was more or less voluntary: for example the position of Æscferð son of Ecglāf, who was a Northumbrian hostage in Wessex; he fought under Byrhtnōð against Vikings in the Battle of Maldon on 10 August 991 AD (ref. lines 265 etseq), and probably died in battle there.  See also Homeric Question, as Greek `Ομηρος means "Homer" and also "hostage".  Sometimes the word "hostage" is used metaphorically, for example: "The school did not buy the land because its headmaster missed the train to the meeting because of a road traffic accident; the whole matter thus proved to be "hostage" to one misbehaving carriage horse."

Dutch law.

In Dutch law the state can take people 'hostage' ("gijzeling" in Dutch) to force people to appear in court or (in civil cases) if the person refuses to pay his or her debts. In the latter case, the person in question is imprisoned one day for each €50 that are owed without cancellation of the debt.

A hostage is a person seized by a criminal abductor in order to compel another party such as a relative, employer, law enforcement or government to act, or refrain from acting, in a certain way, often under threat of serious physical harm to the hostage(s) after expiration of an ultimatum. The 1911 edition of the "Encyclopædia Britannica" defines a hostage as "a person who is handed over by one of two belligerent parties to the other or seized as security for the carrying out of an agreement, or as a preventive measure against certain acts of war."

人质,即是被俘虏者掳走的人。这词最早的用意是指在战争里,某一方将敌人的人捉走,然后向敌方提出条件,以方便威胁对方。但到了近代,人质一词意即被犯罪者绑架,接着强求人质的亲属,雇主或甚至该政府做出某些事情,或控制其举动,尤其是在威胁的态度下进行。在特别的情况下,例如绑架者提出的限期已到(如发出最后通牒来通知),而对方没有回应或拒绝其要求,绑架者将会伤害人质。


List of municipalities of the Netherlands

Municipal status.

As a second level administrative division municipalities are the third tier of public administration in the Netherlands after the central government and the provinces. The Netherlands is a decentralized unitary state, which means that the central government is supreme and delegates certain tasks to lower levels of government by law. The different levels do, however, make work agreements, which give municipalities a certain degree of independence in their policy decisions. Municipalities are responsible for a wide variety of public services, which include land-use planning, public housing, management and maintenance of local roads, waste management and social security. After the dissolution of the Netherlands Antilles in 2010 three special municipalities (officially public bodies) were formed. These municipalities function the same as regular municipalities and are grouped together as the Caribbean Netherlands and are not part of a province.  The municipalities are governed by both a board of mayor and aldermen and a municipal council. The municipal council, which is titled island council in the special municipalities, is elected every four years. The number of members in the council ranges from nine members for the smallest municipalities to forty-five members for the largest. It is the highest administrative body in the municipality and controls public policy. The executive power lies with the executive board, which consists of a mayor, titled lieutenant governor in the special municipalities, and multiple aldermen, titled island deputies in the special municipalities. The mayor is appointed for six years at a time by the crown and the alderman are elected by the municipal council, typically after each municipal election. The mayor is responsible for public order and is the first in command during emergencies, all other tasks are distributed freely between mayor and aldermen. The exact portfolio for each person differs between each municipality. Official municipal boundaries were first drawn up in 1832 in the Netherlands after a cadastre was formed. The "Municipalities Act" of 1851, written by prime minister Thorbecke, led to the disappearance of small municipalities. Throughout the years, less populous municipalities have been merged. They were either added to the larger neighbouring cities or multiple smaller municipalities merged into a larger new municipality with a new name. The number of municipalities reduced from 1,209 in 1850 to 537 in 2000; there are 355 municipalities. During this time, multiple mergers occurred simultaneously in large parts of individual provinces; the municipal boundaries were basically redrawn in these regions. In the 19th and large parts of the 20th century, municipal mergers were forced by the central government. This policy changed in the end of the 20th century; local support for the merger is now a large part of the decision-making process. The larger, merged municipalities are intended to handle an increasing workload because more public services are delegated from higher levels of government to the municipalities. Another reason for municipal mergers is the assumption that larger municipalities are more efficient in performing their tasks than smaller ones.  Municipalities have the right to decentralize themselves and form submunicipalities as an additional level of government. This right and the submunicipalities will cease to exist in the near future to reduce the number of levels of government. Only Amsterdam, where the districts are called, and Rotterdam, where the districts are called, consist of such formal subdivisions. The Hague, Almere, Breda, Eindhoven, Enschede, Groningen, Nijmegen, Tilburg, and Utrecht have instituted as well, although they do not have the same legal submunicipal status. For administrative use by municipalities and data collection by Statistics Netherlands all municipalities are subdivided into districts (), which in turn are subdivided into neighbourhoods (). These subdivisions have, in contrast to the submunicipalities, no formal status.

As of January 2020, there are 355 municipalities () plus 3 special municipalities () in the Netherlands. The latter is the status of three of the six island territories that make up the Dutch Caribbean. Municipalities are the second-level administrative division, or public bodies (), in the Netherlands and are subdivisions of their respective provinces. Their duties are delegated to them by the central government and they are ruled by a municipal council that is elected every four years. Municipal mergers have reduced the total number of municipalities by two-thirds since the first official boundaries were created in the mid 19th century. Municipalities themselves are informally subdivided into districts and neighbourhoods for administrative and statistical purposes.

荷兰所有的省份的下一级行政区划均为市镇()。截至2019年1月,荷兰共有355个市镇和3个「特别市」(正式名称为公共实体,)。市镇是其所属省分的下一级行政区划,意即市镇是荷兰的第二级行政区划。荷兰中央政府将职权下放给市镇,并由市议会(每四年进行一次选举)治理。荷兰政府后陆续推行市的合并,大幅减少了市镇的数量,目前大约是自十九世纪中期行政区划划定以来的三分之一。市镇又可因行政或统计的需求,被非正式地划分为「社区」()和「邻里」()等地区。


Structure and operating principles.

Photomultipliers are typically constructed with an evacuated glass housing (using an extremely tight and durable glass-to-metal seal like other vacuum tubes), containing a photocathode, several dynodes, and an anode. Incident photons strike the photocathode material, which is usually a thin vapor-deposited conducting layer on the inside of the entry window of the device. Electrons are ejected from the surface as a consequence of the photoelectric effect. These electrons are directed by the focusing electrode toward the electron multiplier, where electrons are multiplied by the process of secondary emission. The electron multiplier consists of a number of electrodes called "dynodes". Each dynode is held at a more positive potential, by ≈100 Volts, than the preceding one. A primary electron leaves the photocathode with the energy of the incoming photon, or about 3 eV for "blue" photons, minus the work function of the photocathode. A small group of primary electrons is created by the arrival of a group of initial photons. (In Fig. 1, the number of primary electrons in the initial group is proportional to the energy of the incident high energy gamma ray.) The primary electrons move toward the first dynode because they are accelerated by the electric field. They each arrive with ≈100 eV kinetic energy imparted by the potential difference. Upon striking the first dynode, more low energy electrons are emitted, and these electrons are in turn accelerated toward the second dynode. The geometry of the dynode chain is such that a cascade occurs with an exponentially-increasing number of electrons being produced at each stage. For example, if at each stage an average of 5 new electrons are produced for each incoming electron, and if there are 12 dynode stages, then at the last stage one expects for each primary electron about 5 ≈ 10 electrons. This last stage is called the anode. This large number of electrons reaching the anode results in a sharp current pulse that is easily detectable, for example on an oscilloscope, signaling the arrival of the photon(s) at the photocathode ≈50 nanoseconds earlier.  The necessary distribution of voltage along the series of dynodes is created by a voltage divider chain, as illustrated in Fig. 2. In the example, the photocathode is held at a negative high voltage of order 1000 V, while the anode is very close to ground potential. The capacitors across the final few dynodes act as local reservoirs of charge to help maintain the voltage on the dynodes while electron avalanches propagate through the tube. Many variations of design are used in practice; the design shown is merely illustrative.  There are two common photomultiplier orientations, the "head-on" or "end-on" (transmission mode) design, as shown above, where light enters the flat, circular top of the tube and passes the photocathode, and the "side-on" design (reflection mode), where light enters at a particular spot on the side of the tube, and impacts on an opaque photocathode. The side-on design is used, for instance, in the type 931, the first mass-produced PMT. Besides the different photocathode materials, performance is also affected by the transmission of the window material that the light passes through, and by the arrangement of the dynodes. Many photomultiplier models are available having various combinations of these, and other, design variables. The manufacturers manuals provide the information needed to choose an appropriate design for a particular application.

History.

The invention of the photomultiplier is predicated upon two prior achievements, the separate discoveries of the photoelectric effect and of secondary emission.

Photoelectric effect.

The first demonstration of the photoelectric effect was carried out in 1887 by Heinrich Hertz using ultraviolet light. Significant for practical applications, Elster and Geitel two years later demonstrated the same effect using "visible" light striking alkali metals (potassium and sodium). The addition of caesium, another alkali metal, has permitted the range of sensitive wavelengths to be extended towards longer wavelengths in the red portion of the visible spectrum.  Historically, the photoelectric effect is associated with Albert Einstein, who relied upon the phenomenon to establish the fundamental principle of quantum mechanics in 1905, an accomplishment for which Einstein received the 1921 Nobel Prize. It is worthwhile to note that Heinrich Hertz, working 18 years earlier, had not recognized that the kinetic energy of the emitted electrons is proportional to the frequency but independent of the optical intensity. This fact implied a discrete nature of light, i.e. the existence of "quanta", for the first time.

Secondary emission.

The phenomenon of secondary emission (the ability of electrons in a vacuum tube to cause the emission of additional electrons by striking an electrode) was, at first, limited to purely electronic phenomena and devices (which lacked photosensitivity). In 1899 the effect was first reported by Villard. In 1902, Austin and Starke reported that the metal surfaces impacted by electron beams emitted a larger number of electrons than were incident. The application of the newly discovered secondary emission to the amplification of signals was only proposed after World War I by Westinghouse scientist Joseph Slepian in a 1919 patent.

The race towards a practical electronic television camera.

The ingredients for inventing the photomultiplier were coming together during the 1920s as the pace of vacuum tube technology accelerated. The primary goal for many, if not most, workers was the need for a practical television camera technology. Television had been pursued with primitive prototypes for decades prior to the 1934 introduction of the first practical camera (the iconoscope). Early prototype television cameras lacked sensitivity. Photomultiplier technology was pursued to enable television camera tubes, such as the iconoscope and (later) the orthicon, to be sensitive enough to be practical. So the stage was set to combine the dual phenomena of photoemission (i.e., the photoelectric effect) with secondary emission, both of which had already been studied and adequately understood, to create a practical photomultiplier.

First photomultiplier, single-stage (early 1934).

The first documented photomultiplier demonstration dates to the early 1934 accomplishments of an RCA group based in Harrison, NJ. Harley Iams and Bernard Salzberg were the first to integrate a photoelectric-effect cathode and single secondary emission amplification stage in a single vacuum envelope and the first to characterize its performance as a photomultiplier with electron amplification gain. These accomplishments were finalized "prior" to June 1934 as detailed in the manuscript submitted to Proceedings of the Institute of Radio Engineers (Proc. IRE). The device consisted of a semi-cylindrical photocathode, a secondary emitter mounted on the axis, and a collector grid surrounding the secondary emitter. The tube had a gain of about eight and operated at frequencies well above 10 kHz.

Magnetic photomultipliers (mid 1934–1937).

Higher gains were sought than those available from the early single-stage photomultipliers. However, it is an empirical fact that the yield of secondary electrons is limited in any given secondary emission process, regardless of acceleration voltage. Thus, any single-stage photomultiplier is limited in gain. At the time the maximum first-stage gain that could be achieved was approximately 10 (very significant developments in the 1960s permitted gains above 25 to be reached using negative electron affinity dynodes). For this reason, multiple-stage photomultipliers, in which the photoelectron yield could be multiplied successively in several stages, were an important goal. The challenge was to cause the photoelectrons to impinge on successively higher-voltage electrodes rather than to travel directly to the highest voltage electrode. Initially this challenge was overcome by using strong magnetic fields to bend the electrons' trajectories. Such a scheme had earlier been conceived by inventor J. Slepian by 1919 (see above). Accordingly, leading international research organizations turned their attention towards improving photomultiplers to achieve higher gain with multiple stages.  In the USSR, RCA-manufactured radio equipment was introduced on a large scale by Joseph Stalin to construct broadcast networks, and the newly formed All-Union Scientific Research Institute for Television was gearing up a research program in vacuum tubes that was advanced for its time and place. Numerous visits were made by RCA scientific personnel to the USSR in the 1930s, prior to the Cold War, to instruct the Soviet customers on the capabilities of RCA equipment and to investigate customer needs. During one of these visits, in September 1934, RCA's Vladimir Zworykin was shown the first multiple-dynode photomultiplier, or "photoelectron multiplier". This pioneering device was proposed by Leonid A. Kubetsky in 1930 which he subsequently built in 1934. The device achieved gains of 1000x or more when demonstrated in June 1934. The work was submitted for print publication only two years later, in July 1936 as emphasized in a recent 2006 publication of the Russian Academy of Sciences (RAS), which terms it "Kubetsky's Tube." The Soviet device used a magnetic field to confine the secondary electrons and relied on the Ag-O-Cs photocathode which had been demonstrated by General Electric in the 1920s.  By October 1935, Vladimir Zworykin, George Ashmun Morton, and Louis Malter of RCA in Camden, NJ submitted their manuscript describing the first comprehensive experimental and theoretical analysis of a multiple dynode tube — the device later called a "photomultiplier" — to Proc. IRE. The RCA prototype photomultipliers also used an Ag-O-Cs (silver oxide-caesium) photocathode. They exhibited a peak quantum efficiency of 0.4% at 800 nm.

Electrostatic photomultipliers (1937–present).

Whereas these early photomultipliers used the magnetic field principle, electrostatic photomultipliers (with no magnetic field) were demonstrated by Jan Rajchman of RCA Laboratories in Princeton, NJ in the late 1930s and became the standard for all future commercial photomultipliers. The first mass-produced photomultiplier, the Type 931, was of this design and is still commercially produced today.

Improved photocathodes.

Also in 1936, a much improved photocathode, CsSb (caesium-antimony), was reported by P. Görlich. The caesium-antimony photocathode had a dramatically improved quantum efficiency of 12% at 400 nm, and was used in the first commercially successful photomultipliers manufactured by RCA (i.e., the 931-type) both as a photocathode and as a secondary-emitting material for the dynodes. Different photocathodes provided differing spectral responses.

Spectral response of photocathodes.

In the early 1940s, the JEDEC (Joint Electron Device Engineering Council), an industry committee on standardization, developed a system of designating spectral responses. The philosophy included the idea that the product's user need only be concerned about the response of the device rather than how the device may be fabricated. Various combinations of photocathode and window materials were assigned "S-numbers" (spectral numbers) ranging from S-1 through S-40, which are still in use today. For example, S-11 uses the caesium-antimony photocathode with a lime glass window, S-13 uses the same photocathode with a fused silica window, and S-25 uses a so-called "multialkali" photocathode (Na-K-Sb-Cs, or sodium-potassium-antimony-caesium) that provides extended response in the red portion of the visible light spectrum. No suitable photoemissive surfaces have yet been reported to detect wavelengths longer than approximately 1700 nanometers, which can be approached by a special (InP/InGaAs(Cs)) photocathode.

RCA Corporation.

For decades, RCA was responsible for performing the most important work in developing and refining photomultipliers. RCA was also largely responsible for the commercialization of photomultiplers. The company compiled and published an authoritative and widely used "Photomultiplier Handbook". RCA provided printed copies free upon request. The handbook, which continues to be made available online at no cost by the successors to RCA, is considered to be an essential reference.  Following a corporate break-up in the late 1980s involving the acquisition of RCA by General Electric and disposition of the divisions of RCA to numerous third parties, RCA's photomultiplier business became an independent company.

Lancaster, Pennsylvania facility.

The Lancaster, Pennsylvania facility was opened by the U.S. Navy in 1942 and operated by RCA for the manufacture of radio and microwave tubes. Following World War II, the naval facility was acquired by RCA. "RCA Lancaster," as it became known, was the base for the development and the production of commercial television products. In subsequent years other products were added, such as "cathode-ray" tubes, photomultiplier tubes, motion-sensing light control switches, and closed-circuit television systems.

Burle Industries.

Burle Industries, as a successor to the RCA Corporation, carried the RCA photomultiplier business forward after 1986, based in the Lancaster, Pennsylvania facility. The 1986 acquisition of RCA by General Electric resulted in the divestiture of the RCA Lancaster New Products Division. Hence, 45 years after being founded by the U.S. Navy, its management team, led by Erich Burlefinger, purchased the division and in 1987 founded Burle Industries.  In 2005, after eighteen years as an independent enterprise, Burle Industries and a key subsidiary were acquired by Photonis, a European holding company Photonis Group. Following the acquisition, Photonis was composed of Photonis Netherlands, Photonis France, Photonis USA, and Burle Industries. Photonis USA operates the former Galileo Corporation Scientific Detector Products Group (Sturbridge, Massachusetts), which had been purchased by Burle Industries in 1999. The group is known for microchannel plate detector (MCP) electron multipliers—an integrated micro-vacuum tube version of photomultipliers. MCPs are used for imaging and scientific applications, including night vision devices.  On 9 March 2009, Photonis announced that it would cease all production of photomultipliers at both the Lancaster, Pennsylvania and the Brive, France plants.

Hamamatsu.

The Japan-based company Hamamatsu Photonics (also known as Hamamatsu) has emerged since the 1950s as a leader in the photomultiplier industry. Hamamatsu, in the tradition of RCA, has published its own handbook, which is available without cost on the company's website. Hamamatsu uses different designations for particular photocathode formulations and introduces modifications to these designations based on Hamamatsu's proprietary research and development.

Photocathode materials.

The photocathodes can be made of a variety of materials, with different properties. Typically the materials have low work function and are therefore prone to thermionic emission, causing noise and dark current, especially the materials sensitive in infrared; cooling the photocathode lowers this thermal noise. The most common photocathode materials are Ag-O-Cs (also called S1) transmission-mode, sensitive from 300–1200 nm. High dark current; used mainly in near-infrared, with the photocathode cooled; GaAs:Cs, caesium-activated gallium arsenide, flat response from 300 to 850 nm, fading towards ultraviolet and to 930 nm; InGaAs:Cs, caesium-activated indium gallium arsenide, higher infrared sensitivity than GaAs:Cs, between 900–1000 nm much higher signal-to-noise ratio than Ag-O-Cs; Sb-Cs, (also called S11) caesium-activated antimony, used for reflective mode photocathodes; response range from ultraviolet to visible, widely used; bialkali (Sb-K-Cs, Sb-Rb-Cs), caesium-activated antimony-rubidium or antimony-potassium alloy, similar to Sb:Cs, with higher sensitivity and lower noise. can be used for transmission-mode; favorable response to a NaI:Tl scintillator flashes makes them widely used in gamma spectroscopy and radiation detection; high-temperature bialkali (Na-K-Sb), can operate up to 175 °C, used in well logging, low dark current at room temperature; multialkali (Na-K-Sb-Cs), (also called S20), wide spectral response from ultraviolet to near-infrared, special cathode processing can extend range to 930 nm, used in broadband spectrophotometers; solar-blind (Cs-Te, Cs-I), sensitive to vacuum-UV and ultraviolet, insensitive to visible light and infrared (Cs-Te has cutoff at 320 nm, Cs-I at 200 nm).

Window materials.

The windows of the photomultipliers act as wavelength filters; this may be irrelevant if the cutoff wavelengths are outside of the application range or outside of the photocathode sensitivity range, but special care has to be taken for uncommon wavelengths. Borosilicate glass is commonly used for near-infrared to about 300 nm. High borate borosilicate glasses exist also in high UV transmission versions with high transmission also at 254 nm. Glass with very low content of potassium can be used with bialkali photocathodes to lower the background radiation from the potassium-40 isotope. Ultraviolet glass transmits visible and ultraviolet down to 185 nm. Used in spectroscopy. Synthetic silica transmits down to 160 nm, absorbs less UV than fused silica. Different thermal expansion than kovar (and than borosilicate glass that's expansion-matched to kovar), a graded seal needed between the window and the rest of the tube. The seal is vulnerable to mechanical shocks. Magnesium fluoride transmits ultraviolet down to 115 nm. Hygroscopic, though less than other alkali halides usable for UV windows.

Usage considerations.

Photomultiplier tubes typically utilize 1000 to 2000 volts to accelerate electrons within the chain of dynodes. (See Figure near top of article.) The most negative voltage is connected to the cathode, and the most positive voltage is connected to the anode. Negative high-voltage supplies (with the positive terminal grounded) are often preferred, because this configuration enables the photocurrent to be measured at the low voltage side of the circuit for amplification by subsequent electronic circuits operating at low voltage. However, with the photocathode at high voltage, leakage currents sometimes result in unwanted "dark current" pulses that may affect the operation. Voltages are distributed to the dynodes by a resistive voltage divider, although variations such as active designs (with transistors or diodes) are possible. The divider design, which influences frequency response or rise time, can be selected to suit varying applications. Some instruments that use photomultipliers have provisions to vary the anode voltage to control the gain of the system.  While powered (energized), photomultipliers must be shielded from ambient light to prevent their destruction through overexcitation. In some applications this protection is accomplished mechanically by electrical interlocks or shutters that protect the tube when the photomultiplier compartment is opened. Another option is to add overcurrent protection in the external circuit, so that when the measured anode current exceeds a safe limit, the high voltage is reduced.  If used in a location with strong magnetic fields, which can curve electron paths, steer the electrons away from the dynodes and cause loss of gain, photomultipliers are usually magnetically shielded by a layer of soft iron or mu-metal. This magnetic shield is often maintained at cathode potential. When this is the case, the external shield must also be electrically insulated because of the high voltage on it. Photomultipliers with large distances between the photocathode and the first dynode are especially sensitive to magnetic fields.

Applications.

Photomultipliers were the first electric eye devices, being used to measure interruptions in beams of light. Photomultipliers are used in conjunction with scintillators to detect Ionizing radiation by means of hand held and fixed radiation protection instruments, and particle radiation in physics experiments. Photomultipliers are used in research laboratories to measure the intensity and spectrum of light-emitting materials such as compound semiconductors and quantum dots. Photomultipliers are used as the detector in many spectrophotometers. This allows an instrument design that escapes the thermal noise limit on sensitivity, and which can therefore substantially increase the dynamic range of the instrument.  Photomultipliers are used in numerous medical equipment designs. For example, blood analysis devices used by clinical medical laboratories, such as flow cytometers, utilize photomultipliers to determine the relative concentration of various components in blood samples, in combination with optical filters and incandescent lamps. An array of photomultipliers is used in a gamma camera. Photomultipliers are typically used as the detectors in flying-spot scanners.

High-sensitivity applications.

After 50 years, during which solid-state electronic components have largely displaced the vacuum tube, the photomultiplier remains a unique and important optoelectronic component. Perhaps its most useful quality is that it acts, electronically, as a nearly perfect current source, owing to the high voltage utilized in extracting the tiny currents associated with weak light signals. There is no Johnson noise associated with photomultiplier signal currents, even though they are greatly amplified, e.g., by 100 thousand times (i.e., 100 dB) or more. The photocurrent still contains shot noise.  Photomultiplier-amplified photocurrents can be electronically amplified by a high-input-impedance electronic amplifier (in the signal path subsequent to the photomultiplier), thus producing appreciable voltages even for nearly infinitesimally small photon fluxes. Photomultipliers offer the best possible opportunity to exceed the Johnson noise for many configurations. The aforementioned refers to measurement of light fluxes that, while small, nonetheless amount to a continuous stream of multiple photons.  For smaller photon fluxes, the photomultiplier can be operated in photon-counting, or Geiger, mode (see also Single-photon avalanche diode). In Geiger mode the photomultiplier gain is set so high (using high voltage) that a single photo-electron resulting from a single photon incident on the primary surface generates a very large current at the output circuit. However, owing to the avalanche of current, a reset of the photomultiplier is required. In either case, the photomultiplier can detect individual photons. The drawback, however, is that not every photon incident on the primary surface is counted either because of less-than-perfect efficiency of the photomultiplier, or because a second photon can arrive at the photomultiplier during the "dead time" associated with a first photon and never be noticed.  A photomultiplier will produce a small current even without incident photons; this is called the "dark current". Photon-counting applications generally demand photomultipliers designed to minimise dark current.  Nonetheless, the ability to detect single photons striking the primary photosensitive surface itself reveals the quantization principle that Einstein put forth. Photon counting (as it is called) reveals that light, not only being a wave, consists of discrete particles (i.e., photons).

Photomultiplier tubes (photomultipliers or PMTs for short), members of the class of vacuum tubes, and more specifically vacuum phototubes, are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum. These detectors multiply the current produced by incident light by as much as 100 million times or 10 (i.e., 160 dB), in multiple dynode stages, enabling (for example) individual photons to be detected when the incident flux of light is low. The combination of high gain, low noise, high frequency response or, equivalently, ultra-fast response, and large area of collection has maintained photomultipliers an essential place in low light level spectroscopy, confocal microscopy, Raman spectroscopy, fluorescence spectroscopy, nuclear and particle physics, astronomy, medical diagnostics including blood tests, medical imaging, motion picture film scanning (telecine), radar jamming, and high-end image scanners known as drum scanners. Elements of photomultiplier technology, when integrated differently, are the basis of night vision devices. Research that analyzes light scattering, such as the study of polymers in solution, often uses a laser and a PMT to collect the scattered light data.

光电倍增管(Photomultiplier,简称PMT),是一种对紫外光、可见光和近红外光极其敏感的特殊真空管。它能使进入的微弱光信号增强至原本的10倍,使光信号能被测量。