120411181
Recent progress in techniques utilized for particle accelerator
Particle accelerators are widely used in scientific research and industry. Recently, techniques utilized for accelerator are developed rapidly in China. We briefly review the recent progress in this field and primarily focus on superconducting RF, innovative structures for particle production and acceleration and beam diagnosis. Several advanced compact user facilities are also introduced.
121908829
Amplitude and phase stability studies in a DC superconducting injector
The DC superconducting injector will be used in the PKU-THz facility which consists of a DC-gun and a 3+1/2-cell superconducting cavity. The cavity must accelerate the electron beam to 5.82 MeV which is susceptible to perturbations because of its narrow bandwidth. In this paper, the sources and influences of the perturbations in the 3+1/2-cell cavity are discussed. It is shown that the control system is essential for the cavity. The design of a feedback based digital RF low level control system for the 3+1/2-cell cavity is accomplished.
123097701
The design of a five-cell high-current superconducting cavity
Energy recovery linacs are promising for achieving high average current with superior beam quality. The key component for accelerating such high-current beams is the superconducting radio-frequency cavity. The design of a 1.3 GHz five-cell high-current superconducting cavity has been carried out under cooperation between Peking University and the Argonne National Laboratory. The radio-frequency properties, damping of the higher order modes, multipacting and mechanical features of this cavity have been discussed and the final design is presented.
54601336
LLRF CONTROL SYSTEM FOR PKU DC-SC PHOTOCATHODE INJECTOR
A digital low level RF control system based on FieldProgrammable Gate Array (FPGA) with high precision is being developed for the stable operation of upgraded Direct Current-Superconductive (DC-SC) photocathode injector at Peking University. The design of this Low level radio frequency (LLRF) control system is described, including both hardware and internal algorithm. The system is designed to achieve the requirement of ±0.1% for amplitude stability and ±0.1 o for phase stability.
123774404
Stable Operation of the 2 K Cryogenic System for the Superconducting Accelerator at Peking University
A superconducting energy recovery linac test facility (PKU-SETF) was built at Peking University, and a 2K cryogenic system, which is the first closed-loop 2K cryogenic system for a superconducting accelerator in China, was constructed for the 1.3 GHz 3+1/2 cell dc-SRF injector. The main accelerator consists of two nine-cell TESLA-type superconducting cavities of the PKU-SETF The commissioning and stable operation of this 2 K cryogenic system was carried out. A helium pressure stability of better than ±0.1 mbar and a total refrigeration capacity of 65 W at a temperature of 2K was reached.
122621857
Cold RF test and associated mechanical features correlation of a TESLA-style 9-cell superconducting niobium cavity built in China
The RF performance of a 1.3 GHz 9-cell superconducting niobium cavity was evaluated at cryogenic temperatures following surface processing by using the standard ILC-style recipe. The cavity is a TESLA-style 9-cell superconducting niobium cavity, with complete end group components including a higher order mode coupler, built in China for practical applications. An accelerating gradient of 28.6 MV/m was achieved at an unloaded quality factor of 4 × 109. The morphological property of mechanical features on the RF surface of this cavity was characterized through optical inspection. Correlation between the observed mechanical features and the RF performance of the cavity is attempted.
117075864
Production of J / psi + c anti-c through two photons in e+ e- annihilation
We study the production of $J/\psi+c\bar{c}$ in $e^+e^-$ annihilation through two virtual photons. The cross section is estimated to be 23 fb at $\sqrt{s}=10.6$ GeV, which is smaller by a factor of six than the calculated cross section for the same process but through one virtual photon. As a result, while the annihilation into two photons may be important for certain exclusive production processes, the big gap between the inclusive production cross section $\sigma(e^+e^- \to J/\psi + c\bar{c})\simeq$ 0.9pb observed by Belle and the current nonrelativistic QCD prediction of $\simeq$0.15pb still remains very puzzling. We find, however, as the center-of-mass energy increases ($\sqrt{s}>20$ GeV) the production through two virtual photons $e^+e^- \to 2\gamma^* \to J/\psi + c\bar{c}$ will prevail over that through one virtual photon, because in the former process the photon fragmentation into $J/\psi$ and into the charmed quark pair becomes more important at higher energies.
55770786
HIGH PRECISION PROGRAMMABLE OF TPS QUADRUPOLE MAGNET POWER SUPPLY
In 1993, the first of Taiwan light source was held on October 16. First beam stored in the storage ring and facility at synchrotron radiation research centre (SRRC) was opened to users and the full energy injection to 1.5Gev after seven years. In 2007, the president of Executive Yuan Taiwan had been announcement to set up a third-generation synchrotron radiation. Taiwan Photon Source (TPS) project total budget of NT6, 885 million from 2007~ 2013. TPS project will improve technical capability to build to3.3Gev electron energy. Totally had been installed 1032sets of magnet power supplies for the storage ring and 152 sets for the injector. In the future, Taiwan photon source set up complete and operation, it will offer one of the world's brightest synchrotron x-ray sources.
55862722
A KICKER PULSE POWER SUPPLY WITH LOW JITTER
The performance of kicker pulse power supplies is the main parameter to increase injection efficiency of storage ring that is an important issue for laboratory of synchrotron radiation research. The output current waveform of a kicker pulse power supply with low timing jitter is our goal for years that must satisfy the Top-Up mode injection requirement of NSRRC. In the past years kicker pulse power supplies of storage ring of NSRRC are immersed in isolation oil to sustain high voltage operational environment that led difficult to maintain, electronic component degrading and uneasy to tune parameters. Air-cooling and air-isolation is adopted in the new design structure for kicker pulse power supply system and an pre-trigger unit MA2709A is installed to trigger thyratron tube EEV1536A, a kicker pulse power supply with low timing jitter 1~2ns(p-p) is obtained and could satisfy for Top-Up mode injection and maintenance is more easier than before.
138669855
External Energy Dump for Superconducting Magnet of the Uni-polar Power System
23597079
The fabrication and characterization of an S-band RF-gun cavity
A single cell rf-gun cavity is designed and fabricated for the purpose of examining the feasibility of installing a thermionic rf-gun at NSRRC instead of a photocathode rf- gun considered previously. The operating frequency of the rf-gun cavity is set at 2856 MHz in order to utilize the available XK-5 klystron and linac. The fabricated parts of the OFHC copper cavity are brazed together in-house and then the cavity is characterized by rf measurement. It shows that the cavity gives very good character in terms of high quality factor, relaxed tuning range, adequate coupling coefficient, and reasonable reproducibility. The properties of the cavity are further explored by measuring the field profile and its response to an rf pulse in which the filling time is deduced. The measurement results of this brazed cavity are described and summarized in this report.