38996638
Nanosecond Electron Beam Generation and Instrumentation at SLAC
of the present SLAC injector including the latest beam chopping equipment. Two off-axis guns can each be grid-modulated with trains of pulses as short as 5 nanoseconds. An initial 39.667 MHz beam deflector has sufficient deflecting field to reject adjacent electron bunches of the 2856 MHz prebunched beam, thereby loading one RF bucket of the accelerator every 12.5 nanoseconds. Fast pulse amplifiers can be used in conjunction with the chopping system to produce any spacing which is a multiple of 12.5 nanoseconds. After the first accelerator section (35 MeV) a quarter wave resonant balanced deflector chops beams to 1 nanosecond for SPEAR injection. A second reverse traveling wave deflector is used in conjunction with the upstream deflector to generate 25 or;50 nanosecond spaced single bunch beams.
118704913
NLC Electron Injector Beam Dynamics
The Next Linear Collider (NLC) being designed at SLAC requires a train of 90 electron bunches 1.4 ns apart at 120 Hz. The intensity and emittance required at the interaction point, and the various machine systems between the injector and the IP determine the beam requirements from the injector. The style of injector chosen for the NLC is driven by the fact that the production of polarized electrons at the IP is a must. Based on the successful operation of the SLC polarized electron source, a similar type of injector with a DC gun and subharmonic bunching system is chosen for the NLC.
117399426
A Resonant Cavity Approach to Non-Invasive, Pulse-to-Pulse EmittanceMeasurement
We present a resonant cavity approach for non-invasive, pulse-to-pulse, beam emittance measurements of non-circular multi-bunch beams. In a resonant cavity, desired field components can be enhanced up to Q{sub L{lambda}}/{pi}, where Q{sub L{lambda}} is the loaded quality factor of the resonant mode {lambda}, when the cavity resonant mode matches the bunch frequency of a bunch-train beam pulse. In particular, a quad-cavity, with its quadrupole mode (TM{sub 220} for rectangular cavities) at beam operating frequency, rotated 45{sup o} with respect to the beamline, extracts the beam quadrupole moment exclusively, utilizing the symmetry of the cavity and some simple networks to suppress common modes. Six successive beam quadrupole moment measurements, performed at different betatron phases in a linear transport system determine the beam emittance, i.e. the beam size and shape in the beam's phase space, if the beam current and position at these points are known. In the presence of x-y beam coupling, ten measurements are required. One measurement alone provides the rms-beam size of a large aspect ratio beam. The resolution for such a measurement of rms-beam size with the rectangular quad-cavity monitor presented in this article is estimated to be on the order of ten microns. A prototype quad-cavity was fabricated and preliminary beam tests were performed at the Next Linear Collider Test Accelerator (NLCTA) at the Stanford Linear Accelerator Center (SLAC). Results were mainly limited by beam jitter and uncertainty in the beam position measurement at the cavity location. This motivated the development of a position-emittance integrated monitor.
17815790
Polarized electron sources for linear colliders
Linear colliders require high peak current beams with low duty factors. Several methods to produce polarized e{sup {minus}} beams for accelerators have been developed. The SLC, the first linear collider, utilizes a photocathode gun with a GaAs cathode. Although photocathode sources are probably the only practical alternative for the next generation of linear colliders, several problems remain to be solved, including high voltage breakdown which poisons the cathode, charge limitations that are associated with the condition of the semiconductor cathode, and a relatively low polarization of {le}5O%. Methods to solve or at least greatly reduce the impact of each of these problems are at hand.
36965886
A traveling wave accelerator with HOM outcouplers for FELs
The application to FELs (free-electron lasers) of RF electron guns with laser-driven photocathodes has opened the door to developing efficient optical FELs. The next task is to develop accelerator structures which can transport such beams with a minimum of beam degradation. A low-cost approach to this using four 1.26-m constant gradient (CG) TW sections driven in parallel by a SLAC 5045 klystron is suggested. Using CG sections makes the higher order modes incoherent due to the linearly decreasing group velocity along the structure. Together with incorporating higher-order-mode outcouplers, this system is predicted to accelerate 1 nC per micropulse, 0.4 A per macropulse to 75 MeV from an injection energy of 5 MeV. Emittance growth is predicted to be 5 mm-mr.<<ETX>>
15840236
Effects of alternating cell misalignments on the DDS
The authors study some effects of cell misalignments in accelerator structures in which each cell is displaced the same amount and direction but with sign which alternates from cell to cell. In particular they study the manifold radiation in a damped detuned structure (DDS1) and wakefield effects in a uniform constant impedance structure. A synchronous wave aliasing phenomenon is observed. In previous treatments the effect of cell misalignment has been modeled by replacing it by beam displacement. Here they compare finite difference simulation of cell misalignment with the beam displacement model. They conclude with discussions about the relevance of the results for general misalignment profiles.
120089999
Two-body final states in K-p interactions at 14.3 GeV/c
Event selection and weighting. In Fig. 1 a), the distribution of the square of the missing mass to the K0 in all zero-prong plus one K ~ events is displayed; a clear neutron signal is visible with a half-width of approximately 0.4 (GeV)L In the study of reaction (1) we use all events with missing mass less than the A(1236) mass. The cross-section is corrected for the few neutron events above this cut by double-counting the symmetrical region below the neutron mass. We also correct for the background reaction
123045321
Evidence for local compensation of transverse momentum in pp collisions at 200 and 300 GeV/c
Evidence is presented for local compensation of transverse momentum in pp collisions at 200 and 300 GeV/c. The data are compared with a model which contains no dynamical transverse-momentum correlations. These data are used to determine a lower bound on the slope of the Pomeranchuk trajectory. (AIP)
59889859
Computer facilities for Isabelle data handling
The analysis of data produced by Isabelle experiments will need a large system of computers. Included in the array should be a substantial computer system at each Isabelle intersection in use. These systems must include enough computer power to keep experimenters aware of the status of the experiment. This will require at least one very fast sophisticated processor in the system, the size depending on the experiment. Other features of the intersection systems must be a good, high speed graphic display, ability to record data on magnetic tape at 500 to 1000 KB, and a high-speed link to a central computer. The operating system software must support multiple interactive users. A substantially larger capacity computer system, shared by the six intersection region experiments, must be available with good turnaround for experimenters while Isabelle is running. The computer mainframes should ideally be compatible members of the same family of computers. A very large computation load will be generated by the post experiment data reduction. Much of this may have to be run at lower priority. A computer support group will be required to maintain the computer system and to provide and maintain software common to all experiments. Such software support maymore » include providing a compatible compiler. Special superfast computing hardware or special function processors constructed with microprocessor circuitry may be necessary both in the data gathering and data processing work. Thus, both the local and central processors should be chosen with the possibility of interfacing such devices in mind.« less
125417837
New Geometry of Muon Walls in October 1997 Tilecal Beam Test
Computer controlled positioning system of muon walls is described. Suitable setting for the leakage detection during the extended barrel module 0 beam test is explained in details.
17714212
The NLC positron source
A baseline design for the NLC positron source based on the existing SLC positron system is described. The proposed NLC source consists of a dedicated S-band electron accelerator, a conventional positron production and capture system utilizing a high-Z target and an adiabatic matching device, and an L-band positron linac. The invariant transverse acceptance of the capture system is 0.06 m/spl middot/rad, ensuring an adequate positron beam intensity for the NLC.