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>>
124416371
CTF3 Drive-Beam Injector Design
The Two-Beam Accelerator concept is one of the most promising methods for producing RF power for future linear colliders. In particular it allows upgrades to multiTeV energies. One of its challenges is the production of the high current drive beam, which as it passes through decelerating structures, produces RF power for acceleration of the main beam. These challenges must be studied at a smaller scale test facility.
271221
MITIGATION OF EMITTANCE DILUTION DUE TO TRANSVERSE MODE COUPLING IN THE L-BAND LINACS OF THE ILC †
The main L-band linacs of the ILC accelerate 2820 bunches from a center of mass of 10 GeV to 500 GeV (and in the proposed later upgrade, to 1 TeV). The emittance of the vertical plane is approximately 400 times less than that of the horizontal plane. Provided the vertical and horizontal mode dipole frequencies are degenerate then the motion in each plane is not coupled. However, in reality the frequency degeneracy is split and the eigenmodes are shifted due to inevitable manufacturing errors introduced in fabricating 20,000 cavities. This gives rise to a transverse coupling in the horizontal-vertical motion and can readily lead to a dilution in the emittance in the vertical plane. We investigate means to ameliorate this effect dilution by splitting the horizontal-vertical tune of the lattice.
2871115
A spectral function method applied to the calculation of the wake function for the NLCTA
The equivalent circuit representation of the dipole modes of the SLAC damped detuned structure (DDS) which is being fabricated at LAC has been analyzed by three different methods. The first two are based upon a modal analysis: in the first, damped modes are found by a first order perturbation in the cell to damping manifold coupling strength; while in the second, preferred when the coupling strength is large (as is the case for the SLAC structure) they are determined exactly (a time consuming procedure). The third method, which the authors report here, expresses the wake as a modal sum for modes whose frequencies place them outside the propagation bands of the manifolds (a minor contribution) plus a Fourier like integral of a spectral function over the propagation band of the manifolds (the major contribution). They will present comparisons to previous calculations, assessment of appropriate domains of applicability, and applications to the SLAC structure with matched and mismatched manifold terminations.
18624388
High-Efficiency Resonant Cavity Quadrupole Moment Monitor
Measurement of the beam quadrupole moment at several locations can be used to reconstruct the beam envelope and emittance parameters. The measurements can be performed in a non-intercepting way using a set of quadrupole-mode cavities. We present a cavity design with an optimized quadrupole moment shunt impedance. The cavity properties can be characterized using a wire test method to insure symmetry about the central axis, and alignment to nearby position sensing cavities. The design and characterization of the prototype structure is discussed.
125455835
Design and performance of a pressurized drift tube chamber for the GEM muon system
122509981
Search for direct electron production in p-p and p-Be collisions at 12 GeV/c
We have made a systematic search for direct e/sup +/ and e/sup -/ production in p-p and p-Be collisions at 12 GeV/c incident proton momentum. Data were collected at c.m. angles of 20/sup 0/, 35/sup 0/, 63/sup 0/, and 84/sup 0/. We find no evidence for the previously reported rise in the ratio e/..pi.. at low momentum transfer. The data are consistent with zero direct electron production from other than previously known sources.
118734978
High resolution magnetic spectrometer for antiproton physics at rest and low energies
A spectrometer is being installed in a high-intensity antiproton beam (LESBII) at the AGS. The beam momentum entering the target will be known to approximately +- /sup 1///sub 2/%. The target is surrounded by a stereoscopic cylindrical drift chamber, and thus the total charge of the event will be measured. Since the vertex will be reconstructed with an accuracy of approximately +- 2 mm, studies of annihilations with high resolution down to approximately 150 MeV/c will be possible. On one side of the target a large-aperture (2.3 x .62 m/sup 2/) magnet covered on both sides with drift chambers and triggering--TOF scintillation counters, will measure particle and ..gamma..-ray energies with high resolution, as well as identify particles. The primary objective is to look for peaks in the ..gamma.. spectra coming from annihilations at rest by converting them in a thin (.05 x/sub 0/) radiator before the magnet. Narrow peaks (< 1 MeV) which are produced with frequencies of approximately 10/sup -3/ or better are expected to be seen as 5 sigma effects. The principle and details of the spectrometer are presented.
118557074
Anti-p p annihilations into pi+ pi-, k+ k-, pi+ pi- pi0, and pi+ pi- neutrals near center-of-mass energy 2200 mev
121351026
Three and higher order rapidity distributions in pp collisions at 200 GeV/c
Abstract Three-particle rapidity distributions have been studied for different charged multiplicities in pp interactions at 200 GeV/ c . Appropriately defined semi-inclusive three-particle correlations are found to be sufficiently small, leading us to conclude that the three-particle density can be expressed in terms of one- and two-particle densities. For events with more than four charged particles, a superposition approximation for the three-particle density holds surprisingly well. This approximation enables us to express all higher order rapidity distributions in terms of one- and two-particle distributions alone.