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.
18642583
Application of a Mapping Function Technique to the Design of Damped Detuned Structures and to the Rapid Calculation of Their Wakefields
In order to reduce the dipole wake encountered by the first few bunches accelerated in a multi-bunch NLC scenario the DDS (damped detuned structure) was redesigned such that a much improved Gaussian fall-off occurs in the initial wake-function. From the 9 parameterized model of DDS1 the authors use a mapping function to allow DDS 3 and 4 to be modeled and hence avoid additional and prohibitively time consuming MAFIA runs. The equivalent circuit parameters and geometrical parameters are treated as functions of the synchronous frequency and are readily mapped onto the new synchronous frequencies. The new geometrical parameters form a family where each is associated with the iris diameter.
117213612
Calculation of positron source yields
Two recent failures of the positron source solenoid have led to a design study of more conservative coils. A Monte Carlo program has been used to calculate the distribution in phase space of the electromagnetic shower from the target of the SLAC positron source. Positron and electron yields were calculated for copper and tungsten targets. A ray tracing program was used to calculate the acceptance of the focusing system. The existing source makes use of an adiabatically tapered solenoid. The yield of this system has been compared with 3 alternatives: two possible modifications of the tapered solenoid, and a focusing system using a short solenoid as a quarter wave transformer. The calculated yield for the existing system is in reasonable agreement with experimental observation.
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.
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.
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.
120049678
Strength of the antineutrino-proton neutral-current interaction
Using the Fermilab 15-foot hydrogen bubble chamber exposed to a broad-band $\overline{\ensuremath{\nu}}$ and $\ensuremath{\nu}$ beam, we have studied the neutral-to-charged-current cross-section ratio $R$ for interactions on protons. The ratio ${R}^{\overline{\ensuremath{\nu}}p}$ is found assuming various forms of the neutral-current couplings. The data are consistent with the predictions of the Weinberg-Salam model and, assuming this model, we obtain ${R}^{\overline{\ensuremath{\nu}}p}=0.42\ifmmode\pm\else\textpm\fi{}0.13$.
116487099
The trace of the energy momentum tensor and the lattice interaction measure at finite temperature
122880341
Search for a double-pomeron-exchange contribution in the reaction K-p --> K-(pi-pi+)p at 14.3 GeV/c
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.
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)