55891907
Recent Beam Performance and Developments at SLAC
The purpose of this paper is to describe recent developments at SLAC which have contributed to improvements in beam operation. The paper will be divided into two parts. The first will summarize overall beam performance and operational efficiency in delivering beams to various experiments. The second will be devoted to specific developments such as the achievement of higher energies, increasingly narrow energy spectra, higher beam breakup current thresholds, chopped beams and improvements in pulse-to-pulse operation. The discussion will include a description of various new pulsed devices such as pulsed quadrupoles, improvements in the positron source and new beam loading measurements obtained for very short pulses.
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.
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.
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>>
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.
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.
123454883
Four-charged-particle final states from the interaction of 2.7 gev/c pi-plus on deuterium
187201784
An Assembly Procedure for Drift Tube Chambers
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.
117016085
Inclusive production of lambda and neutral kaon in K−p interactions at 3.93 GeV/c and 14.3 GeV/c
SummaryLambda and neutral-kaon production is studied in K−p interactions at 3.93 and 14.3 GeV/c. Topological inclusive cross-sections are given at both energies. Invariant cross-sections for lambdas and neutral kaons are presented as a function of the Feynmanx-variable and are found to decrease in magnitude and vary their shapes with energy. The

$$AK\overline K $$

 production, which represents (9±2)% and (29±3)% of the lambda inclusive cross-section at 3.93 GeV/c and 14.3 GeV/c respectively, yields mainly backward lambdas. The shapes of the transverse-momentum invariant distributions vary withx, but are roughly independent of energy. The lambda polarization is studied as a function ofx at both incident momenta: for fast lambdas it is negative, as observed in reactions where nucleon exchange is dominant.RiassuntoSi studia la produzione di particelle lambda e di kaoni neutri nelle interazioni K−p a 3.93 e 14.3 GeV/c. Per entrambi i valori dell'energia si danno le sezioni d'urto inclusive topologiche. Si presentano le sezioni d'urto invarianti per particelle lambda e kaoni neutri in funzione della variabilex di Feynman e si trova che diminuiscono in grandezza e cambiano di forma con l'energia. La produzione di

$$AK\overline K $$

, che rappresenta il (9±2)% e il (29±3)% della sezione d'urto inclusiva delle particelle lambda rispettivamente a 3.93 GeV/c e 14.3 GeV/c, dà per lo più particelle lambda che vanno all'indietro. Gli andamenti delle distribuzioni invarianti dell'impulso trasversale variano conx, ma sono approssimativamente indipendenti dall'energia. Si studia la polarizzazione delle particelle lambda in funzione dix per entrambi i valori dell'impulso incidente: per particelle lambda veloci è negativa, come si è osservato in reazioni in cui predomina lo scambio di nucleoni.РезюмеИсследуется рождение ламбда и нейтрального каона в K−p взаимодействиях при 3.93 ГэВ/с и 14.3 ГэВ/с. При обеих энергиях приводятся топологические инклюзивные поперечные сечения. Инвариантные поперечные сечения для ламбда и нейтральных каонов представлены в виде функции фейнмановскойx переменной. Получено, что поперечные сечения уменьшаются по величине и изменяют свою форму с энергией.

$$AK\overline K $$

 рождение, которое составляет соответственно (9±2)% и (29±3)% ламбда инклюзивного поперечного сечения при 3.93 ГэВ/с и 14.3 ГэВ/с, образует в основном ламбда-частицы, летящие в обратном направлении. Формы инвариантных распределений для поперечного импульса изменяются с «x», но вгрубом приближении не зависят от энергии. Исследуется поляризация ламбда, как функцияx для обоих начальных испульсов: для быстрых ламбда-частиц поляризация отрицательная, как наблюдается в реакциях, где доминирует нуклонный обмен.