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.
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.
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.
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.
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>>
116422220
A Measurement of K0(L) --> pi+ pi- pi0 Decay Parameters
The decay ${K}_{L}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ has been studied in an experiment using the Argonne 12-ft hydrogen bubble chamber exposed to a ${K}_{L}^{0}$ beam of momentum 550 \ifmmode\pm\else\textpm\fi{} 35 MeV/c. After radiative corrections to the data, a fit using a matrix element of the form ${|M|}^{2}\ensuremath{\propto}1+\frac{g({s}_{3}\ensuremath{-}{s}_{0})}{{{m}_{{\ensuremath{\pi}}^{+}}}^{2}}+h{[\frac{({s}_{3} \ensuremath{-} {s}_{0})}{{{m}_{{\ensuremath{\pi}}^{+}}}^{2}}]}^{2} + k{[\frac{({s}_{1} \ensuremath{-} {s}_{2})}{{{m}_{{\ensuremath{\pi}}^{+}}}^{2}}]}^{2}$ gives $g = 0.681\ifmmode\pm\else\textpm\fi{}0.24$, $h = 0.095\ifmmode\pm\else\textpm\fi{}0.032$, and $k = 0.024\ifmmode\pm\else\textpm\fi{}0.010$. The branching ratio $\frac{\ensuremath{\Gamma}({K}_{L}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0})}{\ensuremath{\Gamma}({K}_{L}^{0}\ensuremath{\rightarrow}\mathrm{charged})}$ was measured to be 0.163 \ifmmode\pm\else\textpm\fi{} 0.003. These results, when compared to those obtained in other ${K}_{L}^{0}$ and ${K}^{\ifmmode\pm\else\textpm\fi{}}$ decay experiments, indicate a substantial $\ensuremath{\Delta}g\frac{1}{2}$ contribution to the ${K}_{L}^{0}$ decay amplitude.
118557074
Anti-p p annihilations into pi+ pi-, k+ k-, pi+ pi- pi0, and pi+ pi- neutrals near center-of-mass energy 2200 mev
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.
122880341
Search for a double-pomeron-exchange contribution in the reaction K-p --> K-(pi-pi+)p at 14.3 GeV/c
55614129
Codes and supersymmetry in one dimension
Adinkras are diagrams that describe many useful supermultiplets in D=1 dimensions. We show that the topology of the Adinkra is uniquely determined by a doubly even code. Conversely, every doubly even code produces a possible topology of an Adinkra. A computation of doubly even codes results in an enumeration of these Adinkra topologies up to N=28, and for minimal supermultiplets, up to N=32.