22707371
Emittance Calculations for the Stanford Linear Collider Injector
A computer code has been implemented for on-line acquisition and analysis of data for emittance measurements of the SLC injector beam. The beam emittances have been determined experimentally using this code; measured beam emittance values have been found to be within expectations. When the system operates in the automatic mode, an emittance measurement takes less than two minutes. This emittance measurement method has been thoroughly tested and has been extended to other regions of the SLC system. Resultant beam sigma matrices are used in the lattice design models to calculate the strengths of quadrupoles required for the optical matching of the CID beam into the SLC Linac.
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.
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.
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>>
17568135
Topology Types of Adinkras and the Corresponding Representations of N -Extended Supersymmetry
We present further progress toward a complete classification scheme for describing supermultiplets of N-extended worldline supersymmetry, which relies on graph-theoretic topological invariants. In particular, we demonstrate a relationship between Adinkra diagrams and quotients of N-dimensional cubes, where the quotient groups are subgroups of $(Z_2)^N$. We explain how these quotient groups correspond precisely to doubly even binary linear error-correcting codes, so that the classification of such codes provides a means for describing equivalence classes of Adinkras and therefore supermultiplets. Using results from coding theory we exhibit the enumeration of these equivalence classes for all cases up to 26 supercharges, as well as the maximal codes, corresponding to minimal supermultiplets, for up to 32 supercharges.
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.
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)
21235770
Pore morphologies in disordered nanoporous thin films.
Materials with nanometer size heterogeneities are commonplace in the chemical and biological sciences (e.g, polymer blends, microemulsions, gels) and often exhibit complex morphologies. Although this morphology has a dramatic effect on the materials' properties, it is often difficult to accurately characterize. We describe a method, using small-angle X-ray scattering data, of generating representative three-dimensional morphologies of isotropic two-phase materials where the morphology is disordered, and we apply this to thin films containing nanometer sized pores with a range of porosities (4-44%). These representations provide a visualization of the pore morphology, give the pore size scale and extent of interconnection, and permit the determination of the transitions from closed pore to interconnected pores to bicontinuous morphology.
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.