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The dual-axis radiographic hydrodynamic test (DARHT) facility uses bremsstrahlung radiation source spots produced by the focused electron beams from two linear induction accelerators (LIAs) to radiograph large hydrodynamic experiments driven by high explosives. Radiographic resolution is determined by the size of the source spot, and beam emittance is the ultimate limitation to spot size. On the DARHT-II LIA, we measure an emittance higher than predicted by theoretical simulations, and even though this accelerator produces submillimeter source spots, we are exploring ways to improve the emittance. Some of the possible causes for the discrepancy have been investigated using particle-in-cell codes. The simulations establish that the most likely source of emittance growth is a mismatch of the beam to the magnetic transport, which can cause beam halo. [ABSTRACT FROM PUBLISHER]

A novel bidirectional compression electron gun is designed for a W-band sheet beam traveling-wave tube. A parabolic curved cathode and a beam focusing electrode based on spline interpolation curves are proposed to obtain a beam with good quality. Two directional compressions are introduced to reduce the beam loading of cathode. A 30-kV, 0.97-A beam is emitted by a curved 0.112-cm2 cathode with a beam loading of 8.66 A/cm2. The beam at waist position is 1.4 mm $\times0.4$ mm with a compression ratio of 2 and 10 in two directions separately. Studies of beam emittance and sensitivity of beam dynamics to mechanical errors are also carried out to understand the influence of structure parameters on electron gun performance. [ABSTRACT FROM AUTHOR]

Cosmic Ray Energetics And Mass (CREAM) is a balloon-borne experiment to directly measure the elemental spectra of protons to iron nuclei with energies up to ∼1015 eV. Energies of these cosmic-ray particles are measured by an ionization calorimeter comprised of 20 layers of 1 radiation length thick tungsten plates and 20 layers of 0.5 mm diameter scintillating fibers. Each tungsten plate is 500 x 500 x 3.5 mm³ and the fibers are grouped into fifty 1 cm wide ribbons. After construction, the CREAM-III calorimeter was tested at CERN, the European high energy physics lab, in the H2 beam line of the SPS. Following the CERN test, the calorimeter was integrated into the CREAM-III instrument, and flown successfully in the 3rd flight of the project, during the 2007/8 Antarctic campaign. We present the performance of the CREAM-III calorimeter in lab and beam tests. [ABSTRACT FROM AUTHOR]

We report large current- and temperature-induced beam-steering effects, observed in the far-field distribution of InP-based quantum-cascade lasers emitting around 7.8-μm wave-length operated in pulsed mode. Changing the temperature within a narrow range of ∼ 10°C around room-temperature leads to a change in the direction of the output beam, as given by the central lobe in the far-field intensity distribution, from +11° to -13° as measured relative to the resonator axis. This beam steering effect is linked to changes in the lateral mode distribution, as revealed by time-resolved spectroscopy of the lasing spectrum. [ABSTRACT FROM AUTHOR]

Several current particle-antiparticle collider designs require the beams to collide at a small angle. In order. to make the luminosity comparable to that of beams colliding head-on, transverse deflecting cavities known as crab cavities will be used. Additional modes, other than the required "crabbing" mode are excited by the beam and if these are excited resonantly then an appreciable dilution of the beam emittance will occur. We provide a singlemode analysis of the damping requirements on the dipole modes which will minimize the resulting angular kicks to the beams, by deriving an explicit solution for the frequency offset of the mode from a bunch harmonic for maximum deflection of bunches, using a novel analytical technique. [ABSTRACT FROM AUTHOR]

Presents an analytical inversion formula for uniformly attenuated fan-beam projections. Derivation of Tretiak and Metz' algorithm; Steps followed in implementing the algorithm for reconstructing exponential fan-beam projections; Difference in parallel-beam and fan-beam implementations.

Studies the performance of a prototype compact muon solenoid Hadron Barrel Calorimeter (HCAL) in a test beam. Experimental set up; Description of the electromagnetic and hadronic response ratio of hadron calorimeter; Optimization of the HCAL design.