No abstract

Understanding of microchannel plate (MCP) detectors with x-ray energy is important for applications in high energy density research such as broadband imaging and x-ray spectroscopy. The relative sensitivity with photon energy for Cu∕Au coated MCPs in the range of 250eV<hν<5000eV has been measured at the National Synchrotron Light Source. A model of this response that includes contributions from secondary photoelectron yield and interactions with multiple channels is presented. This model is shown to agree with the measured MCP response to <20% over the majority of the spectral range using cross sections determined from an independent analysis of the MCP glass composition.

The DARHT-II linear-induction accelerator has been successfully operated at 1.2-1.3 kA and 12.5-12.7 MeV to demonstrate the production and acceleration of an electron beam. Beam pulse lengths for these experiments were varied from 0.5 s to 1.2 s full-width half-maximum. A low-frequency inductance-capacitance (LC ) oscillation of diode voltage and current resulted in an oscillation of the beam position through interaction with an accidental (static) magnetic dipole in the diode region. There was no growth in the amplitude of this oscillation after propagating more than 44 m through the accelerator, and there was no loss of beam current that could be measured. The results of these initial experiments are presented in this paper.

A gas Cerenkov detector with a 12-MeV threshold for gamma-ray detection has been built for use on the OMEGA laser system to record high-energy gamma rays emitted during DT gas burn. Recording the 16.7-MeV gamma ray while discriminating against the lower energy 14-MeV neutron-induced gammas is an important objective using this detector system. Detector design, sensitivity, and background studies were possible using the Integrated Tiger Series Monte Carlo code modified to include Cerenkov production and full time-history of all particles. The results of this code were iterated with the ASAP optics code to optimize the light collection system, while providing the radiation shielding and stray light baffles to minimize backgrounds. As an initial test of the instrument, 8-20 MeV electrons from the Idaho State University linear accelerator were used in lieu of gamma rays. The primary results of these tests are that electron-produced Cerenkov has been observed and the Cerenkov threshold curve established for this instrument.

No abstract