No abstract

As part of the Dual Axis Radiography Hydrotest Facility, Phase I1 (DARHT 11) Multipulse Bremsstrahlung Target effort, we have been performing an investigation of ( I ) the possible adverse effects of backstreaming ion emission from the Bremsstrahlung converter target and(2) the hydrodynamic behavior of the target after the electron beam interaction. Theory predictions show that the first effect would primarily be manifested in the static focusing system as a rapidly varying x-ray spot. From experiments performed on ETA-11, we have shown that the first effect is not strongly present when the beam initially interacts with the target. Electron beam pulses delivered to the target after formation of a plasma are strongly affected, however. Secondly, we have performed measurements of the time varying target density after disassembly was initiated by the electron beam. The measurements presented show that the target density as a function of time compares favorably with our LASNEX models.

Using dielectric wall accelerator technology, we are developing a compact induction accelerator system primarily intended for pulsed radiography. The accelerator would provide a 2-kA beam with an energy of 8 MeV, for a 20-30 ns flat-top. The design goal is to generate a 2-mm diameter, 10-rad x-ray source. We have a physics design of the system from injector to the x-ray converter. We present the results of injector modeling and PIC simulations of beam transport. We also discuss the predicted spot size and the on-axis x-ray dose.

This is a preprint of a paper intended for publication in a journal or proceedings. Since changes may be made before publication, this preprint is made available with the understanding that it will not be cited or reproduced without the permission of the author. This report has been reproduced directly from the best available copy.

The second axis of the Dual Axial radiography Hydrodynamic Test (DARHT-II) facility at LANL is currently in the commissioning phase [1]. The beam parameters for the DARHT-II machine will be nominally 18 MeV, 2 kA and 1.6 µs. this makes the DARHT-II downstream system the first system ever designed to transport a high current, high energy and long pulse beam [2]. We will test these physics issues of the downstream transport system on a scaled DARHT-II accelerator with a 7.8-MeV and 660-A beam at LANL before commissioning the machine at its full energy and current. The scaling laws for various physics concerns and the beam parameters selection is discussed in this paper.