DARHT-II commissioning status

The injector for the second axis of the Dual-Axis Radiographic Hydrotest Facility (DARHT n) is now undergoing commissioning tests at Los Alamos National Laboratory. A Marx generator develops a 3.2 M V , 2 ps pulse that is applied to the diode through a high voltage (or Marx) dome, current stalk and high voltage insulator column. The 2 kA electron beam source is a 165-mmdiameter thermionic dispenser cathode operating near 120 kV/cm. The extracted beam enters a series of eight pulsed power-driven injector induction, cells that accelerate the beam to approximately 4.5 MeV. The beam then passes through a beamhead clean-up zone (BCUZ) to "scrape off the off-energy portion of the beam (the beam leading edge and, to a lesser extent, the beam trailing edge). A crowbar switch fKed at the end of 2 ps produces a short fall time.This pap& focuses on the electrical and mechanical design and testing of the Marx generator. The Marx consists of 88 stages, each half stage of which is a +/-50 kV type E PFN. The Marx was tested for over 8000 shots before shipment to Los .Alamos and demonstrated 6 ns jitter and good reliability with only 8 prefires out of. 5000shots. At the end of.December 2002,-qearly 800 shots have been fned in the process of commissioning the DARHT machine: The results of both series~of ihese.tests are given in this paper.

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Beam Clean-up Zone Calculations for 2.5MV, 1.4kA Experiments on DARHT-2

Tang¹,

Hughes

Ekdahl

et al. 2007

2007 IEEE 34th International Conference on Plasma Science (ICOPS)

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The injector for the second axis of the Dual-Axis Radiographic Hydrotest Facility (DARHT) produces 2 us, 2kA, 3.2 MeV electron beam with a nominal rise time of 600 ns'. The injector diode is powered through a ceramic column by a Marx generator. The off-energy electrons (beam head and tail) during the rise and fall time are mismatched to the magnetic transport channel. These electrons may hit the accelerating gaps, resulting in insulator flashover or a vacuum arc. The beam cleanup zone (BCUZ)2 has been designed to remove low energy beam electrons and to keep mismatched charge from reaching the downstream accelerator. Eliminating the beam head requires a strongly dispersive magnetic field tune in the BCUZ. In this paper, we will present simulation results on developing a beam cleanup tune and on the beam transport through BCUZ for 2.5MeV, 1.4kA experiments on DARHT-2 using the particle-in-cell code Lsp and the envelope code Lamda. The energy loss and wall temperature rise, electron stimulated desorption due to beam scrape-off in the BCUZ and the effects of slow approach to the flat top on transport of the beam body are also investigated. In addition, the experimentally measured voltage profiles for the injector diode and the accelerating cells were used in these simulations. The current transport from Lamda calculations is compared with Lsp results.1. M.

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DARHT-II commissioning status

Cited by 5 publications

References 1 publication

Pinhole imaging to observe spatial jitters of a triple-pulse X-ray source on the Dragon-II LIA

Pinhole imaging to observe spatial jitters of a triple-pulse X-ray source on the Dragon-II LIA

Design and performance of the Marx generator for the DARHT second axis electron injector

Beam Clean-up Zone Calculations for 2.5MV, 1.4kA Experiments on DARHT-2

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