D. M. Weidenheimer

The reflex-diode HPM source on Aurora

The most recent in a series of experiments to develop the reflex diode as a source of microwaves on the Aurora relativistic electron-beam pulser is described. An overall output has been achieved for radial extraction of approximately 400 J in microwave bursts from approximately 100 to 150 ns at frequencies below 1 GHz. The diagnostics for radial extraction have included directional couplers, card calorimeters, and free-field sensors. The authors have varied the anode-cathode spacing, downstream microwave reflector, and a second anode foil, but, within the range of variations, no strong trends have been noted. >

Bremsstrahlung risetime shortening by diode geometry reconfiguration

Experimental and theoretical studies on one arm of the Aurora flash x-ray machine have indicated that it is possible to lower the risetime of the bremsstrahlung produced at a single Aurora diode by increasing the AK gap of the diode. In an experimental setup employing a cylindrically symmetrical toroidal cathode, the local spatial distribution of bremsstrahlung pulse shape at the thick tantalum converter was measured at 10 radial positions by 10 Compton diodes placed at the converter. Additionally, bremsstrahlung produced at distances of 2, 3, 4, and 5 meters from the converter was measured by Pilot B scintillation counters. As the AK gap was widened, the early part of the bremsstrahlung pulse was diverted in the radial direction of the magnetically insulated transmission line (MITL) feeding the diode. The bremsstrahlung risetime at 3 meters from the bremsstrahlung target was reduced from about 60 to 18 ns by increasing the AK gap from 11 to more than 19 inches.

Aurora Synchronization Improvement

The Aurora flash x-ray simulator has undergone a series of hardware upgrades over the past five years. The upgrades have improved simulator reliability and have provided new environments for hardness testing. Recently, synchronization of the four pulse-forming lines (PFLs) has been significantly improved over the original design. The four parallel PFLs are now synchronized to within 10 ns over 60% of the shots. This paper describes the current switching scheine, reports the current timing statistics, and discusses the effects of improved synchronization on hardness test parameters such as shot to shot, reproducibility of the dose.

Generating High-Power Microwaves With The Aurora Pulser

A series of experiments is underway to utilize the virtual-cathode-driven oscillator as a source of high-power microwaves on Aurora. The most recent experiment launched 270 J per pulse to resistive terminations through eight radial waveguides, with the frequency in a band around 750 MHz. The highest power, ~10 GW in a short burst, was obtained with a second foil placed 0.5 m downstream of the anode. The peak power in a single waveguide exceeded 1 GW. This report compares the most recent measurements with those from previous experiments at Aurora and discusses the microwave extraction efficiency.

Development of the Aurora high-power microwave source

Work begun in 1986 has continued on the reflex-diode oscillator mounted on one of the four Aurora

Measurement of fluence and flux of proton beams using differentially filtered diamond detectors and radiachromic film

OM10-MV,

On-board laser-triggered multi-layer semiconductor power switch

OM22-(Omega) pulse lines. This is a preliminary report on the most recent work, which extracted microwaves radially into 18 rectangular WR-975 waveguides around the virtual cathode. Two additional arms upstream of the anode extracted microwaves around the real cathode. Vestigial-loop, waveguide directional couplers measured the radially extracted microwave energy. The output is typically 50 to 100 J/arm, for the frequencies between 0.6 and 1.0 GHz. Effects were compared from two cathode tips differing by a factor of

The Aurora accelerator's triggered oil switch

OM2 in diameter. Additional parameter variations have included the anode/cathode spacing and the positioning of a second foil.

Electrical Breakdown in Transformer Oil in Large Gaps

Differentially filtered, photoconductive, neutron-irradiated diamond detectors have been employed to investigate the temporal and energy distribution of an intense pulsed proton beam. Results were compared against measurements obtained using differentially filtered radiachromic film, electromagnetic (EM) techniques, time-of-flight techniques, and calorimetric instruments.