Bremsstrahlung risetime shortening by diode geometry reconfiguration

• Published in: IEEE transactions on nuclear science 1992-12, Vol.39 (6), p.2070-2077
• Main Authors: Bushell, M., Fleetwood, R., Judy, D., Merkel, G., Smith, M., Nguyen, K., Weidenheimer, D.
• Format: Article
• Language: English
• Subjects: Cathodes; Diodes; Exact sciences and technology; Geometry; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Insulation; Ionizing radiation; Physics; Pulse measurements; Pulse shaping methods; Shape measurement; Toroidal magnetic fields; Transmission line measurements; X- and γ-ray instruments and techniques
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/23.211405

The Aurora flash X-ray machine was recently modified to offer an unfocused mode so that ionizing radiation is spread over a larger volume. An attempt was made to ascertain whether a faster bremmstrahlung risetime can be achieved. Experimental studies on one arm of the Aurora flash X-ray machine indicated that it is possible to lower the risetime of the bremsstrahlung produced at a single Aurora diode by increasing the anode-cathode (AK) gap of the diode and by increasing the length of the magnetically insulated transmission line (MITL) leading up to the diode. In an experimental setup using a cylindrically symmetrical toroidal cathode, the local spatial distribution of bremsstrahlung pulse shapes at the thick tantalum converter was measured at 10 radial positions by 10 Compton diodes placed at the converter. Additionally, bremsstrahlung produced at a distance of 2 m from the converter was measured by plastic scintillation counters. As the AK gap was widened, the early part of the bremsstrahlung pulse was diverted in the radial direction of the MITL feeding the diode. The bremsstrahlung risetime at 3 m from the bremsstrahlung target was reduced from about 60 to 18 ns by increasing the AK gap from 11 to 19 in. or more.< >