A COST EFFECTIVE X-RAY DETECTOR FOR PLASMA FOCUS DIAGNOSTICS

Abstract

A time-resolved rugged X-ray detector (XRD) which may be used in intense radiation environment is developed. The detector is used to study the X-ray emission from a low-energy (2.3 kJ) Mather-type plasma focus energized by a 32 μF single capacitor, using hydrogen and argon (3:2) mixture as gas filling. In the detector, the electron emitter is made of nickel and aluminum. The sensitivity of the detector with nickel cathode is found to be very low. No signal could be recorded by masking the detector with even the 2 μm thick Al foil. When Al cathode is used in the XRD, the sensitivity of the detector increases abruptly. To stop the optical/ultraviolet radiation from approaching the active area, it is masked with 6 μm Al filter. It is found that an XRD with nickel cathode is not useful for X-ray detection in a low-energy plasma focus. However, due to its excellent response to vacuum ultraviolet radiation (≤600 Å), it may find application in the study of the axial rundown of current sheath, and its velocity. The X-ray emission from focus plasma is the highest at 0.5 mbar. With increase in pressure, the emission is dropped. At filling pressures of 2.0–2.5 mbar, the X-ray emission increases again. High X-ray emission at 0.5 mbar is due to interaction of energetic electrons in the current sheath with the anode surface, whereas moderately high emission at 2.0–2.5 mbar is caused by an axially moving shockwave.