Generation of high-energy x-radiation using a plasma flow switch

Abstract

Experiments with coaxial plasma guns at currents in excess of ten megamperes have resulted in the production of high-voltage pulses (0.5 MV) and hard x radiation (10–200 keV). The x-radiation pulse occurs substantially after the high-voltage pulse suggesting that high-energy electrons are generated by dynamic processes in a very high speed (≳106 m/s), magnetized plasma flow. Such flows, which result from acceleration of relatively low-density plasma (10−4 vs 1.0 kg/m3) by magnetic fields of 20–30 T, support high voltages by the back electromotive force-u×B during the opening switch phase of the plasma flow switch. A simple model of classical ion slowing down and subsequent heating of background electrons can explain spectral evidence of 30-keV electron temperatures in fully stripped aluminum plasma formed from plasma flows of 1–2 × 106 m/s. Similar modeling and spectral evidence indicates tungsten ion kinetic energies of 4.5 MeV and 46 keV electron temperatures of a highly stripped tungsten plasma.

Evolving approaches to pulsed X-ray sources

“…The electron temperature of the pinch depends on the final implosion velocity [37] m/s (5) where , , and . To optimize K-shell yield, the implosion velocity for Ar must be about 50 cm s, this increases to above 100 cm s for higher materials.…”

Compact Transformer Drive for High-Current Applications

“…Thus, figures-of-merit are maximizing the magnetic energy in the coaxial guns at peak current, maximizing the peak current itself, and achieving adequate armature speed at the time of switch opening. Experimentally [9], [11], speeds in excess of 60 km/s for the plasma armature when it reaches the end of the center conductor appear adequate to separate the armature from slower, thermal plasma from the conductor surface. For the present PHELIX values of L s = 24 nH and (L E C) 1/2 = 3.12 μs, and with the inductance gradient of previous PFS experiments [9] of L do = 57.5 nH/m for r 2 /r 1 = 4/3, the characteristic speed is u c = 134 km/s.…”

High-Speed Photography and Digital Optical Measurement Techniques for Geomaterials: Fundamentals and Applications

“…The disadvantages include: the movable mechanical device inside increases its complexity and fragility (Field 1983), the number of frames is limited, undesired measurement errors of the multi-sensor system might be introduced by manufacturing differences of each CCD (Kirugulige and Tippur 2009; Moulart et al 2011), alignment issues could also cause individual frames to be spatially shifted from each other, and the weight and sizes to some extent restrict portability. Typical applications of such high-speed camera include detonics (Held 1987), mechanical experiments (Sarva et al 2007), plasma observations (Turchi et al 1991), crack propagation and terminal ballistics (Draxler 2005). Representative models are the Cordin 560 and 580 (Company 2012a;Company 2012b).…”