Post-pinch generation of electron beam in a low energy Mather-type plasma focus device

Abstract

The post-pinch generation of electron beam in a low energy Mather-type plasma focus (PF) device has been investigated. A fast-calibrated Rogowski coil was used to monitor the emission of electron beam. A two-channel diode X-ray spectrometer along with suitable filters provided the records of energy spectrum of X-ray radiation. Single time-period emissions of electron beam with duration of 100 to 20 ns were recorded in the high range of the device operating pressure (0.8-2 mbar). However, in the low range regime (0.2-0.8 mbar), occurrence of single spike electron beam with duration of 150 ± 50 ns, as well as multi-emission of electrons with duration of 400 ± 50 ns, was visible. A multi-peak of tube voltage along with multi-time-period radiation of X-rays dominated by copper lines (Cuk α and Cuk β ) was noticeable in the low-pressure range. The generated electron beam during the post-pinch phase of anomalous resistances is suspected to be the main source of X-ray radiation. This can also be related to the turbulence of the plasma column during the occurrence of anomalous resistances.

Plasma heating and emission of runaway charged particles in a plasma focus device

“…The analyses have shown that plasma resistance may reach 0.2 Ω during the phase with anomalous resistances and the minimum anode voltage to generate hard X-rays in this phase is about 13 kV [12]. Single and multiple peaks of an electron beam that are highly correlated with the radiated X-rays and anode voltage have been studied [13].…”

“…A high-voltage probe with a rise time of about 2 ns is used to measure the anode voltage. The working gas is argon [9][10][11][12][13]. The solid anode is 2 cm in diameter with a flat top of 1 cm in diameter at the center and a rounded edge.…”

Common features of particle beams and x-rays generated in a low energy dense plasma focus device

“…The capacitance was 10 lF and the static inductance of 150 nH. [10][11][12][13] The radius of central electrode (anode) was 1 cm and the ratio of the radius of cathode to the radius of anode was 3. A Tektronix P6015A high voltage probe was used to monitor the tube voltage.…”

“…A photomultiplier tube (PMT) in conjunction with a suitable plastic scintillator, a four-channel diode X-ray spectrometer (DXS), a faraday cup, and a fast Rogowski coil have been used to measure the x-ray radiation and charged particle beams emissions from the device. [10][11][12][13] All signals were transmitted by a three-meter long 50 X coaxial cables with equal-length and recorded by a four-channel, 100 MHz, 1 GSP digital Tektronix oscilloscope.…”

“…10 Figure 3 shows typical behaviors of the tube voltage, the electron beam emission intensity, and DXS x-ray intensity signals. 12 The electron beam signal shows several sharp peaks accompanied by the less dominant peaks of the tube voltage and x-ray signals which are generated by interaction between the electron beam and the copper anode tip. Figure 4 shows the expanded traces of electron beam and discharge current near a peak of the electron beam emission.…”