Anomalous resistivity effect on multiple ion beam emission and hard x-ray generation in a Mather type plasma focus device

Abstract

Multi ion beam and hard x-ray emissions were detected in a high inductance (more than 100 nH) Mather type plasma focus (PF) device at different filling gas pressures and charging voltages. The signal analysis was performed through the current trace, as it is the fundamental signal from which all of the phenomena in a PF device can be extracted. Two different fitting processes were carried out according to Lee’s computational (snow-plow) model. In the first process, only plasma dynamics and classical (Spitzer) resistances were considered as energy consumer parameters for plasma. This led to an unsuccessful fitting and did not answer the energy transfer mechanism into plasma. A second fitting process was considered through the addition of anomalous resistance, which provided the best fit. Anomalous resistance was the source of long decrease in current trace, and multi dips and multi peaks of high voltage probe. Multi-peak features were interpreted considering the second fitting process along with the mechanisms for ion beam production and hard x-ray emission. To show the important role of the anomalous resistance, the duration of the current drop was discussed.

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

“…The phenomenological simulation analysis has been carried out based on the Lee model and it has been speculated that the occurrence of anomalous resistances is responsible for the generation of multiple bursts of energetic particle beams and x-ray emission in such a low energy device. 10 The energy spectrum of the radiated x-ray shows significant contribution of the copper k-a line as the result of the interaction between the electron beam, presumably generated by anomalous resistances, and the anode tip. 13 In this letter, the energy balance in the discharge circuit of the plasma focus device will be analyzed qualitatively and quantitatively to explain the generation of energetic charged particle beams and x-rays.…”

“…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.…”

“…The discharge current either slows down in the rate of increase during the 1st tube voltage or decrease noticeably after the 2nd and 3rd voltage peaks. 10 Based on the time-of-flight analysis of the particle flux signal, with the x-ray signal as the zero time reference, the energy of these ions up to MeV has been estimated. 10 Figure 2 shows two peaks in the hard x-ray signal with approximately 30 ns delay relative to the peaks of tube voltage signal.…”

“…10 Based on the time-of-flight analysis of the particle flux signal, with the x-ray signal as the zero time reference, the energy of these ions up to MeV has been estimated. 10 Figure 2 shows two peaks in the hard x-ray signal with approximately 30 ns delay relative to the peaks of tube voltage signal. 10 Figure 3 shows typical behaviors of the tube voltage, the electron beam emission intensity, and DXS x-ray intensity signals.…”

“…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.…”