Universiti Teknologi Malaysia Institutional Repository

Some generalised characteristics of the electro-dynamics of the plasma focus in its axial phase: illustrated by an application to independantly determine the drive current fraction and the mass swept-up fraction

Lee, Sing and Saw, Sor Heoh and Hegazy, Hosam and Ali, Jalil and Damideh, Vahid and Fatis, N. and Kariri, H. and Khabrani, A. and Mahasi, A. (2014) Some generalised characteristics of the electro-dynamics of the plasma focus in its axial phase: illustrated by an application to independantly determine the drive current fraction and the mass swept-up fraction. Journal of Fusion Energy, 33 (3). pp. 235-241. ISSN 0164-0313

Full text not available from this repository.

Official URL: http://dx.doi.org/10.1007/s10894-013-9658-1

Abstract

We describe the axial phase of the Mather plasma focus by two coupled equations of motion and circuit. We non-dimensionalised these equations resulting in two coupled equations which are characterised by only three scaling parameters α, β and δ which are ratios of electrical to transit times, inductances and impedances respectively. The normalised current waveform, trajectory and speed profile are unique for each combination of α, β, δ which are the ratios of characteristic times (electrical discharge vs. axial transit), inductances (tube inductance vs. static inductance) and impedances (stray resistance vs. electrical surge impedance). This leads to important information and insight into various aspects of the axial phase. In the present work we show that in a time-matched plasma focus shot we deduce the value of axial phase current fraction fc simply by measuring the calibrated voltage waveform and the uncalibrated current waveform. The scaling parameters β and δ are fixed; and by form-fitting the measured current waveform to the normalised current waveform using the value of α of the shot is determined uniquely; from which the peak current and the ratio of peak to average speed [the speed form factor (SFF)] are obtained. The average transit speed is measured by time-of-flight using the voltage upturn as indicator of end of axial phase. Then the SFF yields the peak speed. The measured voltage (back EMF), peak current and peak axial speed (all at the end of axial phase) allows the unambiguous measurement of fc. The value of the mass swept-up fraction fm is deduced from α which is the ratio of the characteristic discharge and the characteristic transit times, both deduced during the non-dimensionalisation of the equations. Analysis of a time-matched shot in the INTI PF at 15 kV, 3 Torr D2 gave fc = 0.68 and fm = 0.05.

Item Type:Article
Uncontrolled Keywords:plasma focus, axial phase
Subjects:Q Science
Divisions:Science
ID Code:62625
Deposited By: Widya Wahid
Deposited On:19 Jun 2017 11:47
Last Modified:19 Jun 2017 11:47

Repository Staff Only: item control page