STUDY OF PLASMA ELECTRON TEMPERATURE OF THE PINCH FILAMINT AND X-RAY EMISSION FROM THE ANODE TIP IN A LOW ENERGY (2.3 kJ) MATHER TYPE PLASMA FOCUS

Muhammad, Shafiq (2003) STUDY OF PLASMA ELECTRON TEMPERATURE OF THE PINCH FILAMINT AND X-RAY EMISSION FROM THE ANODE TIP IN A LOW ENERGY (2.3 kJ) MATHER TYPE PLASMA FOCUS. Doctoral thesis, Quaid-i-Azam University, Islamabad.

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Abstract

X- ray emission from a low energy (2.3 kJ) plasma focus energized by a 32 JlF capacitor charged at 12 KeV is investigated two fold: i) The continuum! bremsstrahlung X-rays are analyzed to obtain information about the electron plasma temperature in the pinch filament, and the X-radiation are employed for backlighting of a test of object (copper mesh), ii) X-ray emission in different energy windows, and its fluence anisotropy is investigated. To determine the plasma electron temperature by continuum X-ray analysis, Co is selected as a filter, which discriminates the line radiation from the back ground impurities like carbon, nitrogen and oxygen, or the radiation from plasma focus electrodes, which are commonly made of copper. It is found to be a good choice to diagnose 0.5-7 KeV hot plasma in a device like plasma focus. The electron temperature at different deuterium filling pressures is found to vary from 2 - 5 KeV. It is about 2.5 KeV at 0.5 mbar. With increase in pressure, the temperature increases and attains its maximum value of 5 KeV at 2.5 mbar, and then gradually decreases to 2 KeV at 4.5 mbar. For argon plasma, the electron temperature at different filling pressures is found to vary from 1.5-7.0 KeV. It is about 5 KeV at 0.25 mbar, which increases to about 7 KeV at 0.5 mbar and then decreases to 1.5 ke V at 2.25 mbar. When the device is operated with argon as the filling gas, the bulk of X-radiation emission is observed from the region close to the anode tip. These radiation are found suitable for backlighting in Al (1-1.56 KeV) and Ti (2.9-4.96 ke V) energy transmission bands. A simple technique to measure the fluence anisotropy of X-rays emitted from a source is presented. The simplicity of the technique and response curves of the photographic film along with corresponding filters enable one to readily use the same for diagnostic purposes in different sources like plasma focus, vacuum spark, Z-pinch and laser produced plasmas. As an application example, the technique is employed to measure fluence anisotropy of X-ray emission in a low energy plasma focus operated with hydrogen. It is found that with increase in hydrogen filling pressure, the anisotropy of X-ray emission is enhanced, although the total emission is lowered. It reveals that at lower filling pressure of 0.75 mbar, the X-ray emission is dominant due to interaction of energetic electrons in the current sheath, whereas at 2.5 mbar, the contribution of energetic electron beam is much higher. K-series line radiation emission of Mo and Cu is studied with hydrogen as the filling gas. The measurable X-ray flux is observed in the pressure range of 0.5-3.5 mbar. Mo and Cu K-line radiation emission has the highest values of about 0.05 J/sr and 0.17 J/sr respectively at a filling pressure of 2.0 mbar. The corresponding efficiencies are 0.03% and 0.09% respectively. Total X-ray emission and efficiency in 47t-geometry are also obtained with values 4.12 J and 0.2% at 2.0 mbar. The emission in different energy windows, by employing high Z inserts (Pb, W or Mo) at the anode tip is investigated also. The X-ray flux from the focus region is observed measurable within the pressure range 0.25-3.5 mbar of hydrogen. The maximum emission in 47t-geometry is found 29.4:t0.2, 3.43:t0.05 and 4.00:t0.02 joules with Pb, Wand Mo inserted anodes respectively and corresponding wall plug efficiencies for X-ray generation are 1.28%, 0.15% and 0.2%. The X-ray emission is found dominantly as a result of electron beam activity at the anode tip that is confirmed by the images recorded by the pinhole camera.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: plasma electron temperature, pinch filamint, plasma focus, fluence anisotropy, vacuum spark, z-pinch, k-series line radiation emission
Subjects: Q Science > QC Physics
Depositing User: Muhammad Khan Khan
Date Deposited: 29 Sep 2016 10:32
Last Modified: 29 Sep 2016 10:32
URI: http://eprints.hec.gov.pk/id/eprint/1874

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