I= X-RAY EMISSION SCALING LAW FOR A LOW ENERGY (1-5KJ) PLASMA FOCUS WITH DIFFERENT METAL INSERTS AT THE ANODE TIP
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Title of Thesis
X-RAY EMISSION SCALING LAW FOR A LOW ENERGY (1-5KJ) PLASMA FOCUS WITH DIFFERENT METAL INSERTS AT THE ANODE TIP

Author(s)
MUHAMMAD SHARIF
Institute/University/Department Details
Department of Physics/ Quaid-i-Azam University, Islamabad
Session
2006
Subject
Number of Pages
116
Keywords (Extracted from title, table of contents and abstract of thesis)
x-ray emission scaling law, plasma focus, anode tip, mather type plasma focus, dense plasma focus, x-radiation

Abstract
The work reported in this thesis is based on the systematic investigation of x-rays emitted from a Mather type plasma focus by varying charging voltage (capacitor bank energy/ discharged current) to devise x-ray emission scaling laws. A three channel x-ray detector consisting of Quantrad Si PIN-diodes masked with Co, Ni, Cu, Mo, Ti, Ag, and Pb filters is employed for time-resolved measurements. Time-integrated x-ray measurements are performed with a multi-pinhole camera with suitable filters' thickness.

First a 9 µF capacitor bank along with a triggertron type sparkgap, charged at 12 kV to 20 kV (0.6-1.8 kJ), that provides 100 kA to 175 kA peak discharge current is used. In the first experiment titanium K-series line radiation and total x-ray yield is measured with Ti insert at 15 kV charging voltage with hydrogen filling. The second experiment is performed with Cu flat tip anode; argon is used as a working gas and the charging voltage is varied from 12 kV to 20 kV. In the third experiment with Cu flat tip anode and hydrogen filling; charging voltage is varied from 16 kV to 20 kV to study the Cu-Ka line radiation. The ratio of the Cu-Ka to total x-ray emission varies from 0.20 to 0.30, whereas the highest value of ratio of Cu-Ka to continuous x-ray emission is about 0.46. In another experiment, an appropriate cut at the anode tip increases side-on x-ray flux three times as compared to that of a tapered anode.

For further experimentation a 12.5 µF single capacitor along with the field distortion type pressurized spark gap, which is charged at 19kV to 29 kV (2.3-5.2 kJ) giving peak discharge current of about 185 kA to 290 kA is employed. In the first experiment, the variation of x-ray emission for Cu flat tip anode is studied for charging voltage varying from 19 kV to 27 kV. The rest of the experiments are conducted with Mo and W anode inserts for Mo K-series and the total x-ray yield. Scaling laws are devised for Cu-Kα and Mo K-series as well as for total x-ray emission in these experiments.

It is observed that the radiated energy strongly depends upon the filling pressure as well as on the type of the gas and the insert. There is a significant increase in the characteristic and the total x-ray emission with the increase of charging voltage and stored energy. Observation reveals that with hydrogen filling x-ray emission is decreased as compared to argon filling. The K-series emission may result due to interaction of energetic electron beam emitted from the focus region and the energetic electrons in the current sheath with the anode tip. The hard filters do not transmit the x-rays emitted from the pinch column and this region is not visible. X-ray pinhole images demonstrate that a significant amount of x-ray emission is from the anode tip.

Download Full Thesis
1678.38 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
148.31 KB
2 1 Introduction 1
334.89 KB
  1.1 Dense Plasma Focus 1
  1.2 X-Ray Emission Scaling Laws In Different Sources 10
  1.3 Motivation For The Present Work And Layout Of The Thesis 18
3 2 X-Rays From A Plasma Focus 25
604.57 KB
  2.1 Dense Plasma Focus €“ Experimental 25
  2.2 X-Radiation Emission From Plasma Filament 36
  2.3 X-Ray Emission From Anode Tip 39
  2.4 X-Ray Detection And Measurement 41
4 3 Tailoring Of Characteristic X-Radiation 57
677.09 KB
  3.1 Titanium K - Series Radiation 58
  3.2 Cu- Kα Line Radiation 66
  3.3 Molybdenum K-Series Radiation (12.5 œf Single Capacitor, 19 - 27 Kv Charging) 87
  3.4 (12.5 µf Single Capacitor, 19 - 29 Kv Charging) 92
  3.5 X-Ray Emission Scaling Law In Plasma Focus 95
  3.6 Discussion Of Results 102
5 4 Conclusions And Suggestions For Future Experiments
66 KB
  4.1 Conclusions 112
  4.2 Suggestions For Future Experiments 116