Investigation and Optimization of Neon Soft X-ray of the INTl Plasma Focus at 12 kV
This thesis describes the theoretical and experimental investigations of the x-ray (specifically neon soft x-ray) properties and the plasma dynamics of the INTl Plasma Focus. The purpose of the research is two-fold, firstly to optimize the neon SXR yield of the iNTl Plasma Focus (3 kJ, Mather...
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Format: | Thesis |
Language: | English |
Published: |
2015
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Subjects: | |
Online Access: | http://eprints.intimal.edu.my/31/1/PhD%202.pdf http://eprints.intimal.edu.my/31/ |
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Summary: | This thesis describes the theoretical and experimental investigations of the
x-ray (specifically neon soft x-ray) properties and the plasma dynamics of the INTl
Plasma Focus. The purpose of the research is two-fold, firstly to optimize the neon
SXR yield of the iNTl Plasma Focus (3 kJ, Mather type) machine; and secondly to
investigate the correlation of the characteristic neon SXR signal pulse with the
plasma focus dynamics.
The optimization of the SXR yield involved three steps. Firstly the
optimization was carried out numerically using the 6 phase Lee Model Code (version
RADPFV6.lb). The numerical experiments were accomplished at 12 kV to
determine the optimum configuration for the electrodes using the INTl PF machine.
The model parameters were determined and retained as fm = 0.05, f = 0.7, frnr = 0.2
and fcr 0.8. The pressure (P), anode length (z), and anode radius (a) were
parametrically varied while the value of cathode radius (b) was fixed at 3.2 cm.
Secondly, the optimization experiments carried out at Centre for Plasma Research,
INTl International University were guided by the numerical experiments with an
optimized anode (‘a’ =1.2 cm and z =7.3 cm) designed as a screw-on type that
retained the original radius until it just emerged out of the insulator sleeve. Thirdly,
enhancement of yield was attempted by doping neon with krypton (Ne 97.5% + Kr
2.5%, Ne 95% + Kr 5%, Ne 90% + Kr 10% and Ne 80% + Kr 20%). Series of
experiments using the original anode (‘a’ =0.95 cm and z l6 cm) were performed in
the laboratory at 12 kV and operating neon gas pressure of 2.0 Torr. These
experimental results were verified using the Lee Model code by adjusting the
pressure for each admixture. The adjustments considered volumetric proportions of
neon taking into account the difference in atomic weights (Ne-20 and Kr-84).
Finally, the cdrrelation of characteristic neon SXR pulse with the plasma focus
dynamics was investigated using a) the original anode of 16 cm length and 0.95 cm
radius in neon, b) the optimized anode of 7.3 cm length and 1 .2 cm radius in neon
and c) the different Ne-Kr admixtures. Using the Lee Model code, an excel template
was developed to plot the SXR pulse with the fitted measured and computed current traces. The template also shows different time markers such as the radial phase, the
reflected shock phase, the start and end of the pinch and the anomalous resistance
phase.
Results show that there is good agreement between the measured and
computed SXR yield for the original anode and the optimized anode operated in
neon. The dimensionally optimized anode has an improved SXR yield by a factor of
1 .5 when compared to the original anode.
The correlation study of the characteristic neon SXR pulse enabled the
characterization of shots as normal (N-good shots) and not-normal (MN-bad shots).
¡n all experiments (original anode, optimized anode and the Ne-Kr admixtures) the
characteristic neon SXR pulse starts between the start of the reflected shock phase
and the start of the pinch phase (usually I O ns before the start of the pinch phase) for
all N type or good shots. For all of the NN type or bad shots, the characteristic neon
SXR pulse signal occurs either too early (before the start of the reflected shock
phase) or too late (after the start of the pinch phase). All of the shots with neon
doped with Kr up to 2.5% are good shots of N type. With increased doping, the
quality of the shots was found to deteriorate, with most shots being NN type. |
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