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Repetitive plasma focus operation in argon for SXR micromachining
Author
Srivastava, Asutosh
Supervisor
Lee, Sing
Lee, Paul Choon Keat
Abstract
NX2 machine is a high repetitive rate compact Plasma Focus (PF) device developed for micro-lithography using neon as a working gas. This report investigates the X-ray output from NX2 using argon. In the first part of our experiment, we have compared the X-ray output and current waveform of argon plasma and neon plasma with that of computational output. Experiments were carried out under various experimental conditions, such as different anode lengths, filling gas pressures of neon and argon, mixture of gases with argon and different charging voltages.
PIN diodes were used to investigate the soft X-ray yield from the plasma focus. The results show that the X-ray emission with neon as a working gas has a yield of around 10Joules. X-ray using argon as a working gas and mixture of argon with other gases show yield around 1 Joule with the peak X-ray of 10J.
The current waveform justified our experimental observation of not getting X-rays for argon, as there was much weaker focus formation for argon plasma in comparison to neon plasma in the old NX2 configuration.
In the improved version of NX2 machine, we use a Dense Plasma Focus (DPF) device NX2, with improved insulator, electrode, and switching configuration, and Argon as a filling gas to concentrate the main part of its radiation near 4 A. In this case micro machining process can be implemented if plasma can reach Tpl ≥ 1 keV and relatively hard X-rays can be emitted.
There are at least three possible ways to get the above parameters, if we explore three successive phases of plasma dynamics in DPF, namely - a shock wave contraction at the chamber axis, a quiescent ("first compression") phase, and the unstable ("necking") phase.
In the first method one uses a mixture of a heavy gas (e.g. krypton) with argon to produce a separation of the two gases at the shock wave front. Subsequently a "heavy shell" will compress argon. In the second method, one increases a current sheath velocity in pure argon, and in the process of its faster compression the pinch will reach a high enough temperature. In the third method, one uses a mixture of a light gas (ultimately deuterium) with argon to produce hot spots by plasma necking, and this results in the local collapse of plasma. In our study of the three methods, we obtained around one joule of argon SXR yield in the wavelength of 3 to 4 A with indication of higher X-ray yield, using the third method.
PIN diodes were used to investigate the soft X-ray yield from the plasma focus. The results show that the X-ray emission with neon as a working gas has a yield of around 10Joules. X-ray using argon as a working gas and mixture of argon with other gases show yield around 1 Joule with the peak X-ray of 10J.
The current waveform justified our experimental observation of not getting X-rays for argon, as there was much weaker focus formation for argon plasma in comparison to neon plasma in the old NX2 configuration.
In the improved version of NX2 machine, we use a Dense Plasma Focus (DPF) device NX2, with improved insulator, electrode, and switching configuration, and Argon as a filling gas to concentrate the main part of its radiation near 4 A. In this case micro machining process can be implemented if plasma can reach Tpl ≥ 1 keV and relatively hard X-rays can be emitted.
There are at least three possible ways to get the above parameters, if we explore three successive phases of plasma dynamics in DPF, namely - a shock wave contraction at the chamber axis, a quiescent ("first compression") phase, and the unstable ("necking") phase.
In the first method one uses a mixture of a heavy gas (e.g. krypton) with argon to produce a separation of the two gases at the shock wave front. Subsequently a "heavy shell" will compress argon. In the second method, one increases a current sheath velocity in pure argon, and in the process of its faster compression the pinch will reach a high enough temperature. In the third method, one uses a mixture of a light gas (ultimately deuterium) with argon to produce hot spots by plasma necking, and this results in the local collapse of plasma. In our study of the three methods, we obtained around one joule of argon SXR yield in the wavelength of 3 to 4 A with indication of higher X-ray yield, using the third method.
Date Issued
2001
Call Number
QC718.5.D9 Sri
Description
Pg. 56 is missing
Date Submitted
2001