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Title: Anode length optimization in a modified plasma focus device for optimal x-ray yields

Abstract

The effect of anode length and operating gas pressure on the x-ray emission from a nitrogen-filling modified plasma focus device has been investigated. The time-resolved investigation of x ray was carried out by using a five-channel photodiode x-ray spectrometer. The maximum x-ray yield is seen to increase with the increase in the anode length from 110 to 125 mm. Further increase in the anode length to 130 mm causes the x-ray yields to decrease. The highest x-ray yield of 4.5 J into 4{pi} sr was found for 125 mm anode length, which is 0.2% of the input energy. The average x-ray photon energy was estimated by using half-value thickness method and found to be 8.4 keV. The electron temperature of the plasma was estimated to be around 3 keV by x-ray intensity ratio method. The space-resolved x-ray-emitting zones for all the anodes were captured by a pinhole-based x-ray imaging camera and the images were scanned for different gray levels by using a MATLAB computing software. These gray level spectra show that the image for a 125 mm anode length is more intense than that for the other anode. In addition to this, the gray level spectrum shows some highly densemore » spot inside the image, which is the so-called hot spot, emitting relatively higher energy x rays. Our results indicate that the plasma focus device could be optimized to a great extent for optimal x-ray yield by using an appropriate anode length.« less

Authors:
; ;  [1];  [2]
  1. Centre of Plasma Physics, Sonapur, Kamrup 782 402, Assam (India)
  2. (Japan)
Publication Date:
OSTI Identifier:
20787776
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 99; Journal Issue: 1; Other Information: DOI: 10.1063/1.2158134; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANODES; ELECTRON TEMPERATURE; HOT SPOTS; IMAGES; ION TEMPERATURE; KEV RANGE 01-10; LENGTH; M CODES; NITROGEN; OPTIMIZATION; PHOTONS; PINCH EFFECT; PLASMA; PLASMA DIAGNOSTICS; PLASMA FOCUS; PLASMA FOCUS DEVICES; TIME RESOLUTION; X-RAY SOURCES; X-RAY SPECTROMETERS

Citation Formats

Neog, N.K., Mohanty, S.R., Hotta, E., and Department of Energy Sciences, Tokyo Institute of Technology, Yokohama 226-8502. Anode length optimization in a modified plasma focus device for optimal x-ray yields. United States: N. p., 2006. Web. doi:10.1063/1.2158134.
Neog, N.K., Mohanty, S.R., Hotta, E., & Department of Energy Sciences, Tokyo Institute of Technology, Yokohama 226-8502. Anode length optimization in a modified plasma focus device for optimal x-ray yields. United States. doi:10.1063/1.2158134.
Neog, N.K., Mohanty, S.R., Hotta, E., and Department of Energy Sciences, Tokyo Institute of Technology, Yokohama 226-8502. Sun . "Anode length optimization in a modified plasma focus device for optimal x-ray yields". United States. doi:10.1063/1.2158134.
@article{osti_20787776,
title = {Anode length optimization in a modified plasma focus device for optimal x-ray yields},
author = {Neog, N.K. and Mohanty, S.R. and Hotta, E. and Department of Energy Sciences, Tokyo Institute of Technology, Yokohama 226-8502},
abstractNote = {The effect of anode length and operating gas pressure on the x-ray emission from a nitrogen-filling modified plasma focus device has been investigated. The time-resolved investigation of x ray was carried out by using a five-channel photodiode x-ray spectrometer. The maximum x-ray yield is seen to increase with the increase in the anode length from 110 to 125 mm. Further increase in the anode length to 130 mm causes the x-ray yields to decrease. The highest x-ray yield of 4.5 J into 4{pi} sr was found for 125 mm anode length, which is 0.2% of the input energy. The average x-ray photon energy was estimated by using half-value thickness method and found to be 8.4 keV. The electron temperature of the plasma was estimated to be around 3 keV by x-ray intensity ratio method. The space-resolved x-ray-emitting zones for all the anodes were captured by a pinhole-based x-ray imaging camera and the images were scanned for different gray levels by using a MATLAB computing software. These gray level spectra show that the image for a 125 mm anode length is more intense than that for the other anode. In addition to this, the gray level spectrum shows some highly dense spot inside the image, which is the so-called hot spot, emitting relatively higher energy x rays. Our results indicate that the plasma focus device could be optimized to a great extent for optimal x-ray yield by using an appropriate anode length.},
doi = {10.1063/1.2158134},
journal = {Journal of Applied Physics},
number = 1,
volume = 99,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • X-ray emission from a 2.3-5.3 kJ Mather-type plasma focus [Phys. Fluids 7, 5 (1964)] employing copper, molybdenum, and tungsten anode tip is studied. Argon is used as a working gas. Characteristic Cu K{alpha} and Mo K-series emission and their ratio to the continuous x-rays are determined. From the variation of the x-ray yield data with filling pressure at different charging voltages, scaling laws are obtained. X-ray pinhole images demonstrate that a significant amount of x-ray emission is from the anode tip. The comparison of the ratio of characteristic to continuum radiation for copper anode with typical x-ray tube data revealsmore » that the contribution of very high energy electron beam from the focus region for x-ray generation through thick target bremsstrahlung mechanism is not significant. Rather, electrons with energy of the order of, or even less than, the charging voltage are responsible for bulk of the x-ray emission.« less
  • In this paper, neutron emission from a 3 KJ Mather-type plasma focus is studied. Specifically, the behavior of system with the change in anode length is investigated. Anode lengths of high and low fluence anisotropy as well as for high neutron yield are identified. Experiment also suggest the possibility of ion beam generation leading to neutron production via beam-plasma interaction.
  • An indirect method to infer the spectra, based on the measurement of the beam intensity transmission through different metallic samples, is described in this communication. A Plasma Focus device (5.67 kJ, 30 kV) was studied as a pulsed hard x ray source, operated with deuterium at a filling pressure in the range of 3 to 5 mbar. Relevant spectral components belonging to the 50 - 150 keV range with a single maximum located in the 75 - 85 keV region were obtained for the radiation coming out of the Plasma Focus chamber, which is made of stainless steel.
  • In a 200 J fast miniature plasma focus device about 17- and 10-fold increase in x-ray yield in spectral ranges of 0.9-1.6 keV and 3.2-7.7 keV, respectively, have been obtained with deuterium-krypton (D{sub 2}-Kr) admixture at operating pressures of {<=}0.4 mbar. In the pressure range of >0.4-1.4 mbar, about twofold magnification in average x-ray yield along with broadening of optimum pressure range in both spectral ranges were obtained for D{sub 2}-Kr admixtures. An order of magnitude enhancement in x-ray yields at low pressures for admixture operation will help in achieving high performance device efficiency for lithography and micromachining applications.
  • The effect of insulator sleeve material on x-ray emission from a 2.3 kJ Mather type plasma focus device operated in argon-hydrogen mixture is investigated. The time and space resolved x-ray emission characteristics are studied by using a three channel p-i-n diode x-ray spectrometer and a multipinhole camera. The x-ray emission depends on the volumetric ratio of argon-hydrogen mixture as well as the filling pressure and the highest x-ray emission is observed for a volumetric ratio 40% Ar to 60%H{sub 2} at 2.5 mbar filling pressure. The fused silica insulator sleeve produces the highest x-ray emission whereas nonceramic insulator sleeves suchmore » as nylon, Perspex, or Teflon does not produce focus or x-rays. The pinhole images of the x-ray emitting zones reveal that the contribution of the Cu K{alpha} line is weak and plasma x-rays are intense. The highest plasma electron temperature is estimated to be 3.3 and 3.6 keV for Pyrex glass and fused silica insulator sleeves, respectively. It is speculated that the higher surface resistivity of fused silica is responsible for enhanced x-ray emission and plasma electron temperature.« less