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X-Ray Analysis for Electron Beam Enhancement in the Plasma Focus Device*

Published online by Cambridge University Press:  06 March 2019

R. L. Gullickson  and
R. H. Barlett
R. L. Gullickson
Affiliation:
Lawrence Livermore Laboratory Livermore, California 94550
R. H. Barlett
Affiliation:
Lawrence Livermore Laboratory Livermore, California 94550
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Abstract

The plasma focus device, a form of linear pinch discharge, produces an intense x-ray and neutron (D2) burst from a magnetically heated dense plasma. Rapidly changing magnetic fields at pinch time generate large axial electric fields which accelerate electrons and ions. In the experiments reported here the x-ray production during the plasma pinch of a 96 kilojoule (at 20 kV) plasma focus device was measured.

The purpose of these experiments was to evaluate the energy in accelerated electrons in the plasma focus device and to learn how to enhance these electron hursts. Well focused, megampere electron beams at a few hundred kilovolts, lasting less than 10 nanoseconds have applications in fusionable pellet heating experiments. (1) X-rays were monitored to evaluate these electron bursts using a defocusing bent crystal spectrometer, doubly diffused silicon (PIN) detectors, with Ross filters, thermoluminescent dosimeters (TLDs) with filters, and x-ray pinhole photography.

Thermoluminescent dosimeters indicated maximum x-ray yields of 140 joules above 3 keV at 57.3 kilojoules stored energy (16 kV) for a conversion efficiency to x-rays of 0.2%. 40 joules are above 60 keV and 15 joules above 80 keV. The hard x-ray pulse typically rises in 3 ns and frequently has a pulse width less than 10 ns. The low energy x-ray spectrum consists almost entirely of lines from the high Z anode insert, and the high energy spectrum is characteristic of a nonthermal power law distribution with an exponent of 2.2 ± 0.8. Peak hard x-ray production is obtained at 1 torr deuterium in contrast to peak neutron production (3 x 1010) at 5 torr. The addition of argon reduces total x-ray yield and increases the relative fraction of soft x-rays.

These measurements suggest that the plasma focus produces 1200 joules of electrons with an average energy of 150 keV, in 10 nanoseconds with a stored energy of 57.3 kilojoules. This is a power of 1.2 × 1011 watts and power density of 1.5 × 1013 watts cm−2.

Type
Research Article
Information
Advances in X-Ray Analysis , Volume 18: Twenty-Third Annual Conference on Applications of X-ray Analysis, August 7-9, 1974 , 1974 , pp. 184 - 196
Copyright
Copyright © International Centre for Diffraction Data 1974

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Footnotes

*

Work was performed under the auspices of the U. S. Atomic Energy Commission.

References

1. Sahlin, H. L., “Theoretical Aspects of Collective Ion Acceleration,” Proc. of Conf. On Electrostatic and Electromagnetic Confinement of Plasmas, 1974.Google Scholar
2. Ware, K. D., et al., “Operation of a 720 kJ, 60 kV, Dense Plasma Focus Device,” Bulletin of the Amer. Phys. Soc. II, 18, 10, 1361 (1973).Google Scholar
3. Freeman, B., et al, “Plasma Focus Solid Target Interactions,” Proc. of the Fifth European Conference on Plasma Physics and Controlled Fusion, Grenoble, France, 1972.Google Scholar
4. Beckner, E. H., “Production and Diagnostic Measurements of Kilovolt High Density Deuterium., Helium, and Neon Plasmas, Journal of Applied Physics, 37, 13, 4944 (1966).Google Scholar
5. Beclmer, E. H., “Pulsed High Density Source of X-Rays,” Review of Sci. Insts., 38, 4, 507 (1967).Google Scholar
6. Beckner, E. H., “Detailed Measurement of X-Ray Emission Spectra of High Density Kilovolt Plasmas,” Los Alamos Report LA-3770, Sept. 1967.Google Scholar
7. Mather, J. W., “Formation of a High Density Deuterium Plasma Focus,” Physics of Fluids, 8, 2, 366 (1965).Google Scholar
8. Mather, J. W., Bottoms, P. J., “Characteristics of a Dense Plasma Focus Discharge, Phys. Fluids, 11, 3, 611 (1968).Google Scholar
9. Mather, J. W., et. al, “Recent Studies of Dense Plasma Focus,” Proc. of IAEA 4th Conf. on Plasma Phys. and Cont, Nucl. Fus. Res., 1971.Google Scholar
10. van Paassen, H. L. L., et al, “X-Ray Spectra from Dense Plasma Focus Devices,” Phys. Fluids, 13, 10, 2606 (1970).Google Scholar
11. Bernstein, M. J., et al, “Time Correlations of X-Ray Spectra with leutron Emission from a Plasma Focus Discharge,” Phys. Rev. Lett., 27, 13, 844 (1971).Google Scholar
12. Lee, J. H., et al, “Hard X-Ray Spectrum of a Plasma Focus,” plasma Physics,. 13, 347 (1971).Google Scholar
13. Johnson, D. J., “Study of the X-Ray Production Mechanism of the Dense Rlasma Focus, Journal Applied Physics, 45, 3, (1974).Google Scholar
14. Mertz, A. H., “Dense Plasma Focus X-Ray Emission: Studies and Applications, Air Force Inst, of Tech., Wright-Patterson AFB, Ohio, March 1973.Google Scholar
15. Belyaeva, I. F., Filippov, N. V., ‘’Location of Fast Deuterons in a Plasma Focus,” Nuclear Fusion 13, 881 (1973).Google Scholar
16. Conrads, H., et al, “Velocity Distribution of the Ions Producing Neutrons in a Plasma Focus,” Phys. Fluids, 13, 1, 209 (Jan 72) and private communications with H. L. Sahlin.Google Scholar
17. Gullickson, R. L., “Experimental Determination of Laser Enhancement of the Dense Plasma Focus,” Bull. Amer, Phys. Soc. II, 17, 5, 691 (1972).Google Scholar
18. Mayer, F., Priyate CommunicationGoogle Scholar
19.Ch. Maisonneir, Private CommunicationGoogle Scholar
20. Gribkov, V. A., et al, “Beam Heating in a Plasma Focus,” ZhETF Pis. Red. 18, 1, 11 (1973).Google Scholar
21. Bazdenkov, S. V., et al, “Possible Mechanism of Breaking the Current Sheath in a Noncylindrical Z Pinch,” ZhETF Pis. Red. 18, 3, 199 (1973).Google Scholar
22. Johnson, D. J., “X-Ray Spectral Measurement System for Nanosecond Plasmas,” Review of Scientific Instruments, 45, 2, 191 (1974).Google Scholar
23. Edvards, A. L., “Users Manual for the Buckle X-Ray Deposition Program,” UCID-30023, Rev, 1, Lawrence Livermore Lab., 1972.Google Scholar
24. Lee, T. N., “High Density Ionization with an Intense Linear Focus Discharge,” Proc. of Conf, on Electrostatic and Electromatnetic Confinement, March 1974.Google Scholar
25. Ebert, P. J., et al, “Production of Monoenergetic X-Ray Sources or Known Absolute Intensity,” Noc. Inst, and Methods, 99, Feb. 15, 1972, p. 29.Google Scholar
26. Compton, A. H., Allison, S. K., “X-Rays in Theory and Experiment,” 2ed, Van Nostrand, 1935, p. 90.Google Scholar
27. Evans, R. D., “The Atomic Nucleus,” McGraw-Hill, 1955, p. 617.Google Scholar