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Experiments on a Toroidal Screw Pinch with Various Field Programming

Abstract

In the toroidal screw pinch ISAR-IV (large diameter 60 cm, aspect ratio 5, maximum storage, energy 140 kj) attempts were made to get an improved stability of the plasma by different kinds of field programming. The best results were obtained with positive trapped B{sub z}-fields and simultaneous switching of main B{sub z}-field and I{sub z}-current. In this case the dense plasma column (n{sub e} Almost-Equal-To 2-3 x 10{sup 16} , kT Almost-Equal-To 50-100 eV, {beta} Almost-Equal-To 15-20%) is surrounded by a force-free plasma ({beta} = 1%) with weak shear and it behaves stably for, at least, 25 {mu}s. The resulting containment time nr of near 10{sup 12} s cm{sup -3} remains a factor of 2-3 below the upper limit given by the classical diffusion. The following loss of the equilibrium position near the coil axis ({Delta} Almost-Equal-To 1-2 cm) is connected to a strong damping of the axial plasma current which starts near the end of the containment. It may be assumed that the increase of the effective plasma resistance mainly results from a contact of the force-free regions with the tube wall. Attempts were made to improve the containment by suitable programming of a plasma z-current. The results are  More>>
Authors:
Zwicker, H.; Wilhelm, R.; Krause, H. [1] 
  1. Max-Planck-Institut Fuer Plasmaphysik, EURATOM-Association, Garching, Munich, Federal Republic of Germany (Germany)
Publication Date:
Oct 15, 1971
Product Type:
Conference
Report Number:
IAEA-CN-28/B-6
Resource Relation:
Conference: 4. International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Madison, WI (United States), 17-23 Jun 1971; Other Information: 7 refs., 7 figs.; Related Information: In: Plasma Physics and Controlled Nuclear Fusion Research 1971. Vol. I. Proceedings of the Fourth International Conference on Plasma Physics and Controlled Nuclear Fusion Research| 708 p.
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCURACY; ASPECT RATIO; COMPRESSION; CONTAINMENT; ELECTRIC CURRENTS; LIMITERS; MAGNETOHYDRODYNAMICS; PLASMA; PLASMA INSTABILITY; PROGRAMMING; QUARTZ; Q-VALUE; SCREW PINCH; TOKAMAK DEVICES; TRAPPING; WAVELENGTHS
OSTI ID:
22127461
Research Organizations:
International Atomic Energy Agency, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Other: ISSN 0074-1884; TRN: XA13M2874082540
Submitting Site:
INIS
Size:
page(s) 251-258
Announcement Date:
Sep 12, 2013

Citation Formats

Zwicker, H., Wilhelm, R., and Krause, H. Experiments on a Toroidal Screw Pinch with Various Field Programming. IAEA: N. p., 1971. Web.
Zwicker, H., Wilhelm, R., & Krause, H. Experiments on a Toroidal Screw Pinch with Various Field Programming. IAEA.
Zwicker, H., Wilhelm, R., and Krause, H. 1971. "Experiments on a Toroidal Screw Pinch with Various Field Programming." IAEA.
@misc{etde_22127461,
title = {Experiments on a Toroidal Screw Pinch with Various Field Programming}
author = {Zwicker, H., Wilhelm, R., and Krause, H.}
abstractNote = {In the toroidal screw pinch ISAR-IV (large diameter 60 cm, aspect ratio 5, maximum storage, energy 140 kj) attempts were made to get an improved stability of the plasma by different kinds of field programming. The best results were obtained with positive trapped B{sub z}-fields and simultaneous switching of main B{sub z}-field and I{sub z}-current. In this case the dense plasma column (n{sub e} Almost-Equal-To 2-3 x 10{sup 16} , kT Almost-Equal-To 50-100 eV, {beta} Almost-Equal-To 15-20%) is surrounded by a force-free plasma ({beta} = 1%) with weak shear and it behaves stably for, at least, 25 {mu}s. The resulting containment time nr of near 10{sup 12} s cm{sup -3} remains a factor of 2-3 below the upper limit given by the classical diffusion. The following loss of the equilibrium position near the coil axis ({Delta} Almost-Equal-To 1-2 cm) is connected to a strong damping of the axial plasma current which starts near the end of the containment. It may be assumed that the increase of the effective plasma resistance mainly results from a contact of the force-free regions with the tube wall. Attempts were made to improve the containment by suitable programming of a plasma z-current. The results are presented. Experiments with one quartz limiter inside the torus improved the equilibrium but introduced instabilities at the new surface of the dilute plasma. To obtain more information about the outer region, the dilute plasma was produced without a dense core and separated from the tube walls by weak adiabatic compression. Under these Tokamak-like conditions the q-value was varied. In the region of q Almost-Equal-To 1 there appeared instabilities which seem to haver higher m-modes and rather short wavelengths. In a different kind of field programming the field distribution of the ''diffuse pinch'' was realized within an accuracy of 5-10% (kT Almost-Equal-To 100 eV, {beta} Almost-Equal-To 30%). In contrast to the predictions of MHD-theory, stability was observed only for about 3 {mu}s. Then the plasma is totally destroyed, presumably by resistive instabilities. (author)}
place = {IAEA}
year = {1971}
month = {Oct}
}