Review of the {ital Z}-pinch
- Blackett Laboratory, Imperial College, London SW7 2BZ (England)
The dense {ital Z}-pinch is undergoing a renaissance of research following the development of large terawatt pulse-power generator sources and the theoretical modeling of radiative collapse and of conditions for controlled fusion. The issue of macroscopic stability has been made clearer with the construction of a universal diagram delineating regimes in parameter space for the importance of various physical effects. Of particular interest is the regime in which large ion Larmor radius effects are important, since under conditions for fusion with end losses and also for a strong radiative collapse the ion Larmor radius is about 20{percent} of the pinch radius; this coincides with a minimum in the growth rate of {ital m}=0 and {ital m}=1 modes in two kinetic models for a parabolic density profile. At Imperial College {ital Z}-pinch experiments have commenced on the MAGPIE generator (2.4 MV, 336 kJ, 200 ns). In common with other solid fiber experiments on terawatt and smaller machines there is a tendency at low line density for the ablating coronal plasma to expand, consistent with the triggering of lower hybrid turbulence due to the high drift velocity which prevents the current density from being sufficient to provide an inward pinching force to overcome the pressure gradient. At higher line density, when the ion Larmor radius is small, bright spots appear on the axis with a lifetime of about 10 ns. The connection of these with MHD {ital m}=0 instabilities will be discussed. At later times there can be an abrupt disruption of the discharge accompanied by a hard X-ray burst, and, for CD{sub 2} fibers a neutron pulse also. One possible explanation of this phenomenon is end losses of plasma, leading to a fall of line density below a critical value which triggers a high anomalous resistivity accompanied by the onset of runaway electrons and accelerated ions. A similar triggering would occur if the line density is lowered in a {ital m}=0 neck region. (Abstract Truncated)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 279526
- Report Number(s):
- CONF-9410130-; ISSN 0094-243X; TRN: 96:023387
- Journal Information:
- AIP Conference Proceedings, Vol. 345, Issue 1; Conference: 1994 International Conference on Plasma Physics, Foz do Iguacu (Brazil), 24 Oct - 4 Nov 1994; Other Information: PBD: Sep 1995
- Country of Publication:
- United States
- Language:
- English
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