Plasma-surface interactions in the ZT-40M reversed-field pinch
Plasma-surface interactions strongly influence the properties of plasma produced in the ZT-40M reversed-field pinch, which generally operates without discrete limiters. Z/sub eff/ data and spectroscopy, together with total radiated power, and measured impurity accumulations on collector probes demonstrate that metal impurities play a determining role in ZT-40M's performance. Plasma currents of 60 to 400 kA routinely generate total betas of 5 to 10% (assuming T/sub i/ = T/sub e/). ZT-40M's inherently large ohmic heating power yields T/sub e/ greater than or equal to 500 eV for 400 kA flat-top discharges with anti n/sub e/ approx. 4 x 10/sup 19/ m/sup -3/. Pulse duration at the lower currents has reached approx.35 ms. Energy confinement time Tau/sub E/ has reached 0.7 ms for discharges with anti n/sub e/ = 8 x 10/sup 19/ m/sup -3/ and T/sub e/ = 330 eV at a current of 330 kA. Magnetic field errors intrinsic to the winding and core configuration create localized, intense plasma-surface interactions that define the present operating boundary for ZT-40M. Discharge cleaning, either pulsed or glow, of the Inconel vacuum vessel increases the deuterium recycling rate and decreases the impurity fractions, leading to discharges with higher density and lower temperature, loser Z/sub eff/, lower resistive anomaly factor, and better overall confinement of particles and energy. Carbon films approx.40 monolayers thick are used in ZT-40M to simulate the recycling, fueling, and sputtering conditions that may be encountered in next generation devices with large areas of carbon.
- Research Organization:
- Los Alamos National Lab., NM (USA); Sandia National Labs., Livermore, CA (USA)
- DOE Contract Number:
- AC04-76DR00789; W-7405-ENG-36
- OSTI ID:
- 5851587
- Report Number(s):
- LA-UR-86-1809; CONF-860522-3; ON: DE86011226
- Resource Relation:
- Conference: 7. international conference on plasma surface interactions in controlled fusion devices, Princeton, NJ, USA, 5 May 1986
- Country of Publication:
- United States
- Language:
- English
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