TMX-U thermal-barrier experiments

• Published in: IEEE transactions on plasma science Vol. 16; no. 1; pp. 1 - 10
• Main Authors: Simonen, T.C., Allen, S.L., Barter, J.D., Casper, T.A., Correll, D.L., Carter, M.R., Clauser, J.F., Dimonte, G., Foote, J.H., Futch, A.H., Goodman, R.K., Grubb, D.P., Hill, D.N., Hooper, E.B., Hornady, R.S., James, R.A., Molvik, A.W., Nexsen, W.E., Porter, G.D., Rognlien, T.D., Silver, E.H., Stallard, B.W., Turner, W.C., Wood, R.D.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-02-1988; Institute of Electrical and Electronics Engineers
• Subjects: Cyclotrons; Electrons; Exact sciences and technology; Heating; Laboratories; Loss measurement; Magnetic confinement and equilibrium; Mirrors; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma confinement; Plasma temperature; Radio frequency; Temperature distribution; Magnetic configuration; Plasma confinement; Tandem mirror configuration; Experimental study; Thermal barrier; Plasma heating
• ISSN: 0093-3813; 1939-9375
• DOI: 10.1109/27.3782

Thermal-barrier experiments in the Tandem Mirror Experiment Upgrade (TMX-U) are reported, along with progress made at the Lawrence Livermore National Laboratory in plasma confinement and central-cell heating. Thermal barriers in TMX-U improved axial confinement by two orders of magnitude over a limited range of densities, compared with confinement in single-cell mirrors at the same ion temperature. It is shown that central-cell radial nonambipolar confinement scales as neoclassical theory and can be eliminated by floating the end walls. Radial ambipolar losses can also be measured and reduced. The electron energy balance is improved in tandem mirrors to near classical, resulting in T/sub e/ up to 0.28 keV. Electron cyclotron heating (ECH) efficiencies up to 42%, with low levels of electron microinstability, were achieved when hot electrons in the thermal barrier were heated to average betas as large as 15%. The hot-electron distribution was measured from X-rays and is modeled by a Fokker-Planck code that includes heating from cavity radio-frequency (RF) fields.< >