ATF EDGE PLASMA TURBULENCE STUDIES USING A FAST RECIPROCATING LANGMUIR PROBE

[摘要] Electrostatic turbulence on the edge of the Advanced Toroidal Facility (ATF) torsatron is investigated experimentally with a fast reciprocating Langmuir probe (FRLP) array. Initial measurements of plasma electron density n(e) and temperature T(e) and fluctuations in density (n approximately e) and plasma floating potential (phi approximately f) are made in ECH plasmas at 1 T. At the last closed flux surface (LCFS, r/aBAR approximately 1), T(e) almost-equal-to 20-40 eV and n(e) almost-equal-to 10(12) cm-3 for a line-averaged electron density nBAR(e) = (3-6) x 10(12) cm-3. Relative fluctuation levels, as the FRLP is moved into core plasma where T(e) > 20 eV, are n approximately e/n(e) almost-equal-to 5%, and e-phi approximately f/T(e) almost-equal-to 2 n approximately e/n(e) about 2 cm inside the LCFS. The observed fluctuation spectra are broadband (40-300 kHz) with kBAR-rho-s less-than-or-equal-to 0.1, where kBAR is the wavenumber of the fluctuations and rho-s is the ion Larmor radius at the sound speed. The propagation direction of the fluctuations reverses to the electron diamagnetic direction around r/aBAR < 1. The phase velocity and the electron drift velocity are comparable (v(ph) approximately v(de). The fluctuation-induced particle flux is comparable to fluxes estimated from the particle balance using the H-alpha spectroscopic measurements. Many of the features seen in these experiments resemble the features of ohmically heated plasmas in the Texas Experimental Tokamak (TEXT).

[发布日期] 1990-12-01

[效力级别]  Proceedings Paper