ATF edge plasma turbulence studies using a fast reciprocating Langmuir probe

Technical Report · Tue Jan 01 04:00:00 EST 1991

DOI:https://doi.org/10.2172/6134449· OSTI ID:6134449

Uckan, T.; Hidalgo, C.; Bell, J. D.; Harris, J. H.; Dunlap, J. L.; Dyer, G. R.; Mioduszewski, P. K.; Wilgen, J. B. ^[1]; Ritz, C. P.; Wootton, A. J.; Rhodes, T. L.; Carter, K. ^[2]

---

1. Oak Ridge National Lab., TN (USA)
2. Texas Univ., Austin, TX (USA). Fusion Research Center

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{sub e} and temperature T{sub e} and fluctuations in density ({tilde n}{sub e}) and plasma floating potential ({tilde {phi}}{sub f}) are made in electron cyclotron heated plasmas at 1 T. At the last closed flux surface (LCFS, r{radical}a {approximately} 1), T{sub e} {approx} 20--40 eV and n{sub e} {approx} 10{sup 12} cm{sup {minus}3} for a line-averaged electron density {bar n}{sub e} = (3--6) {times} 10{sup 12} cm{sup {minus}3}. Relative fluctuation levels, as the FRLP is moved into core plasma where T{sub e} > 20 eV, are {tilde n}{sub e}/n{sub e} {approx} 5% and e{tilde {phi}}{sub f}/T{sub e} {approx} 2{tilde n}{sub e}/n{sub e} about 2 cm inside the LCFS. The observed fluctuation spectra are broadband (40--300 kHz) with {bar k}{rho}{sub s} {le} 0.1, where {bar k} is the wavenumber of the fluctuations and {rho}{sub s} is the ion Larmor radius at the sound speed. The propagation direction of the fluctuations reverses to the electron diamagnetic direction around r{radical}a < 1. The phase velocity and the electron drift velocity are comparable (v{sub ph} {approximately} v{sub de}). The fluctuation-induced particle flux is comparable to fluxes estimated from the particle balance using the H{sub {alpha}} spectroscopic measurements. Many of the features seen in these experiments resemble the features of ohmically heated plasmas in the Texas Experimental Tokamak (TEXT). 18 refs., 10 figs.

• Research Organization: Oak Ridge National Lab., TN (USA)
• Sponsoring Organization: DOE; USDOE, Washington, DC (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6134449
• Report Number(s): ORNL/TM-11545; ON: DE91010487
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101* -- Fusion Energy-- Plasma Research-- Confinement
Heating
&amp; Production
700102 -- Fusion Energy-- Plasma Research-- Diagnostics
ATF TORSATRON
CLOSED PLASMA DEVICES
ECR HEATING
ELECTRIC PROBES
ELECTRON DENSITY
ELECTRON TEMPERATURE
FLUCTUATIONS
HEATING
HIGH-FREQUENCY HEATING
LANGMUIR PROBE
PLASMA DENSITY
PLASMA HEATING
PROBES
STELLARATORS
THERMONUCLEAR DEVICES
TORSATRON STELLARATOR
TURBULENCE
VARIATIONS
WAVE PROPAGATION