Characteristics of edge plasma turbulence on the ATF torsatron

Technical Report · Fri Mar 01 00:00:00 EST 1991

DOI:https://doi.org/10.2172/5618594· OSTI ID:5618594

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

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

Measurements of electrostatic fluctuations on the edge of the Advanced Toroidal Facility (ATF) torsatron are used to study the role of the edge turbulence in the particle transport in this current-free magnetic configuration. Spatial profiles of the plasma electron density n{sub e}, temperature T{sub e}, and fluctuations in density ({tilde n}{sub e}) and in the plasma floating potential ({tilde {phi}}{sub f}) are measured at the edge in electron cyclotron heated plasmas using a Langmuir probe array. At the last closed flux surface (LCFS), r/a {approx} 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}. The relative fluctuation levels decrease as the probe is moved into the core plasma. For T{sub e} > 10 eV, {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} at r/a = 0.95. The measured fluctuations spectra are broadband (40--300 kHz) with {bar k}{rho}{sub s} {approx} 0.05--0.1, where {bar k} is the average wave number of the fluctuations and {rho}{sub s} is the ion Larmor radius at the sound speed. Near the LCFS, the density fluctuations can be approximated by {tilde n}{sub e}/n{sub e} {approx} 0.4/{bar k}L{sub n}, where L{sub n} is the gradient scale length of n{sub e}. The propagation direction of the fluctuations reverses to the electron diamagnetic direction at r/a < 1. The phase velocity of the fluctuations and the electron drift velocity are comparable. The particles flux estimated from the fluctuations is consistent with fluxes obtained from the particle balance using the H{sub {alpha}} spectroscopic measurements. Many of the features seen in the ATF edge fluctuations resemble those of ohmically heated plasmas in the Texas Experimental Tokamak.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5618594
• Report Number(s): ORNL/TM-11623; ON: DE91012981
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ATF TORSATRON
CHARGED-PARTICLE TRANSPORT
TURBULENCE
ECR HEATING
ELECTRON DENSITY
ELECTRON TEMPERATURE
EXPERIMENTAL DATA
FLUCTUATIONS
LANGMUIR PROBE
CLOSED PLASMA DEVICES
DATA
ELECTRIC PROBES
HEATING
HIGH-FREQUENCY HEATING
INFORMATION
NUMERICAL DATA
PLASMA HEATING
PROBES
RADIATION TRANSPORT
STELLARATORS
THERMONUCLEAR DEVICES
TORSATRON STELLARATOR
VARIATIONS
700103* - Fusion Energy- Plasma Research- Kinetics