Characteristics of edge plasma turbulence on the ATF torsatron

Journal Article · Mon Apr 01 04:00:00 EST 1991 · Physics of Fluids B; (USA)

DOI:https://doi.org/10.1063/1.859882· OSTI ID:5838474

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]

---

1. Fusion Energy Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (USA)
2. Fusion Research Center, The University of Texas, Austin, Texas 78712 (USA)

Measurements of electrostatic fluctuations on the edge of the Advanced Toroidal Facility (ATF) torsatron (Fusion Technol. {bold 10}, 179 (1986)) 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 {ital n}{sub {ital e}}, temperature {ital T}{sub {ital e}}, and fluctuations in density ({ital {tilde n}}{sub {ital e}}) and in the plasma floating potential ({tilde {phi}}{sub {ital f}} ) are measured at the edge in electron cyclotron heated plasmas using a Langmuir probe array. At the last closed flux surface (LCFS), {ital r}/{ital a}{approx}1, {ital T}{sub {ital e}}{approx}20--40 eV, and {ital n}{sub {ital e}}{approx}10{sup 12} cm{sup {minus}3} for a line-averaged electron density {ital {bar n}}{sub {ital 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 {ital T}{sub {ital e}}{gt}20 eV, {ital {tilde n}}{sub {ital e}}/{ital n}{sub {ital e}}{approx}5%, and {ital e}{tilde {phi}}{sub {ital f}} /{ital T}{sub {ital e}}{approx}2{ital {tilde n}}{sub {ital e}}/{ital n}{sub {ital e}} at {ital r}/{ital a}=0.95. The measured fluctuation spectra are broadband (40--300 kHz) with {ital {bar k}}{rho}{sub {ital s}}{approx}(0.05--0.1), where {ital {bar k}} is the average wave number of the fluctuations and {rho}{sub {ital s}} is the ion Larmor radius at the sound speed. Near the LCFS, the density fluctuations can be approximated by {ital {tilde n}}{sub {ital e}}/{ital n}{sub {ital e}} {approx}0.4/{ital {bar k}L}{sub {ital n}}, where {ital L}{sub {ital n}} is the gradient scale length of {ital n}{sub {ital e}}. The propagation direction of the fluctuations reverses to the electron diamagnetic direction at {ital r}/{ital a}{lt}1. The phase velocity of the fluctuations and the electron drift velocity are comparable.

• DOE Contract Number: AC05-84OR21400; FG05-89ER53295
• OSTI ID: 5838474
• Journal Information: Physics of Fluids B; (USA), Journal Name: Physics of Fluids B; (USA) Vol. 3:4; ISSN 0899-8221; ISSN PFBPE
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700102* -- Fusion Energy-- Plasma Research-- Diagnostics
ATF TORSATRON
CLOSED PLASMA DEVICES
ECR HEATING
ELECTRIC PROBES
ELECTRON DENSITY
ELECTRON TEMPERATURE
ELECTROSTATICS
END EFFECTS
FLUCTUATIONS
HEATING
HIGH-FREQUENCY HEATING
LANGMUIR PROBE
PLASMA
PLASMA DIAGNOSTICS
PLASMA HEATING
POTENTIALS
PROBES
STELLARATORS
THERMONUCLEAR DEVICES
TORSATRON STELLARATOR
TURBULENCE
VARIATIONS