Electron Bernstein wave electron temperature profile diagnostic (invited)
Electron cyclotron emission (ECE) has been employed as a standard electron temperature profile diagnostic on many tokamaks and stellarators, but most magnetically confined plasma devices cannot take advantage of standard ECE diagnostics to measure temperature. They are either ''overdense,'' operating at high density relative to the magnetic field (e.g., {omega}{sub pe}>>{Omega}{sub ce} in a spherical torus) or they have insufficient density and temperature to reach the blackbody condition ({tau}>2). Electron Bernstein waves (EBWs) are electrostatic waves that can propagate in overdense plasmas and have a high optical thickness at the electron cyclotron resonance layers as a result of their large k{sub perp}. In this article we report on measurements of EBW emission on the CDX-U spherical torus, where B{sub 0}{approx}2kG, <n{sub e}>{approx}10{sup 13}cm{sup -3} and T{sub e}{approx}10--200eV. Results are presented for electromagnetic measurements of EBW emission, mode converted near the plasma edge. The EBW emission was absolutely calibrated and compared to the electron temperature profile measured by a multipoint Thomson scattering diagnostic. Depending on the plasma conditions, the mode-converted EBW radiation temperature was found to be {<=}T{sub e} and the emission source was determined to be radially localized at the electron cyclotron resonance layer. A Langmuir triple probe and a 140 GHz interferometer were employed to measure changes in the edge density profile in the vicinity of the upper hybrid resonance where the mode conversion of the EBWs is expected to occur. Initial results suggest EBW emission and EBW heating are viable concepts for plasmas where {omega}{sub pe}>>{Omega}{sub ce}.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40204871
- Journal Information:
- Review of Scientific Instruments, Vol. 72, Issue 1; Other Information: Othernumber: RSINAK000072000001000285000001; 500101CON; PBD: Jan 2001; ISSN 0034-6748
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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