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A large-angle, 60-GHz collective Thomson scattering (CTS) diagnostic system for localized measurements of DT alpha-particle velocity distribution and fraction is being implemented on TFTR. Calculations of expected CTS spectra, signal-to-noise ratio per receiver channel, and estimated error in determining the temperature and fraction of alpha particles are being carried out. The experimental spectra are simulated by adding noise to the theoretical calculation by a Monte Carlo technique. Error analysis is then performed by using a relative intensity calibrated nonlinear curve fitting code to calculate the desired plasma parameters (T[sub i], T[sub α], n[sub α]/n[sub i]). Simulation results indicate that expected background emission of 20 eV during Supershot in TFTR poses no problem to the experiment. Also short integration times (<10 ms) can be used to resolve the energetic ion features, thus offering a possibility for the study of temporal evolution of energetic ion velocity distribution during a single plasma shot. [ABSTRACT FROM AUTHOR]

Collective Thomson scattering in the Tara Tandem Mirror axicell at MIT was accomplished with a 137-GHz, ∼0.4-kW, 75-ms pulsed gyrotron. Ion cyclotron waves, ion Bernstein wave harmonics, and other plasma fluctuations possibly due to microinstabilities and magnetohydrodynamic (MHD) activity have been observed during ion cyclotron resonance frequency (ICRF) heating. The observation of ion Bernstein waves may be due to an enhanced ion thermal fluctuation spectrum in an ICRF heated plasma. [ABSTRACT FROM AUTHOR]

High-power, large-angle (> 10°), collective Thomson scattering diagnostics can provide localized density and velocity distribution data of confined alpha particles, ICRH simulated alpha particles, and ions related to ICRH and neutral beam energy deposition. Millimeter-wave gyrotron systems are under development for TFTR and JET. Scattering with a submillimeter gyrotron is being investigated for Alcator C-Mod. Major design issues include plasma accessibility, scattering angle, orientation to magnetic field, spectra of non-Maxwellian velocity distributions, signal-to-noise ratio, refraction, electron cyclotron emission, and beam and viewing dumps. [ABSTRACT FROM AUTHOR]

In D-T plasmas, the understanding of the physics of confined a particles is extremely valuable for the future fusion plasma device. Among the various proposed α diagnostics, an X-mode collective Thomson scattering system employing a high-power gyrotron source (P...200 kW, f=60 GHz, pulse length ...0.5 s, and modulation frequency=10-25 kHz) is being designed for TFTR. The detailed description of the gyrotron source, transmission lines, optical designs, beam and viewing dump design, and receiver system will be presented in this paper. In particular, the test results of the beam and viewing dump indicate that the stray light can be reduced by 60 dB. The background emission level (∼20 eV) near 60-GHz range during high Q discharge may also be reduced with beam and viewing dump further. The optical system is designed to measure the radial profile of a particles and to orient the incident wavevector (k[sub 0]) to test the electromagnetic effects of the scattered spectrum. Prior to the study of α physics in D-T plasmas, this scattering system will be used to measure not only a bulk ion temperature but also the scattered spectrum due to fast ions produced by NB and ICRF heating in TFTR. This work was supported by the U.S. Department of Energy Contract No. DE-AC02-76-CHO-3073. [ABSTRACT FROM AUTHOR]