Confined trapped-alpha behavior in TFTR deuterium-tritium plasmas

Technical Report · Wed Oct 01 04:00:00 EDT 1997

DOI:https://doi.org/10.2172/304219· OSTI ID:304219

Medley, S S; Budny, R V; Redi, M H; Roquemore, A L; White, R B ^[1]; Duong, H H; Fisher, R K ^[2]; Petrov, M P ^[3]; Gorelenkov, N N ^[4]

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1. Princeton Univ., NJ (United States). Princeton Plasma Physics Lab.
2. General Atomics, San Diego, CA (United States)
3. A.F. Ioffe Physical-Technical Inst., St. Petersburg (Russian Federation)
4. TRINITI, Troitsk (Russian Federation)

Confined trapped-alpha energy spectra and differential radial density profiles in TFTR D-T plasmas are obtained with the Pellet Charge-eXchange (PCX) diagnostic which measures high energy (E{sub {alpha}} = 0.5--3.5 MeV), trapped alphas (v{sub {parallel}}/v = - 0.048) at a single time slice ({Delta}t {approximately} 1 msec) with a spatial resolution of {Delta}r {approximately} 5 cm. Tritons produced in D-D plasmas and RF-driven ion tails (H, {sup 3}He or T) were also observed and energetic tritium ion tail measurements will be discussed. PCX alpha and triton energy spectra extending up to their birth energies were measured in the core of MHD-quiescent discharges where the expected classical slowing down and pitch angle scattering effects are not complicated by stochastic ripple diffusion and sawtooth activity. Both the shape of the measured alpha and triton energy distributions and their density ratios are in good agreement with TRANSP predictions, indicating that the PCX measurements are consistent with classical thermalization of the fusion-generated alphas and tritons. From calculations, these results set an upper limit on possible anomalous radial diffusion for trapped alphas of D{sub {alpha}} {le} 0.01 m{sup 2}s{sup {minus}1}. Outside the core, where the trapped alphas are influenced by stochastic ripple diffusion effects, the PCX measurements are consistent with the functional dependence of the Goldston-White-Boozer stochastic ripple threshold on the alpha energy and the q-profile. In the presence of strong sawtooth activity, the PCX diagnostic observes significant redistribution of the alpha signal radial profile wherein alphas are depleted in the core and redistributed to well outside the q = 1 radius, but apparently not beyond the energy-dependent stochastic ripple loss boundary.

• Research Organization: Princeton Univ., Princeton Plasma Physics Lab., NJ (United States)
• Sponsoring Organization: USDOE Office of Energy Research, Washington, DC (United States)
• DOE Contract Number: AC02-76CH03073; FG03-92ER54150
• OSTI ID: 304219
• Report Number(s): PPPL--3272; ON: DE98050519
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALPHA PARTICLES
D-T OPERATION
ENERGY SPECTRA
ION DENSITY
NEUTRAL PARTICLE ANALYZERS
PLASMA DIAGNOSTICS
SAWTOOTH OSCILLATIONS
TAIL IONS
TFTR TOKAMAK