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Title: An investigation of alpha-like particles in the DIII-D tokamak using fusion-product diagnostics

Two important issues associated with alpha physics, the single-particle behavior and the effect of collective fast-ion-driven instabilities on fast-ion confinement, have been studied in the DIII-D tokamak using fusion product diagnostics. The single-particle behavior of alpha-like tritons and [sup 3]He ions produced in deuterium-deuterium fusion reactions is studied using the d(t,n)[alpha] and d([sup 3]he,p)[alpha] fusion reactions. Fusion-produced MeV ions exhibit classical behavior in high field (B[sub T] [ge] 1.0 T) DIII-D discharges, including the new class of [open quotes]very high[close quotes] confinement plasmas. However, discharges with strong sawtooth, fishbone, or TAE activity exhibit anomalous fusion product losses. For the high field discharges without strong MHD activity, the data imply an effective diffusion coefficient smaller than [approximately]0.1 m[sup 2]/s, but in the presence of strong MHD activity, the effective diffusion of the MeV ions exceeds 1.0 m[sup 2]/s. Collective alpha particle processes are simulated by means of neutral beam injected energetic ion minorities. Toroidicity-induced Alfven Eigenmodes (TAE) are observed in DIII-D when energetic beam ions ([approximately]75 keV) are used to destabilize the mode. Measurements of the neutron emission indicate that up to 70% of the injected power is lost during strong TAE activity. Measurements of the poloidal distribution of fast-ion lossesmore » suggest that the losses are greatest near the vessel midplane. Fast-ion losses in discharges with combined fishbones and TAE bursts are 1.5 to 2 times greater than losses in fishbone discharges without TAE activity. The scaling of fast ion losses with MHD mode amplitude exhibits no threshold in the mode amplitude, suggesting that mode-particle pumping is the dominant loss mechanism.« less
Authors:
Publication Date:
OSTI Identifier:
7041595
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Thesis (Ph.D.)
Publisher:
Irvine, CA (United States); Univ. of California
Research Org:
California Univ., Irvine, CA (United States)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; HELIUM 3; CHARGED PARTICLE DETECTION; TOKAMAK DEVICES; DEUTERON REACTIONS; PLASMA INSTABILITY; TRITONS; HEAVY ION FUSION REACTIONS; PLASMA CONFINEMENT; CHARGED PARTICLES; CHARGED-PARTICLE REACTIONS; CLOSED PLASMA DEVICES; CONFINEMENT; DETECTION; EVEN-ODD NUCLEI; HELIUM ISOTOPES; INSTABILITY; ISOTOPES; LIGHT NUCLEI; NUCLEAR REACTIONS; NUCLEI; RADIATION DETECTION; STABLE ISOTOPES; THERMONUCLEAR DEVICES 700360* -- Fusion Reactions-- (1992-)