Neutron and hard x-ray measurements during pellet deposition in TFTR

Technical Report · Sun Jun 01 04:00:00 EDT 1986

DOI:https://doi.org/10.2172/5405763· OSTI ID:5405763

Heidbrink, W W; Milora, S L; Schmidt, G L; Schneider, W; Ramsey, A

Measurements of neutrons and hard x rays are made with a pair of plastic scintillators during injection of deuterium pellets into deuterium TFTR plasmas. Three cases are investigated. During ohmic heating in plasmas with few runaway electrons, the neutron emission does not increase when a pellet is injected, indicating that strong acceleration of the pellet ions does not occur. In ohmic plasmas with low but detectable levels of runaway electrons, an x-ray burst is observed on a detector near the pellet injector as the pellet ablates, while a detector displaced 126/sup 0/ toroidally from the injector does not measure a synchronous burst. Reduced pellet penetration correlates with the presence of x-ray emission, suggesting that the origin of the burst is bremsstrahlung from runaway electrons that strike the solid pellet. In deuterium beam-heated discharges, an increase in the d-d neutron emission is observed when the pellet ablates. In this case, the increase is due to fusion reactions between beam ions and the high density neutral and plasma cloud produced by ablation of the pellet; this localized density perturbation equilibrates in about 700 ..mu..sec. Analysis of the data indicates that the density propagates without forming a sharp shock front with a rapid initial propagation velocity (greater than or equal to 2 x 10/sup 7/ cm/sec) that subsequently decreases to around 3 x 10/sup 6/ cm/sec. Modelling suggests that the electron heat flux into the pellet cloud is much less than the classical Spitzer value.

• Research Organization: Princeton Univ., NJ (USA). Plasma Physics Lab.
• DOE Contract Number: AC02-76CH03073
• OSTI ID: 5405763
• Report Number(s): PPPL-2346; ON: DE86013630
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700104* -- Fusion Energy-- Plasma Research-- Plasma Kinetics-Experimental-- (-1987)
DEUTERIUM
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
FUEL PELLETS
HYDROGEN ISOTOPES
ISOTOPES
LEPTONS
LIGHT NUCLEI
MEASURING INSTRUMENTS
NEUTRON SPECTRA
NUCLEI
ODD-ODD NUCLEI
PELLET INJECTION
PELLETS
RADIATION DETECTORS
RUNAWAY ELECTRONS
SCINTILLATION COUNTERS
SPECTRA
STABLE ISOTOPES
TFTR TOKAMAK
THERMONUCLEAR REACTORS
TOKAMAK TYPE REACTORS
X-RAY SPECTRA