Nature 279, 626 - 628 (14 June 1979); doi:10.1038/279626a0

Measurement of the neutron spectra from beam-heated PLT plasmas

J. D. STRACHAN, P. COLESTOCK, H. EUBANK, L. GRISHAM, J. HOVEY, G. SCHILLING, L. STEWART, W. STODIEK, R. STOOKSBERRY & K. M. YOUNG

Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08544

MEASUREMENTS of the neutron spectra from the PLT tokamak plasma are reported here which provide information on the centre-of-mass velocity of the reacting deuteron pairs. The observation in PLT of no significant directed velocity yields additional evidence that the neuterons are produced by a thermonuclear process. Previous spectral measurements on other fusion devices have often determined that the neutron emission was non-thermonuclear and resulted from a small 'tail' component of energetic ions¹⁻³. The neutron spectra indicated a directed velocity of the reacting deuterons and thus non-thermonuclear neutron emission if the injected neutral beam ions were deuterium. In this condition, the neutron spectra were consistent with the expected beam-induced d(d,n) ³He reactions. However, if the heating beam used hydrogen, then the neutron spectra are consistent with a thermonuclear neutron emission resulting from the beam heating of the bulk deuterons in the plasma.

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