Effects of sawtooth crashes on beam ions and fusion product tritons in JET

F. B. Marcus, J. M. Adams, D. S. Bond, M. A. Hone, P. J.A. Howarth, O. N. Jarvis, M. J. Loughlin, G. J. Sadler, P. Van Belle, N. Watkins

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

The JET neutron emission profile monitor is used to measure the 2.5 MeV and 14 MeV neutron emission line integrals before and after sawtooth crashes in high d-d neutron yield, hot ion H mode plasmas in the Joint European Torus (JET). Deuterium-deuterium (d-d) fusion produces 2.5 MeV neutrons and 1 MeV tritons (t) at nearly equal rates from its two reaction channels. A plasma current of 3 MA is sufficiently high to contain most of the fusion product tritons, which have birth orbit gyroradii and velocity space distributions similar to those of the 3.5 MeV or particles from d-t fusion. By examining neutron emission line integrals and tomographically deduced local emissivity profiles, an upper limit of 10% can be placed on the net fraction of fusion product tritons which are displaced from the plasma axis by those sawtooth crashes studied. This is a much smaller net fraction than that typically observed, 35-55%, for displaced injected neutral beam deuterium ions. A study of the response of beam injected deuterium ions to a sawtooth crash shows that the change in their axial density depends on the precrash spatial width of the neutron emissivity profile. The fusion product tritons, which have a large precrash spatial width, respond weakly to a crash. This weak response is consistent with the behaviour of the analogous d-d beam thermal neutrons when extrapolated to the corresponding emissivity spatial width. The implication of these observations is that beam ions and 3.5 MeV alpha particles in JET may be relatively resilient to sawtooth clashes, when the spatial width of their density is sufficiently large.

Original languageEnglish
Article numberI08
Pages (from-to)687-701
Number of pages15
JournalNuclear Fusion
Volume34
Issue number5
DOIs
StatePublished - 1994
Externally publishedYes

Fingerprint

Dive into the research topics of 'Effects of sawtooth crashes on beam ions and fusion product tritons in JET'. Together they form a unique fingerprint.

Cite this