Measurement of impurity induced neutralization of MeV energy helium ions in JET plasmas

摘要

Impurity induced neutralization (IIN) was shown to be a dominant neutralization mechanism for MeV energy protons in JET plasmas (1). This discovery made possible a way for non-perturbing measurements, using a high energy neutral particle analyzer NPA), of energy distribution function f (E) of ICRF driven MeV energy ions of hydrogen isotopes, and interpretation of the measurements(1, 2). analogously, neutralization of fusion alpha-particles was predicted to occur due to double charge-exchange (2CX) eactions with two-electron species A~((Z-2)+) of main intrinsic plasma impurities, He, Be and C (3), according to the process: He~(2+) + A~((Z-2)+) (1s~2) -> He~0 (1s~2) + A~(Z+) (1) In this paper we present first experimental evidence for processes (1), obtained from measurement of f (E) for MeV energy ~3He~(2+) ions during ICRF heating of ~3He minority in deuterium plasmas(D(~3He)). This result makes feasible non-perturbing measurements of DT fusion alpha-particles in the core of fusion plasmas, such as in JET, using a NPA.