The Anomalous Currents In The Front Foils of the JET Lost Alpha Diagnostic KA-2

F.E. Cecil, V. Kiptily, A. Salmi, A. Horton, K. Fullard, A. Murari, D. Darrow, K. Hill and JET-EFDA Contributors

Princeton University. Plasma Physics Laboratory.

关键词: Alpha Particlestokamaks;    Nickel;    Gold;    70 Plasma Physics And Fusion Technology;    Apertures;   

RP-ID  :  PPPL-4620
RP-ID  :  DE-ACO2-09CH11466
RP-ID  :  1013256

美国|英语

来源: UNT Digital Library

【 摘 要 】

We have examined the observed currents in the front foils of the JET Faraday cup lost alpha particle diagnostic KA-2. In particular, we have sought to understand the currents during Ohmic plasmas for which the ion flux at the detectors was initially assumed to be negligible. We have considered two sources of this current: plasma ions #2; both deuterium and impurity#3; in the vicinity of the detector #2; including charge exchange neutrals#3; and photoemission from scattered UV radiation. Based upon modeling and empirical observation, the latter source appears most likely and, moreover, seems to be applicable to the currents in the front foil during ELMy H-mode plasmas. A very thin gold or nickel foil attached to the present detector aperture is proposed as a solution to this problem, and realistic calculations of expected fluxes of lost energetic neutral beam ions during TF ripple experiments are presented as justification of this proposed solution.