The anomalous currents in the front foils of the JET lost alpha diagnostic KA-2

Journal Article · Fri Oct 15 04:00:00 EDT 2010 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3502040· OSTI ID:22055770

Cecil, F E ^[1]; Kiptily, V; Salmi, A; Horton, A; Fullard, K ^[2]; Murari, A ^[3]; Darrow, D; Hill, K ^[4]

---

1. Colorado School of Mines, Golden, Colorado 80401 (United States)
2. Culham Science Center, Euratom/CCFE Fusion Association, Abingdon, Oxon (United Kingdom)
3. Consorzio RFX-Associazione EURATOM ENEA per la Fusione, I-35127 Padova (Italy)
4. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

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 (both deuterium and impurity) in the vicinity of the detector (including charge exchange neutrals) 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.

• OSTI ID: 22055770
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 10 Vol. 81; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALPHA PARTICLES
CHARGE EXCHANGE
DEUTERIUM
EDGE LOCALIZED MODES
FARADAY CUPS
FOILS
GOLD
H-MODE PLASMA CONFINEMENT
JET TOKAMAK
NICKEL
PHOTOEMISSION
PLASMA
PLASMA IMPURITIES
PLASMA JETS
SIMULATION
ULTRAVIOLET RADIATION