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

F.E. Cecil, V. Kiptily, Antti Salmi, JET EFDA Contributors

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)

Abstract

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.
Original languageEnglish
Article number10D326
JournalReview of Scientific Instruments
Volume81
Issue number10
DOIs
Publication statusPublished - 2010
MoE publication typeA1 Journal article-refereed

Fingerprint

Metal foil
foils
Detectors
Plasmas
detectors
Fluxes
ions
Alpha particles
plasma currents
Ions
neutral beams
Photoemission
Deuterium
ripples
charge exchange
Ultraviolet radiation
Ion beams
alpha particles
deuterium
photoelectric emission

Keywords

  • deuterium
  • gold
  • nickel
  • plasma diagnostics
  • plasma impurities
  • plasma toroidal confinement
  • plasma transport processes
  • Tokamak devices

Cite this

Cecil, F.E. ; Kiptily, V. ; Salmi, Antti ; Contributors, JET EFDA. / The anomalous currents in the front foils of the JET lost alpha diagnostic KA-2. In: Review of Scientific Instruments. 2010 ; Vol. 81, No. 10.
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abstract = "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.",
keywords = "deuterium, gold, nickel, plasma diagnostics, plasma impurities, plasma toroidal confinement, plasma transport processes, Tokamak devices",
author = "F.E. Cecil and V. Kiptily and Antti Salmi and Contributors, {JET EFDA}",
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The anomalous currents in the front foils of the JET lost alpha diagnostic KA-2. / Cecil, F.E.; Kiptily, V.; Salmi, Antti; Contributors, JET EFDA.

In: Review of Scientific Instruments, Vol. 81, No. 10, 10D326, 2010.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - The anomalous currents in the front foils of the JET lost alpha diagnostic KA-2

AU - Cecil, F.E.

AU - Kiptily, V.

AU - Salmi, Antti

AU - Contributors, JET EFDA

PY - 2010

Y1 - 2010

N2 - 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.

AB - 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.

KW - deuterium

KW - gold

KW - nickel

KW - plasma diagnostics

KW - plasma impurities

KW - plasma toroidal confinement

KW - plasma transport processes

KW - Tokamak devices

U2 - 10.1063/1.3502040

DO - 10.1063/1.3502040

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JO - Review of Scientific Instruments

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ER -