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Title: Comparison of multialkali and GaAs photocathode detectors for Joint European Torus edge light detection and ranging Thomson scattering profiles

Abstract

The Joint European Torus (JET) tokamak has two light detection and ranging (LIDAR) Thomson scattering systems, one for the core and one dedicated to the edge T{sub e} and n{sub e} profiles. The LIDAR scheme is unique to JET and is envisaged for use on ITER. The system's spatial resolution is defined by the convolution product of its components: laser pulse duration, detector response time, and digitizer speed. The original multialkali photocathode microchannel plate photomultipliers dictated the response time, resulting in a 12 cm spatial resolution along the line of sight. In the edge LIDAR system, this is improved by aligning the line of sight with the flux surfaces, thus improving the effective spatial resolution to 2 cm depending on the plasma configuration. To meet demands for better edge gradient resolution, an upgrade to higher quantum efficiency detectors was proposed. Four GaAs photocathode detectors have been procured, two of which surpass expectations. These detectors are shown to have a more than two times higher effective quantum efficiency and their response time is at least twice as fast as the multialkali detectors. Combined with a fast digitizer this improves the spatial resolution by a factor of two, down to one centimetermore » effective, depending on plasma configuration.« less

Authors:
; ; ; ;  [1]
  1. FOM-Rijnhuizen, Ass. Euratom-FOM, TEC, PO Box 1207, 3430 BE Nieuwegein (Netherlands)
Publication Date:
OSTI Identifier:
20641185
Resource Type:
Journal Article
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 75; Journal Issue: 10; Conference: 15. topical conference on high temperature plasma diagnostics, San Diego, CA (United States), 19-22 Apr 2004; Other Information: DOI: 10.1063/1.1787923; (c) 2004 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); JET-EFDA Contributors; Journal ID: ISSN 0034-6748
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; GALLIUM ARSENIDES; ITER TOKAMAK; JET TOKAMAK; LIGHT SCATTERING; MAGNETIC SURFACES; OPTICAL RADAR; PHOTOCATHODES; PHOTODETECTORS; PHOTOMULTIPLIERS; PLASMA DIAGNOSTICS; QUANTUM EFFICIENCY; SEMICONDUCTOR MATERIALS; SPATIAL RESOLUTION; THOMSON SCATTERING

Citation Formats

Kempenaars, M, Nielsen, P, Pasqualotto, R, Gowers, C, Beurskens, M, Consorzio RFX-Associazione Euratom-Enea sulla Fusione, Corso Stati Uniti 4, I-35127 Padova, EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon, OX14 3DB, and FOM-Rijnhuizen, Ass. Euratom-FOM, TEC, PO Box 1207, 3430 BE Nieuwegein. Comparison of multialkali and GaAs photocathode detectors for Joint European Torus edge light detection and ranging Thomson scattering profiles. United States: N. p., 2004. Web. doi:10.1063/1.1787923.
Kempenaars, M, Nielsen, P, Pasqualotto, R, Gowers, C, Beurskens, M, Consorzio RFX-Associazione Euratom-Enea sulla Fusione, Corso Stati Uniti 4, I-35127 Padova, EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon, OX14 3DB, & FOM-Rijnhuizen, Ass. Euratom-FOM, TEC, PO Box 1207, 3430 BE Nieuwegein. Comparison of multialkali and GaAs photocathode detectors for Joint European Torus edge light detection and ranging Thomson scattering profiles. United States. https://doi.org/10.1063/1.1787923
Kempenaars, M, Nielsen, P, Pasqualotto, R, Gowers, C, Beurskens, M, Consorzio RFX-Associazione Euratom-Enea sulla Fusione, Corso Stati Uniti 4, I-35127 Padova, EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon, OX14 3DB, and FOM-Rijnhuizen, Ass. Euratom-FOM, TEC, PO Box 1207, 3430 BE Nieuwegein. 2004. "Comparison of multialkali and GaAs photocathode detectors for Joint European Torus edge light detection and ranging Thomson scattering profiles". United States. https://doi.org/10.1063/1.1787923.
@article{osti_20641185,
title = {Comparison of multialkali and GaAs photocathode detectors for Joint European Torus edge light detection and ranging Thomson scattering profiles},
author = {Kempenaars, M and Nielsen, P and Pasqualotto, R and Gowers, C and Beurskens, M and Consorzio RFX-Associazione Euratom-Enea sulla Fusione, Corso Stati Uniti 4, I-35127 Padova and EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon, OX14 3DB and FOM-Rijnhuizen, Ass. Euratom-FOM, TEC, PO Box 1207, 3430 BE Nieuwegein},
abstractNote = {The Joint European Torus (JET) tokamak has two light detection and ranging (LIDAR) Thomson scattering systems, one for the core and one dedicated to the edge T{sub e} and n{sub e} profiles. The LIDAR scheme is unique to JET and is envisaged for use on ITER. The system's spatial resolution is defined by the convolution product of its components: laser pulse duration, detector response time, and digitizer speed. The original multialkali photocathode microchannel plate photomultipliers dictated the response time, resulting in a 12 cm spatial resolution along the line of sight. In the edge LIDAR system, this is improved by aligning the line of sight with the flux surfaces, thus improving the effective spatial resolution to 2 cm depending on the plasma configuration. To meet demands for better edge gradient resolution, an upgrade to higher quantum efficiency detectors was proposed. Four GaAs photocathode detectors have been procured, two of which surpass expectations. These detectors are shown to have a more than two times higher effective quantum efficiency and their response time is at least twice as fast as the multialkali detectors. Combined with a fast digitizer this improves the spatial resolution by a factor of two, down to one centimeter effective, depending on plasma configuration.},
doi = {10.1063/1.1787923},
url = {https://www.osti.gov/biblio/20641185}, journal = {Review of Scientific Instruments},
issn = {0034-6748},
number = 10,
volume = 75,
place = {United States},
year = {Fri Oct 01 00:00:00 EDT 2004},
month = {Fri Oct 01 00:00:00 EDT 2004}
}