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

TitleComparison of multialkali and GaAs photocathode detectors for Joint European Torus edge light detection and ranging Thomson scattering profiles
Publication TypeJournal Article
Year of Publication2004
AuthorsM. Kempenaars, P. Nielsen, R. Pasqualotto, C. Gowers, M. Beurskens
JournalReview of Scientific Instruments
Volume75
Number10
Pagination3894-3896
Date PublishedOct
Type of ArticleArticle
ISBN Number0034-6748
Accession NumberISI:000224755900154
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-e and n(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. (C) 2004 American Institute of Physics.

URL<Go to ISI>://000224755900154
Division

Fusion Physics

Department

Instrumentation development

PID

25dc5da24c866c1479455e4575f98b6d

Alternate TitleRev. Sci. Instrum.

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