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Title: Broad-band efficiency calibration of ITER bolometer prototypes using Pt absorbers on SiN membranes

The energy resolved efficiency of two bolometer detector prototypes for ITER with 4 channels each and absorber thicknesses of 4.5 μm and 12.5 μm, respectively, has been calibrated in a broad spectral range from 1.46 eV up to 25 keV. The calibration in the energy range above 3 eV was performed against previously calibrated silicon photodiodes using monochromatized synchrotron radiation provided by five different beamlines of Physikalische Technische Bundesanstalt at the electron storage rings BESSY II and Metrology Light Source in Berlin. For the measurements in the visible range, a setup was realised using monochromatized halogen lamp radiation and a calibrated laser power meter as reference. The measurements clearly demonstrate that the efficiency of the bolometer prototype detectors in the range from 50 eV up to ≈6 keV is close to unity; at a photon energy of 20 keV the bolometer with the thick absorber detects 80% of the photons, the one with the thin absorber about 50%. This indicates that the detectors will be well capable of measuring the plasma radiation expected from the standard ITER scenario. However, a minimum absorber thickness will be required for the high temperatures in the central plasma. At 11.56 keV, the sharp Pt-L{submore » 3} absorption edge allowed to cross-check the absorber thickness by fitting the measured efficiency to the theoretically expected absorption of X-rays in a homogeneous Pt-layer. Furthermore, below 50 eV the efficiency first follows the losses due to reflectance expected for Pt, but below 10 eV it is reduced further by a factor of 2 for the thick absorber and a factor of 4 for the thin absorber. Most probably, the different histories in production, storage, and operation led to varying surface conditions and additional loss channels.« less
Authors:
;  [1] ;  [2] ; ; ;  [3]
  1. Max-Planck-Institut für Plasmaphysik (IPP), EURATOM Association, Boltzmannstr. 2, 85748 Garching (Germany)
  2. Max-Planck-Institut für Plasmaphysik (IPP), EURATOM Association, Teilinstitut Greifswald, Wendelsteinstraße 1, 17491 Greifswald (Germany)
  3. Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin (Germany)
Publication Date:
OSTI Identifier:
22220215
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 84; Journal Issue: 12; Other Information: (c) 2013 Euratom; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ABSORPTION; BESSY STORAGE RING; EV RANGE 01-10; ITER TOKAMAK; KEV RANGE; LASERS; LIGHT SOURCES; PHOTODIODES; POWER METERS; SILICON NITRIDES; SYNCHROTRON RADIATION; X RADIATION