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

Journal Article · Sun Dec 15 04:00:00 EST 2013 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4834755· OSTI ID:22220215

Meister, H.; Willmeroth, M. ^[1]; Zhang, D. ^[2]; Gottwald, A.; Krumrey, M.; Scholze, F. ^[3]

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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)

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{sub 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.

• OSTI ID: 22220215
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 12 Vol. 84; 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
ABSORPTION
BESSY STORAGE RING
EV RANGE 01-10
ITER TOKAMAK
KEV RANGE
LASERS
LIGHT SOURCES
PHOTODIODES
POWER METERS
SILICON NITRIDES
SYNCHROTRON RADIATION
X RADIATION