Dichroic filters to protect milliwatt far-infrared detectors from megawatt ECRH radiation

Journal Article · Wed Oct 15 04:00:00 EDT 2008 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.2965777· OSTI ID:21266534

Bertschinger, G; Oosterbeek, J W ^[1]; Endres, C P; Lewen, F ^[2]

---

1. Institut fuer Energieforschung-Plasmaphysik, Forschungszentrum Juelich, Association EURATOM-FZJ, Trilateral Euregio Cluster, 52425 Juelich (Germany)
2. I. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany)

Dichroic filters have been used to shield effectively the far infrared (FIR) detectors at the interferometer/polarimeter on TEXTOR. The filters consist of metal foils with regular holes, the hole diameter, the mutual spacing and the thickness of the foils are chosen to transmit radiation at the design frequency with transmission >90%. The attenuation at the low frequency end of the bandpass filter is about 30 dB per octave, the high frequency transmission is between 20% and 40%. The filters have been used to block the stray radiation from the megawatt microwave heating beam to the detectors of the FIR interferometer, operating with power on the detector in the milliwatt range. If required, the low frequency attenuation can be still enhanced, without compromising the transmission in the passband. The FIR interferometer used for plasma density and position control is no longer disturbed by electromagnetic waves used for plasma heating.

• OSTI ID: 21266534
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 10 Vol. 79; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ATTENUATION
BEAMS
CONTROL
DESIGN
ECR HEATING
FILTERS
FOILS
INTERFEROMETERS
MICROWAVE HEATING
PLASMA
PLASMA DENSITY
PLASMA DIAGNOSTICS
POLARIMETERS
RF SYSTEMS
STRAY RADIATION
TEXTOR TOKAMAK
THICKNESS
TRANSMISSION