Avalanche photodiode based detector for beam emission spectroscopy

Journal Article · Fri Oct 15 04:00:00 EDT 2010 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3488458· OSTI ID:22055738

Dunai, D; Zoletnik, S; Sarkoezi, J ^[1]; Field, A R ^[2]

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1. KFKI Research Institute for Particle and Nuclear Physics, EURATOM Association, P.O. Box 49, H-1525 Budapest (Hungary)
2. EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom)

An avalanche photodiode based (APD) detector for the visible wavelength range was developed for low light level, high frequency beam emission spectroscopy (BES) experiments in fusion plasmas. This solid state detector has higher quantum efficiency than photomultiplier tubes, and unlike normal photodiodes, it has internal gain. This paper describes the developed detector as well as the noise model of the electronic circuit. By understanding the noise sources and the amplification process, the optimal amplifier and APD reverse voltage setting can be determined, where the signal-to-noise ratio is the highest for a given photon flux. The calculations are compared to the absolute calibration results of the implemented circuit. It was found that for a certain photon flux range, relevant for BES measurements ({approx_equal}10{sup 8}-10{sup 10} photons/s), the new detector is superior to both photomultipliers and photodiodes, although it does not require cryogenic cooling of any component. The position of this photon flux window sensitively depends on the parameters of the actual experimental implementation (desired bandwidth, detector size, etc.) Several detector units based on these developments have been built and installed in various tokamaks. Some illustrative results are presented from the 8-channel trial BES system installed at Mega-Ampere Spherical Tokamak (MAST) and the 16-channel BES system installed at the Torus Experiment for Technology Oriented Research (TEXTOR).

• OSTI ID: 22055738
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 10 Vol. 81; 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
AMPLIFIERS
BEAM EMITTANCE
CALIBRATION
COOLING
ELECTRIC POTENTIAL
ELECTRONIC CIRCUITS
EMISSION SPECTROSCOPY
GAIN
MAST TOKAMAK
NOISE
PHOTODIODES
PHOTOMULTIPLIERS
PHOTONS
PLASMA
QUANTUM EFFICIENCY
SIGNAL-TO-NOISE RATIO
TEXTOR TOKAMAK
VISIBLE RADIATION