Constraints on escaping alpha particle detectors for ignited tokamaks

Zweben, S. J.; Boivin, R. L.; Liew, S. L.; Owens, D. K.; Strachan, J.D.; Ulrickson, M.

doi:10.1063/1.1141559

Cited by 8 publications

(2 citation statements)

References 9 publications

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“…In studies of the protons and tritons from DD plasmas in TFTR, it has already been ossible to identify some important features: first-orbit losses; toroidal field ripple-induced d?ffasion of t r a p ed a-particle orbits; ripple-trapped a-particles in the magnetic wells between toroidaffield coils; losses due to MHD instabilities; and beam-ion loss when TAE modes were present. Extrapolating these probes to an ignited tokamak is im ortant but difficult (Zweben et al, 1990B). The probes necessarily have to be close t o the pfasma and therefore sustain very high heat loads, high neutron fluxes and ossibly intense integrated a-particle energy.…”

Section: Alpha Source Measurementmentioning

confidence: 99%

The status of alpha-particle diagnostics

Young

Johnson

1992

Plasma Phys. Control. Fusion

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There is a flurry of activity to complete alpha-particle diagnostics so that they can undergo some ex erimental testing in DT plasmas on J E T or TFTR prior to implementation on ITER. 8uccessful measurements of escaping charged fusion products have been made in DD plasmas, and the a-particle source can be well characterized by neutron profile measurement, These methods can be extrapolated to DT plasmas. Measurement of the confined aarticles requires a new technique. Collective Thomson scattering, methods involvin cgarge-exchange interactions and nuclear reactions with impurities will be discusse5. Some assessment is given of the capabilities of these techniques, bearing in mind the potential for their use in the physics phase of the ITER program. KEYWORDS a-particles; fusion neutral particle anafysis; charge-exchange recombination spectroscopy.

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Section: Alpha Source Measurementmentioning

confidence: 99%

The status of alpha-particle diagnostics

Young

Johnson

1992

Plasma Phys. Control. Fusion

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“…Fast-ions loss detectors (FILD) have been installed in several tokamaks [1][2][3][4] to diagnose the loss of these highly energetic particles [2,5,6]. These losses can, for example, reduce the efficiency of external heating systems like neutral beam injection (NBI) or ion cyclotron resonance heating (ICRH) and damage the plasma facing components [7].…”

Section: Introductionmentioning

confidence: 99%

Thermo-mechanical limits of a magnetically driven fast-ion loss detector in the ASDEX Upgrade tokamak

Hidalgo-Salaverri¹,

Gonzalez-Martin²,

Ayllon-Guerola³

et al. 2022

J. Inst.

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A real-time control system is being developed for a magnetically driven Fast-Ion Loss Detector (FILD) at the ASDEX Upgrade tokamak. The insertion of the diagnostic head will be adjusted in real-time to react to changes in the graphite head temperature, plasma position and appearance of MHD instabilities. The graphite probe head of the detector is exposed to an intense heat flux (located ∼3–5 cm from separatrix). The control algorithm performance is constrained by: the graphite head sublimation temperature, the ultimate stress limit, the reaction time of the controller and the retraction time. In this work, the temperature and thermal induced stress distribution on the probe head are assessed to determine what temperature-related magnitude is the limiting factor. The heat flux at the probe head has been estimated using the time-averaged parallel heat flux measured at the divertor target via infrared thermography. A field line tracing algorithm determines which regions of the probe head receives a weighted heat flux due to shadowing (self-induced or from other structures) and the incidence angle of the field lines. A finite element model is used to simulate the temporal evolution of the graphite head temperature and to obtain the induced thermal stress. The temperature spatial distribution at the probe head is validated against measurements of the probe head for different FILD systems showing a good agreement. These measurements have been obtained from visible cameras with an infrared filter. The model concludes that the maximum stress (∼100 MPa) does not overcome the graphite mechanical limit (170 MPa) and that the probe head is not affected by fatigue. Therefore, the graphite sublimation temperature (2000 °C) is set as the limiting factor of the new control system.

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Operating experiences with the TFTR escaping alpha detectors

Zweben

Boivin

Darrow

et al. 1992

Review of Scientific Instruments

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This paper reviews the operating experiences obtained with a set of scintillator-based escaping fast ion detectors which have been used successfully for several years on the TFTR tokamak. There have been several operational problems which need to be resolved before these detectors are used to measure 3.5 MeV DT alphas in 1993. The main problem has been overheating by edge plasma heat flux for large major radius plasmas, when the detectors were not shadowed by the adjacent limiter. Other problems have been due to runaway electron-induced x-ray flux and scintillator and foil damage.

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Constraints on escaping alpha particle detectors for ignited tokamaks

Cited by 8 publications

References 9 publications

The status of alpha-particle diagnostics

The status of alpha-particle diagnostics

Thermo-mechanical limits of a magnetically driven fast-ion loss detector in the ASDEX Upgrade tokamak

Operating experiences with the TFTR escaping alpha detectors

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