Bolometer developments in diagnostics for magnetic confinement fusion

Meister, H.; Bernert, M.; Biel, W.; Han, Ming; Ingesson, L. C.; Mukai, K.; Penzel, F.; Peterson, B.J.; Reichle, R.; Reinke, M.L.; Schmitt, Stefan; Zhang, D.

doi:10.1088/1748-0221/14/10/c10004

Cited by 18 publications

(10 citation statements)

References 41 publications

(50 reference statements)

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“…A 20× increase in the Ne puff results in the core radiation increasing from 4 MW to 8 MW. The movement of the simulated radiation front is expected to be observable by the ITER bolometry system [27,28], and the reduction in the divertor flux and T e is inversely proportional to the Ne puff level without discontinuous behavior that is sometimes observed in experiment and simulation, e.g., the 'T e cliff' seen in DIII-D [24,29]. These observations are promising for potential control of the detachment level by gas input.…”

Section: Discussionmentioning

confidence: 86%

High gas throughput SOLPS-ITER simulations extending the ITER database to strong detachment

et al. 2022

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SOLPS-ITER simulations performed for $Q_{DT}$ = 10, $P_{SOL}$ = 100 MW burning plasmas on ITER extend the existing database to high values of separatrix averaged neon impurity concentration ($\cne$ $\approx$ 6\%) and divertor neutral pressure ($\pdiv$ $>$ 25 Pa) in order to determine the heat flux mitigation capability of these scenarios and whether strongly detached states are accessible. In the existing database of ITER simulations, the level of detachment was limited to cases where the integral ion flux to the outer target was greater than 80\% of the value at rollover, with the impurity radiation localized near the target. With the possibility of narrow heat flux channels and increased deposited power due to tile shaping, it is important to explore operation at a higher degree of detachment. Two series of simulations were explored to extend the database of SOLPS simulations. By increasing the deuterium and neon puff rates proportionally, the peak divertor energy flux ($\qpm$) is decreased from 5 to 3 $\mathrm{MW/m^2}$ while $\pdiv$ increased from 11 to 27 Pa. By increasing only the neon puff, $q_{\perp,max}$ can be reduced to $\mathrm{< 1 MW/m^2}$ while $\pdiv$ is maintained at $\sim 11$ Pa. As the neon puff level is increased, the position of the impurity radiation peak is shifted towards the X-point. At the highest neon puff levels with steady-state solutions, the electron temperature is reduced below 1 eV across 50 cm of each divertor target. The new cases extend previously observed tight relationships in power and momentum loss factors to low electron temperature.

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Section: Discussionmentioning

confidence: 86%

High gas throughput SOLPS-ITER simulations extending the ITER database to strong detachment

et al. 2022

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“…The detectors are particularly sensitive to impurity line radiation, whose spectrum is mainly in the VUV and soft x-ray (SXR) range (300 nm to 0.2 nm). Both the substrate and the Pt resistors are radiation resistant, and the overall design is a prototype for the ITER bolometer detectors under development [40]. The production variations between the sensor and the reference resistors are <2%, providing low offsets of the bolometer bridge, which is important to reduce the effects of thermal offset drift on signal accuracy [41], especially for long-pulse, high-power discharges.…”

Section: The Bolometer Diagnosticmentioning

confidence: 99%

Bolometer tomography on Wendelstein 7-X for study of radiation asymmetry

et al. 2021

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The algorithm for bolometer tomography at Wendelstein 7-X (W7-X) has been recently improved using a novel regularization functional, based on relative gradient smoothing of the sought radiation profile. It has been validated using radiation patterns provided by 3D modeling under real plasma conditions as phantoms and then applied to bolometer measurements performed during the first divertor operation phase of W7-X. The following results are presented: (1) edge-localized 2D radiation patterns with clearly resolved magnetic island radiation structures, (2) an up-down asymmetry in the impurity radiation that is not captured by the 3D edge plasma transport modeling, (3) reversal of the asymmetry with reversed magnetic field direction. Further analysis reveals a poloidal variation of the emissivity in the outer confined plasma region with a field-direction dependent asymmetry, also supported by the soft x-ray measurements. This asymmetry is considered to be related to asymmetric impurity distributions, driven by the pronounced ion-impurity friction force at the plasma edge where the collisionality of the W7-X plasma is sufficiently high to develop impurity asymmetry as predicted by neoclassical theory of parallel impurity transport.

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“…Especially for the understanding of the plasma radiation distribution during impurity seeding [2], used to reduce the heat load on the divertor through enhanced radiation, two-dimensional (2D) radiation profiles, obtained through tomographic inversion of line averaged signals from collimated bolometer detectors [3]- [5], will play the main role. The resistive bolometer is a standard diagnostic and will be installed in ITER as the main bolometer diagnostic [6]. The resistive bolometers are typically installed in arrays distributed around a single poloidal cross-section to give the 2D radiation profile at that toroidal location [3].…”

Section: Introductionmentioning

confidence: 99%

Estimates of foil thickness, signal, noise, and nuclear heating of imaging bolometers for ITER

Peterson¹,

Nishitani²,

Reichle³

et al. 2022

J. Inst.

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Imaging bolometers have been studied for ITER to serve as a complementary diagnostic to the resistive bolometers for the measurement of radiated power. Two tangentially viewing InfraRed imaging Video Bolometers (IRVB) could be proposed for an ITER equatorial port, one having a view of the entire plasma cross-section (core viewing) and one tilted down 43 degrees from the horizontal to view the divertor (divertor viewing). The IRVBs have 7 cm (horizontal) by 9 cm (vertical) Pt sensor foils, 6 mm × 6 mm apertures, 15 × 20 pixels and focal lengths of 7.8 cm and 21 cm, respectively. Using SANCO and SOLPS models for a 840 m3 plasma radiating 67.3 MW, synthetic images from the IRVBs are calculated to estimate the maximum signal strengths to be 246 W/m2 and 62 W/m2, respectively. We propagate the X-ray energy spectra from the models through the synthetic diagnostics to give the photon energy spectrum for each IRVB pixel, which are used to calculate the fraction of the power absorbed by the foil as a function of foil thickness. Using a criteria of >95% absorbed power fraction, we selected foil thicknesses of 30 μm and 10 μm, respectively. We used these thicknesses and assumed IR systems having 105 fps, 1024×1280 pixels and sensitivities of 15 mK, to calculate the IRVB sensitivities of 3.19 W/m2 and 1.05 W/m2, and signal to noise ratios of 77 and 59, respectively. Using the Monte Carlo Nuclear Particle code we calculated for the core viewing IRVB the foil heating by neutrons to be 1.0 W/m2 and by gammas to be 117 W/m2. This indicates that countermeasures may be needed to remove the nuclear heating signal.

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Bolometer developments in diagnostics for magnetic confinement fusion

Cited by 18 publications

References 41 publications

High gas throughput SOLPS-ITER simulations extending the ITER database to strong detachment

High gas throughput SOLPS-ITER simulations extending the ITER database to strong detachment

Bolometer tomography on Wendelstein 7-X for study of radiation asymmetry

Estimates of foil thickness, signal, noise, and nuclear heating of imaging bolometers for ITER

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