Automated in situ line of sight calibration of ASDEX Upgrade bolometers

Penzel, F.; Meister, H.; Bernert, M.; Sehmer, T.; Trautmann, Thomas; Kannamüller, M.; Koll, J.; Koch, Alexander W.

doi:10.1016/j.fusengdes.2014.03.075

Cited by 3 publications

(2 citation statements)

References 13 publications

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“…The impact on resulting parameters such as the total radiated power of the plasma P rad has to be assessed as a whole because its uncertainty will depend on the used method (e.g. explicit tomographic method and its boundary conditions) and other quantities such the inaccuracies of the LOS characteristics [6] and its alignment [7].…”

Section: Discussion and Further Workmentioning

confidence: 99%

Calibration parameter drift compensation of metal resistive bolometers operating in a thermal varying environment

Penzel

Meister

Giannone

et al. 2017

Fusion Engineering and Design

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The ITER bolometer diagnostic will have to provide accurate measurements of the plasma radiation in a varying thermal environment of up to 250• C. Current fusion experiments perform regular in-situ calibration of the sensor properties, assuming stable calibration parameters within short discharge times, e.g. 10 s on ASDEX Upgrade. For long-pulse fusion experiments, e.g. W7-X, the diagnostic is operated with water cooling for achieving a stable temperature environment. However, ITER will be equipped with about seventy bolometer cameras and is planned to have discharge times of up to 1 h. Due to space restrictions, active cooling is not available for all locations. Thus, an alternative approach is required to allow for compensation of the changing calibration values due to thermal drifts. This paper demonstrates a method using the Wheatstone bridge current of the sensor to calculate in real-time the changing calibration values, such as the heat capacity and the thermal time constant. It is shown, that the thermal calibration parameter drift can be calculated by either extrapolating from the initial values or using a previously determined look-up table. Measurements in the ITER bolometer vacuum test facility (IBOVAC), used to simulate ITER-relevant thermal and vacuum environment, show that the change of the calibration values can be predicted during repeated thermal cycles over a duration sufficient for ITER discharges and even longer. Confidence intervals for the typical in-situ calibration method are determined and compared with the proposed extrapolation and look-up method for ITER, showing that these methods provide an equivalent quality of the measurement results.

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Section: Discussion and Further Workmentioning

confidence: 99%

Calibration parameter drift compensation of metal resistive bolometers operating in a thermal varying environment

Penzel

Meister

Giannone

et al. 2017

Fusion Engineering and Design

Self Cite

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“…The line-integrated electron density is measured by 5 interferometers with different lines of sight [17]. There are two detectors that measure the total bremsstrahlung radiation and 128 bolometers that measure the line-integrated radiation along different lines of sight [18]. In the lower divertor, the line integrated radiation is measured by an AXUV camera along 16 lines of sight [19].…”

Section: Aug Real-time Diagnosticsmentioning

confidence: 99%

Overview of advances in ASDEX Upgrade plasma control to support critical physics research for ITER and beyond

Kudlacek,

David,

Gomez

et al. 2024

Nucl. Fusion

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The successful operation of fusion reactors requires operatingscenarios with good core confinement and acceptable first wall heat loads, thatare stable and robust to external perturbations. This poses both physical andtechnological challenges. One of the technologies addressing these challengesis a complex feedback control system. They support advances in physicalunderstanding and help to ensure stable operating conditions. Operatingmarginally stable plasmas often leads to off-normal events (such as disruptions)and feedback control can prevent these to some extent.This contribution gives an overview of the main results of the developmentand operation of the feedback control algorithms on ASDEX Upgrade (AUG).Fueling actuators, using a combination of gas valves and pellet injection, cansimultaneously control neutral density of the divertor and the density of theplasma core above the Greenwald limit. Impurity injection is employed to controlthe position of the X-point radiator, allowing the creation of an ELM-suppressedH-mode with high radiation fraction. Heating actuators are used to controlthe plasma energy content, which supports advanced tokamak experiments andenables stable I-mode operation, and the electron temperature control, whichsupports turbulence studies. In control technology, AUG has pioneered the useof virtual actuators, which allow effective use of the limited number of heatingactuators, adaptive control policies, and exception handling. Such technologieswill also be used in ITER. Advanced nonlinear state observers (RAPTOR,RAPDENS) and codes to evaluate the power deposition properties (RABBIT,TORBEAM) are available for routine use in the AUG feedback controllers.Extensive use of the AUG Discharge Control System (DCS) further enhancesthe research capabilities of this machine.

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Design and implementation of a prototype infrared video bolometer (IRVB) in MAST Upgrade

Reinke

Lipschultz

Thornton

et al. 2023

Review of Scientific Instruments

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A prototype infrared video bolometer (IRVB) was successfully deployed in the Mega Ampere Spherical Tokamak Upgrade (MAST Upgrade or MAST-U), the first deployment of such a diagnostic in a spherical tokamak. The IRVB was designed to study the radiation around the lower x-point, another first in tokamaks, and has the potential to estimate emissivity profiles with spatial resolution beyond what is achievable with resistive bolometry. The system was fully characterized prior to installation on MAST-U, and the results are summarized here. After installation, it was verified that the actual measurement geometry in the tokamak qualitatively matches the design; this is a particularly difficult process for bolometers and was done using specific features of the plasma itself. The installed IRVB measurements are consistent both with observations from other diagnostics, including magnetic reconstruction, visible light cameras, and resistive bolometry, as well as with the IRVB-designed view. Early results show that with conventional divertor geometry and only intrinsic impurities (for example, C and He), the progression of radiative detachment follows a similar path to that observed for large aspect ratio tokamaks: The peak of the radiation moves along the separatrix from the targets to the x-point and high-field side midplane with a toroidally symmetric structure that can eventually lead to strong effects on the core plasma inside the separatrix.

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Automated in situ line of sight calibration of ASDEX Upgrade bolometers

Cited by 3 publications

References 13 publications

Calibration parameter drift compensation of metal resistive bolometers operating in a thermal varying environment

Calibration parameter drift compensation of metal resistive bolometers operating in a thermal varying environment

Overview of advances in ASDEX Upgrade plasma control to support critical physics research for ITER and beyond

Design and implementation of a prototype infrared video bolometer (IRVB) in MAST Upgrade

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