Design of a diagnostic residual gas analyzer for the ITER divertor

Biewer, T. M.; Graves, Van; Andrew, P.; Pat, Lukens,; Shimada, M.; Hughes, S.; Boussier, B.; Johnson, D.; Hillis, D.L.; Vayakis, G.; Walsh, M.

doi:10.1016/j.fusengdes.2015.04.053

Cited by 13 publications

(7 citation statements)

References 5 publications

(2 reference statements)

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“…The JET neutral gas analysis system of JET has been improved for the upcoming DT operation. In particular the newly upgraded sub-divertor gas analysis diagnostic with its new OGA and radiation hard RGAs, compatible with the ITER environment, will provide vital input to the development of the ITER DRGA [22] in the most relevant environment currently available.…”

Section: Discussionmentioning

confidence: 99%

Neutral gas analysis for JET DT operation

et al. 2020

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Section: Discussionmentioning

confidence: 99%

Neutral gas analysis for JET DT operation

et al. 2020

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“…The OGA, a spectroscopic observation of a cold plasma discharge of residual gas at elevated pressure, is a secondary system for gas composition analysis included in the DRGA system [1].…”

Section: B In-vessel Residence Timementioning

confidence: 99%

Improvements on the Diagnostic Residual Gas Analyzer at Wendelstein 7-X

Schlisio

Ravelli

Harris

et al. 2022

IEEE Trans. Plasma Sci.

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Exhaust gas analysis provides key information on fusion processes, divertor operation, and wall state in fusion experiments and future reactors. The diagnostic residual gas analyzer (DRGA) concept has been developed for ITER with a focus on fast helium and hydrogen isotope detection. The first operation of the prototype DRGA (P-DRGA) at the stellarator Wendelstein 7-X showed potential for improvement in terms of magnetic sensor shielding, data acquisition automation, and potential new additions to the cluster of sensors on the P-DRGA. More recently, a Monte Carlo simulation of the flow of the mixed gas species effluent from the pressure-reducing orifice, down to about 8-m sampling tube and into the analysis region of the sensors, has been found to generally agree with previous calculations and measurements but revealed potential backstreaming effects for light gases, with impact on detection limits both for the prototype and for the ITER DRGA currently in design. For the upcoming campaign of the prototype, an enhanced soft iron shield will safeguard the gauges against magnetic stray field influence. The newly introduced shielding has been tested for its effect on magnetic stray fields and found to reduce the inside residual field by about two orders of magnitude.

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“…Due to this, these techniques commonly struggle with having a response time compatible with plasma particle and impurity lifetimes in the divertor region. However clever vacuum engineering can mit- igate this effect 10 . The Wisconsin In-Situ Penning gauge was developed to fill this gap and offers a first in-situ partial neutral pressure measurement in magnetic fusion devices.…”

Section: Introductionmentioning

confidence: 99%

Wisconsin In Situ Penning (WISP) gauge: A versatile neutral pressure gauge to measure partial pressures in strong magnetic fields

Kremeyer

Flesch

Schmitz

et al. 2020

Review of Scientific Instruments

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A new type of in-vessel Penning gauge, the Wisconsin In-Situ Penning (WISP) gauge, has been developed and successfully operated in the Wendelstein 7-X (W7-X) island divertor baffle and vacuum vessel. The capacity of the quantitative measurements of the neutral reservoir for light impurities, in particular helium, is important for tokamaks as well as stellarator divertors in order to avoid fuel dilution and radiative energy loss. Penning gauges assisted by spectroscopy are a powerful tool to obtain the total neutral pressure as well as fractional neutral pressures of specific impurities. The WISP gauge is a miniaturized Penning gauge arrangement, which exploits the ambient magnetic field of magnetic confinement fusion experiments to establish the Penning discharge. Then, in-situ spectroscopy is conducted to separate the fractional neutral pressures of hydrogen, helium and possibly also other impurities. The WISP probe head was qualified using the magnetic field of the Magnetized Dusty Plasma Experiment, MDPX, at Auburn University between 0.25 T and 3.5 T [E. Thomas, Journal of Plasma Physics 81 ( 2015)]. The in-depth quantitative evaluation for hydrogen and helium will be shown as well as an exploration of nitrogen, argon and neon. A power law scaling between current I and pressure p: I = f (Gas,V) • p n(Gas, B) was shown. The factor f is gas and anode potential dependent, while n is gas and magnetic field strength dependent. Pressure measurements from 0.1 mbar and down to 1 × 10 −5 mbar were achieved, demonstrating a reliable operation range for relevant pressure levels in the divertor and main vessel regions in current and future fusion devices, with a time resolution of up to 1 kHz. The lowest achievable pressure measurement increases with increasing B and can be shifted with the anode potential V .At Wendelstein 7-X the WISP probe head was mounted on an immersion tube set up that reaches through the cryostat and places the probe head close to the plasma. Two probe heads were positioned in the different divertor pump gaps, top and bottom, and one close to the plasma on the mid-plane in one module. The gauges were in-situ calibrated together with the ASDEX pressure gauges [G. Haas and H. Bosch, Vacuum 51, 39 (1998)]. Data was taken during the entire operation phase 1.2b (OP1.2b) and measurements were coherent with other neutral gas pressure gauges. For the spectroscopic partial pressure measurements, channels of a spectroscopic detection system based on photo-multipliers, so-called Filterscope [R. Colchin, Review of scientific instruments 74, 2068 (2003)] provided by Oak Ridge National Lab (ORNL) were used.

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Design of a diagnostic residual gas analyzer for the ITER divertor

Cited by 13 publications

References 5 publications

Neutral gas analysis for JET DT operation

Neutral gas analysis for JET DT operation

Improvements on the Diagnostic Residual Gas Analyzer at Wendelstein 7-X

Wisconsin In Situ Penning (WISP) gauge: A versatile neutral pressure gauge to measure partial pressures in strong magnetic fields

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