Advances in radiated power control at DIII-D

D. Eldon; E. Kolemen; D. A. Humphreys; A. W. Hyatt; Aaro Järvinen; A. W. Leonard; A. G. McLean; A. L. Moser; T. W. Petrie; M. L. Walker

doi:10.1016/j.nme.2019.01.010

Advances in radiated power control at DIII-D

D. Eldon, E. Kolemen, D. A. Humphreys, A. W. Hyatt, Aaro Järvinen, A. W. Leonard, A. G. McLean, A. L. Moser, T. W. Petrie, M. L. Walker

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Research output: Contribution to journal › Article › Scientific › peer-review

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Abstract

Feedback control of radiated power from the lower divertor P _{rad, div, L} has been implemented in the DIII-D Plasma Control System (PCS). A realtime sensor for P _{rad, div, L} has been constructed from 12 foil bolometer channels which agrees with standard post-shot analysis to within 20%. Results with the 12-channel sensor are compared to initial proof-of-concept tests with a single channel as a proxy for P _{rad, div, L} , showing that the upgraded sensor is necessary to overcome limitations of the proxy channel strategy in DIII-D. Using N ₂ seeding under feedback control, P _{rad, div, L} has been increased by up to 150% above unseeded levels, and a radiated power fraction f _rad of 80% has been demonstrated, although feedback controlled gas flow is steadier at f _rad = 55%. Spatial coverage is broad enough to enable P _rad control during the strike point sweeps which are commonly used to generate pseudo-2D divertor Thomson measurements in DIII-D divertor experiments. Use of this control reveals challenges that may affect next step devices, which will require actively controlled extrinsic impurity seeding in order to manage heat loads. When operating at high f _rad , changes in pedestal T _e (caused by ELMs in these experiments but could come from other disturbances) resulted in large perturbations to P _rad which were destabilizing to the feedback controller.

Original language	English
Pages (from-to)	285-290
Number of pages	6
Journal	Nuclear Materials and Energy
Volume	18
DOIs	https://doi.org/10.1016/j.nme.2019.01.010
Publication status	Published - Jan 2019
MoE publication type	A1 Journal article-refereed

Keywords

Divertor
Fusion
Plasma control
Radiation
Tokamak

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1016/j.nme.2019.01.010

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title = "Advances in radiated power control at DIII-D",

abstract = " Feedback control of radiated power from the lower divertor P rad, div, L has been implemented in the DIII-D Plasma Control System (PCS). A realtime sensor for P rad, div, L has been constructed from 12 foil bolometer channels which agrees with standard post-shot analysis to within 20%. Results with the 12-channel sensor are compared to initial proof-of-concept tests with a single channel as a proxy for P rad, div, L , showing that the upgraded sensor is necessary to overcome limitations of the proxy channel strategy in DIII-D. Using N 2 seeding under feedback control, P rad, div, L has been increased by up to 150% above unseeded levels, and a radiated power fraction f rad of 80% has been demonstrated, although feedback controlled gas flow is steadier at f rad = 55%. Spatial coverage is broad enough to enable P rad control during the strike point sweeps which are commonly used to generate pseudo-2D divertor Thomson measurements in DIII-D divertor experiments. Use of this control reveals challenges that may affect next step devices, which will require actively controlled extrinsic impurity seeding in order to manage heat loads. When operating at high f rad , changes in pedestal T e (caused by ELMs in these experiments but could come from other disturbances) resulted in large perturbations to P rad which were destabilizing to the feedback controller. ",

keywords = "Divertor, Fusion, Plasma control, Radiation, Tokamak",

author = "D. Eldon and E. Kolemen and Humphreys, {D. A.} and Hyatt, {A. W.} and Aaro J{\"a}rvinen and Leonard, {A. W.} and McLean, {A. G.} and Moser, {A. L.} and Petrie, {T. W.} and Walker, {M. L.}",

note = "Funding Information: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, 1 Publisher Copyright: {\textcopyright} 2019",

year = "2019",

month = jan,

doi = "10.1016/j.nme.2019.01.010",

language = "English",

volume = "18",

pages = "285--290",

journal = "Nuclear Materials and Energy",

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AU - Eldon, D.

AU - Kolemen, E.

AU - Humphreys, D. A.

AU - Hyatt, A. W.

AU - Järvinen, Aaro

AU - Leonard, A. W.

AU - McLean, A. G.

AU - Moser, A. L.

AU - Petrie, T. W.

AU - Walker, M. L.

PY - 2019/1

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N2 - Feedback control of radiated power from the lower divertor P rad, div, L has been implemented in the DIII-D Plasma Control System (PCS). A realtime sensor for P rad, div, L has been constructed from 12 foil bolometer channels which agrees with standard post-shot analysis to within 20%. Results with the 12-channel sensor are compared to initial proof-of-concept tests with a single channel as a proxy for P rad, div, L , showing that the upgraded sensor is necessary to overcome limitations of the proxy channel strategy in DIII-D. Using N 2 seeding under feedback control, P rad, div, L has been increased by up to 150% above unseeded levels, and a radiated power fraction f rad of 80% has been demonstrated, although feedback controlled gas flow is steadier at f rad = 55%. Spatial coverage is broad enough to enable P rad control during the strike point sweeps which are commonly used to generate pseudo-2D divertor Thomson measurements in DIII-D divertor experiments. Use of this control reveals challenges that may affect next step devices, which will require actively controlled extrinsic impurity seeding in order to manage heat loads. When operating at high f rad , changes in pedestal T e (caused by ELMs in these experiments but could come from other disturbances) resulted in large perturbations to P rad which were destabilizing to the feedback controller.

AB - Feedback control of radiated power from the lower divertor P rad, div, L has been implemented in the DIII-D Plasma Control System (PCS). A realtime sensor for P rad, div, L has been constructed from 12 foil bolometer channels which agrees with standard post-shot analysis to within 20%. Results with the 12-channel sensor are compared to initial proof-of-concept tests with a single channel as a proxy for P rad, div, L , showing that the upgraded sensor is necessary to overcome limitations of the proxy channel strategy in DIII-D. Using N 2 seeding under feedback control, P rad, div, L has been increased by up to 150% above unseeded levels, and a radiated power fraction f rad of 80% has been demonstrated, although feedback controlled gas flow is steadier at f rad = 55%. Spatial coverage is broad enough to enable P rad control during the strike point sweeps which are commonly used to generate pseudo-2D divertor Thomson measurements in DIII-D divertor experiments. Use of this control reveals challenges that may affect next step devices, which will require actively controlled extrinsic impurity seeding in order to manage heat loads. When operating at high f rad , changes in pedestal T e (caused by ELMs in these experiments but could come from other disturbances) resulted in large perturbations to P rad which were destabilizing to the feedback controller.

KW - Divertor

KW - Fusion

KW - Plasma control

KW - Radiation

KW - Tokamak

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JO - Nuclear Materials and Energy

JF - Nuclear Materials and Energy

ER -

Advances in radiated power control at DIII-D

Abstract

Keywords

UN SDGs

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