Advances in radiated power control at DIII-D

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

doi:10.1016/j.nme.2019.01.010

Title: Advances in radiated power control at DIII-D

Journal Article · Tue Jan 01 00:00:00 EST 2019 · Nuclear Materials and Energy

DOI:https://doi.org/10.1016/j.nme.2019.01.010· OSTI ID:1769975

; Kolemen, E.; Humphreys, D. A.; Hyatt, A. W.; Järvinen, A. E.; Leonard, A. W.; McLean, A. G.; Moser, A. L.;

;

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 N₂ seeding under feedback control, P_{rad, div, L} has been increased by up to 150% above unseeded levels, and a radiated power fraction frad 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 Te (caused by ELMs in these experiments but could come from other disturbances) resulted in large perturbations to Prad which were destabilizing to the feedback controller.

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Research Organization:: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES); USDOE National Nuclear Security Administration (NNSA)

Grant/Contract Number:: AC52-07NA27344; FC02-04ER54698; AC02-09CH11466; SC001587

OSTI ID:: 1769975

Alternate ID(s):: OSTI ID: 1529181

Report Number(s):: LLNL-JRNL-777067; S2352179118301777; PII: S2352179118301777

Journal Information:: Nuclear Materials and Energy, Journal Name: Nuclear Materials and Energy Vol. 18 Journal Issue: C; ISSN 2352-1791

Publisher:: ElsevierCopyright Statement

Country of Publication:: Netherlands

Language:: English

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Cited by: 22 works

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