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Title: Long pulse EBW start-up experiments in MAST

Abstract

Start-up technique reported here relies on a double mode conversion (MC) for electron Bernstein wave (EBW) excitation. It consists of MC of the ordinary (O) mode, entering the plasma from the low field side of the tokamak, into the extraordinary (X) mode at a mirror-polarizer located at the high field side. The X mode propagates back to the plasma, passes through electron cyclotron resonance (ECR) and experiences a subsequent X to EBW MC near the upper hybrid resonance (UHR). Finally the excited EBW mode is totally absorbed at the Doppler shifted ECR. The absorption of EBW remains high even in cold rarefied plasmas. Furthermore, EBW can generate significant plasma current giving the prospect of a fully solenoid-free plasma start-up. First experiments using this scheme were carried out on MAST [1]. Plasma currents up to 33 kA have been achieved using 28 GHz 100kW 90ms RF pulses. Recently experimental results were extended to longer RF pulses showing further increase of plasma currents generated by RF power alone. A record current of 73kA has been achieved with 450ms RF pulse of similar power. The current drive enhancement was mainly achieved due to RF pulse extension and further optimisation of the start-up scenario.

Authors:
 [1];  [1];  [2];  [2];  [2];  [2];  [1];  [1];  [1];  [1];  [1];  [2];  [3];  [4];  [5];  [6]
  1. Culham Science Centre, Abingdon (United Kingdom)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Ioffe Institute, St. Petersburg (Russia)
  4. Univ. of Tokyo, Kashiwa (Japan)
  5. Kyoto Univ., Kyoto (Japan)
  6. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1214589
Grant/Contract Number:
AC02-09CH11466
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
EPJ Web of Conferences
Additional Journal Information:
Journal Volume: 87; Journal ID: ISSN 2100-014X
Publisher:
EDP Sciences
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Shevchenko, V. F., Baranov, Y. F., Bigelow, T., Caughman, J. B., Diem, S., Dukes, C., Finburg, P., Hawes, J., Gurl, C., Griffiths, J., Mailloux, J., Peng, M., Saveliev, A. N., Takase, Y., Tanaka, H., and Taylor, G. Long pulse EBW start-up experiments in MAST. United States: N. p., 2015. Web. doi:10.1051/epjconf/20158702007.
Shevchenko, V. F., Baranov, Y. F., Bigelow, T., Caughman, J. B., Diem, S., Dukes, C., Finburg, P., Hawes, J., Gurl, C., Griffiths, J., Mailloux, J., Peng, M., Saveliev, A. N., Takase, Y., Tanaka, H., & Taylor, G. Long pulse EBW start-up experiments in MAST. United States. doi:10.1051/epjconf/20158702007.
Shevchenko, V. F., Baranov, Y. F., Bigelow, T., Caughman, J. B., Diem, S., Dukes, C., Finburg, P., Hawes, J., Gurl, C., Griffiths, J., Mailloux, J., Peng, M., Saveliev, A. N., Takase, Y., Tanaka, H., and Taylor, G. 2015. "Long pulse EBW start-up experiments in MAST". United States. doi:10.1051/epjconf/20158702007. https://www.osti.gov/servlets/purl/1214589.
@article{osti_1214589,
title = {Long pulse EBW start-up experiments in MAST},
author = {Shevchenko, V. F. and Baranov, Y. F. and Bigelow, T. and Caughman, J. B. and Diem, S. and Dukes, C. and Finburg, P. and Hawes, J. and Gurl, C. and Griffiths, J. and Mailloux, J. and Peng, M. and Saveliev, A. N. and Takase, Y. and Tanaka, H. and Taylor, G.},
abstractNote = {Start-up technique reported here relies on a double mode conversion (MC) for electron Bernstein wave (EBW) excitation. It consists of MC of the ordinary (O) mode, entering the plasma from the low field side of the tokamak, into the extraordinary (X) mode at a mirror-polarizer located at the high field side. The X mode propagates back to the plasma, passes through electron cyclotron resonance (ECR) and experiences a subsequent X to EBW MC near the upper hybrid resonance (UHR). Finally the excited EBW mode is totally absorbed at the Doppler shifted ECR. The absorption of EBW remains high even in cold rarefied plasmas. Furthermore, EBW can generate significant plasma current giving the prospect of a fully solenoid-free plasma start-up. First experiments using this scheme were carried out on MAST [1]. Plasma currents up to 33 kA have been achieved using 28 GHz 100kW 90ms RF pulses. Recently experimental results were extended to longer RF pulses showing further increase of plasma currents generated by RF power alone. A record current of 73kA has been achieved with 450ms RF pulse of similar power. The current drive enhancement was mainly achieved due to RF pulse extension and further optimisation of the start-up scenario.},
doi = {10.1051/epjconf/20158702007},
journal = {EPJ Web of Conferences},
number = ,
volume = 87,
place = {United States},
year = 2015,
month = 3
}

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  • Start-up technique reported here relies on a double mode conversion (MC) for electron Bernstein wave (EBW) excitation. It consists of MC of the ordinary (0) mode, entering the plasma from the low field side of the tokamak, into the extraordinary (X) mode at a mirror-polarizer located at the high field side. The X mode propagates back to the plasma, passes through electron cyclotron resonance (ECR) and experiences a subsequent X to EBW MC near the upper hybrid resonance (UHR). Finally the excited EBW mode is totally absorbed at the Doppler shifted ECR. The absorption of EBW remains high even inmore » cold rarefied plasmas. Furthermore, EBW can generate significant plasma current giving the prospect of a fully solenoid-free plasma start-up. First experiments using this scheme were carried out on MAST [1]. Plasma currents up to 33 kA have been achieved using 28 GHz 100kW 90ms RF pulses. Recently experimental results were extended to longer RF pulses showing further increase of plasma currents generated by RF power alone. A record current of 73kA has been achieved with 450ms RF pulse of similar power. The current drive enhancement was mainly achieved due to RF pulse extension and further optimisation of the start-up scenario.« less
  • Ears of mice were treated with a 0.5% 8-MOP solution topically plus UVA radiation (1.5-2.5 J/cm2). After PUVA radiation, skin responses to intradermal injection with mast cell liberators, including compound 48/80 (2.5 mg/ml, 10 microliter) and concanavalin A (Con-A) (2.0 mg/ml), or with a mixture of 5-hydroxytryptamine (5-HT) and histamine as vasodilator (1.0 mg/ml and 50 mM, respectively) were examined with time (2 h-14 days). At each time point, an ear swelling response (ESR) was measured with a dial thickness gauge. The rate of mast cell degranulation and mast cell numbers were assessed by light microscopy using toluidine blue-stained semithinmore » (1 micron) sections. ESR induced by compound 48/80 or Con-A was significantly suppressed dose-dependently (greater than 42% inhibition) by PUVA between 2 h-3 days postirradiation as compared with that in nonirradiated control mice, and the value returned to normal levels by 7-14 days. Compound 48/80- or Con-A-induced mast cell degranulation (%) was remarkably decreased between 2 h-3 days (greater than 48% inhibition) in accordance with the suppression in ESR and it was restored to the rates in nonirradiated controls by 7-14 days. Neither ESR nor percent degranulation was affected by UVA radiation only (less than 3.5 J/cm2) or application of 8-MOP only. 5-HT plus histamine-mediated ESR was not altered at all by PUVA throughout the experimental period. Since PUVA radiation itself at given doses did not produce measurable ESR, mast cell degranulation, or a reduction in mast cell numbers, and since PUVA did not affect a normal vascular response to vasodilator, it seemed that decreased skin reactivity to mast cell degranulators by PUVA might be due to a PUVA-induced noncytolytic alteration in mast cell release mechanisms.« less
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