Operation of Alcator C-Mod with high-Z plasma facing components with and without boronization

E. Marmar; Y. Lin; B. Lipschultz; P. Bonoli; C. Fiore; M. Greenwald; I. Hutchinson; J. Irby; M. Reinke; J. Rice; J. Terry; S. Wolfe; S. Wukitch; D. Whyte; S. Scott

Operation of Alcator C-Mod with high-Z plasma facing components with and without boronization

E. Marmar, Y. Lin, B. Lipschultz, P. Bonoli, C. Fiore, M. Greenwald, I. Hutchinson, J. Irby, M. Reinke, J. Rice, J. Terry, S. Wolfe, S. Wukitch, D. Whyte, S. Scott

Physics

Research output: Chapter in Book/Report/Conference proceeding › Chapter

Abstract

High-Z Plasma Facing Components (PFCs) are considered necessary for reactors due to their low tritium (T) retention, capability to handle high heat fluxes with low erosion, and robustness to nuclear damage and activation. Recent Alcator C-Mod experiments provide divertor tokamak operational experience utilizing all-metallic solid high-Z (molybdenum) PFCs, comparing boronized and unboronized surfaces. To assess the influence of boron coatings in plasma performance, previously deposited boron was removed from all PFC surfaces before the 2005 campaign. Subsequently, ICRF-heated H-modes were readily achieved, but energy confinement enhancements over L-mode were small. Molybdenum radiation is implicated. After boronization the Mo density was reduced by a factor of more than 10, and energy confinement doubled. The positive effects of boronization wear off, correlated with ICRF input energy. On the basis of experiments which included between-shot boronization, as well as from visual inspection, it appears that the Mo affecting the core comes from a small fraction of PFC surfaces, where the boron coating erodes rapidly. The evidence points to sputtering from RF sheath enhancement as the most important erosion mechanism.

Original language	English
Title of host publication	33rd EPS Conference on Plasma Physics 2006, EPS 2006
Pages	17-20
Number of pages	4
Volume	1
Publication status	Published - 1 Jan 2006

Cite this

@inbook{8cbe0d3325454c51a4fb50a714027ad0,

title = "Operation of Alcator C-Mod with high-Z plasma facing components with and without boronization",

abstract = "High-Z Plasma Facing Components (PFCs) are considered necessary for reactors due to their low tritium (T) retention, capability to handle high heat fluxes with low erosion, and robustness to nuclear damage and activation. Recent Alcator C-Mod experiments provide divertor tokamak operational experience utilizing all-metallic solid high-Z (molybdenum) PFCs, comparing boronized and unboronized surfaces. To assess the influence of boron coatings in plasma performance, previously deposited boron was removed from all PFC surfaces before the 2005 campaign. Subsequently, ICRF-heated H-modes were readily achieved, but energy confinement enhancements over L-mode were small. Molybdenum radiation is implicated. After boronization the Mo density was reduced by a factor of more than 10, and energy confinement doubled. The positive effects of boronization wear off, correlated with ICRF input energy. On the basis of experiments which included between-shot boronization, as well as from visual inspection, it appears that the Mo affecting the core comes from a small fraction of PFC surfaces, where the boron coating erodes rapidly. The evidence points to sputtering from RF sheath enhancement as the most important erosion mechanism.",

author = "E. Marmar and Y. Lin and B. Lipschultz and P. Bonoli and C. Fiore and M. Greenwald and I. Hutchinson and J. Irby and M. Reinke and J. Rice and J. Terry and S. Wolfe and S. Wukitch and D. Whyte and S. Scott",

year = "2006",

month = jan,

day = "1",

language = "English",

isbn = "9781622763337",

volume = "1",

pages = "17--20",

booktitle = "33rd EPS Conference on Plasma Physics 2006, EPS 2006",

}

TY - CHAP

T1 - Operation of Alcator C-Mod with high-Z plasma facing components with and without boronization

AU - Marmar, E.

AU - Lin, Y.

AU - Lipschultz, B.

AU - Bonoli, P.

AU - Fiore, C.

AU - Greenwald, M.

AU - Hutchinson, I.

AU - Irby, J.

AU - Reinke, M.

AU - Rice, J.

AU - Terry, J.

AU - Wolfe, S.

AU - Wukitch, S.

AU - Whyte, D.

AU - Scott, S.

PY - 2006/1/1

Y1 - 2006/1/1

N2 - High-Z Plasma Facing Components (PFCs) are considered necessary for reactors due to their low tritium (T) retention, capability to handle high heat fluxes with low erosion, and robustness to nuclear damage and activation. Recent Alcator C-Mod experiments provide divertor tokamak operational experience utilizing all-metallic solid high-Z (molybdenum) PFCs, comparing boronized and unboronized surfaces. To assess the influence of boron coatings in plasma performance, previously deposited boron was removed from all PFC surfaces before the 2005 campaign. Subsequently, ICRF-heated H-modes were readily achieved, but energy confinement enhancements over L-mode were small. Molybdenum radiation is implicated. After boronization the Mo density was reduced by a factor of more than 10, and energy confinement doubled. The positive effects of boronization wear off, correlated with ICRF input energy. On the basis of experiments which included between-shot boronization, as well as from visual inspection, it appears that the Mo affecting the core comes from a small fraction of PFC surfaces, where the boron coating erodes rapidly. The evidence points to sputtering from RF sheath enhancement as the most important erosion mechanism.

AB - High-Z Plasma Facing Components (PFCs) are considered necessary for reactors due to their low tritium (T) retention, capability to handle high heat fluxes with low erosion, and robustness to nuclear damage and activation. Recent Alcator C-Mod experiments provide divertor tokamak operational experience utilizing all-metallic solid high-Z (molybdenum) PFCs, comparing boronized and unboronized surfaces. To assess the influence of boron coatings in plasma performance, previously deposited boron was removed from all PFC surfaces before the 2005 campaign. Subsequently, ICRF-heated H-modes were readily achieved, but energy confinement enhancements over L-mode were small. Molybdenum radiation is implicated. After boronization the Mo density was reduced by a factor of more than 10, and energy confinement doubled. The positive effects of boronization wear off, correlated with ICRF input energy. On the basis of experiments which included between-shot boronization, as well as from visual inspection, it appears that the Mo affecting the core comes from a small fraction of PFC surfaces, where the boron coating erodes rapidly. The evidence points to sputtering from RF sheath enhancement as the most important erosion mechanism.

UR - http://www.scopus.com/inward/record.url?scp=84872657568&partnerID=8YFLogxK

M3 - Chapter

AN - SCOPUS:84872657568

SN - 9781622763337

VL - 1

SP - 17

EP - 20

BT - 33rd EPS Conference on Plasma Physics 2006, EPS 2006

ER -

Operation of Alcator C-Mod with high-Z plasma facing components with and without boronization

Abstract

Other files and links

Cite this