ICRF boronization - A new technique towards high efficiency wall coating for superconducting tokamak reactors

Abstract

A new technique for wall conditioning that will be especially useful for future larger superconducting tokamaks, such as ITER, has been successfully developed and encouraging results have been obtained. Solid carborane powder, which is non-toxic and non-explosive, was used. Pulsed RF plasma was produced by a non-Faraday shielding RF antenna with RF power of 10 kW. The ion temperature was about 2 keV with a toroidal magnetic field of 1.8 T and a pressure of 3 × 10-1 Pa. Energetic ions broke up the carborane molecules, and the resulting boron ions struck and were deposited on the first wall. In comparison with glow discharge cleaning boronization, the B/C coating film shows higher adhesion, more uniformity and longer lifetime during plasma discharges. The plasma performance was improved after ICRF boronization.

ICRF Wall Conditioning: Present Status and Developments for Future Superconducting Fusion Machines

“…Given this feature and the encouraging conditioning/cleaning results recently achieved on the present-day tokamaks and stellarators (summarized in Refs. [4][5][6][7][9][10][11][12][13][14][15][16]), ICWC was recently confirmed as a functional requirement on the ITER ICRF heating and current drive system [17]. Therefore, further development of the ITER relevant ICWC scenarios with conventional ICRF antennas is an important and urgent task.…”

“…Plasma density build-up and its homogeneity: The plasma production process has been studied in present-day tokamaks and stellarators under various conditions [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][20][21][22][23]. The ICRF plasmas with typical density n e ≈3×10…”

Vacuum operation of first divertor campaign on EAST

“…CVV has two parts, main body and current lead part. The former contains all the superconducting coils and inner and outer thermal shields with the volume of about 160 m 3 . The later is comprised of two current lead tanks and current lead transfer lines, and the volume is about 22 m 3 .…”

“…The primary advantage is that it could be applied with the existing of the toroidal magnetic field. The technique was successfully used on HT-7 [3], and becomes one of the routine conditioning methods, especially for boronization and between discharges.…”

“…In the HT-7 superconducting tokamak campaigns, it's observed that boronization could suppress efficiently the high and low Z impurities in the plasma [3]. Same material, carborane (C 2 B 10 H 12 ) is used for EAST.…”