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

TLDR

The technique uses solid carborane powder and a 10 kW pulsed‑RF plasma generated by a non‑Faraday shielding antenna, with 2 keV ions in a 1.8 T field at 3×10⁻¹ Pa, to dissociate carborane and deposit boron ions onto the first wall. ICRF boronization yields a B/C coating with superior adhesion, uniformity, and lifetime compared to glow‑discharge cleaning, and improves plasma performance in superconducting tokamak reactors such as ITER.

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.