INITIAL BORONIZATION OF PBX-M USING ABLATION FROM SOLID BORONIZED PROBES

Boronization was performed by plasma ablation of two solid boronized t arget probes. Probe-1, in a mushroom shape, consisted of a 10.7% boron ized two-dimensional carbon-carbon composite containing 3.6 g of boron in a B4C binder. Probe-2, in a rectangular shape, consisted of an 86% boronized graphite felt composite containing 19.5 g of 40-mum boron p articles. Probe-1 boronization deposited approximately 26 monolayers O f boron. After boronization with Probe-1, the loop voltage in 1-MW neu tral-beam-heated plasmas decreased 27%, and volt-second consumption de creased 20%. Strong peripheral spectral lines from low-Z elements decr eased by factors of approximately 5. The central oxygen density decrea sed 15 to 20%. Carbon levels initially increased during boronization b ut were significantly reduced after boronization. The total radiated p ower during neutral beam injection decreased by 43%. Probe-2 boronizat ion deposited approximately 70 monolayers. Probe-2 boronization exhibi ted similar improved plasma conditions, but for some parameters, a sma ller percentage change occurred because of the previous boronization w ith Probe-1. The ablation rates of both probes were consistent with fr ont-face temperatures above the boron melting point. The results demon strate the performance of two different boronized probe materials and the relative simplicity and effectiveness of solid target boronization as a convenient, real-time impurity control technique.