Plasma Treatment of Bulk Niobium Surfaces for SRF Cavities

Two types of electric discharges were used to demonstrate the validity of plasma surface treatment for superconducting radio-frequency (SRF) cavities. The experiments were performed on disc-shaped Nb samples and compared with identical samples treated with buffer chemical polishing (BCP) techniques. Surface analysis indicates comparable or superior properties of plasma-treated samples. These promising results are still preliminary and additional work is in progress

Cross sections and transport properties of positive ions in BF3 plasmas

Boron produced in plasma devices continues to be the main p-type dopant in ion implantation of semiconductor devices. Yet plasma parameters of most frequently used Boron rich gas, BF3, are not well established. Time resolved measurements of ion energy distributions in the cathode boundary [1] of a pulsed dc plasma doping system revealed possible role of the charge-transfer collisions between singly charged ions of various mass. The cross sections for scattering of B+, BF+ and BF2+ ions on BF3 molecule are calculated by using Nanbu's theory [2] separating elastic from reactive collisions. A Monte Carlo simulation technique was applied to perform calculations of transport parameters in DC electric fields