Effect of He addition to Ar as the discharge gas on the substrate surface temperature during thermal plasma jet (TPJ) annealing is investigated. The maximum surface temperature (T-max) increases from 1370 to 1470 K with increasing He fraction (R-HE) from 0 to 28%, then decreases to 1040 K with increasing R-HE to 86%. It has been confirmed that the TPJ is efficiently concentrated when He addition is around 30%, which suggests that the increase in T-max= is due to the increase in the power density induced by thermal pinch effect. By adding 30% He and increasing the total gas flow rate to 15.4 L/min, T-max is increased to 1580 K. (c) 2007 Elsevier B.V All rights reserved.