Conventional equipments used for low pressure plasma spraying are designed for a chamber pressure of a few tens of mbar. During the past three years, an increasing interest for thermal spray under very low pressure conditions (as low as 1 mbar) was encountered but no significant advances concerning the spray gun design was proposed. However, it is clear that actual tools do not allow providing uniform plasma jets and that the produced jets present successive expansions and constrictions due to a poor adaptation of the nozzle exit pressure regarding to the chamber one. In the present paper, the use of a nozzle extension is proposed. The holding nozzle is a lengthened F4 type one and the diverging part of the nozzle is formed by a fastened external extension. The design of the nozzle extension is a bell-contoured Laval type one and its dimensions (exit diameter and length) are much higher than for conventional diverging nozzles. An improvement in the jet homogeneity and uniformity is expected.