To overcome some problems imvolving the argon ICP-MS, helium ICP-MS device
was developed using an enhanced vortex flow torch. Because a secondary disc
harge in the interface region is the main problem for practical use, we con
structed a new vessel for measuring the discharge. The basic characteristic
s of the plasma in the interface region were measured by a Langmuir probe m
ethod. The electron temperature (T-e) and the electron number density (n(e)
) values at an RF input power of 700 W were 2.7 eV and 3.7 x 10(5) cm(-3),
respectively, for a position 6 mm from the sampler orifice. The T-e values
were higher, but the n(e) values were much lower than these of Ar ICP-MS. T
he probe measurements also indicated that the Mach disk position in this de
vice was about 8 mm from the sampler orifice.