Measurements of plasma properties in an interface for helium ICP-MS using a Langmuir probe

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.