A new SF₆ inlet system with a modified Faraday collector alignment of Finnigan MAT-251 mass spectrometer for sulfur isotope measurement

抄録

A new inlet system for the preparation of SF₆ gas by fluorination of sulfide minerals, suitable for both in-situ laser ablation and powder samples, was connected to the existing CO₂ inlet system of the Finnigan MAT-251 mass spectrometer at Shizuoka University. The preparation line is composed of a fluorine generator, two types of reaction chambers, capacitance manometer, KBr canister and liquid nitrogen slush connected by pneumatic bellows valves. It also includes a working standard SF₆ gas reservoir and a machine standard SF₆ gas reservoir for routine analyses. The preparation line can hold high vacuum conditions without appreciable leaks for intervals more than that required to complete one sample measurement. For simultaneous measurement of [127], [128], [129] and [131] isotopes of SF₅⁺, we have renovated Faraday collectors by reducing its body thickness from 4.5 mm to 3.5 mm and realigned the collector configuration of the mass spectrometer. Preliminary results of δ³⁴S values for working standard SF₆ gas gave high precession of ±0.003‰ . Further modifications in the collector assembly are in progress for the simultaneous measurement of the closely spaced ion trajectory of [127], [128] and [129] isotopes of SF₅⁺.