A Low-Blank, Metal System for Rare-Gas Analysis

Abstract

A low-blank, metal system for extracting and purifying rare gases was constructed to connect with a low-background, metal mass spectrometer which had been used in analyses of xenon previously. In melting samples, different two kinds of inner crucibles are employed, which are put in a tantalum crucible to prevent it from destructive attack by sample materials. With the inner crucible of tantalum, blanks are typically 1.4×10-9cm3STP for4He, (1±0.3)×10-11cm3STP for 20Ne, (0.97±0.13)×10-8cm3STP for40Ar, <7×10-13cm3STP for84Kr, and<3×10-13cm3STP for132Xe. With the inner crucible of crystallized alumina, the blanks for 20Ne and40Ar are more by a factor of five on the average than those with the tantalum inner crucible, while the 4He blank is similar to that with the tantalum inner crucible. Most of hindrance ions could be separated from rare gases with a high resolution power(=500)of the spectrometer. To examine the system, rare gases from iron meteorite El Taco were measured. Data of the isotopic analyses of He, Ne and Ar from El Taco are given. The system is suitable for the isotopic analyses of extremely low quantities of rare gases