Dual collector cycloidal mass spectrometer for precision analysis of hydrogen isotopes

Abstract

The cycloidal mass spectrometer design of Andrew⁽¹⁾ has been adapted to dual ion collection for hydrogen isotope analysis. Difficulties experienced by Andrew with thermal expansion of the wire used to produce uniform electric fields were overcome by using 0.05 mm diameter tungsten wire. The focal lengths for ion beams M/e = 2 and 3, are 2 and 3 cm respectively. The sensitivity is about two orders of magnitude higher than for magnetic sector mass spectrometers of similar size. Under normal operating conditions the H₃⁺ production is 10% of the total ion current HD⁺ and H₃⁺, and the reproducibility of δD measurements is better than ±0.5 per mil. Increase of the resolving power to 600 for separation of ³He⁺ from HD⁺ and H₃⁺ ions appears feasible.