I was fairly sure that the fluctuations that I was observing on the Europa
20/20 Hydra were not temperature induced.

1.They were regular sine waves with a period of 15 min and I couldn't
detect any similar periodicity in temperatures (room, magnet, collector
assembly).
2. I have two other Europa mass specs in the same room which do not exhibit
the problem.

I find that if I close down the inlet crimp to reduce the pressure at the
source from 4 e-6 mbar to 2 e-6 mbar.
The wave disappears (or becomes lost in the noise) and the precision
improves considerably.  This effect is reversible on opening the crimp.

Some sort of resonance in the inlet?
David Harris
Stable Isotope Facility
Department of Agronomy and Range Science
122 Hunt Hall
UC Davis, Davis CA 95616
Voice (530) 754 7517, Fax 752 4361
http://stableisotopefacility.ucdavis.edu