I have a source from a SIRA series instrument that is performing very badly in terms of linearity. There is a shift of as much as 8 per mille in the 46/44 ratio during a standard run with the gas depleting from the cold finger of a dual inlet. With retuning of the source I can reduce this to ca. 5 per mille but no better. Does anyone have any hints regarding tuning, filament change etc. which may help solve this problem or will I need to change the complete source assembly. I should add that I have 3 other similar sources all running on instruments in my lab. and all behaving perfectly in terms of linearity. Moreover the linearity is quite robust with respect to tuning, filament age etc. This leads me to suspect that there may be a fundamental problem with the other source that may only be resolved by repalcing the complete assembly! Any hints. ideas will be gratefully accepted! Paul -----Original Message----- From: Frank Pawellek <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Date: Friday, February 13, 1998 1:43 PM Subject: Re: turbo pumps All, ..to add another opinion: we've been running Balzers turbo pumps on four machines (06x and 180) for up to five years now, without any breakdowns. >From the very start the air cooling for all the pumps was replaced by more efficient water cooling. In our opinion keeping the working temperature low seems to be crucial for a long life of the pumps. Regards, Frank +++++++++++++++++++++++++++++++++++++++++++++++ Frank Pawellek Institut fuer Geologie Lehrstuhl fuer Sediment- und Isotopengeologie Ruhr-Universitaet Bochum Universitaetsstrasse 150 44801 Bochum Germany Phone: +49-234-700-5458 Fax: +49-234-7094-571 +++++++++++++++++++++++++++++++++++++++++++++++