Hi Mark
We had a LOT of pain with icing, and it really comes down to one thing:
water in the gN2. And don't expect to measure some other way whether
you have it, because your X-stream (or Cobra) is the most sensitive
water meter there is.
In our case, the symptom was the X-stream (and later Cobra) blocking up
after between several days and several hours. And we solved it by
ditching the gN2 generators we were using, and organising boil-off gN2
(much purer).
The secondary effect of sample icing: we'd see this as well if we had
something (e.g. collimator) poking into the cold stream*: that causes
turbulence which draws in moisture. Worst case you see ice flakes flick
onto the crystal in real time; best case you get an ice ball after a
few minutes to hours.
(* technically, the stationary phase between the cold and warm streams.)
Hope that helps.
phx
Mark Agacan wrote:
Apologies for this slightly off topic question:
I am having a great deal of trouble with my X-Stream 2000 cryostream system and I wondered if other users have similar problems.
I've replaced almost all components (new GAST compressors, helium recharges, filters, etc., etc.) in the last couple of months but there is almost always icing of any cryo within 10 - 20 minutes of mounting a loop, and it is adversely affecting data collections.
It appears like there is too much moisture in the cold or wam streams but the tubes have been fully dried out as per Rigaku advice.
This X-Stream is attached to a generator with inverted phi axis and and i'm wondering if this could be the source of the problem, as the X-Stream for another generator in the same laboratory with normal phi axis does not ice up. Can some sort of turbulence around the loop caused by backdraft from the cryo hitting the inverted phi axis / camera mount cause excess humidity and lead to icing on the pin, loop and crystal?
Has anyone else got this problem? Any suggestions would be very gratefully
appreciated.
Best Wishes,
Mark
_____________________________________
Dr Mark Agacan
Scientific Officer,
Division of Biological Chemistry
and Drug Discovery,
Wellcome Trust Biocentre,
College of Life Sciences,
Dow St.,
University of Dundee,
Dundee, DD1 5EH
Tel: +44 1382 388751
Fax: +44 1382 345764
_____________________________________
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