We've been able to run months with an old Xstream 2000 system, so that shouldn't be the problem. Unlike Frank, we haven't had problems with water in the nitrogen from a nitrogen generator.
If Frank is correct, that it's water, then either the molecular sieves need to be replaced, or there is ice buildup and blockage in the coldhead. Usually blockage in the coldhead means that you can't get down in temp, or can't maintain it within 1 degree or less. We do bring the temp up, run it at RT over the weekend to dry things out, and then bring it down for routine cooling. If it's turbulence, then you don't have the warm and cold flow rates set correctly. One thing you can see immediately, upon getting down to 100K, is how far is the frosting plume from the tip of the nozzle. If you adjust the flow rates, you can move that plume, caused by turbulence, closer or further from the nozzle. It's also possible that there is something in the nozzle that is causing turbulence no matter what the flow rates are, and your vendor needs to look at that. Bernie Santarsiero On Mon, January 12, 2009 6:11 am, Frank von Delft wrote: > 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 >> _____________________________________ >> The University of Dundee is a registered Scottish charity, No: SC015096 >> >
