[3dem] CCD maintenance
Svetomir B Tzokov
s.b.tzokov at sheffield.ac.uk
Thu Jun 23 02:37:31 PDT 2011
From your explanation it looks like you have the same problem we had recently with our CCD camera.
The chip of our camera got partially de-coupled (only remained coupled in the centre), because the level of the coupling oil got very low (after some problems we had we the camera cooling). My understanding is that this is a rare problem, with a tricky solution. The chip coupling oil is very viscous and the camera needs to be topped up with a needle through a tiny port between the chip connectors. Fortunately, we have a very good engineer who managed to do this without a problem.
However, our camera is different from yours, it is an old 1K CCD.
You should insist for the GATAN engineers to check the coupling of the chip. Your new (presumably in warranty) camera is not working properly, it is their responsibility to fix it.
There is different approaches to how to prevent oil/ice build-up on the camera. The standard GATAN advice is to warm up the camera once a month. Another thing is simply to switch off the cooling of the camera (or the camera itself) once or twice a month. This is what we do. I have heard of places that don't use the cooling of the camera at all(!) for normal work (all you get is more noise in the images). So I guess this depends on how you use your microscopes and how well maintained is the vacuum system. After 7-8 years of use with biological specimens at room temperature and occasional Cryo-EM, both our cameras don't have any significant damage from permanent oil staining.
You last question - leaving of the Cryo-holder in the microscope after your session is a good way to look after it - but again that depends on how comfortable you feel about your microscope vacuum system being able to cope with that and if the microscope is free. A cryo-holder plasma cleaner is the best way to keep your Cryo holder in good shape. If - like us - you don't have one of those, your dedicated pumping station can do the job.
Good luck with GATAN!
On 23 Jun 2011, at 00:49, Jingchuan Sun wrote:
> Our 4K CCD Gatan camera has ring shaped shadow after install half year. It could be removed after doing Gain Reference, but appeal again several days later. It looks like oil and continue changes. Gatan manual suggest to warm the CCD to remove the oil, otherwise would permanently stain the camera by electron beam. How often should the CCD be warmed up?
> Also should the CCD camera switched off when not in use?
> Another question: should the specimen holder with the last cryo grid be left in goniometer and do the smart heat? Or remove the holder is better?
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