[3dem] K3 CDS mode issue

[Wim Hagen]


Hi Dan,

Our K3 has/had this exact problem from the very start when it was installed. For SPA one can somewhat work around the problem, but it’s a killer for tomography. Gatan played a bit with the detection settings for CDS mode (which required a GMS upgrade), that somewhat fixed the gain ref symptoms, but a subsequent ApoF SPA test of normal vs CDS mode showed zero difference in performance. We kinda left it there and only use normal mode on that system.

Hearsay:
- Some systems have this in normal mode, or CDS mode or both modes.
-Some systems were fine after swapping the chip.
- One system was fine after swapping the K3 power supply.

Best,

Wim Hagen
EMBL Heidelberg


> On 17. Dec 2021, at 02:44, Daniel Toso <dtoso at berkeley.edu> wrote:
> 
> Hello Everyone, 
> 
> We have been having an issue with one of our older K3 cameras since last year. Namely, in CDS mode we are getting stripes in our images that do not get removed by gain correction and become worse as the dose goes further from 7.5 e-/pixel/sec., which will occur quite often in thicker ice. See attached image for an example.
> 
> We tried having Gatan (Ametek) fix the issue but they do not have a solution beyond buying a new sensor.
> 
> I was wondering if this is a widespread issue. Also, if there is any solution besides no longer imaging in CDS mode. We have heard that it is also seen at UCSF. Any advice would be appreciated.
> 
> Thanks very much!
> 
> Best regards,
> 
> Dan
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