[3dem] FEI-VPP phase change to opposite direction
jamonshi at gmail.com
Thu Jan 26 16:34:21 PST 2017
To firmly answer your question, I tried 5 accessible ones of all 6 VPPs
at three different positions (#3, 30, 60). The behavior are the same,
with a variable degree. In deed, there was more than a month delay from
VPP delivery to installation due to engineer schedule. However, it was
sealed in the container. Thanks for the input.
On 01/27/2017 01:29 AM, Danev, Radostin wrote:
> Hi Jian,
> If the CTF rings are moving outwards (make sure you are underfocus!)
> that means positive charging. The reason is most probably
> contamination on the phase plate film. If the heater is working
> properly (voltage ~ 4.0V, current ~ 25 mA) then the contamination is
> pre-existing, deposited during manufacturing, transport or handling of
> the phase plate. Are all VPP slots showing the same behavior?
> *From:* 3dem [3dem-bounces at ncmir.ucsd.edu] on behalf of Sacha De Carlo
> [sacha.decarlo at dectris.com]
> *Sent:* Thursday, January 26, 2017 8:32 AM
> *To:* jamon
> *Cc:* 3dem at ncmir.ucsd.edu
> *Subject:* Re: [3dem] FEI-VPP phase change to opposite direction
> Could it be that the holder, with the new VPP, is no longer sitting in
> the back focal plane, where it should be?
> In any case, these are things to check with you FEI service engineer.
> All the best,
> On Thu, Jan 26, 2017 at 6:11 AM, jamon <jamonshi at gmail.com
> <mailto:jamonshi at gmail.com>> wrote:
> Dear Lister,
> We just changed our FEI Volta Phase Plate on Krios. But after
> activation, the phase changed to opposite direction, the FFT rings
> moves outward instead of inwards as it should be. The gold
> particles all looks all white as if in overfocus. I had never seen
> such behavior with previous two VPPs we had. Did anybody have
> similar experience? Thanks in advance.
> Best Regards,
> Jian SHI
> Manager, Cryo Electron Microscopy Facility
> Center for BioImaging Science
> National University of Singapore
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