[3dem] FEI-VPP phase change to opposite direction

[jamon]

Dear Rado,


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.


Best Regards,

Jian


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?
>
> Cheers,
>
> Rado
>
> ------------------------------------------------------------------------
> *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,
> Sacha
>
>
>
> 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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