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

[Danev, Radostin]

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.

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Jian SHI
Manager, Cryo Electron Microscopy Facility
Center for BioImaging Science
National University of Singapore


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