[3dem] Pre-Specimen Shutter (Yu, Xiaodi [JRDUS])

[Wim Hagen]

Dear Tim,

A mechanical shutter will be too slow.

Best,

Wim

> On 24. Jun 2020, at 16:36, Tim Gruene <tim.gruene at univie.ac.at> wrote:
> 
> Dear Wim,
> 
> thanks a lot for the detailed explanation!
> 
> Are there reasons for not having a mechanical shutter in a TEM? I would
> think a metal lid at, e.g. the Condenser 2 aperture would be very small
> and the removal should be fast enough to not disturb most
> applications.
> 
> 
> Best,
> Tim
> 
> 
> 
> On Wed, 24 Jun 2020 13:05:37 +0200
> Wim Hagen <hagen at embl.de <mailto:hagen at embl.de>> wrote:
> 
>> Tecnai and CM microscopes did not have a dedicated coil to blank the
>> beam pre-specimen, so the gun deflector coils where used to blank the
>> beam, hence "Gun Deflector (beam blanker)". Since deflector
>> electronics were noisy at the time, they were filtered and thus slow,
>> which could be seen when opening the column valves on a e.g. normal
>> Tecnai: the beam would slowly move in from the side of the screen.
>> On cryo-systems the gun deflector electronics filter was removed so
>> it was fast enough for blanking purposes, but you didn’t want to do
>> STEM on those systems as the noise on the gun coils would ruin
>> things. On Titan systems a true dedicated blanker coil was
>> introduced, hence "Gun blanker (pre-specimen shutter)", but some
>> parts in software still use the gun deflection coils, hence a
>> confusing mix of things, depending on which software one uses to
>> control the camera. Talos/Glacios does not have a dedicated blanker
>> ("Gun blanker (pre-specimen shutter)”), everything is still done
>> through the gun deflection coils ("Gun Deflector (beam blanker)”).
>> All the newer scopes have better deflection electronics, so no
>> filtering needed, so shuttering is fast enough, so far…. Best, Wim
>> 
>>> On 24. Jun 2020, at 03:19, Matthews-Palmer, Teige
>>> <t.matthews-palmer14 at imperial.ac.uk> wrote:
>>> 
>>> Can anyone explain the difference between Gun Deflector (beam
>>> blanker) and Gun Blanker (pre-specimen shutter)? Gun Blanker sounds
>>> either like a mechanical shutter hardware option not installed; or
>>> part of the Gun Deflector - but then why is it a separate device in
>>> the microscope control software?
>>> 
>>> Grateful for any explanations!
>>> Teige
>>> 
>>>> On 24 Jun 2020, at 02:02, Jason Kaelber <jason.kaelber at rutgers.edu
>>>> <mailto:jason.kaelber at rutgers.edu <mailto:jason.kaelber at rutgers.edu>>> wrote:
>>>> 
>>>> This email from jason.kaelber at rutgers.edu <mailto:jason.kaelber at rutgers.edu>
>>>> <mailto:jason.kaelber at rutgers.edu <mailto:jason.kaelber at rutgers.edu>> originates from outside
>>>> Imperial. Do not click on links and attachments unless you
>>>> recognise the sender. If you trust the sender, add them to your
>>>> safe senders list
>>>> <https://urldefense.com/v3/__https://spam.ic.ac.uk/SpamConsole/Senders.aspx__;!!Mih3wA!VFParMj59ZHBcjRq4bZfapb6-MrwsKanClm_O9bCr_8yFnjrCicS3CNQKZ0L4R0o_Q$ <https://urldefense.com/v3/__https://spam.ic.ac.uk/SpamConsole/Senders.aspx__;!!Mih3wA!VFParMj59ZHBcjRq4bZfapb6-MrwsKanClm_O9bCr_8yFnjrCicS3CNQKZ0L4R0o_Q$>>
>>>> to disable email stamping for this address. Hello Xiaodi, The
>>>> Blanker/Shutter Monitor window is showing what you would expect it
>>>> to show if everything is working. When the deflector coil
>>>> (pre-specimen shutter) is displayed as orange (N/A), the
>>>> Blanker/Shutter Monitor window does not know the instantaneous
>>>> state because it is controlled by the camera. Unfortunately you
>>>> would also see the orange if it's almost working but the camera is
>>>> not controlling the blanking correctly (very rare). Cheers, Jason
>>>> 
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> 
> 
> 
> -- 
> --
> Tim Gruene
> Head of the Centre for X-ray Structure Analysis
> Faculty of Chemistry
> University of Vienna
> 
> Phone: +43-1-4277-70202
> 
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