[3dem] parameters for K2 super-resolution

[Zongli Li]

Hi Garry,

When collecting SPA images with K2 summit, we always use super-resolution
mode at a nominal mag of 31,000x for most samples. The image quality from
2x binned super-resolution images is better than normal counting mode image
without binning. The dose rate is 8 e-/physical pixel/s (2
e-/super-resolution pixel/s, same as Marcus mentioned). Normally 40-50
frames per movie stack with sub-frame time of 200/250 ms.

Hope this helps,

Zongli

On Wed, Sep 20, 2017 at 11:22 AM, Garry P Morgan <Garry.Morgan at colorado.edu>
wrote:

> Hi,
>
> we’ve been collection SPA images with a K2 Summit on a Tecnai F30; so far
> we have only used counting mode at a nominal magnification of 31,000x.
> we’d like to try using super-resolution at a lower mag (i.e., nominal mag
> of 20,000x) to get a wider field of view with a roughly equivalent pixel
> size.  i’m wondering if anyone is doing this as a standard for their SPA
> data acquisition? and if so, how are you setting up your acquisition
> parameters? i.e., frame time and number of frames.  because the dose is so
> much lower at the lower mag, it takes a significantly longer total
> acquisition time (20-30 seconds) to achieve our desired sample dose. in
> order to keep the number of frames in the movie stack to ~40 (so that the
> movie stack file size isn’t too large), we would need to increase the frame
> exposure time to between 0.5 and 1.0 sec. however, i’m worried this longer
> frame time would incorporate too much drift and essentially nullify the
> whole point of using the K2 and drift correction. i would appreciate any
> thoughts and advice on this.
>
> one more question…Gatan recommends a dose rate no more than
> 10e-/ubpxel/sec going to the K2 while in counting mode. i  believe we were
> told the dose rate should be 2.5e-/ubpixel/sec for super-resolution mode.
> can anyone tell me if this is true, or is the dose rate of 10e-/ubpixel/sec
> in regular counting mode actually the same as 2.5e- dose rate in super-res
> mode because of the 0.5x binning?  in other words, can i use the same beam
> intensity for for unbinned counting mode and super-res mode?
>
> thanks,
> Garry
>
> _______________________________________________
> 3dem mailing list
> 3dem at ncmir.ucsd.edu
> https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.ncmir.ucsd.edu/pipermail/3dem/attachments/20170920/7c98f7e5/attachment-0001.html>