Try reading out at higher rates to reset adc and decharge things between darks. 



What we potentially know as of :

  • It seems the Rayonix is getting overcharged at the central pixels.
  • This charging is long lasting.
  • When we take the dark the charge is persisting.
  • The dark is then full of streaks.
  • The processing by the dark on the raw image is ruining the data.


Email thread w/ Rayonix.

Kaz

Unfortunately, the image I sent you was taken with our DAQ, so I don't have a capxure image for that particular frame.  

Well, the detector delivers a Tiff, even if you collect via your DAQ - is that not available any more?
Maybe you can re-create that image from capxure?

But what you say about the overloading does make sense.  I've had situations where my dark images show an airscatter-like afterglow.  I'm not sure what we can do about the overloading of the center pixels, since the beam is going through the center hole, and there is alot of air scatter.  
Presumably, if we lower the flux enough such that we don't see over-saturation in the center pixels, the odd streaks would go away.

Yes, I would think so. You are not just overloading the pixels a little bit, you are overloading them by multitudes.

-Christine
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Christine R.A. Muchmore. Ph.D.
COO
Rayonix, L.L.C.
1880 Oak Ave, Evanston, IL60201
ph:847 869 1548   fx: 847 869 1587
toll-free (US&Canada): 1 877 627 9729
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

From: Christine R.A. Muchmore <cram@rayonix.com>
Sent: Tuesday, November 14, 2023 12:47 PM
To: Nakahara, Kazutaka <nakahara@slac.stanford.edu>
Cc: Rosenberg, Daniel J <djr@slac.stanford.edu>; Ross Doyle <ross@rayonix.com>; Apollo Gama <gama@rayonix.com>; Gee, Leland <lbgee@slac.stanford.edu>; Hansson, Conny <conny-h@slac.stanford.edu>
Subject: Re: Rayonix detector image showing odd streaks

 
Kaz,

My apologies, I overlooked the one dark image you sent. It definitely does not look normal, most likely the phosphor is still glowing from the strong overload.
You might have to attenuate the beam.

Thanks for looking at the images.  Just to confirm, you don't see the streaks in the raw image, but you do see them in the corrected images?
If so, that sounds, as you mentioned, to be a software/correction issue where we're applying the wrong dark.

You might not be able to get a good dark, as long as you are so massively overloading the detector.

However, there might also be a different problem: with this strongly overloaded area there is "bloom", the CCD pixels essentially spill over.
This might cause a strange pattern when the CCD's are read out, and the spatial correction is applied.
 

  Just to make sure, when we take a dark, I simply hit "Take new background" in capxure.  Do we care about the integration time when we do this, or is the dark an average-over-time?  

The dark image is two standard very short exposures averaged. It is all handled automatically when you click on "take a new background".

Unfortunately, I took a dark right after I took those images, so I suspect the old dark was overwritten...

I can try to see if these streaks appear with lower flux, though I think we tried it and did see the streaks (Daniel can correct me if I'm wrong). 

12keV is not an unusual energy for the Rayonix detectors - people use them in that range all the time without any strange effects.

In your email you attached a screen shot of an image that looked very different from the overloaded capxure images you sent.
Can you send us the original image file from that shot? It would be a lot easier to trouble shoot this without the massive overload.

-Christine


 

Regards,
Kaz

nakahara@slac.stanford.edu
cell: 650-391-7914
office:  x5725
ASC lab:  x3805
From: Christine R.A. Muchmore <cram@rayonix.com>
Sent: Tuesday, November 14, 2023 12:05 PM
To: Nakahara, Kazutaka <nakahara@slac.stanford.edu>
Cc: Rosenberg, Daniel J <djr@slac.stanford.edu>; Ross Doyle <ross@rayonix.com>; Apollo Gama <gama@rayonix.com>
Subject: Re: Rayonix detector image showing odd streaks

 
Hi Kaz

Unfortunately you did not include the dark images that were used with these raw/corrected files.
The raw images do not show the streak pattern, so the dark image might be introducing it to the corrected frame.
We need to know what the dark image looks like.
You can request to save raw, corrected and dark in capxure.

I have never seen this type of pattern, but I have not seen such severely overloaded areas around the beamstop, either.
Is this massive overloaded area from sample scattering or air scatter? 
It is not a good idea to so totally overload the CCD's in the center. A direct beam hit can damage the detector and depending on the flux the overloaded zone could sustain damage.
The raw images show overload in an area of the CCDs that is not even coupled to the fiberotic taper. That is either electron spill over between pixels or the direct beam going into the detector? Just guessing.

Can you please confirm that the detector still delivers normal images when not overloaded?
I know this is at an XFEL, but can you reduce the flux at 12 keV or go to lower energy?

-Christine

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Christine R.A. Muchmore. Ph.D.
COO
Rayonix, L.L.C.
1880 Oak Ave, Evanston, IL60201
ph:847 869 1548   fx: 847 869 1587
toll-free (US&Canada): 1 877 627 9729
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~




On Mon, Nov 13, 2023 at 1:13 PM 'Nakahara, Kazutaka' via info <info@rayonix.com> wrote:

Hi,

We're seeing the same vertical streaks that I've been talking about before.  Here's an image as seen by our DAQ at 12keV.  Do you guys have a sense of what might be causing this?  I've uploaded 20231113_capxureimages.tar.gz to your incoming ftp server.  The gzip file contains raw and corrected images of the same 12keV beam.  

Regards,
Kaz

nakahara@slac.stanford.edu

cell: 650-391-7914
office:  x5725
ASC lab:  x3805

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