[RASMB] Optima AUC Interference optics question

[Laue, Thomas]

Hi-
I agree with Bo- there is some piece of crud ~6.5 cm in your optics. I would check out the most exposed places first- with the lens (or lens cover) at the bottom of the chamber. The remaining optics should be sealed… if they are open for some reason, the horizontal surfaces on the lower track would be my next place to look. A bit of history, the lower track originally was hermetically sealed to allow a slight vacuum to be pulled to eliminate air convection from contributing to the fringe displacement. As it turned out, the ‘rocking’ of the bottom chamber lens during a heating/cooling cycle swamped the fringe disturbance from convection.
Cheers-
Tom

From: RASMB <rasmb-bounces at list.rasmb.org> On Behalf Of Borries Demeler
Sent: Saturday, May 1, 2021 2:59 PM
To: Jeff Arthur <jarthur at kbibiopharma.com>
Cc: rasmb at list.rasmb.org
Subject: Re: [RASMB] Optima AUC Interference optics question

Caution - External Email

Take a look at the original images, there is probably a black spot at this position somewhere in the image. My guess is you have dirt in the optics or dead pixels in the camera. This noise  offsets the Fourier transform and you get random fringe shifts. If the noise streaks through the entire image at the same radial position it is likely just dirt. Carefully inspect the top of the camera and see if you can see anything stuck on the top and remove it carefully. Anything below that should be addressed by Beckman service.
-Borries




On Fri, Apr 30, 2021 at 9:46 PM Jeff Arthur <jarthur at kbibiopharma.com<mailto:jarthur at kbibiopharma.com>> wrote:
Hi Everyone,

I am having an issue with the interference optics on my Optima and I am hoping to get any advice on how to troubleshoot.  The issue is screenshot below, which shows two successive scans on each of two cells. My last couple runs have a blip at ~6.5 cm.  It is present in every cell, so I assume that it is instrument related.  At radial positions lower than the blip, the fringe shift is inconsistent between successive scans, which is creating difficulties in analyzing the results, even if the region immediately surrounding 6.5 cm is excluded from the raw data.  It’s probably coincidental,  but I also noticed that the revolution counter decreased significantly immediately before this issue cropped up.  Before the issue it was ~550,000, and not it is ~450,000.

Thanks for the help!
Jeff

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