[RASMB] lamp intensity drop

[Karen Fleming]

When I was at Yale, I used to clean the lamp every week. I thought that  
was too much, but it was what we had to do to keep the signal to noise  
up. In my conversations with people, it became apparent that the  
frequency at which the lamp must be cleaned varied from instrument to  
instrument.
-Karen F.
****************************************************
Karen G. Fleming, Ph.D.
Assistant Professor
Thomas C. Jenkins Department of Biophysics
Johns Hopkins University
3400 North Charles Street
Baltimore, MD 21218

Voice: 410-516-7256
Fax:	410-516-4118
****************************************************
On Jun 28, 2005, at 4:35 AM, Dror Noy wrote:

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> Hi all,
> We encounter a very annoying behavior in our XLA and I'd like to check  
> with the forum if this is a specific or general problem.
> After running many scans the UV intensity of the flash lamp is reduced  
> dramatically. This is caused by some kind of chemical reaction at the  
> lamp surface that makes a brownish hallow that absorbs UV. It is a  
> known phenomenon and Beckman recommends cleaning the lamp surface with  
> tooth paste abnd tooth brush. It really works. Our problem is that it  
> happens too frequently on our machine. My recent observation is that  
> it took about 750 radial scans (6.0 to 7.2 cm at 0.003 cm step) to  
> decrease the intensity at 230 nm by half. Does this look like a  
> "normal" half-life?
> Thanks,
> Dror
> =========================
> Dror Noy, Ph.D.
> Structural Biology Dept.
> Weizmann Institute of Science
> Rehovot 76100
> Israel
>
> e-mail: dror.noy at weizmann.ac.il
> Tel: (972)-8-934 2525
> Fax: (972)-8-934 4154
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