Fwd: [RASMB] lamp intensity drop

Dror Noy dror.noy at weizmann.ac.il
Thu Jun 30 17:02:00 PDT 2005


> From: eperdue at beckman.com
> Date: 00:29:51 GMT+03:00 30 יוני 2005
> To: dror.noy at weizmann.ac.il
> Subject: [RASMB] lamp intensity drop
>
>
> This is perfectly normal for instruments with older optics and is  
> caused from
> the peak UV intensity ( 20,000 watts ) and the hydrocarbon molecules  
> from the
> system oils causing a bullseye on the lamp. Systems made since about 5  
> years ago
> came with an extra window that sits down inside the monochrometer  
> mount which
> isolates the lamp face from the oils, so the buildup is greatly  
> reduced. This
> window is able to be easily cleaned by the user, but typically doesn't  
> get
> severe buildup because it's farther from the lamp. Older systems can be
> upgraded, but it's not cheap as multiple parts must be changed to have
> compatibility ( $ 5-7K ) or so. One common thing I see users commonly  
> do is to
> always use a high number of replicas. This increases your lamp flashes  
> and
> speeds up the deposit. After lamp cleaning ( I use an eraser, acetone,  
> then
> ethanol ), try to use a low number of replicates ( 3-5 ) and save  
> anything over
> that for final scans or if you see a great increase in system noise.  
> One
> interesting fact is that the system can loose about 80% of the  
> original UV
> energy and still meet the noise spec. This is great for UV scans, but  
> less
> encouraging if you capture the scans using intensity and convert which  
> some
> users do but not a method that was taken into account when the system  
> was
> designed. I hope this helps.
>
> Erby E. Perdue Jr.
> Customer Support Supervisor
> Technical Specialist Team
> Mid-Atlantic Region
> Customer Support  800-742-2345
>
> ----- Forwarded by Erby Perdue/Remote/BII on 06/29/2005 05:18 PM -----
>
>                       "Dror Noy"
>                       <dror.noy at weizman        To:        
> rasmb at server1.bbri.org
>                       n.ac.il>                 cc:
>                       Sent by:                 Subject:  [RASMB] lamp  
> intensity drop
>                       rasmb-admin at serve
>                       r1.bbri.org
>
>
>                       06/28/2005 04:35
>                       AM
>
>
>
>
>
>
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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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>
>
=========================
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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