[RASMB] lamp intensity drop

[John Philo]

Just to clarify, I believe the extra window that Erby Perdue is referring to
is an optional accessory, NOT a standard component on the newer instruments.
Because that window can be removed from inside the chamber using its own
special tool, without opening the cabinet, this makes the cleaning easy and
safe to do. Thus this may especially be a good option when you have many
different instrument users and don't want all of them messing around inside
the instrument.

And yes, many of us remove the carbon buildup using pencil erasers rather
than toothpaste.

John

-----Original Message-----
From: rasmb-admin at server1.bbri.org [mailto:rasmb-admin at server1.bbri.org] On
Behalf Of Dror Noy
Sent: Thursday, June 30, 2005 2:03 PM
To: rasmb at server1.bbri.org
Subject: Fwd: [RASMB] lamp intensity drop


----------------------------------------------------------------------------
------
The older archived RASMB emails can be found at:
http://rasmb-email.bbri.org/rasmb_archives
and current archives at http://rasmb-email.bbri.org/pipermail/rasmb/
Search All the Archives at: http://rasmb-email.bbri.org/rasmb_search.html
----------------------------------------------------------------------------
------

> From: eperdue at beckman.com
> Date: 00:29:51 GMT+03:00 30 éåðé 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
>
>
>
>
>
>
> ----------------------------------------------------------------------
> -
> -----------
>
> The older archived RASMB emails can be found at: 
> http://rasmb-email.bbri.org/rasmb_archives
> and current archives at http://rasmb-email.bbri.org/pipermail/rasmb/
> Search All the Archives at:
> http://rasmb-email.bbri.org/rasmb_search.html
> ----------------------------------------------------------------------- 
> -----------
>
>
> 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 _______________________________________________
> RASMB mailing list
> RASMB at rasmb-email.bbri.org
> http://rasmb-email.bbri.org/mailman/listinfo/rasmb
>
>
>
=========================
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
_______________________________________________
RASMB mailing list
RASMB at rasmb-email.bbri.org
http://rasmb-email.bbri.org/mailman/listinfo/rasmb