[RASMB] max out photomultiplier

[John Philo]

Hermes,
 
Definitely you should always power down the centrifuge before the slit
assembly is removed! Yes I believe photomultipliers can show some slow
recovery after excessive light exposure, but if the intensity has not
recovered by now I don't think it will without intervention, and you will
probably need to bring in the service engineer.
 
However it is possible that the problem is not in the PMT itself. The
intensity loss might have been caused by the attempted cleaning of the slit
assembly---it is very easy to block the slit itself with debris, or possibly
you did not put the two little lenses back in quite correctly. Also my
understanding is that there is an integrated circuit amplifier located
within the base of the PMT housing, and this too can be damaged if there is
excessive PMT current (too much light). So unfortunately you might need an
entire PMT assembly, not just a new PMT.
 
Good luck,
 
John

-----Original Message-----
From: rasmb-bounces at rasmb.bbri.org [mailto:rasmb-bounces at rasmb.bbri.org] On
Behalf Of Hermes Reyes Caballero
Sent: Saturday, May 12, 2007 8:05 AM
To: rasmb at rasmb.bbri.org
Subject: [RASMB] max out photomultiplier



Dear RASMB members,

 

I was cleaning the slit ensemble in the XL-A and I though of cleaning the
PMT too. So I did it with ethanol and expose the PMT to the light when the
machine was turn on. I read somewhere in this forum that can cause the PMT
to max out, and in fact the intensity was around 6-fold lower than before
the cleaning procedure. I turn off the machine for 12 hrs and the intensity
is still very low, with no apparent recovery. Does anybody know if this PMT
will comeback? 

 

Have a nice day!!

 

Hermes

 

 

Hermes Reyes_Caballero PhD. Candidate
The Giedroc Lab
Department of Biochemistry & Biophysics
Texas A&M University
2128 TAMU Room 419
College Station, Texas 77843-2128
Phone: (979) 845-6828

 

 

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