[ RadSafe ] low energy gamma-spikes pranks done withphotomultiplier tubes! Whisker was inside the PM tube
parthasarathy k s
ksparth at yahoo.co.uk
Thu Sep 30 21:23:14 CDT 2010
The whisker was inside the PM Tube! That is why I wrote about it.
From: Cary Renquist <cary.renquist at ezag.com>
To: The International Radiation Protection (Health Physics) MailingList
<radsafe at health.phys.iit.edu>
Sent: Fri, 1 October, 2010 2:26:29
Subject: Re: [ RadSafe ] low energy gamma-spikes pranks done withphotomultiplier
The low background detectors probably used lead-free solder and thus are
prone to "tin whisker" growth.
I guess that one needs to use roman-era lead for the solder...
cary.renquist at ezag.com
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of parthasarathy
Sent: Thursday, 30 September 2010 09:34
To: The International Radiation Protection (Health Physics) Mailing List
Subject: Re: [ RadSafe ] low energy gamma-spikes pranks done
I recall that in our formative years in the Bhabha Atomic Research
used to all sort of crazy things with photomultiplier tubes. In our
one of my colleagues used a magnet of considerable strength and
displaced the electrode of a PM tube with disastrous consequences!
Indeed we studied the response by removing the electrostatic shields.
studied influence of earth's magnetic field; if I recall correctly it
significant for large area photomultiplier tubes.
While on this, let me describe a very interesting experience we had
large area photomultipliers.
The Department of Medical Physics, University of Leeds had an
the Nuclear Enterprises by which the company used to pass on low
photomultipliers with sodium iodide (Tl) crystals as integral line
for studies. While working with one such units our routine was to record
(0.66 MeV) gamma line and TL-208 (2.61 MeV) gamma line at the beginning.
we found that both these lines have shifted considerably down. It
there was some change in the internal electrode structure which led to
A well experienced member of the technical staff told us that he had
an event earlier; he went through his old records and located a
that in large area PM tubes small whisker like structures can develop
as a short circuit lowering the voltages between electrodes. The impact
will be considerable if it happens at the initial stages. The remedy was
a very low voltage high current pulse between the suspected electrodes
off the whisker. Once this was done the gamma lines appeared in the
channels of the multichannel analyser.
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