Re: Re[2]: Questions on EBWs and EMs

[Brian_Gaulke@hc-sc.gc.ca]

Brian Gaulke
03/03/98 05:49 PM

I used to work in a US Naval shipyard (PSNS in Bremerton, WA).  We once had
some equipment show up contaminated unexpectedly.  It too was surveyed
using an instrument with a scintillation detector.  Upon investigation,
however, the readings were only elevated while the equipment was hanging
from a large portal crane's hook.  The elevated readings appeared to be
caused by static charging of the equipment due to the earth's normal 100
V/m electric field between the top of the crane and where the load was
hanging.  My guess was that the resulting electric fields were affecting
the performance of the PMT.  Might you be experiencing something similar in
the vicinity of the electron gun?

Brian R. Gaulke, CHP
Head, Dosimetry Section
Radiation Protection Bureau
Health Canada
brian_gaulke@hc-sc.gc.ca





Alex.Zapantis @ ea.gov.au on 98/03/03 17:01:45

Please respond to radsafe@romulus.ehs.uiuc.edu

To:   radsafe @ romulus.ehs.uiuc.edu
cc:    (bcc: Brian Gaulke)
Subject:  Re[2]: Questions on EBWs and EMs




Hi all
I was the RSO at an Australian University a couple of years ago, and
surveyed
the electron microscopes used there. I also found no increase above
background
at the operator position, but I did find an appreciable increase
immediately
against the column in the vicinity of the electron gun. Unfortunately the
instrument I was using was a simple ratemeter (reading in CPM/CPS) attached
to a
scintillation detector and was not calibrated for doserate at the low
energies I
was measuring. I found this surprising and asked the EM manager to inform
the
manufacturer of our findings and seek comment. I can't remember what the
outcome
was, but in any case, it was not significant from a radiation protection
viewpoint.
Regards


Alex Zapantis
Health Physicist
Supervising Scientist Group
Email : alex.zapantis@ea.gov.au
Fax : (int+) 61 2  6217 2060
Phone: (int+) 61 2 6217 2037
PO Box E305
Kingston ACT 2604
AUSTRALIA
The Supervising Scientist Group is Part of Environment Australia