RE: GM Calibration Question

["Burns, Thomas" <BURNST@coned.com>]

Hi Malek,

Jim is correct. Also the columniation of the beam is also important. This to
may be affected by the geometry.

Tom
> -----Original Message-----
> From:	Jim Vandergrift [SMTP:jfvande@yahoo.com]
> Sent:	Friday, December 03, 1999 6:05 AM
> To:	Multiple recipients of list
> Subject:	Re: GM Calibration Question
> 
> The standard rules I have always used are:
> (1) the orientation of the probe to the calibration
> beam (field) is the same as the orientation normally
> used in actual surveying regardless of the detector
> type, and
> (2) GM detectors are very energy dependent, when
> attempting to use them for exposure measurements
> (mR/hr) and must be calibrated with a radiation
> source, as near as possible, to the radiation you
> expect to use the detector with. 
> 
> 
> 
> --- Malek Chatila <mc02@aub.edu.lb> wrote:
> > 
> > Dear All,
> > 
> > I have few related questions concerning the
> > calibration of GM probes that I
> > hope you might clarify for me.
> > 
> > 1. When calibrating an open-end window GM probe, the
> > probe is placed
> > perpendicular to the beam axis, i.e. the window is
> > not directly facing the
> > radiation beam, is this correct? 
> > 2. When calibrating a pancake GM probe, the pancake
> > window is placed
> > directly facing the beam, is this correct?
> > 
> > The problem that I am having is the following:  when
> > trying to calibrate a
> > pancake probes that are coupled to Victoreen's THYAC
> > IV survey meters, the
> > meters constantly over read by 50 % when the pancake
> > probe window is placed
> > facing the radiation beam while an accurate reading
> > is obtained when the
> > pancake probe handle is placed perpendicular to the
> > beam axis i.e. the
> > window facing down and the beam axis is horizontal. 
> > 
> > 
> > Thank you in advance for your assistance.
> > 
> > Sincerely,
> > 
> > Malek Chatila
> > American University of Beirut
> > Email: mc02@aub.edu.lb
> > 
> > 
> > 
> > 
> >
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