GM Calibration Question

[Malek Chatila <mc02@aub.edu.lb>]

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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