separate from the fixed wire element because of electrostatic
repulsion. When the dosimeter is being charged, the charging knob on
the charger, when turned, generates the static electricity. The
spacing or deflection between the quartz fiber and the support wire is
a function of the applied voltage generated by turning the charging
knob on the charger. When the dosimeter is placed in a radioactive
field, gamma rays ionize the air in the ionization chamber. This
produces ion pairs in the chamber, which are attached to the fiber and
wire and partly neutralize their original charge. Therefore, the
indicating fiber moves toward the support wire a distance proportional
to the total amount of radiation to which the dosimeter has been
exposed.
Figure 5-2.
Cross-Sectional View of Dosimeter
NOTE
Some IM-93/UD and IM-93A/UD Dosimeters may have the word
rad instead of the word roentgens stamped on their
calibration scale. The term cGy can be substituted for
roentgen or rad.
4.
Total Dose Range.
The IM-93/UD and IM-93A/UD have the same scale. The dosimeters will
measure gamma radiation on a scale from 0 to 600 cGy, (Figure 5-3).
The IM-147/PD measures gamma radiation from 0 to 50 cGy, (Figure 5-4).
IS0345
5-4
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