5.2.7.2.1.2 Even if a single operation stated in 4.2.4 cannot be performed,
the dosimeter should not be verified and should be sent for repair.
5.2.7.3 DER and DE measurement should be performed on the phantom
with 30x30x15 cm dimensions, with PMMA walls
(polymethylmethacrylate, front wall thickness - 2.5 mm, other walls
thickness – 10 mm); the phantom should be filled with distilled water.
5.2.7.3.1 During measurement the dosimeter should be placed close to
the phantom surface, directed to a gamma source. The indicator of the
dosimeter should be directed towards the gamma source.
5.2.7.4 Calculation of the main relative permissible error of DER
measurement is performed as follows.
5.2.7.4.1 Prepare the dosimeter for DER measurement and program
zero value of DER threshold level.
5.2.7.4.2 Fix the dosimeter on the phantom according to item 5.2.7.3 in
the УПГД-3Б carriage so that the mechanical center of the УПГД-3Б
collimator coincides with the mechanical center of the detector.
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