Calibration. Three radiation sources, s 250-kv Xray generator,
a 2eS-Mev Ven de Graaff generetor, and a 200-curie Co” source were used
in the calibration of the Project 2.2 instruments, The “Conrad” detectors
were calibreted with the 200-curie Co™ source and the 250-kv Xray genere-
tor. The initial gaema instrunents, the "Gueteves" and the photomultiplier
feedback circuit detectors, were calibrated with the 250-kv Xray and the
2.5Mev Yan de Greaff generator.
The 250-ky ray machine was operated at am applied potential of
250: kv, and 10-ma current. The Xray beam was hardened with 1 m= of cadmiun
filtration te give an effective energy of 1% kev.
The instrument
response to this bean wae the sane as for Co, eince the instrument
responee is flat to below 123 kev. The maximm usable exposure rateof
attainable with this,Kray generstor (consistent with good geometry) wes
6,400 x/hr.
The Van de Graaff generator was operated at 1.0, 1.5, and 2.C Mov,
resulting in a maximm rate of 10° x/he,
The 200-curle field calibrator was specifically designed for operation
under EPG weather conditions. The main components are the source con~
tainer and the control trailer. The source container is ade of stainless
steel, and the plug end rise tube essembly of Mone) metal. The source,
inclosed in a double-walled Monel capsule, is raised and lowered pneumatically and is supported by three spring-loaded pins, one of which
actuates a microswitch to indicate when the source is up.
en
The Co™ 4s in pellet form and fills a space 0.39 tnetitein diwates
and 1.98 inches in length. The total Monel metal shielding (capsules and
rise tube) is 0,33 inches, The source was calibrated in the field over