‘
a7
The maximum pulse-repetition rate of these instmments is 1,0
puises/sec, the maximm rate that my be resolved by the recorder
(a Cook Research Laboratory MA-33 eight-channel magnetic-tape recorder).
Typical calibrations for these detectors are show in Figure 2.3.
Figure &.4 shows the energy dependence of the Scintillon-phosphor
Gustave I detector, relative to co ganms rediation at a rate of 100 r/br.
To reduce the errors due to flutter and wow, a 1,000-cycle tine base was
recorded on the tape similtancously with the gama-exposure-rate data.
Ac Amricen Time Products transistorized frequency standard witt ec
accuracy of 10.02 percent was used to provide the tine bese.
2.2.4
Photomiltiplier Feedbeck Circuit.
Initial Instrumest Systex.
This system is essentially the same as that used during Operation Cashle
(Seference 2).
‘The detecting element, a Scintillon phosphor 2.75 inches
in diumeter by 0.5 inches in heigrtt mounted in e bekeiite biec. fer electro:
equilibriuxn, was placed ingide a blast~-resistant housing at tec toy of a
light pipe.
The output of the crystal after passing through the light
‘The photomltiplier
pipe was detected by an RCA 6199 photomultiplier tube.
tae was used in ea 100-percent-feedback circult which helé the photomultiplier tube anode current nearly constant, regardless of the incident
light flux, by reducing the dynode voltage (Pigure 2.5).
fhe gain of a
photomultiplier tube with constant anode current is approximately proportional to the antilog of the dynode voltage.
In this manner, ea useful
@ynomic range of about « factor of 10! was reslized.
ST,
Log LD
eal