2.2
Mechanical Description
The instrument consists of two units, excluding recorders, the
“Top Hat" detector and the Control Box.
cables.
These are interconnected by
The "Top Hat" detector is housed in a 12" high by 8" diameter
aluminum cylinder;
closed at one end ty a welded plated and her-
metically sealed to an aluminum base plate at the other,
The "Sep
Hat" housing provides a hermetic seal *o prevent aiidity from
affecting the high impedance sections of the detector and amplifier
circuits.
The phetomultiplier gain oentrols are Brought through the
base plate by sealed shafts.
The veltage ragulators for the
photomultipliers, the dynode voltage divider networks, and the
logarithmic amplifiers are within the housing with the unregulated
high voltage fed through the base plate through hermetic seal
connectors.
The phosphor-photomultiplier assemblies are mounted
perpendicularly to the base plate over thinned eut sections
of the
plate (1/16" thickness to reduce attenuation Of rays being measured).
‘The phosphors are provided with 1" thick peripheral lead shields fy
minimize radiation effects should the plane become contaminated.
The shielding also provides the characteristic of Figure 9.
The
control circuit is mounted in a water tight box, on" wide by 7*
high by 34” deep.
The control box houses a high voltage vibrator supply, the batteries
and all controls with the exception of the photomultiplier tube
gain controls.
The controls that are used during a survey are mounted
on the cover of the
control box.
These are the RANGE switch, B PLUS
set adjustment, altitude compensation, SET and the MANUA] ALTITUDE contral.
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