2 BCAEON
.
All batteries taking up these voltages were in duplicate and connected in parallel as insurance
against failure.
NT6 Willard 6-v<.i wet cells were used for filament power in lieu of dry cells because of
the greater current requirement which these cells could furnish.
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The cathode-ray tube was mounted inside a Mu-metal cylinder to shield it from the earth’a
magnetic field.
The ground points of the beta-signal circuit and of the cathode-ray tube were connected to
the recording unit case through a 100-megohm resistor to drain any static charges and to
provide a high impedance to any possible short to the case from any part of the recordingunit circult.
A 16-mm Kodak Cine E strip camera photographed the variation of the signals on the
cathode--ray-tube screen and generated a time base proportional to the film speed. Since the
speed of the camera varies noticeably, accurate time intervals could not be determined by
measuring film lengths. Oscillator circuits were used to generate 5- and 100-cycle pulses to
neon bulbs mounted on the oscilloscope screen. Thus a series of 0.20- and 0.01-sec timing
marks were included in the film record, directly below the beta-signal trace. The 0.20-sec
timing marks were included merely as an aid in counting the 0.01-sec marks.
The camera was powered by a bank of 22'4-volt dry batteries. With approximately a
2-ampdrain, the batteries were reliavle only for two to three runs of about 1 min each. However, for the measurement time involved the power was sufficient. For repeated trial runs
the camera was powered by external batteries connected through monitoring cable C (Fig. 3.5).
A timing-oscillator circuit is shown in Fig. 3.6. Each timing light oscillator consisted of a
Weinbridge oscillator and peaking circuit. The oscillator output was a voltage spike great
enough to flash the GE51 neon bulb and sufficient to give sharp timing marks on the recording
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CONTROL SYSTEM
The control system consisted of two external master Edgerton, Germeshausen & Grier,
Inc. (EG&G)relays and nine sealed-type relays mounted in the recording unit ¢nd in the
photomultiplier battery box. The master relays, ncrmally open, closed to give Liming signals
at H—1 min and H—5 sec, respectively.
The H-1m relay activated the circuits of a hold-down relay and five switch relays
(Fig. 3.7), which turned on the power supplies to the photomultiplier and the filaments of the
cathode-ray tube and timing oscillators. The H—5 sec relay activated a hoid-down relay, a
switch relay for the camera-motor power, the foil calibration circuit, and the power for the
delay relay. After a predetermined time the delay relay closed and burned out a fuse which
turned off power to all internal relays and to the camera motor.
Although the relays were rated at 24 volts, 45 volts was used to give them a greater
closing force and prevent the contacts from. chattering when hit by a shock.
The heater voltage for the delay relay (Amperite 6N060) was obtained from the
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oscillator-filament 6-volt battery (Fig. 3.5).
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film. Filament and plate voltages were supplied by duplicated dry batteries.
.
To factlitate calibration and last-minute adjustments in the field, an access window
(Fig. 2.1), covered by a removable plate, was cut on the side of the aluminum cylinder which
housed the recording unit. The following checks and adjustments could be accomplished
through the window:
1. Check functioning of timing light.
2. Check camera-lens settings.
$. Insert or replace control fuse.
4. Adjust electron beams on CRT screen for focus, brightness, and position.
5. Set photomultiplier load to locate output-signal level at desired point on screen (final
field calibration adjustment).
19
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