cording intervals of 12 hours and 60 hours were used. with tape transport speeds of 0.25 and 0.05 in, sec.
respectively. These speeds were accurate to =2 percent for the entire“recording imterval. Both recorders
were of identical construction with the exception of the drive motors. A single 6.7-volt mercury-battery
stack having a capacity of 14.000 ma-hr powered each recorder.
The 12-hour recorder was driven by a
2-watt motor operating at a speed of 6.000 rpm and regulated by a centrifugal governor. A 0.75-watt.
chronometrically governed motor rotating at 900 rpm operated the 60-hour recorder. Both recorders
utilized gear reduction and worm-geardrive. The tape was guided in the conventional manner. Metal
friction plates on the feed spindle established an average tape tension of about 4 ounces.
Contacts on the
recorder turned off the instrument when a conductive section of tape at the end of the reel passed over
them to cause a circuit closure. Both recorders were developed at U.S. Naval Radiological Defense Laboratory (NRDL) in conjunction with the Precision Instruments Company. San Carlos, California.
The dose increments chosen for the low- and high-range ionization chambers were 0.243 mr and 0.243
r, respectively.
At the maximum intensity of each range. the maximum-usable pulse packing on the tape
limited the recycling rate of the electrometer to 100 cps (87,500 r/hr) for the 12-hour recording interval
and to 20 cps (17,500 r/hr) for the 60-hour interval. These dose increment and dose-rate values apply
only to the particular detector orientation and gamma energy chosen for the calibration (Appendix B).
As radiation data was recorded on the two channels of the three-channel tape. bits were recorded on
the third channel at 3.75-second intervals to establish a time reference for data reduction. The time bits
were generated by a cam-operated switch driven by a low-power. 6-volt, direct-current. chronometricall
governed motor. The accuracyof these pulses was +0.5 percent. The timer was manufactured by the
Haydon Company and was used because of its known accuracy and high reliability.
The function of the control circuit was to start and to turn off the instrument. Power to all the motors
and to the filaments was controlled by means of a latching relay. This relay could be activated locally br
a switch on the instrument or remotely by a contact closure through a cable into the instrument. The in-
strument could be turned off by deactivation of the relay with the switch on the instrument or bv the tapeactuated turnoff switch on the recorder.
Mercurybatteries were used to power the motors and the filaments in order to take advan:age of the
high current capacity and flat-discharge characteristics these batteries offer. In addition, a mercury
batterv with very-low current drain was used in the electrometer-calibration circuit to restrict calibration
shift to less than +1 percent during the expected life of the battery. Chamber bias and transistor bias
were supplied by carbon hatteries.
in excess of 250 hours.
With the exception of the motor battery. the minimum battery life was
However. the 12-hour recorder could be operated in excess of 26 hours and the
60-hour recorder in excess of 80 hours without a battery change.
A.3
DESIGN LIMITS FOR OPERATION
All components were designed to operate under the following maximum conditions: (1) a shock of 15 g
at 11 msec in all planes. (2) vibrations of 12 g at frequencies up to 45 cps in all planes. (3) temperature
within the detector of 120 degrees F, (4) temperature within the main instrument assembly at 155 degrees
F, (5) ambient relative humidity of 100 percent. and (6) a static overpressure of 5 psi. During the opera-
tion, satisfactory performance beyond these limits was frequently observed.
A4
SHOCK MOUNTING
The GITR instruments were installed throughout the three target ships.
Because of the high shock ex-
pected on these platforms. all instruments were shock mounted for approximately 6 inches of deflection.
An eight-point suspension from steel springs in lines through the center of gravity of the instruinent was
used to support the main instrument assembly.
The natural frequency of the suspension was about 5 cps.
The detector unit was supported from four springs in a horizontal plane through the center of gravity of
the unit.
AS
The suspension had a natural frequency of 7 cps and allowed 5 inches of deflection.
REMOTE-STARTING CIRCUIT
The limited recording time of the instruments and the requirement for unattended operation necessitated
remote triggering of the instrument installations. A Shipboard svstem was designed to meet this require~
ment (Figure A.5). The svstem consisted of the EG&G tone receiver and minus~5-munute relay, which was
connected to the project control panel and relay system. The relay system consisted of latching relays.
which were spaced throughout the ship. When activated by the timing signal. each latching relay started
83