CHAPTER 6
CONCLUSIONS AND RECOMMENDATIONS
Standardization of the beta densitometer was attained to a large degree at Ivy. All densitometers were built and installed alike. However, each had its characteristic calibration
curve which is strongly dependent on the voltage sensitivity of the cathode-ray tube and
especially on the phctotube used. As available commercial phototubes become more standardized, so will densitometers. Densitometer accuracy, now reliable to 10 per cent or better, will
be more accurate as better phototubes (high sensitivity, less fatigue, negligible dark current,
etc.) become available. Calibration will be more accurate,
At Ivy a suitable phosphor (made by Earl Fullman, Group GMX-5, LASL) was finally made
available for densitometer use. This phosphor eliminated the need for amplifier circuits and
their power supplies. It appears chat densitometers ‘vill continue to use phosphors.
Two of the simplifications incorporated in the jensitometers at Ivy may not be applicable
in densitometers to be used with smaller or nominal bombs. The elimination of shielding and
of a second phototube to subtract background radiation was made possible by the low background radiation that was encountered at the Ivy Mike densitometer stations. This condition
will not hold in smaller bombs (yields in the order of 100 kt or less} at ranges of interest.
Unless advances in electronics make it unnecessary, densitometers for use with nominal or
smaller bombs wili require a second phototube and also lead shielding around the phototubes.
Experience at Operation Tumbler showed that these are reasonable modifications to make.
The success of the d-c beta densitometer at Ivy makes the d-c beta densitometer a
preferred choice over the a-c type. The densitometer instrumen‘ation at Ivy also set a
reliable pattern of densitometer circuitry so that emphasis on future improvements can be
shifted {rom circuit design to a search for more rugged battery power supplies and circuit
parts.
Specific improvements that can be made on the Ivy model beta densitometer are as follows:
1. Use double-pole double-throw relays to decrease current per pole and to increase
reliability.
2. If relay contacts persist in sticking, use more rugged-type relays.
3. Use one pair of H—5 sec master relay terminals to close H~1 min circuits in the
event H—1 min signals are faulty. This precaution will prevent losing the density record for
times of arrival greater than 20 sec.
4. Use an internal delay circuit to operate on the H—1 min signal and to close the camera
circuit in approximately 55 sec in the event that the H-5 sec signal is faulty.
5. Use photosensitive relays (Blue Box) to ensure that all circuits close and remain closed
after zero time.
6, Inasmuch as the densitometer has proved to be relatively immune from spurious or
noise signals, one trace of the oscilloscope may be used to record total background radiation
poo eee
Serenans
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