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9. The main source of gamma radiation between 5 and 10
seconds after detonation is the fission fragments since the
neutrons released to air have disappeared and the contribution
from activated elements is negligible at this time.
Because of
air displacement due to shock the recording stations should be
Several recording stations, 2000 to 5000. yards
fairly close.
from the detonation,
consisting of a fluor behind an optical
collinating system, a photocell detector and a recording
oscilloscope,
can give the fission yeild to an accuracy within a
factor of 1.5 to 2, the chief source of uncertainty being in the
estimate of attenuation between the source and the detector
(Appendix "c"),
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This method requires
,
yields of the weapon be declassified
Knowledge of these yields and possession of long
range samples for analysis by another nation would permit that
nation to obtain important design information about our weapons,
Methods of confusing such determinations by the addition of
various materials to the fireball of the Weapon are presently
being investigated.
The cost of this method should not be great
-and there is sufficient time to prepare for its use prior to the
demonstration shot.
This method possesses operational simplicity,
although in common with all methods under consideration, fairly
elaborate security and administrative precedures would have to be
worked out.
er