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3. It should be noted that the above+quoted statements have
been successively less promising as to whether or not the degree
of observation permitted would satisfy the observers that a
particular shot was "clean".
4, It has appeared to the Division of Military Application
that the United States is irrevocably committed to the inviting
of U.N. observers to observe one shot.
Also, the commitment has
implied that (within security requirements) the degree of
observation would be such that an unbiased observer would be
convinced that the shot was "clean",
Therefore DMA, with Labora-
tory representatives and the Commander, JTF-7, has investigated
various means of observation to determine how these two objectives
could be realized.
As a result of our deliberations it appears
that in order to convince an observer of weapon cleanliness,
it is
necessary that he be given or be allowed to obtain information
from which he could calculate, with some degree of accuracy,
lfission to fusion ratio.
Some compromise of design information
could result from revealing this information.
Each of the methods
analyzed could permit this possibility to some degree, unless
certain measures, such as those described in paragraph 7 below,
are taken to prevent the disclosure of additional important
information,
The methods investigated ineludéd the following:
a. To fire two shots of comparable yield (one "clean"
and one conventional) allowing observers after each shot
to monitor with simple counters the intensity of residual
fallout on the Atoll's islands. This method, though
extremely simple, could lead to very unsatisfactory
results.
The land masses are small and the close-in
fallout unpredictable. We could well get hot spots
which would give contradictory and unconvincing evidence.
b. To measure for two comparable medium yield shots
(one “clean” and one conventional) the gamma radiation
‘ close to the fireball during the period 5 to 10 seconds
after the burst. During this period, the fission debris
fragments cause most of the gamma radiation. Through
such measurement, one could secure a basis to judge
comparative "cleanliness".
This method would require
the establishment of instrumentation which might, or