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Experimental photofission thresholds in /sup 235/U, /sup 238/U, /sup 233/U, /sup 239/Pu, and /sup 232/Th

Technical Report ·
OSTI ID:5906637
; ;

An investigation of the photofission thresholds in /sup 235/U, /sup 238/U, /sup 239/Pu, and /sup 232/Th with a 20-MeV betatron is reported. A method of ..cap alpha.. self-cancellation is described which permits the detection of fissions and the determination of threshold energies in the two highly ..cap alpha.. active samples of /sup 233/U and /sup 239/Pu. An investigation of the photoneutron threshold in N and the energy calculation from mass data provided a check of the absolute energy scale obtained from voltage measurements on the betatron. From this investigation the photofission threshold values for /sup 238/U, /sup 235/U, /sup 239/Pu, and /sup 233/U show a maximum difference or spread of 0.23 MeV, whereas the theory predicts a spread of 1.7 MeV. Also, the order of the experimental thresholds is not the same as the predicted order. Emphasis was placed on determining this order as accurately as was possible. For this reason all the isotopes were referred to the /sup 238/U threshold and were investigated in succession with /sup 238/U. The thresholds of /sup 235/U, /sup 238/U, and /sup 232/Th were determined most accurately. According to theory the /sup 238/U threshold should be larger than the /sup 235/U threshold by approximately 0.6 MeV. The experiment showed definitely that the order is reversed with the /sup 235/U threshold the larger one by 0.23 (+-0.10) MeV. The orders of the experimental thresholds for /sup 239/U and /sup 233/U are also not in agreement with theory.

Research Organization:
Argonne National Lab., IL (USA)
OSTI ID:
5906637
Report Number(s):
AECD-2699
Country of Publication:
United States
Language:
English

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Related Subjects

652026* -- Nuclear Properties & Reactions
A=220 & above
Experimental-- Spontaneous & Induced Fission-- (-1987)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ENERGY
FISSION
NUCLEAR REACTIONS
PHOTOFISSION
PHOTONUCLEAR REACTIONS
PLUTONIUM 239 TARGET
TARGETS
THORIUM 232 TARGET
THRESHOLD ENERGY
URANIUM 233 TARGET
URANIUM 235 TARGET
URANIUM 238 TARGET