Investigations of extreme subbarrier fission of [sup 235]U

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7206673

Narayanan, A

An efficient detection setup has been devised for the measurement of thick target fission yields in coincidence with [gamma]-rays. Based on a PVD (Photo Voltaic Device), this arrangement has the sensitivity to detect fission events with cross sections of the order of 10[sup [minus]9] barns (10[sup [minus]33]cm[sup 2]) with a fragment-[gamma] coincidence detection efficiency of 40%. A computer code (PNTF) has been developed to simulate the detector geometry and effects of the thick target, thus enabling the translation of thick target yields to cross sections. For the reaction system 4-12 Mev [sup 1]H + [sup 238]U, it was found that this arrangement was insensitive to backscattered protons and the thick target fission fragment energy spectra compared well with spectra simulated by PONTF. The fission of [sup 235]U in the deep sub-barrier region has been investigated using 200 MeV [sup 197]Au and 20-80 MeV [sup 12]C projectiles. Multiple Coulomb excitation computer codes (COULEX and GOSIA) have been used to investigate the possibility of the fission of [sup 235]U following Coulomb excitation. The first study used the reaction system 200 MeV [sup 197]Au + [sup 235]U. No fission fragments were observed in coincidence with [gamma]-rays for [approximately]10[sup 14] incident projectiles. The excitation function for the fission of [sup 235]U induced by [sup 12]C was measured for projectiles with energies of 20-80 MeV. Deduced branching ratios have been compared for the four experimental systems (1) 1.5-2.5 MeV [sup 1]H + [sup 235]U, (2) 3-4 Mev [sup 4]He [sup 235]U, (3) 200 MeV [sup 197]Au + [sup 235]U and (4) 20-55 MeV [sup 12]C [sup 235]U. It is concluded that more than one mechanism is involved.

• Research Organization: State Univ. of New York, Stony Brook, NY (United States)
• OSTI ID: 7206673
• Country of Publication: United States
• Language: English

Related Subjects

663470* -- Fission-- (1992-)
663590 -- Nuclear Mass Ranges-- A=220 & Above-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ACTINIDE ISO
ACTINIDE NUCLEI
ALPHA DECAY RADIOISOTOPES
BRANCHING RATIO
CARBON 12 REACTIONS
CHARGED-PARTICLE REACTIONS
CROSS SECTIONS
DETECTION
ENERGY RANGE
EVEN-ODD NUCLEI
EXCITATION FUNCTIONS
FISSION
FUNCTIONS
GAMMA DETECTION
GOLD 197 REACTIONS
HEAVY ION REACTIONS
HEAVY NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MEV RANGE
MINUTES LIVING RADIOISOTOPES
NUCLEAR REACTIONS
NUCLEI
RADIATION DETECTION
RADIOISOTOPES
SPONTANEOUS FISSION RADIOISOTOPES
URANIUM 235
URANIUM 238 REACTIONS
URANIUM ISOTOPES