Actinide Production in the Reaction of Heavy Ions withCurium-248

Abstract

Chemical experiments were performed t o examine t h e usefulness of heavy ion t r a n s f e r reactions in producing new, neutron-rich actinide nuclides. A gene r a l quasi-elastic t o deep-inelastic mechanism is proposed, and t h e utility of this method a s opposed t o o t h e r methods (e-g. complete fusion) is discussed.The relative merits of various techniques of actinide t a r g e t synthesis a r e discussed. A description is given of a t a r g e t system designed to remove t h e large a m o u n t s of h e a t generated by t h e passage of a heavy ion b e a m through m a t t e r , t h e r e b y maximizing t h e beam intensity which c a n be safely used in an experiment. Also described is a general separation scheme for t h e actinide elem e n t s f r o m protactinium (Z=91) t o mendelevium ( Z = l O l ) , a n d fast specific proc e d u r e s for plutonium, americium a n d berkelium.The cross sections for t h e production of several nuclides from t h e bomb a r d m e n t of 24sCm with lSO, BsKr a n d lseXe projectiles a t several energies n e a r a n d below t h e Coulomb barrier were determined. The results a r e compared with yields f r o m 4aCa arid 2381J bombardments of 24*Cm. Simple extrapolation of t h e p r o d u c t yields into unknown regions of charge and mass indicates t h a t t h e use of heavy ion transfer reactions t o produce new, neutron-rich above-target species is limited. The substantial production of neutron-rich below-target species, however, indicates t h a t with very heavy ions like lseXe a n d 2ssU t h e new species 248Am, 24gAm and 247Pu should be produced with large cross sections from a 2 4 s~m target.A preliminary, unsuccessful altempl. t o isolate 247Pu is outlined. The failure is probably due t o t h e half life of t h e decay, which is calculated t o be less t h a n 3 minutes. The absolute gamma ray intensities from 251Bk decay, n e c e s s a r y f o r calculating t h e 251Bk cross section, a r e also determined.