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Triple - Humped Fission Barrier and Clusterization in the Actinide Region

Triple - Humped Fission Barrier and Clusterization in the Actinide Region. A. Krasznahorkay Inst. of Nucl. Res. of the Hungarian Acad. of Sci. (ATOMKI) Debrecen, Hungary. Introduction Resonant tunneling Experimental methods Experimental results: Superdeformed (SD) bands in 240 Pu

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Triple - Humped Fission Barrier and Clusterization in the Actinide Region

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  1. Triple-Humped Fission Barrier and Clusterization in the Actinide Region A. Krasznahorkay Inst. of Nucl. Res. of the Hungarian Acad. of Sci. (ATOMKI) Debrecen, Hungary

  2. Introduction • Resonant tunneling • Experimental methods • Experimental results: • Superdeformed (SD) bands in 240Pu • Hyperdeformed (HD) bands in 234U and in 236U • On the shape of the potential barriers • Mass distributions for 236U and for 233Th • Clustering effects • Summary and conclusion

  3. Triple humped fission barrier

  4. Nuclear fission paths

  5. Resonant tunneling through the fission barrier Eres E*, () J,K

  6. The best energy regions for studying the SD and HD states Howard, Möller, ADNDT 25 (1980) 218 Cwiok et al., PLB 322 (1994) 304

  7. Cyclotron laboratory in ATOMKI, Debrecen

  8. The split-pole magnetic spectrometer in ATOMKI

  9. Experimental setup for studying fission (transmission) resonances in ATOMKI (Debrecen)

  10. Low-pressure position sensitive avalanche counters

  11. Experimental setup for studying fission resonances in Garching (Germany)

  12. Experimental results for 240Pu

  13. SD rotational bands in 240Pu

  14. Previous results for 234U P.G. Goldstone et al., PRC 18 (1978) 1706 J. Blons et al., NP A477 (1988) 21 A. Krasznahorkay et al., PRL 80 (1998) 2073

  15. Reanalized angular distributions

  16. Comparison of the resultsobtained for 234U

  17. Recent results for 234U A. Krasznahorkay et al., Phys. Lett B 461 (1999) 15

  18. Results of the fitting

  19. Previous results for 236U • Krasznahorkay et al., PRL 80 • (1998) 2073 P.G. Goldstone et al., PRC 18 (1978) 1706

  20. Angular distribution of the 5.4 MeV band in 236U

  21. Recent results for 236U

  22. Fitting the fission resonances in 236U Not SD but HD bands !!!

  23. On the depth of the third minimum Calculations with the back shifted Fermi-gas model

  24. Determination of the height of the inner barrier E* Lower and higher limits  EA= 5.15 ± 0.20 MeV hA = 1.2 MeV Exp. Data from Goerlach diploma thesis, Univ. MPI Heidelberg (1978), unpublished

  25. On the height of the fission barriers History of the 3. Minimum Möller … PLB 40 (1972) 329 Blons … PRL 41 (1978) 1282 (Howard, Möller, ADNDT 25 (1980) 218 ) Cwiok … PLB 322 (1994) 304

  26. Nuclear molecules

  27. Clusterization in 234U

  28. The shape of 236U in the third minimum

  29. Setup for TOF measurements

  30. On the width of the mass distribution of 236U

  31. Mass distribution measurements with a double ionization chamber C. Budtz-Jörgensen et al., NIM A258 (1987) 209

  32. On the width of the mass distributions of 233Th Target: ThO2 0.1 mg/cm2, diameter 4 cm Neutrons from 7Li(p,n) at ATOMKI then in Karlsruhe, =1.8*106 n/cm2, one week exp.

  33. TKE-mass distribution correlations A=100 A=132 Cold fission Compactfission

  34. TKE-mass correlations in the decay of the HD resonance in 233Th

  35. Summary and conclusions • Fission resonances  SD and HD states • Density of the HD states  depth of the 3rd minimum • Appearence of the HD resonances + isomer population probability  EA • The ˝Th anomaly˝ has been solved. • Mass distribution from the decay of the HD states  heavy clusterization

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