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Sebastian Reichert TU Munich , E12

Study of -Ray Multiplicities of Evaporation Residues in Heavy Fusion Systems Using the MINIBALL Spectrometer. Sebastian Reichert TU Munich , E12. Identification of Super Heavy Elements.

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Sebastian Reichert TU Munich , E12

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  1. Study of-Ray Multiplicitiesof Evaporation Residues in Heavy FusionSystems UsingtheMINIBALL Spectrometer Sebastian Reichert TU Munich, E12

  2. IdentificationofSuper Heavy Elements GSI: Research: Super Heavy Elements. http://www.gsi.de/start/forschung/forschungsgebiete_und_experimente/ nu%starenna/ she_physik/research/ super_heavy_elements.htm • Isle ofStability • Nuclearstructure

  3. Challenges GSI + RIKEN Cold Fusion: Verylittlecrosssection (pbarn)Short lifetimes (μs – ms) γ-energiesunknown FLNR Hot Fusion: Higher crosssection (pbarn)Long lifetimes (ms – d) γ-energiesunknown

  4. Solution: -raymultiplicity

  5. Aimsofourwork • Semi-empiricalmassdependentmultiplicity • Application: Radon • Derivation andfurtherresults  Ch. Berner • Reductionofthebackground • Offline: Searchingforcoincidenesbetweeen-raysand (unknown) γ-energies • Online: Appropriateshieldingofthefissionphotons

  6. Setup • MLL in Garching • Alu-chamberwith 2mm wall thickness • 33% spacecovering • Implantation plate

  7. Mass region Average neutronnumber Karwowski et al. (1982): -ray- -raycoincidencemethod;

  8. Application: Element Radon PtO,4nRn; Beam energy: 87 MeV

  9. PtO,4nRn

  10. PtO,4nRn Coincidence-spectrumofthedecayofthegroundstateat.9 keV

  11. PtO,5nRn PtO,4nRn • -raycoincidencemethod • Rn: • Rn: • Rn: • -ray-raycoincidencemethod • Rn: • Rn:

  12. Comparisonwithfurther-raymultiplicities H. J. Karwowski, S. E. Vigdor, W.W. Jacobs, S. Kailas, P. P. Singh, F. Soga, T. G. Throwe, T. E. Ward, D. L. Wark, and J. Wiggins: Phys. Rev. C Vol. 25, No. 3 (1982).

  13. Reductionofthebackground • Heavy fusionelementsand high beam energies Fusion crosssectionsdecrease, fissionincreases • 1. Approach: Purifyingthespectra • 2. Approach: Suppression ofthefissionphotons N. Shinohara, S. Usuda et al.: Phys. Rev. C 34, 909-913 (1986).

  14. Purifyingthespectra ThC,xn at 67 MeV Coincidence-spectrum: No-rays

  15. γ- coincidentevents ThC,xn Coincidence-spectrum: No-rays Gate on 981 keV: Extractionof-rays?

  16. Suppression ofthefissionphotons • Geometricalconsideration • Evaporation residuestowards Beam direction • Fission productsinto

  17. Suppression ofthefissionphotons

  18. Choice offusion- andfission-peaks NoshieldingShieldingwithslit Improvementoftheratio: 7.2(13)

  19. Summary • Application: Radon • Different multiplicitiesfor different methods • Nuclearstructure • Reductionofthebackground • Offline: Searchingfortransitionenergies •  Resultunclear • Online: Shieldingwithleadpot • Improvementofthefusion- tofissionratio

  20. Solution: -raymultiplicity • Internal conversion: Interaction betweenelect.-magn. fieldsoftheexcitednucleiwithatomicelectrons (mostlyof K-shell). • Vacantshell will befilledfrom an electronof an highershell Charact. X-rayradiation • -rayenergycalculable via Moseley‘slaw

  21. Purifyingthespectra ThC,xn 981 keV 973 keV Resultunclear

  22. Processing todeterminethemultiplicity • -rayCoincidencemethod • Setting gate on decayline • Out oftheoriginatedspectrum: • No absolut effiziencynecessary • Considerationofcascadeswithoutinternalconversion

  23. -ray-raycoincidencemethod • Unsufficientlevelschemeand large A high multiplicity: • Several-rays per decay Gate • Distribution ofcoincidentsignalsatfixedmultiplicity • e.g. measurementofexactlyone-ray • Numbers oftwosimultaneuousmeasured-rays

  24. -ray-raycoincidencemethod • Absolut efficiency necessary • DirtySpectrumCascadeswithat least twiceinternalconversion • Iflowtransitionenergiesknown • -ray-raycoincidencemethod • Gate on γ-energypurifiesspectrum • Applyingthe-ray-raycoincidencemethod also countscascadeswithat least oneinternalconversion

  25. PtO,4nRn • -raycoincidencemethod • -ray-raycoincidencemethod

  26. Reasonsforthe different results 215 MeV 219 MeV No R.-D. Herzberg, S. Moon et al.: Eur. Phys. J. A 42, 333–337 (2009). P. Reiter, T. L. Khoo, T. Lauritsen, C. J. Lister et al.: Phys. Rev. Letters Vol. 84, No. 16 (2000).

  27. Suppression ofthefissionphotons Improvementoftheratio: 7.2(13)

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