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The RI-Beam Factory and Recent Development in Superheavy Elements Search at RIKEN

The RI-Beam Factory and Recent Development in Superheavy Elements Search at RIKEN. Brief introduction to the RI Beam Factory Confirmation of 271 [110] and discovery of a new transuranium isotope 234 Bk. Isao Tanihata RIKEN. RIBF is a multi-disciplinary facility. Nuclear Physics

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The RI-Beam Factory and Recent Development in Superheavy Elements Search at RIKEN

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  1. The RI-Beam Factory andRecent Development in Superheavy Elements Search at RIKEN • Brief introduction to the RI Beam Factory • Confirmation of 271[110] and discovery of a new transuranium isotope 234Bk Isao Tanihata RIKEN

  2. RIBF is a multi-disciplinary facility • Nuclear Physics • Nuclear Astrophysics • Atomic Physics • Material Science • Nuclear Chemistry • Biology • Medicine • Nuclear Power

  3. Nuclear Physics • Probe the limit of nuclear existence and to understand the basic physics of the nuclear landscape • Exploration of the limit of existence • Drip-line nuclei • Nuclei outside the drip lines • Superheavy nuclei • Magic numbers far from the stability • Study of unbalanced nuclear matter and the role of isospin • Explore the new forms and dynamics of nuclei • Neutron skins & halos • Also excitations and correlation • Exotic shapes • Testing of the Standard model and fundamental symmetries and conservation laws

  4. Nuclear Astrophysics • Provide the basic data of nuclear astrophysics • Big bang nucleosynthesis • The CNO cycle to the rp-process • Alpha-rich freeze out • The r-process • Equation of state of asymmetric matter and neutron stars • Highly ionized atoms of unstable nuclei • Remarks • The measurement and the analysis of the nuclei far from stability will provide new test benches for theoretical nuclear models. This should allow one to reformulate these models in a more general form. Hence, the predictive power of these models, when applied to unknown nuclei for nuclear astrophysics applications, will be greatly increased.

  5. Bird Eye View of RIBF 2005

  6. The Beam Delivering Method • AVF cyclotron --> will become free • CNS/RIKEN • Present facility --> primary and secondary beam from ISR • BigRIPS --> two experimental beam lines • MUSES --> ACR, DSR

  7. Accelerator Scheme Accelerators ECR18 RILAC CMS RFQ linac RRC fRC IRC SRC

  8. Primary Beam Energy @RIBF With fRC 1 pµA for all elements

  9. IRC Sector magnet

  10. SRC design

  11. ECRIS-18 ECRIS-18

  12. ECRIS-18 Beam Intensity

  13. RI Beam Separators (Big-RIPS)

  14. Production Target

  15. R.T. Test Result

  16. Rotating Target Extension • Changing target thickness in one rotation • 6000 rpm -> 1 rotation = 10 ms -> 10˚=0.27 ms • Control of 0.3 ms is possible! • 3mm/30cm diameter= 0.57

  17. Experimental Room

  18. Secondary Beam Intensities

  19. Doubly Magic Nuclei Intensity

  20. Search for Superheavy Elements Confirmation in different laboratories is essential!

  21. Advantage of RIKEN Yield = s x T x I x e s = 10-36cm2 (1pb) T = 5x1017/cm2 I = 6x1012 /s (1 particle mA) e = 0.3 Y = 9x10-7 events/s 2.3 /month • Heavy Element Search • High-intensity beam from high-performance accelerator • High-performance recoil separator • Accelerator complex in RIKEN • ECR ion source + RFQ Linac + RILAC + CSM • Highest Energy 5.8AMeV • Highest Intensity 10 particle mA • Gas-filled Recoil Separator GARIS • Velocity & Charge -state focusing • A large acceptance

  22. 284. WE-Heraeus-Seminar 2002/08/08 ECR+RFQ+RILAC + CSM GARIS Ring Cyclotron ECR ion source CSM(Charge State Multiplier) RILAC(RIken Linear ACcelerator)

  23. GARIS

  24. GARIS target with Beam Target and Beam in He gas

  25. Vacuum gas Principle of GARIS qc-1 qc qc+1 <q> • Magnetic rigidity • is independent from • the velocity of a nucleus.

  26. GARIS Detector

  27. 271[110] by 208Pb(64Ni,n)271[110]

  28. 271[110] Summary Reaction 208Pb(64Ni,1n)271[110] Target 208Pb 230 mg/cm2 Efficiency 0.76 Counting rate of PSD 2/s (@ 0.4 pmA) Beam energy 311.2 MeV Total beam dose 8.8x1017 Event number 1 Cross section 2.3 pb Beam energy 314.2 MeV Total beam dose 6.3x1017 Event number 2 Cross section 6.3 pb T(1/2) = 12.9 ms

  29. Collaborators: K. Morita RIKEN K. Morimoto RIKEN D. Kaji RIKEN, Niigata U. And many others

  30. New Isotope of Bk • 197Au(40Ar,3n)234Bk • Beam energy at 196.9 and 188.4 MeV • 1.5~2.5 particle µA • 9 a-chain events have been observed.

  31. 234Bkachains

  32. Decay chain of 234Bk

  33. Comparison of a-decay Q-value • KUTY is the mass formula with shell energies on a spherical-basis, • TUYY is the mass formula with an empirical shell term, • FRDM is the finite-range-droplet model and folded-Yukawa single-particle potential, and • HFBCS is to be based on the Hartree-Fock+BCS method with the MSk7 Skyrmeforce.

  34. SHE search is running at full speed

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