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Mass measurements on neutron-rich nuclei with the CPT mass CARIBU Kumar S. Sharma Department of Physics and Astronomy Winnipeg MB.

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Presentation on theme: "Mass measurements on neutron-rich nuclei with the CPT mass CARIBU Kumar S. Sharma Department of Physics and Astronomy Winnipeg MB."— Presentation transcript:

1 Mass measurements on neutron-rich nuclei with the CPT mass CARIBU Kumar S. Sharma Department of Physics and Astronomy Winnipeg MB

2 Outline Introduction Introduction Past work with the CPT at ANL Past work with the CPT at ANL CARIBU – opportunities for the CPT CARIBU – opportunities for the CPT Current status of the apparatus Current status of the apparatus Conclusion Conclusion

3 Synthesis of the elements from : The r-process plays an important role in the synthesis of the heavier elements The r-process plays an important role in the synthesis of the heavier elements

4 Possible sites for the r-process Why these sources: Why these sources: high density of neutrons high density of neutrons high temperature environments high temperature environments Supernovae???Merging neutron stars???

5 r-process basics Nuclear reactions compete until a balance is reached Abundance maxima along each chain occurs with the neutron separation energy, S n ~ 3 MeV N Z (n,γ) (γ,n) β-β- SeedWaiting-point …

6 The Saha Equation The relative abundances of the elements synthesized in the r-process are determined by the Saha Equation: The relative abundances of the elements synthesized in the r-process are determined by the Saha Equation: determines the equilibrium between neutron capture and photodisintegration in a very hot environment. determines the equilibrium between neutron capture and photodisintegration in a very hot environment. outcome is exponentially dependent on the neutron separation energy. outcome is exponentially dependent on the neutron separation energy. Atomic masses of the nuclides along the reaction paths are needed to determine the neutron separation energy: S n Atomic masses of the nuclides along the reaction paths are needed to determine the neutron separation energy: S n

7 Neutron separation energies Single neutron separation energies: Single neutron separation energies: S n values: [n – (M(Z,N) – M(Z, N-1))]c 2 S n values: [n – (M(Z,N) – M(Z, N-1))]c 2 Double neutron separation energies Double neutron separation energies S 2n values: [2n – (M(Z,N) – M(Z, N-2))]c 2 S 2n values: [2n – (M(Z,N) – M(Z, N-2))]c 2 Converted to appropriate energy units

8 Fission Yields from a 252 Cf source 1 Ci source strength

9 Previous configuration of the CPT

10 New CPT / Previous CPT measurements CPT Fission Fragment Measurements Ongoing program of measurements since March 2008, target 15 keV uncertainty Ongoing program of measurements since March 2008, target 15 keV uncertainty 40 species, 5 have never been previously measured by any means, most others improved by a typical factor of 5 40 species, 5 have never been previously measured by any means, most others improved by a typical factor of 5 Adds to 30 measurements taken at CPT in past years with small gas catcher Adds to 30 measurements taken at CPT in past years with small gas catcher

11 Comparisons with the AME03 CPT U. Hager et al., Phys. Rev. Lett. 96, (2006). JYFLTRAP Deviations from 2003 atomic mass evaluation increase with neutron number Deviations from 2003 atomic mass evaluation increase with neutron number Trends suggest r-process path is closer to stability Trends suggest r-process path is closer to stability

12 S 2n values: [2n – (M(Z,N) – M(Z, N-2))]c 2 More recent work

13 New CPT / Previous CPT measurements Grander Plans

14 What’s moving? CPT Tower CPT Tower Associated electronics and vacuum control Associated electronics and vacuum control

15 Overview of CARIBU

16 CPT at CARIBU CARIBU CPT Stable ion source Buncher Elevator

17 Low energy beamline

18 Requirements at CARIBU Desired precision: ~ 10 – 100 keV Desired precision: ~ 10 – 100 keV Required yield: ions for a measurement Required yield: ions for a measurement Considerations: Considerations: ‘Production’ yield (2-80 mCi) ‘Production’ yield (2-80 mCi) Efficiency (~ 1%) Efficiency (~ 1%) Half-life ~ 1 second Half-life ~ 1 second

19 Plan for measurements Jon’s Dan’s Vastly superior to 238 U fission Get online ASAP Get online ASAP Gas catcher/RFQ operational Gas catcher/RFQ operational Buncher RFQ built and being commisioned Buncher RFQ built and being commisioned CPT assembled and operational CPT assembled and operational Low energy beam line installed Low energy beam line installed Spend 6 to 18 months measuring 100+ masses to < Spend 6 to 18 months measuring 100+ masses to < Goals include r-process and nuclear structure Goals include r-process and nuclear structure

20 Conclusion Previous results among neutron-rich nuclei approaching the r-process path Previous results among neutron-rich nuclei approaching the r-process path Some interesting systematic effects observed Some interesting systematic effects observed Higher yields of these nuclei at CARIBU will allow us to push even further away from stability Higher yields of these nuclei at CARIBU will allow us to push even further away from stability

21 The CPT Collaboration A. Chaudhuri, G. Gwinner, K.S. Sharma J.A. Clark, A.F. Levand, G. Savard, T. Sun, F. Buchinger, J.E. Crawford, S. Gulick, G. Li D. Lascar, R. Segel S. Caldwell, M. Sternberg, J. Van Schelt C.M. Deibel

22 Efficiencies at CARIBU Efficiency: Yield (2-80 mCi 252 Cf; 3% fission branch) Enter gas catcher (~ 50%) Stopped in gas catcher (~ 80%) Extracted from gas catcher (~ 33%) RFQ (~ 80%) Transfer through mass separator (~90%) Buncher (~ 60%) Transfer to Penning trap (~ 33%) Detection (~ 50%) Total: ~ 1% efficiency (excluding 3% fission branch)


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