Mass measurements on neutron-rich nuclei with the CPT mass spectrometer @ CARIBU

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

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

3. Synthesis of the elements • The r-process plays an important role in the synthesis of the heavier elements from : http://www.jinaweb.org/html/pprocess.html

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

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

6. 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. • 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: Sn

7. Neutron separation energies • Single neutron separation energies: • Sn values: [n – (M(Z,N) – M(Z, N-1))]c2 • Double neutron separation energies • S2n values: [2n – (M(Z,N) – M(Z, N-2))]c2 • Converted to appropriate energy units

8. Fission Yields from a 252Cf 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 • 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

11. JYFLTRAP U. Hager et al., Phys. Rev. Lett. 96, 042504 (2006). Comparisons with the AME03 CPT • Deviations from 2003 atomic mass evaluation increase with neutron number • Trends suggest r-process path is closer to stability

12. S2n values: [2n – (M(Z,N) – M(Z, N-2))]c2 More recent work

13. New CPT / Previous CPT measurements Grander Plans

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

15. Overview of CARIBU

16. Stable ion source CARIBU Buncher Elevator CPT at CARIBU CPT

17. From isobar separator 50 kV cage 200 kV platform Low energy beamline

18. Requirements at CARIBU • Desired precision: ~ 10 – 100 keV • Required yield: 3000-30000 ions for a measurement • Considerations: • ‘Production’ yield (2-80 mCi) • Efficiency (~ 1%) • Half-life ~ 1 second

19. Vastly superior to 238U fission Jon’s Dan’s Plan for measurements • Get online ASAP • Gas catcher/RFQ operational • Buncher RFQ built and being commisioned • CPT assembled and operational • Low energy beam line installed • Spend 6 to 18 months measuring 100+ masses to < 10-7 • Goals include r-process and nuclear structure

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

21. S. Caldwell, M. Sternberg, J. Van Schelt D. Lascar, R. Segel 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 C.M. Deibel

22. Efficiencies at CARIBU • Efficiency: • Yield (2-80 mCi 252Cf; 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)