in neutron star mergers through mass measurements with the CPT July 1627 2018 Jason clark FRIB and the GW170817 kilonova outline 2 Role of mass measurements in rprocess calculations ID: 1026986
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1. Examining r-process nucleosynthesis in neutron star mergers through mass measurements with the CPTJuly 16-27, 2018Jason clarkFRIB and the GW170817 kilonova
2. outline2Role of mass measurements in r-process calculationsCARIBU: a facility to provide neutron-rich nuclidesThe Canadian Penning Trap (CPT) and mass measurement techniquesResults relevant for understanding rare-earth peak formationOutlook
3. Role of nuclear physics3Uncertainties in the nuclear physics: masses β-decay lifetimes β-delayed neutron emission (n,γ), (α,n) rates fissionabilityETFSI-Q massesETFSI-1 massesSame r-process modelMass numberAbundanceM.R. Mumpower et al., J. Phys. G: Nucl. Part. Phys.42, 034027 (2015).Theories/models agree to some extent in regions where data exists (but not necessarily to the precision required)However, theories/models often diverge quite wildly outside the realm of experimental data
4. Challenges/opportunities in nuclear physics4Challenges:Some of the more interesting isotopes are the hardest to produceThese neutron-rich isotopes are also short-livedProduction of these isotopes generally have contaminantsToo many nuclides, too little time!Solutions:Develop equipment which are fast, efficient, and can handle contaminantsDevelop new facilities which can produce the interesting neutron-rich isotopes in large quantitiesHave theory/models/simulations guide experiments and prioritize measurements
5. Experimentalists guided by theory5We can’t just measure ‘everything’!Too many nuclides, too little time.Demand for ‘beamtime’ at accelerator facilities is high; not every proposal gets accepted, therefore need solid justification as to why particular nuclides need to be measuredOften guided by sensitivity studies to focus research and effortStudies either:Look at how ‘good’ existing nuclear data/models are at reproducing the observed abundances (for example), and see how the change in one nuclide property affects the distribution (ie: how ‘sensitive’ it isWork backwards (reverse engineer) to determine the nuclear physics that should exist for the particular astrophysical trajectoryResults:Which nuclides are important to studyTo what precision do they need to be measuredM.R. Mumpower et al., Prog. Part. Nucl. Phys. 86, 86 (2016).
6. A source of ‘r-process nuclides’: CARIBU (Californium rare isotope breeder upgrade)6‘Stopped’ beam experimental area 252Cf source properties: 3% fission branch 2.6 year half-life ~ 1 Ci (40 billions decays / s ) CARIBU beams can be accelerated through ATLAS to ~ 15 MeV/A Basic properties of fission fragments can be measured with instruments in ‘stopped’ beam area Production of neutron-rich isotopes through fission (252Cf spontaneous fission source)
7. Caribu production: 252Cf source7
8. CARIBU8LOW ENERGY EXPERIMENTAL AREA~1 Ci 252Cf sourceGas catcher (collect fission fragments)Isobar separator (select specific fragment) R ~ 14,000 to 20,000Buncher (transforms continuous CARIBU beam into pulsed beam)BPTX-ARRAYTAPE STATIONCPTMR-TOF (high-resolution mass separation) R ~ 100,000
9. Routing of new caribu low-energy beamline9
10. Routing of new caribu low-energy beamline10
11. Layout/design of new caribu low-energy beamline11Courtesy Rick VondrasekCARIBU isobar separatorATLAS RFQEBISMR-TOFNew low-energy experimental areaExisting low-energy experimental area
12. New low-energy experimental area 12New low-energy experimental area offers more space for experiments, and less gamma/neutron background
13. 13More than 450 neutron-rich nuclides have been measured to ~ 15 keV (0.1 ppm) precision or better with Penning trapsMuch interest in this region has driven the development of new techniques for the mass measurements of nuclides for the astrophysical r processJ. A. Clark and G. Savard, Int. J. Mass Spectrom. 349-350, 81 (2013).Mass measurements
14. Results from initial measurements of neutron-rich nuclides14 In Sn Sb Te I Xe Cs Pr Nd Pm Sm EuGdHigher N Trends indicate nuclei are less bound with neutron excess (affects the location of the r-process path Good agreement with other Penning trap results and reaction Q value measurements Large disagreement with results obtained with β-decay measurementsLess bindingJ. Van Schelt et al., Phys. Rev. Lett. 111, 061102 (2013).J. Van Schelt et al., Phys. Rev. C 85, 045805 (2012).
15. New mass measurement technique: pi-icr15 Replacing channeltron with position-sensitive MCP detectorPhase imaging – ion cyclotron resonance The orbital frequency of the ion’s motion is calculated from the phase change over time.PI-ICRIons from the Penning trap
16. New mass measurement technique: pi-icr16 Replacing channeltron with position-sensitive MCP detectorPhase imaging – ion cyclotron resonanceOnline testing with 133Cs at CPTS. Eliseev et al., Phys. Rev. Lett. 110, 082501 (2013). The orbital frequency of the ion’s motion is calculated from the phase change over time.PI-ICR657844.90(8) Hz
17. 130Ing130Inm130InnSome examples of pi-icr resolution17Hartley et al., Phys. Rev. Lett. 120, 182502 (2018). Resolution obtained with PI-ICR technique surpasses what could be done with conventional TOF-ICR technique (for rare, short-lived isotopes)
18. Measurments of heavy 252Cf fragments made with the cpt18
19. Rare-earth masses19Our version of a low-count experimentSaw ~4-7 counts of 160Nd per hourWeakest isotope studied yet at CARIBU (~1x10-5% branch).
20. “Reverse-engineered” masses20Work carried out by Nicole Vassh, Matt Mumpower, Rebecca Surman, and Gail McLaughlinCalculate the abundance pattern given nuclear data input for a specific astrophysical environmentAdd mass corrections to DZ mass model: Use Markov Chain Monte Carlo to find a set of masses which reproduce the observed abundances at A~165Results for a hot r-process in a neutron star merger windR. Orford, N. Vassh et al., Phys. Rev. Lett. 120, 262702 (2018).
21. Comparison between theory and experiment21Takeaway:See good agreement between experiment and theory given this scenarioRare-earth peak can be created through dynamical mechanism Need to measure more masses and calculate further mass surfaces under different astrophysical conditionsR. Orford, N. Vassh et al., Phys. Rev. Lett. 120, 262702 (2018).Neutron number, NMass – DUZU mass [MeV]
22. Measuring more masses …22Now looking at mass surfaces that would be required to reproduce rare-earth peak under different astrophysical conditions using Laboratory Computing Resource Center (LCRC) at Argonne National LaboratoryStay tuned!Preliminary
23. Reach of present and future facilities23Early sensitivity studies for neutron-star mergers (left) show some key nuclides are currently in reach of CARIBU, and others will be within reach of FRIBSome nuclides may unfortunately never be within reach, but any and all data will help refine modelsR. Surman et al., EPJ Web of Conferences 66, 07024 (2014)
24. Near future: N=126 FACTORY24 Use deep-inelastic reactions to produce neutron-rich isotopes in the N=126 region But there has been a historic challenge of collecting reaction products efficiently: New N=126 facility at Argonne will capitalize on high-intensity beams and high-intensity gas catcher technology Will feed suite of low-energy experiments (masses, decay spectroscopy, …)
25. summary25Mass measurements of r-process nuclides will help to determine where in NS-NS mergers does nucleosynthesis occur, abundance pattern, other r-process sites.Reaching the nuclides involved in the r-process has motivated the construction of new facilities and the development of new measurement techniques.We’re just getting started … lots more to come!
26. Collaboration26F. Buchinger, R. OrfordJ.A. Clark, J.W. Klimes, X. YanA. Aprahamian, M. Brodeur, A. Nystrom, W. Porter, R. Surman, N. VasshM. MumpowerM. Burkey, G. Savard G.C. McLaughlinD.A. Gorelov, T.Y. Hirsh, G.E. Morgan, D. Ray, K.S. Sharma