Nuclear Astrophysics Measurements beyond ReA3 C. M. Deibel - PowerPoint PPT Presentation

Nuclear Astrophysics Measurements beyond ReA3 C. M. Deibel Louisiana State University 1 ReA3 Upgrade Workshop 2015

H. Grawe et al ., Rep. Prog. Phys. 70 , 1525 (2007). 2 ReA3 Upgrade Workshop 2015

Direct vs. Indirect measurements • Reaction rate combines – thermal velocity distribution in stellar plasma (Maxwell-Boltzmann distribution) – probability of tunneling through Coulomb barrier (nuclear cross section) • For resonant reaction rates: – exponentially dependent on resonance energy: E r – linearly dependent on resonance strength: ωγ Rolfs & Rodney (1988) • Measure reaction rates: – directly – indirectly 3 ReA3 Upgrade Workshop 2015

Direct Measurements with SECAR • Recoil separator planned for ReA/FRIB • Targets: – windowless gas target JENSA already installed at ReA – extended gas target to be developed • Direct measurements of ( p, γ ) and ( α , γ ) reactions – capture on nuclei up to A = 65 – 1 x 10 -17 rejection SECAR Working Group: Tonight 16:00 (BPS 1400) 4 ReA3 Upgrade Workshop 2015

Direct ( α ,p ) Reaction p Measurements with Active Targets RIB recoil (via window) • Array for Nuclear Astrophysics and Structure with Exotic Nuclei (ANASEN) – active gas target detector – proportional counter surrounded by Si detector array • Successful runs with both stable and radioactive beams at Florida State University – 14 N( α ,p ) 17 O – 18 Ne( α ,p ) 21 Na 14 N( α ,p ) 17 O • First experimental run with reaccelerated RIB from ReA3: – 37 K( p,p ) 37 K 5 ReA3 Upgrade Workshop 2015

Indirect Measurements Needed • Support for future direct measurements – nuclear structure must be well understood to make efficient use of ReA/FRIB beams • location of resonance energies • spins & branching ratios à strength of resonances • Alternatives to direct measurements – low cross section reactions – low beam intensities – reactions between two unstable species • ( n, γ ) reactions for r -process • fusion reactions between unstable nuclei (e.g. 24 C + 24 C) 6 ReA3 Upgrade Workshop 2015

Indirect Measurements of rp -process giant star white dwarf or neutron star • Rapid proton capture ( rp ) process: – series of ( p, γ ) reactions and β decays – occurs in classical novae and X- ray bursts H-He-rich • Reaction rates often dominated by specific resonances: – affect final elemental abundances – determine observables (i.e. light curves) • Indirect ( p, γ ) and ( α , γ ) reaction rate studies: – ( d,n ) and ( d,n γ ) – ( 3 He, d ) – ( 6 Li, d ) time (s) Cyburt et al., AJSS (2010) 7 ReA3 Upgrade Workshop 2015

rp -process Sensitivity Studies Type I X-ray bursts Classical Novae • Reaction rates of interest: – ( p, γ ) – ( α , γ ) – ( α ,p ) – ( p, α ) A. Parikh et al ., ApJ SS 178 , 110 (2008). C. Iliadis et al ., APJ SS 142 , 105 (2002) 8 ReA3 Upgrade Workshop 2015

57 Cu( p, γ ) 58 Zn via 57 Cu( d,n ) 58 Zn* with GRETINA • 57 Cu( p, γ ) 58 Zn largest, unmeasured uncertainty in XRB nucleosynthesis around 56 Ni waiting point • Studied d ( 57 Cu, 58 Zn) n at NSCL – 58 Zn identified with S800 γ rays from 58 Zn* detected with GRETINA – • Measurements of resonance energies and tentative spins reduce reaction rate uncertainties by 3 orders of magnitude C. Langer et al ., PRL 113, 032502 (2014) 9 ReA3 Upgrade Workshop 2015

57 Cu( p, γ ) 58 Zn via 57 Cu( d,n ) 58 Zn* with GRETINA • 57 Cu( p, γ ) 58 Zn largest, unmeasured uncertainty in XRB nucleosynthesis around 56 Ni waiting point • Studied d ( 57 Cu, 58 Zn) n at NSCL – 58 Zn identified with S800 γ rays from 58 Zn* detected with GRETINA – • Measurements of resonance energies and tentative spins reduce reaction rate uncertainties by 3 orders of magnitude • Similar studies with ReA for ( p, γ ) reactions in XRBs: – d ( 59 Cu, 60 Zn) n – d ( 61 Ga, 62 Ge) n – d ( 65 As, 66 Se) n C. Langer et al ., PRL 113, 032502 (2014) 10 ReA3 Upgrade Workshop 2015

( 3 He, d ) in HELIOS Prototype Target fan Si array Si array • HELIcal Orbit Spectrometer (HELIOS) – particle ID via time-of-flight Beam Recoil – no kinematic compression à better resolution Detector – high geometrical efficiency • Measurements of ( p, γ ) resonances using target coupled with HELIOS via ( 3 He, d ) – 14 C( 3 He, d ) 15 N used as commissioning experiment for gas target – resolutions of better than 275-keV FWHM achieved . . . improvements to come 500 mbar D 2 3 He gas target !"#$%&'( )& *+,-.* (a) (b) (c) (gas target) Proton energy (MeV) Z (cm) 11 ReA3 Upgrade Workshop 2015

Solenoid Device at ReA6-12 Step 1: Implement detectors in AT-TPC magnet for ReA3 energies 1 2 Transfer studies: • e.g. 30 P( 3 He, d ) 31 S - ~5 mb/sr - ~10 5 pps; ~15 MeV/u Step 2: New larger, higher-field Addition of γ –ray detection? magnet in ReA12 area using existing • e.g. APOLLO detectors, for E>5 MeV/u Courtesy A. Wuosmaa 12 ReA3 Upgrade Workshop 2015

Transfer Reactions with • JENSA (Jet Experiments in Nuclear Structure and Astrophysics): – installed at ReA3 – first RIB experiment scheduled for Spring 2016: 34 Ar( α ,p ) 37 K – Advantages: • high density: 3 – 10 x 10 18 atoms/cm 2 (~50 µ g/cm 2 3 He) • target purity • no target ladder “shadowing” S. D. Pain, AIP 4 , 041015 (2014) 13 ReA3 Upgrade Workshop 2015

JENSA Data • 20 Ne( d,p ) 21 Ne study – Blue: implanted Ne target – Red: JENSA Ne gas target • Performed at ORNL: – 30 MeV proton beam θ lab = 37° – • Little to no contamination from target using JENSA • 14 N( p,t ) 12 N study with Potential new JENSA levels • Study of unbound states in 12 N • 38 MeV proton beam Courtesy K. Chipps 14 ReA3 Upgrade Workshop 2015

Transfer Reactions with • JENSA (Jet Experiments in Nuclear Structure and Astrophysics): – installed at ReA3 – first RIB experiment scheduled for Spring 2016: 34 Ar( α ,p ) 37 K – Advantages: • high density: 3-10 x 10 18 atoms/cm 2 (~50 µ g/cm 2 3 He) • target purity • no target ladder “shadowing” • ReA6/12 opportunities: – transfer reaction studies: • gas target needed: – e.g. 56 Ni( 3 He,d) 57 Cu • low contamination needed: – e.g. ( d,p ), ( d,n ), ( p,t ) S. D. Pain, AIP 4 , 041015 (2014) 15 ReA3 Upgrade Workshop 2015

r -process nucleosynthesis • Proceeds via rapid neutron captures on extremely neutron rich nuclei • Site unknown – core-collapse supernova – neutron star mergers r-process only solar abundances • Site dictates r -process path – hot r- process – cold r -process C. Sneden, J.J. Cowan, and R. Gallino, ARAA 46 , 241 (2008). Nuclear data needed: • nuclear masses • decay lifetimes • P n values • ( n, γ ) reaction rates 16 ReA3 Upgrade Workshop 2015

Hot r -process sensitivity studies Courtesy M. Mumpower 17 ReA3 Upgrade Workshop 2015

r -process studies via ( d,p ) • Direct capture expected to dominate r -process nucleosynthesis at N = 82 shell closure – calculations of 130 Sn( n, γ ) 131 Sn vary by 3 orders of magnitude • 130 Sn( d,p γ ) 131 Sn @ ORNL with ORRUBA – 130 Sn beam: 4.8 MeV/u, ~2x10 5 ions/s • Results show population of single- particle states – indicated Z = 50 proton shell is intact – L = 1 single particle states are bound à large contribution to DC rate R. L. Kozub et al ., PRL 109 , 172501 (2012) 18 ReA3 Upgrade Workshop 2015

r -process studies via ( d,p ): GODDESS • Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies – ORRUBA Si array + Gammasphere @ ANL • 4 proposals accepted at ATLAS: – GODDESS commissioning [S. Pain] – 95 Mo( d,p γ ) as a ( n, γ ) surrogate [J. Cizewski] – ( d,p γ ) with neutron-rich Xe and Te beams [S. Pain] – study of 19 Ne states for 18 F( p, α ) [D. S. D. Pain, AIP Advances 4 , 041015 (2014) Bardayan] • Measurements of ( d,p γ ) using GRETINA/GRETA with Si detector array at ReA12 – ( n, γ ) cross sections near shell-closers • 105 – 106 pps @ 12 MeV/u 19 ReA3 Upgrade Workshop 2015

(Beta) Oslo Approach to ( n, γ ) • Nuclear level densities and gamma-strength function from β - γ with SuN (TAS) – normalize to systematics – proof-of-principle case: 76 Ge – development of approach to reach more neutron- rich nuclei • Complementary information from reaction studies needed! A. Spyrou et al ., Phys. Rev. Lett. 113 , 232502 (2014) Unfold primary E γ vs. E x → relative ρ (E x ) & f(E γ ) Normalize w/ systematics Statistical (n, γ ) rate 20 ReA3 Upgrade Workshop 2015

ReAx Beams • What are the community’s needs for ReAX beams? – Intensities? • 10 3 - 10 4 ions/s for ( d,p ) in HELIOS-type device – >10 5 ions/s for studies requiring γ –ray coincidence • 10 4 - 10 5 ions/s ( 3 He, d ) • 10 6 – 10 7 ions/s ( d,p γ ) • … – Purity? • high purity beams desirable • coincidence measurements needed for beams with contaminants • … – Time structure? • HELIOS-type measurements require ~80 ns between bunches • nominal rate vs. instantaneous rate • … 21 ReA3 Upgrade Workshop 2015