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

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ReA3 Upgrade Workshop 2015

Nuclear Astrophysics Measurements beyond ReA3

• C. M. Deibel

Louisiana State University

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ReA3 Upgrade Workshop 2015

• H. Grawe et al., Rep. Prog. Phys. 70, 1525 (2007).

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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: Er – linearly dependent on resonance strength: ωγ

• Measure reaction rates:

– directly – indirectly

Rolfs & Rodney (1988)

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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)

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ReA3 Upgrade Workshop 2015

• 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

– 14N(α,p)17O – 18Ne(α,p)21Na

• First experimental run with

reaccelerated RIB from ReA3:

– 37K(p,p) 37K

Direct (α,p) Reaction Measurements with Active Targets

RIB p

recoil

(via window)

14N(α,p)17O

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ReA3 Upgrade Workshop 2015

• 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. 24C + 24C)

Indirect Measurements Needed

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ReA3 Upgrade Workshop 2015

• Rapid proton capture (rp)

process:

– series of (p,γ) reactions and β decays – occurs in classical novae and X- ray bursts

• 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,nγ) – (3He,d) – (6Li,d)

Indirect Measurements of rp-process

giant star

H-He-rich

white dwarf or neutron star

Cyburt et al., AJSS (2010) time (s)

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ReA3 Upgrade Workshop 2015

• A. Parikh et al., ApJ SS 178, 110 (2008).

rp-process Sensitivity Studies

Type I X-ray bursts

• C. Iliadis et al., APJ SS 142, 105 (2002)

Classical Novae

• Reaction rates
• f interest:

– (p,γ) – (α,γ) – (α,p) – (p,α)

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ReA3 Upgrade Workshop 2015

• 57Cu(p,γ)58Zn largest, unmeasured uncertainty in

XRB nucleosynthesis around 56Ni waiting point

• Studied d(57Cu,58Zn)n at NSCL

–

58Zn identified with S800

– γ rays from 58Zn* detected with GRETINA

• Measurements of resonance energies and

tentative spins reduce reaction rate uncertainties by 3 orders of magnitude

57Cu(p,γ)58Zn via 57Cu(d,n)58Zn* with GRETINA

• C. Langer et al., PRL 113, 032502 (2014)

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ReA3 Upgrade Workshop 2015

• 57Cu(p,γ)58Zn largest, unmeasured uncertainty in

XRB nucleosynthesis around 56Ni waiting point

• Studied d(57Cu,58Zn)n at NSCL

–

58Zn identified with S800

– γ rays from 58Zn* 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(59Cu,60Zn)n – d(61Ga,62Ge)n – d(65As,66Se)n

57Cu(p,γ)58Zn via 57Cu(d,n)58Zn* with GRETINA

• C. Langer et al., PRL 113, 032502 (2014)

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ReA3 Upgrade Workshop 2015

(3He,d) in HELIOS

500 mbar D2 (gas target)

!"#$%&'()&*+,-.*

3He gas target Z (cm)

Proton energy (MeV)

(a) (b) (c)

Prototype Si array Si array Recoil Detector Target fan Beam

• HELIcal Orbit Spectrometer (HELIOS)

– particle ID via time-of-flight – no kinematic compression à better resolution – high geometrical efficiency

• Measurements of (p,γ) resonances using

target coupled with HELIOS via (3He,d)

–

14C(3He,d)15N used as commissioning experiment

for gas target – resolutions of better than 275-keV FWHM achieved . . . improvements to come

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ReA3 Upgrade Workshop 2015

Solenoid Device at ReA6-12

Step 1: Implement detectors in AT-TPC magnet for ReA3 energies Step 2: New larger, higher-field magnet in ReA12 area using existing detectors, for E>5 MeV/u 1 2 Transfer studies:

• e.g. 30P(3He,d)31S
• ~5 mb/sr
• ~105 pps; ~15 MeV/u

Addition of γ–ray detection?

• e.g. APOLLO

Courtesy A. Wuosmaa

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ReA3 Upgrade Workshop 2015

• JENSA (Jet Experiments in Nuclear Structure and

Astrophysics):

– installed at ReA3 – first RIB experiment scheduled for Spring 2016:

34Ar(α,p)37K

– Advantages:

• high density: 3 – 10 x 1018 atoms/cm2 (~50 µg/cm2 3He)
• target purity
• no target ladder “shadowing”

Transfer Reactions with

• S. D. Pain, AIP 4, 041015 (2014)

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ReA3 Upgrade Workshop 2015

JENSA Data

Potential new levels

• 14N(p,t)12N study with

JENSA

• Study of unbound

states in 12N

• 38 MeV proton beam
• 20Ne(d,p)21Ne study

– Blue: implanted Ne target – Red: JENSA Ne gas target

• Performed at ORNL:

– 30 MeV proton beam – θlab = 37°

• Little to no contamination from

target using JENSA

Courtesy K. Chipps

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ReA3 Upgrade Workshop 2015

• JENSA (Jet Experiments in Nuclear Structure and

Astrophysics):

– installed at ReA3 – first RIB experiment scheduled for Spring 2016:

34Ar(α,p)37K

– Advantages:

• high density: 3-10 x 1018 atoms/cm2 (~50 µg/cm2 3He)
• target purity
• no target ladder “shadowing”
• ReA6/12 opportunities:

– transfer reaction studies:

• gas target needed:

– e.g. 56Ni(3He,d)57Cu

• low contamination needed:

– e.g. (d,p), (d,n), (p,t)

Transfer Reactions with

• S. D. Pain, AIP 4, 041015 (2014)

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r-process nucleosynthesis

• Proceeds via rapid neutron captures on

extremely neutron rich nuclei

• Site unknown

– core-collapse supernova – neutron star mergers

• Site dictates r-process path

– hot r-process – cold r-process

r-process only solar abundances

• C. Sneden, J.J. Cowan, and R. Gallino, ARAA 46, 241 (2008).

Nuclear data needed:

• nuclear masses
• decay lifetimes
• Pn values
• (n,γ) reaction rates

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Hot r-process sensitivity studies

Courtesy M. Mumpower

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ReA3 Upgrade Workshop 2015

• R. L. Kozub et al., PRL 109, 172501 (2012)

r-process studies via (d,p)

• Direct capture expected to

dominate r-process nucleosynthesis at N = 82 shell closure

– calculations of 130Sn(n,γ)131Sn vary by 3 orders of magnitude

• 130Sn(d,pγ)131Sn @ ORNL with

ORRUBA

– 130Sn beam: 4.8 MeV/u, ~2x105 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

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ReA3 Upgrade Workshop 2015

• S. D. Pain, AIP Advances 4, 041015 (2014)
• Gammasphere ORRUBA Dual

Detectors for Experimental Structure Studies

– ORRUBA Si array + Gammasphere @ ANL

• 4 proposals accepted at ATLAS:

– GODDESS commissioning [S. Pain] –

95Mo(d,pγ) as a (n,γ) surrogate [J.

Cizewski] – (d,pγ) with neutron-rich Xe and Te beams [S. Pain] – study of 19Ne states for 18F(p,α) [D. Bardayan]

r-process studies via (d,p): GODDESS

• Measurements of (d,pγ) using GRETINA/GRETA with Si detector

array at ReA12

– (n,γ) cross sections near shell-closers

• 105 – 106 pps @ 12 MeV/u

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ReA3 Upgrade Workshop 2015

Normalize w/ systematics

(Beta) Oslo Approach to (n,γ)

Unfold primary Eγ vs. Ex → relative ρ(Ex) & f(Eγ) Statistical (n,γ) rate

• Nuclear level densities and gamma-strength

function from β-γ with SuN (TAS)

– normalize to systematics – proof-of-principle case: 76Ge – 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)

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• What are the community’s needs for ReAX beams?

– Intensities?

• 103 - 104 ions/s for (d,p) in HELIOS-type device

– >105 ions/s for studies requiring γ–ray coincidence

• 104 - 105 ions/s (3He,d)
• 106 – 107 ions/s (d,pγ)
• …

– 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
• …

ReAx Beams

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ReA3 Upgrade Workshop 2015

• Many things not covered here:

– other processes (p-process, s-process, etc.) – other types of studies (e.g. ANC measurements, etc.) – future equipment needs

• ReAX offers many opportunities for indirect measurements of

astrophysical significance:

– support for eventual direct studies with FRIB – indirect measurements where direct studies are not feasible

• Needs for nuclear astrophysics studies at ReAX

– high quality beams – appropriate experimental equipment

Summary

THANKS!