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Nuclear Astrophysics with fast radioactive beams. Hendrik Schatz Michigan State University National Superconducting Cyclotron Laboratory Joint Institute for Nuclear Astrophysics JINA. Outline: rp-process r-process. Accreting neutron stars. Bursts and other nuclear processes

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Nuclear Astrophysics with fastradioactive beams

Hendrik SchatzMichigan State University

National Superconducting Cyclotron Laboratory

Joint Institute for Nuclear Astrophysics JINA

  • Outline:

  • rp-process

  • r-process

Accreting neutron stars

  • Bursts and other nuclear processes

  • probe M,R, cooling

  • dense matter EOS, superfluidity, meson condensates, quark matter strange matter

Companion star(H + He envelope)

Accretion disk(H and He fallonto neutron star)


X-ray bursts

Neutron star(H and He burninto heavier elements)

Uncertain models due to nuclear physics

Galloway et al. 2003



Burst models withdifferent nuclear physicsassumptions

Woosley et al. 2003 astro/ph 0307425

Need much more precise nuclear data to make full use of high quality observational data

Reality check: Burst comparison with observations

Precision X-ray observations(NASA’s RXTE)

 GS 1826-24 burst shape changes !(Galloway 2003 astro/ph 0308122)

Nuclear physics needed for rp-process:

(ok – but corrections needed)

  • b-decay half-lives

  • masses

  • reaction ratesmainly(p,g), (a,p)

(in progress)

(just begun)

some experimental

information available(most rates are still uncertain)

Theoretical reaction rate predictions difficult neardrip line as single resonances dominate rate:

Hauser-Feshbach: not applicable

Shell model: available up to A~63 but large uncertainties (often x1000 - x10000)

(Herndl et al. 1995, Fisker et al. 2001)

 Need radioactive beam experiments

(various methods, ISOL and fast beams)

H. Schatz


89.9 keV

New experimental techniques at NSCL applied to 32Cl(p,g)33Ar

Shell model calculation:

predicted level

Herndl et al. 1995

experimentally known level

3.97 MeV 5/2+

Dominate ratein rp-process

3.56 MeV 7/2+

gs 1+

g (~ 2.6 MeV)

32Cl + p

Experimental Goal:

Measure excitation energies of the relevant states

g (1.359 MeV)

Ground state


H. Schatz

Setup for 34Ar(p,d)33Ar measurement

Focal plane:identify 33Ar

S800 Spectrometer at NSCL:







Radioactive 34Ar beam84 MeV/u T1/2=844 ms(from 150 MeV/u 36Ar)

SEGAGe array(14 Detectors)

H. Schatz

with experimental data

shell model only

x 3 uncertainty

x10000 uncertainty

New 32Cl(p,g)33Ar rate – Clement et al. PRL 92 (2004) 2502

Doppler corrected g-rays in coincidence with 33Ar in S800 focal plane:

g-rays from predicted 3.97 MeV state

stellar reaction rate

reaction rate (cm3/s/mole)

33Ar level energies measured:

3819(4) keV (150 keV below SM)

3456(6) keV (104 keV below SM)

temperature (GK)

Typical X-ray burst temperatures

H. Schatz

Burst peak (~7 GK)

Carbon can explodedeep in ocean/crust(but need x10 enhancement)(Cumming & Bildsten 2001)

~ 55% Energy

Heavy nuclei in rp-ashes

~ 45% Energy

  • Disintegration can be main source of energy !

  • Increased opacity leads to correct ignition depth

crust made of Fe/Ni ?

Ashes to ashes – the origin of superbursts ?

(Schatz, Bildsten, Cumming, ApJ Lett. 583(2003)L87

H. Schatz

r (apid neutron capture) process

The r(apid neutron capture) process)

What is the origin of about half of elements > Fe(including Gold, Platinum, Silver, Uranium)

Abundance Observations

Nuclear Physics

graph by J. Cowan

Supernovae ?

n driven wind ? prompt explosions of ONeMg core ?

jets ?

explosive He burning ?

Neutron star mergers ?

Nuclear Physics + Abundance Observations

 only direct experimental constraint on r-process itself

78Ni, 79Cu first bottle necks in n-capture flow (80Zn later)

79Cu: half-life measured 188 ms (Kratz et al, 1991)

78Ni : half-life predicted 130 – 480 ms 3 events @ GSI (Bernas et al. 1997)




H. Schatz

Some recent r-process motivated experiments

ANL/CPT (Cf source) (Clark & Savard et al.)Remeasured masses with high precision

ORNL (ISOL)(d,p) and Coulex

GSI (in-flight fission)Half-lives, Pn values(Schatz, Santi, Stolz et al.)

GSI (in-flight fission)

Masses (IMS)

(Matos & Scheidenberger et al.)

ISOLDE (ISOL)Decay spectroscopy

(Dillmann, Kratz et al. 2003)

MSU/NSCL (fragmentation)

Half-lives, Pn values

GANIL (fragmentation)

Decay spectroscopy, Sorlin et al.

“Fast beam experiments”

H. Schatz

First experiment: r-process in the Ni region (Hosmer et al.)

  • Measure:

  • b-decay half-lives

  • Branchings for b-delayed n-emission

NSCL Neutron detector NERO

3He + n -> t + p


  • Detect:

    • Particle type (TOF, dE, p)

    • Implantation time and location

    • b-emission time and location

    • Neutron-b coincidences

R-process Beam

Si Stack

~ 100 MeV/u

r-process nuclei






time (ms)

Total 78Ni yield:

11 events in 104 h

Particle Identification:

Energy loss in Si ~ Z

Time of flight ~ m/q

H. Schatz

Preliminary results

Ni half-lives as a function of mass number – comparison with “global” models

Half-life (s)

78Ni half-life(11 events)

Mass number

P. Hosmer

H. Schatz

Impact of 78Ni half-life on r-process models

 need to readjust r-process model parameters

H. Schatz

Known half-life

First NSCL experimentscompleted

First NSCL experimentscompleted

Rare Isotope Accelerator (RIA)

  • NSCLcovers large fraction of A<130 r-process

  • big discrepancies among r-process models

  • possibility of multiple r-processes

NSCL and future facilities reach

Experimental Nuclear Physics + Observations Experimental test of r-process models is within reach Vision: r-process as precision probe

H. Schatz


Interesting time in Nuclear Astrophysics where observations and experiments zoom in on most extreme (but common) scenarios

Fundamental questions to be answered: The origin of the elements

Properties of matter under extreme conditions.

  • Need a complementary approach to nuclear astrophysics

    • need a variety of experiment types for a wide range of data

    • need a variety of facilities (ISOL and fragmentation beams, and stable beams too !)

    • need experiment and nuclear theory to:

      • fill in gaps

      • correct for astrophysical environment

      • understand nuclear physics

A range of nuclei in the r- and rp-process are now accessible at the NSCL Coupled Cyclotron Facility.

Need a next generation radioactive beam facilities such as RIA or FAIRto address most of the nuclear physics relevant for astrophysics.

 Collaboration

H. Schatz





Hope College

P.A. DeYoung

G.F. Peaslee


O. Arndt

K.-L. Kratz

B. Pfeiffer


R.R.C. Clement

D. Bazin

W. Benenson

B.A. Brown

A.L. Cole

M.W. Cooper

A. Estrade

M.A. Famiano

N.H. Frank

A. Gade

T. Glasmacher

P.T. Hosmer

W.G. Lynch

F. Montes

W.F. Mueller

P. Santi

H. Schatz

B.M. Sherrill

M.-J. van Goethem

M.S. Wallace


P. Hosmer

F. Montes

R.R.C. Clement

A. Estrade

S. Liddick

P.F. Mantica

C. Morton

W.F. Mueller

M. Ouellette

E. Pellegrini

P. Santi

H. Schatz

M. Steiner

A. Stolz

B.E. Tomlin


P. Reeder

Notre Dame:

A. Aprahamian

A. Woehr


W.B. Walters