Jorge Pereira, INPC 2007 Jorge Pereira ([email protected]) National Superconducting Cyclotron Laboratory (NSCL/MSU) Joint Institute for Nuclear Astrophysics (JINA) Studies of r-process nuclei at NSCL Astrophysical importance of -decay studies in the understanding of the r-process Jorge Pereira, INPC 2007
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Jorge Pereira ([email protected]) National Superconducting Cyclotron Laboratory (NSCL/MSU)
Jorge Pereira, INPC 2007. Studies of r-process nuclei at NSCL Astrophysical importance of b -decay studies in the understanding of the r-process. Jorge Pereira ([email protected]) National Superconducting Cyclotron Laboratory (NSCL/MSU) Joint Institute for Nuclear Astrophysics (JINA). - PowerPoint PPT Presentation
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NSCL Experiments done• P. Hosmer, P. Santi, H. Schatz et al. • F. Montes, H. Schatz et al.• B. Tomlin, P.Mantica, B.Walters et al.• J.Pereira, K.-L.Kratz, A. Woehr et al.
Critical region78Ni
107Zr
NSCL reach
129Rh
Jorge Pereira, INPC 2007
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
70 120 170 220
Mass (A)
Ab
un
da
nc
e (
A.U
.)
Observed Solar Abundances
Model Calculation: Half-Lives fromMoeller, et al. 97
Same but with present 78Ni Result
Exp. 78Ni T1/2 = 110 ms
Predicted 78Ni T1/2: 460 ms
P. Hosmer et al. PRL 94, 112501 (2005)
+100
-60
I)-decay half-live of 78Ni50 waiting point
Half-live of ONE single waiting-point nucleus:
Speeding up the r-process clock
Increase matter flow through 78Ni bottle-neck
Excess of heavy nuclei (cosmochronometry)
Jorge Pereira, INPC 2007
II) “Gross” nuclear structure around 120Rh65 from -decay properties
F. Montes et al., PRC73, 35801 (2006)
Inferring (tentative) nuclear deformations with QRPA model calculations
•Half-lives and Pn-values sensitive to nuclear structure at different energies: (Complementary information to infer nuclear deformation)
•Need microscopic calculations beyond QRPA
•Possible signatures of new shell-structure when approaching r-process path
Jorge Pereira, INPC 2007
II)Probing sustainability of N=82 at 120Pd from -delayed -spectroscopy
B.Walters, B.Tomlin et al., PRC70 034414 (2004)
•No evidence of shell-quenching when approaching waiting point 128Pd at N=74
•Need more E(2+) data at 74<N<82
Jorge Pereira, INPC 2007
III) -decay properties of Zr isotopes beyond mid-shell N=66
•N~66 is at mid-shell: Shape transitions between sudden onset of deformation at N=60 and closed shell at N=82
•Possible double-magic Z=40, N=70: Effects from spherical shape of 110Zr70 observable at 66<N<70? J. Dowaczewski et al.,PRL72, 981 (1994) 10
100
1000
10000
62 63 64 65 66 67 68
N
Ha
lf-l
ife
(m
s)
Zr literature
Zr preliminary
QRPA Def.
QRPA Spher.
J.Pereira et al., in preparation
•Shorter half-life of (potential) waiting-point 107Zr67 may
affect predicted r-process abundances at A~110
•QRPA consistent with spherical shapes beyond mid-shell (possible signatures of double magic N=40 N=70?)
•Urgent need of microscopic calculations beyond QRPA
Jorge Pereira, INPC 2007
Almost all -decay half-lives of r-process nuclei at N=82 and N=126 will be reachable with ISF
pps
Reach for future r-process experiments with new facilities (ISF, FAIR, RIBF…)
Fine!…but what do we do meanwhile?
a) Keep observing abundances and wait for these facilities…
b) Continue r-process studies with theoretically calculated -decay properties (to be confirmed with new measurements)
Jorge Pereira, INPC 2007
Conclusions
•Despite many years of intensive effort, the r-process site continues to be one of the BIG SCIENCE QUESTIONS for the new century – NAS REPORT. New LEPP process complicates the situation
•Besides being direct r-process inputs, beta-decay properties of exotic nuclei turned out to be an effective probe for nuclear structure studies of exotic nuclei
•R-process experimental campaigns at NSCL provide an extensive data body of beta-decay properties of r-process nuclei. Comparisons with calculations microscopic models will improve astrophysical r-process calculations
•New facilities will largely extend the r-process regions accessible. Meanwhile, new observations (SEGUE) and new measurements of exotic n-rich nuclei are highly necessary
Jorge Pereira, INPC 2007
Thanks to:
•NSCL/MSU: Hendrik Schatz, Paul Mantica Ana Becerril, Tom Elliot, Alfredo Estrade, Ron Fox, Daniel Galaviz, Tom Ginter, Mark Hausmann, Paul Hosmer, Linda Kern, Giuseppe Lorusso, Milan Matoš, Fernando Montes
•Univ. Notre Dame: Andreas Woehr Ani Aprahamian, Matt Quinn
•Mainz Universität: Karl-Ludwig Kratz Oliver Arnd, Ruben Kessler, Stefan Hennrich, Bernd Pfeiffer, Florian Schertz
•University of Maryland: William Walters
•JINA and VISTAR collaborations
Jorge Pereira, INPC 2007
Backup Slides
Jorge Pereira, INPC 2007
The Big Question
What is the origin of heavy elements
from iron to uranium ?
One of the “Eleven Science Questions for the New Century” (NAS report “Connecting Quarks with the Cosmos”)
Do we understand the observed heavy-element abundances ?
Jorge Pereira, INPC 2007
What about less enriched stars? (Leftover of Leftover)
Similar observations for Sr, Zr by C.Travaglio et al. Light Element Primary Process (LEPP)
– C. Travaglio et al., ApJ 601, 864 (2004) –
Some stars (e.g. HD122563) show enrichment of lighter elements (Sr-Ag) compared to MAIN r-process
– F.Montes et al., submitted to ApJ –
Jorge Pereira, INPC 2007
[Eu/Fe] Enrichment with main r-process
Light r / Heavy r (Eu) Heavy r / Heavy r (Eu)
What about less MAIN r-process enriched stars?
Consistent with second process producing also Sr-Ag LEPP, identified by Travaglio et al. 2004
Montes et al. to be published
Solar r
Slope indicatesratio of light/heavy)changes for lessenriched stars
Some stars havelight r-elementsat solar level
Heay r-patternrobust andagrees with solar
Light r-elementsat high enrichmentfairly robust andsubsolar
[Y/Eu] [La/Eu]
[Ag/Eu] [Sm/Eu]
[Eu/Fe] [Eu/Fe]
Jorge Pereira, INPC 2007
Trying to fit LEPP pattern with n-capture flow
Low nn and high nn fit low ZLow nn also fits small high Z abundances
Jorge Pereira, INPC 2007
Simmerer (Cowan et al.) /Lodders
-2.50
-2.00
-1.50
-1.00
-0.50
30 40 50 60 70 80 90
Element number
log
Travaglio/Lodders
-2.50
-2.00
-1.50
-1.00
-0.50
30 40 50 60 70 80 90
Element number
log
Conclusions depend on s-process
s-process from Simmerer et al. (Cowan et al.) s-process from Travaglio et al.
Need reliable s-process (models and nuclear data)Clearly something is going on for Z < ~50 (“light” p-process elements)
Need reliable s-process (models and nuclear data)Clearly something is going on for Z < ~50 (“light” p-process elements)
What Nuclear Physics ingredients are really important?
Jorge Pereira, INPC 2007
(Pearson, et al. 1996)
r-process studies in two different regions of Terra Incognita
Two r-process regions were explored:Ge-Br (56≤N≤60): lies in the region prior to the “weak” r-process. It could also constitute part of the seed r-process nuclei
Y-Mo (A ≈110): lies right before the abundance trough prior to the A=130 peak
C.Freiburghaus et al., ApJ516 (1999) 381
100 120 140 160 180 200 22010-4
10-3
10-2
10-1
100
101
Mass number
ETFSI-Q
ETFSI-1
A=110
Z number
Jorge Pereira, INPC 2007
Nuclear Structure motivation
•What do we want to measure? -decay half-lives and Pn-values
•Why?
•They provide insight into nuclear structure in two “critical” r-process regions
• Direct inputs in r-process calculations
Evolution of nuclear shape in two regions of Terra Incognita •Ge-Br (56≤N≤60): does the sudden onset of deformation (at N=60) persist “south” of 96Kr?
•Y-Mo (A ≈110): are there more shape transitions between sudden onset of deformation at N=60 and closed shell at N=82 (new sub-shells?)
Nuclear shape evolution in these two regions will affect substantially the calculated masses and-decay processes: strong impact in r-process
calculated abundances
R.F. Casten, Nucl. Phys. A443 (1985) 1
N. Schunck et al., Phys. Rev. C63 (2004) 061305(R)
Jorge Pereira, INPC 2007
Gross -decay properties used as nuclear structure probes
Gross -decay properties are sensitive to nuclear structure at different energy regimes
5β EQf
βQ
0
ββ1/2 dEE)QR,f(Z,(E)ST
Low energies
β
n
Q
S
ββ1/2n dEE)QR,f(Z,(E)STP
Energies above Sn
Dobaczewski et al., PRL72 (1994) 981
B. Pfeiffer et al., NPA693 (2001) 282
Jorge Pereira, INPC 2007
Jorge Pereira, INPC 2007
Jorge Pereira, INPC 2007
Sensitivity of QRPA to Mass and Deformation
Jorge Pereira, INPC 2007
Preparation of experiments
Nuclei produced by Fragmentation of 136Xe on Be
•Beta Counting System (CS): T1/2
•Neutron Emission Ratio Observer (NERO): Pn
•Special blocking system (Slits + Finger) at Im1 to stop primary-beam charge-state
•BCS and NERO upgrades: VME-based DAQ, migration to production DAQ software (~400 channels), new Ge crystal (tested to be used for particle ID, -spectroscopy)
•Special setup for particle ID based on known sec-isomers with SeGA globes
Jorge Pereira, INPC 2007
Secondary Beam
Experimental Setup
Particle ID Setup (SeGA)
Production Setup (BCS+NERO)
•Isomers (sec) implanted in Al degrader
•Emitted gammas detected with 3 SeGA detectors (6%)
4 Si PIN: E, trigger
1 DSSD (1600 pixels): •4 cm x 4 cm active area•1 mm thick•40-strip pitch in x and y dimensions (1600 pixels)
1 SSSD (16 strips): Veto
BCS (Beta Counting System) NERO (Neutron Emission Ratio Observer)
Boron Carbide Shielding
Polyethylene Moderator
BF3 Proportional Counters
3He ProportionalCounters
•Fragments implanted in DSSD
•Emitted (DSSD)
•Delayed neutrons (NERO)
Jorge Pereira, INPC 2007
(Pearson, et al. 1996)
Conquers of Terra Incognita in r-process campaigns at NSCL
How about future?•What can be done at NSCL for the r-process?
Jorge Pereira, INPC 2007
(Pearson, et al. 1996)
How to reach now new territories at NSCL for r-process studies
Mass knownHalf-life knownTerra Incognita
r process
N=126
N=82
Z=50
Z=82
N=50
Z=28
Fission of 238U at NSCL
• Optimistic results from test (May 2006)
• Beam test development (August 2006)
1. Future experiment to explore region around 128Pd
2. Gain factor 10-100 with respect to Fragmentation of 136Xe
3. Possibility to study E(21+), E(41+) isotopic evolution of nuclei near 132Sn (BCS + SeGA)
4. Possibility to measure masses of waiting-point nuclei e.g. 130Cd with ToF-Btechnique (A1900+S800)
If successful it will allow to go one step farther into Terra Incognita New r-process
regions to be explored at NSCL
Jorge Pereira, INPC 2007
Some advances of what it is coming in the near Future for the r-process
•RF-kicker Fragment Separator:.Purify beam-cocktail. Reduce background due to implanted contaminants in the BCS
•Development of U beams: Extend -decay studies and mass measurements to new r-process regions
•Digital Data Acquisition (DDAQ): Increase SeGA resolutions and efficiencies (tests in progress) and BCS efficiencies (to be implemented). Precise -decay half-lives, Q values and spectroscopy information of new r-process
•LEBIT: Development of gas stopper for future use with reaccelerated beams. Measurement of important reactions occurring in the -process (seed nuclei for the r-process)
•BCS calorimeter: Measurement of Q values for r-process nuclei (additional structure information)
Jorge Pereira, INPC 2007
…and in the Future: NSCL upgrade
NSCL upgrade will open new possibilities in Nuclear Astrophysics
MSU Upgrade Beam intensities (pps)
pps
•Fast beams: A very significant fraction of r-process nuclei will be reached experimentally.
•Integral -decay properties of every r-process waiting-point below A=130 peak (included) and around N=126.
•Spectroscopy studies of waiting-point nuclei at N=82 and N=126: solution of the shell-quenching puzzle.
•Masses of very exotic nuclei: better determination of r-process path (Sn≈2MeV).
•Reaccelerated beams: Direct measurements of important reactions involved in the -process (generation of r-process seed nuclei): (nn,)9Be (di-neutron channel), (n,)9Be, (t,)7Li, 7Li(n,)8Li, 8Li(,n)11B…
•Other Nuclear Astrophysics aspects.
•Majority of reaction rates in rp-process will be within reach with indirect methods. Direct measurements will be achievable up to A<60.
•Measurement of GT-strength for e-capture by all relevant unstable nuclei in SNeI,II will be possible via charge exchange reactions.
•Very important reaction rates: e.g. 12C(,)16O
Jorge Pereira, INPC 2007
Epilogue
Jorge Pereira, INPC 2007
Summary
•Despite many years of active investigation the site of the r-process is still unknown. Nuclear Physics is crucial to solve this mystery
•My main research on the r-process included studies of reaction mechanisms to produce neutron-rich and -decay studies of r-process nuclei:
•GSI: experimental studies of neutron-rich nuclei approaching the r-process region around N=126
•GSI: -decay properties of waiting-point 137Sb abundance spikes around A=130 peak
•NSCL: analysis of nuclear structure of r-process nuclei based on -decay studies abundance pattern around the weak r-process region and the A=110 abundance trough region
•Future developments at NSCL (including upgrade) will open new opportunities to extend our knowledge of the r-process
•NSCL will become the “r-process facility” and one of the dominant laboratories in Nuclear Astrophysics
Jorge Pereira, INPC 2007
• Convince someone to cover the expenses of our adventure
• Develop new tools to reach “Terra Incognita”
• Learn from the natives living in the new territories
The recipe to explore “Terra Incognita”
The conquer of Terra Incognita (or the New World)
…so that finally, Terra Incognita will not be “Incognita” anymore
Jorge Pereira, INPC 2007
Acknowledgements
•NSCL/MSU: Hendrik Schatz, Paul Mantica Ana Becerril, Tom Elliot, Alfredo Estrade, Ron Fox, Daniel Galaviz, Tom Ginter, Mark Hausmann, Vladimir Henzl, Daniela Henzlova, Paul Hosmer, Linda Kern, Giuseppe Lorusso, Milan Matoš, Fernando Montes, Josh Stoker, Andreas Stoltz, Oleg Tarasov, Remco Zegers
•Univ. Notre Dame: Ani Aprahamian, Andreas Woehr, Matt Quinn
•Univ. Santiago de Compostela: Jose Benlliure, Teresa Kurtukian
•Mainz Univ.: Karl-Ludwig Kratz Oliver Arnd, Ruben Kessler, Stefan Hennrich, Bernd Pfeiffer, Florian Schertz
•GSI colaboration: Peter Armbruster, Monique Bernas, Aleksandra Kelic, Valentina Ricciardi, Karl-Heinz Schmidt
•JINA and VISTAR collaborations
Jorge Pereira, INPC 2007
Backup Slides
Jorge Pereira, INPC 2007
OUTLOOK
•Introduction: what is the r-process? What do we need to know to learn about “him”?
•My relationship with the r-process:•When we first met (at GSI): approaching Terra Incognita towards N=126 shell
•Learning more about r-process at GSI: studies around waiting point 137Sb
•R-process experiments at NSCL: incursion into Terra Incognita through two different fronts
•Discovering what NSCL can do for the r-process
•What can we do for “them”? Future perspectives
Jorge Pereira, INPC 2007
(Pearson, et al. 1996)
Present NSCL astrophysical motivated projects
Group Project Project Project
Astrophysics
(H.Schatz)
-decay
(r-process)
Masses
(r-process)p-resonances (rp-process)
HIRA
(B.Linch)
Masses
(rp-process)
2p-correlations
Isospin-EOS
(Neutron Stars)
LEBIT
(G.Bollen, D.Morrisey)
Masses
(rp-process)
Gas cell stopper
(Reaccelerated beams)
S800
(R.Zeger)
(CE-reactions
SNeI, II)
Jorge Pereira, INPC 2007
(Pearson, et al. 1996)
An overview of the present situation of Nuclear Astrophysics at NSCL
Group / People ProjectsSenior researchers
(Faculty/Staff)Post-docs Graduates Undergraduates
Astrophysics
(H.Schatz)4 3 5 3
HIRA
(B.Linch)2 2 2 4 0
S800
(R.Zenger, S.Austin)
3 2 2 0 0
Beta
(P.Mantica)1 1 1 1 0
4 Groups 8 Post-docs
10 Exp. Projects 10 Graduates
6 Faculty/Staff 3 Undergraduates
Clearly NSCL is a natural facility to cover an extensive range of different topics in Nuclear Astrophysics