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Nuclear Physics for Astrophysics with Radioactive Beams
Livius Trache Texas A&M University
EURISOL Workshop
ECT* Trento, Jan. 2006
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Nuclear Physics for Astrophysics with Radioactive Beams
Indirect methods only!
= Seek (structure) information to transform in cross sections at astrophysically relevant energies and reaction rates
For charged part radiative capture: (p,) or (, ) reactions - ANC (p and ) transfer reactions: (7Be,8B), (11C,12N), (13N,14O), (6Li,d), … breakup: 8B, 9C, 23Al, 7Be, etc… charge symmetry – study mirror nucleus (or reaction): ex. (7Li,8Li) for (7Be,8B) Coulomb dissociation - B(E), Trojan Horse Method
(other) spectroscopic info: J, Eres, to estimate direct terms: J, l, config mixings … variae resonances (J, Eres, ’s) – variae, including resonant elastic scatt.
Need good, reliable data to make credible predictions: Optical model parameters for elastic, transfer; breakup S-matrices; masses,
lifetimes, level densities, GT strength distributions, etc… More stable beam studies & RNB !
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Radiative proton capture is peripheral e.g. 7Be(p,)8B
Transfer or breakup vs proton capt in 8B
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
0 10 20 30 40 50 60
radius (fm)
wfc
t,p
rob
ab
w ave fct
transfe r
W hittaker
pr capt
-0 .5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
1 10 100 1000
radius (fm )
Po
t(M
eV)
r
rWCrS l
n ljn ljn lj
)2()( 2/1,2/1
B o u n d sta te fo r r> R N
in – sca tte r in g w f
-0 .5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
1 10 100 1000
radius (fm )
Po
t(M
eV)
r
rWCrS l
n ljn ljn lj
)2()( 2/1,2/1
B o u n d sta te fo r r> R N
in – sca tte r in g w f
)()ˆ()()ˆ()( rrYrrYVT coul
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M S E E e2 2[ ( ) ]
M is: M O r rA B p Bp Bp B B p p i Bp ( , , ) ( ) ( ) ( ) ( )^
( )
Integrate over ξ: M I r O r rBpA
Bp Bp i Bp ( ) ( ) ( )^
( )
Low B.E.: I r CW r
rBpA
Bp
r R
BpA l Bp Bp
Bp
B NA( )
( ),
1
2
2
Find: capture BpAC( ) 2
Direct Radiative proton capture
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Proton Transfer Reactions
A B(A+p)
a(b+p)
p
b
A+a->B+b
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ANC’s measured using stable beams in MDM
• 9Be + p 10B* [9Be(3He,d)10B;9Be(10B,9Be)10B]
• 7Li + n 8Li [12C(7Li,8Li)13C]• 12C + p 13N [12C(3He,d)13N]• 12C + n 13C [13C(12C,13C)12C]
• 13C + p 14N [13C(3He,d)14N;13C(14N,13C)14N]• 14N + p 15O [14N(3He,d)15O]• 16O + p 17F * [16O(3He,d)17F]• 20Ne + p 21Na [20Ne(3He,d)21Na]• 22Ne + n 23Ne [13C(22Ne,23Ne)12C]
beams 10 MeV/u
* Test cases
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ANC’s at TAMU
• 10B(7Be,8B)9Be, 14N(7Be,8B)13C
[7Li beam 130 MeV, 7Be beam 84 MeV]
• 14N(11C,12N)13C
[11B beam 144 MeV, 11C beam 110 MeV]
• 14N(13N,14O)13C [13C beam 195 MeV, 13N beam 154 MeV]
• 14N(17F,18Ne)13C
[work at ORNL with TAMU participation]
from radioactive beams @ 10-12 MeV/nucleon
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1.5 105 pps
RB in-flight production
(p,xn), (p,pxn) reactionsin inverse kinematics
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0 105
Scale (cm) ReactionTelescopes
1.7 mg/cm2
10B Target
Beam StudyDetector
Transfer reactions for ANCs
10B(7Be,8B)9Be 14N(7Be,8B)13C
1.5 mg/cm2
Melamine
• Beam Study Detector: 1 mm Si strip detector• Reaction Telescopes:
105 m Si strip detector 1 mm Si detector
Beam spot 4 mm, deg, E/E~1-1.5%
“dream”?! Better beam!
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Better beams & sd-shell nuclei
17F (10 MeV/n) on melamine; ORNL experimentJ. Blackmon et al, PRC 2005
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Transfer reactions
Conclusions: Can extract ANC from proton transfer reactions -> (p,) rates E/A ~ 10 MeV/nucleon (peripherality) better beams – reaccelerated OK! good detection resolution – magn spectrom at 0 deg. Need good Optical Model Potentials for DWBA! Double folding. Study n-transfer and use mirror symmetry:
Sp=Sn => ANCp=const*ANCn
Data further needed for: Various cases: waiting points, breakout reactions … CNO cycle hot CNO rap rp-process H & He-burning in general
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CI Upgrade (overview)
• Re-activate K150 (88”) cyclotron• Build ion guides and produce RIBs• Inject RIBs to K500 cyclotron• Project deliverables (DOE language):
Use K150 stand-alone and as driver for secondary rare-isotope beams that are accelerated with K500 cyclotron
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MARS
Cave
MDM
Cave
NIMROD
Cave
Heavy Ion Guide
Light Ion Guide
K150 Beam Lines
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Nuclear Astrophysics with upgrade - III
• Rare ion beams in MDM at 10 MeV/u- accelerated beams for transfer reactions around 0o
[large cross sections and high sensitivity]
• Rare ion beams for resonance studies- elastic scattering for resonances with more beams
• Rare ion beams into MARS, MDM– study r-process nuclei masses and lifetimes [(d,p)
react]
(c/o R.E. Tribble)
Study sd-shell nuclei for rp-process
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One-nucleon removal can determine ANC (only!)
Momentum distributions → nljCross section → ANCGamma rays → config mixing
Need: Vp-target & Vcore-target
and reaction mechanism
Calc: F. Carstoiu; Data: see later
P roto n (p )
b
p
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One-nucleon removal = spectroscopic tool
Example of momentum distributions – all types!
E. Sauvan et al. – PRC 69, 044503 (2004).
Cocktail beam: 12-15B, 14-18C, 17-21N, 19-23O, 22-25F
@ 43-68 MeV/nucleon.
normal halo2s1/2
Config mixing
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Summary of the ANC extracted from 8B breakup with different interactions
Data from:
F. Negoita et al, Phys Rev C 54, 1787 (1996)
B. Blank et al, Nucl Phys A624, 242 (1997)
D. Cortina-Gil e a, EuroPhys J. 10A, 49 (2001).
R. E. Warner et al. – BAPS 47, 59 (2002).J. Enders e.a., Phys Rev C 67, 064302 (2003)
Summary of results:
The calculations with 3 different effective nucleon-nucleon interactions are kept and shown:
JLM (blue squares),
“standard” fm (black points) and
Ray (red triangles).
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S17 astrophysical factor (ours)
JLM S17=17.4±2.1 eVb no weights
“standard” S17=19.6±1.2 eVb
Ray S17=20.0±1.6 eVb
Average all:
C2tot = 0.483 0.050 fm-1
S17=18.7±1.9 eVb
(all points, no weights) Published: LT et al.- PRC 69, 2004
For comparison: (7Be,8B) proton transfer at 12 MeV/u A. Azhari e.a. – two targets:10B S17(0) = 18.4 2.5 eVb (PRL ’99)14N S17(0) = 16.9 1.9 eVb (PRC ’99)
Average: Phys Rev C 63, 055803 (2001)
S17(0) = 17.3 1.8 eVb
13C(7Li,8Li)12C at 9 MeV/u (LT e.a., PRC 66, June 2003))
C2tot= 0.455 0.047 fm-1
S17(0) = 17.6 1.7 eVb
S.
p p3 / 2 1 / 21 7
2 203 8 6
eV b
fm C C
-1
New: S17(0) = 18.0 1.9 eVb (G Tabacaru ea, 2004)
New average: S17(0) = 18.2 1.8 eVb New average: S17(0) = 18.2 1.8 eVb
8B breakup
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22Mg(p,)23Al reaction
Gamma-ray space-based telescopes to detect current (on-going) nucleosynthesisAstrophysical -ray emitters 26Al, 44Ti, … and 22NaSatellite observed -rays from 26Al (T1/2=7 ·105 y), 44Ti, etc., but not from 22Na (COMPTEL)
20Ne(p,)21Na(p,)22Mg()22NaDepleted by 22Mg(p, )23Al ?!Dominated by direct and resonant capture to first exc state in 23Al
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23Al versus 23Ne
Structure of 23Al poorly known: only 2 states, no J
Mirror 23Ne has J=5/2+ for g.s. and J=1/2+ for 1-st exc state (Ex=1.017 MeV)
NNDC says: J=3/2+
1/2+
5/2+
23Ne 23Al
J. Caggiano et al., PRC 65, 025802 (2001)
24Mg(7Li,8He)23Al
?
X.Z. Cai et al., Phys Rev C 65, 024610 (2002)
23Al halo nucleus; level inversion?!
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22Mg(p,)23Al reaction in novae
Calculating the astrophysical S-factor in the 2 spin-parity scenarios, if level inversion occurs, the difference is dramatic (upper figure)The resulting reaction rate is 30-50 times larger in the T9=0.1-0.3 temperature range for the case of a 2s1/2 configuration for 23Al g.s.This may explain the absence of 22Na thru the depletion of its 22Mg predecessor in 22Mg(p, )23Al
Direct (2s1/2 or 1d5/2) and resonant capture to first exc state in 23Al (bottom figure).
22Mg(p,)23Al reaction rates
1.E-22
1.E-20
1.E-18
1.E-16
1.E-14
1.E-12
1.E-10
1.E-08
1.E-06
1.E-04
1.E-02
1.E+00
1.E+02
1.E+04
0.01 0.1 1 10T9
Ra
te (
cm
3 /mo
le/s
)
5/2+ direct
5/2+ - resonant
1/2+ direct
22Mg(p,)23Al astrophys S- factordirect capture only
y = 62.815x2 + 1173x + 2016.6
0.E+00
1.E+04
2.E+04
3.E+04
4.E+04
5.E+04
6.E+04
7.E+04
0 0.5 1 1.5 2 2.5 3
Ep (MeV)
S-f
ac
tor
(eV
b)
2s1/2 E1
1d5/2 E1
1d5/2 E1+E2
Poly. (1d5/2 E1+E2)
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23Al breakup experiment
Proposed to measure @GANIL:Momentum distributions for
12C(23Al,22Mg) @50 MeV/uCalculated in the two scenarios:
nlj=2s1/2 (top) or 1d5/2 (bottom).One-proton-removal cross section is
about 2x larger for the 2s1/2 case.Detect -rays in coincidence with
22Mg to determine the core excitation contributions.
Determine J from mom distribDetermine Asymptotic Normalization
Coefficients for 23Al from cross sections and from there the astrophysical S-factor for proton radiative capture leading to 23Al in O-Ne novae.
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Conclusions - Breakup
Can do proton-breakup for ANC! Need:
E/A ~ 30-100 MeV/nucleon (peripherality and model)
Better data to test models and parameters!!!
Can extract ANC from breakup of neutron-rich nuclei, but the way to (n,) cross sections more complex. Need extra work here.
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MARS MARS
Primary beam 24Mg @ 48 MeV/A – K500 CyclPrimary target LN2 cooled H2 gas p=1.6 atm Secondary beam 23Al @ 39.5 MeV/A
24Mg 48A MeV
Purity: 99%Intensity: ~ 4000 ppsFirst time - very pure & intense 23Al
23Al 40A MeV
In-flight RB production
(p,2n) reaction
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decay study of pure RB samples
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23Al - coincidence spectrum
5/2+
7/2+
IAS
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23Mg
23Al 0.446(4)sQec=12240keV
7803 IAS 5/2+7787 (5,7/2)+
6985 5/2+
6575 5/2+
2905 (3,5/2)+
2359 1/2+ NO!2051 7/2+
450 5/2+0 3/2+
22Na Qp=7580 keV
95488456816480037877
β+
β+
1/2+5/2+√
IAS: ft=2140 s +/-5%
Preliminary results!
Y Zhai thesisVE Iacob, et al.
22Na(p,)23Mgresonances
22Mg(p,)23Al
p
0.25%0.48%
0.38%
Proton br. total=1.1%
Tighe ea, LBL 1995Perajarvi ea, JYFL 2000
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Conclusions – “other methods”
Useful to have various methods/tools at hand
Medium size facilities useful: may get things done sooner and cheaper! Valuable for (hands-on) education of students and postdocs! Competition is healthy and necessary!
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14O + p Resonant Elastic Scattering – thick targets, inverse kinematics
V. Goldberg, G. Tabacaru e.a. – Texas A&M Univ., PRC 2004
v con tkT
fE
kTa b
to t ires
i
23 2
2
/
ex p
Will work on:• resonant elastic
scattering• (,p) reactions, etc.
Beam quality – crucial (no impurities)!E < 10 MeV/nucleon
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Nuclear physics for astrophysics. Summary
Indirect methods
transfer reactions (proton or neutron) 5-10 MeV/nucleon Better beams (energy resol, emittance) Magnetic spectrometers at 0° – resolution, large acceptance, raytrace reconstr.
breakup ~ 30-100 MeV/nucleon Can neutron breakup be used for (n,)?! (yes, but need n-nucleus potentials)
Spectroscopic info J , Eres, (masses, etc…) – a variety of tools at hand Resonant elastic scattering: E<10 MeV/nucleon. H2 and He targets. Better models: structure and reaction theories
Need more checks between indirect methods and direct measurements!
Better models/data to predict OMP, make Glauber calc, spectroscopy…
Direct methods: inverse kinematics measurements on windowless gas targets with direct detection of product (magnetic separation). E=0-5 MeV/nucleon. All nucleonic species.