Nuclear Physics for Astrophysics with Radioactive Beams
Livius Trache Texas A&M University
EURISOL Workshop
ECT* Trento, Jan. 2006
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 !
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
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
Proton Transfer Reactions
A B(A+p)
a(b+p)
p
b
A+a->B+b
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
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
1.5 105 pps
RB in-flight production
(p,xn), (p,pxn) reactionsin inverse kinematics
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!
Better beams & sd-shell nuclei
17F (10 MeV/n) on melamine; ORNL experimentJ. Blackmon et al, PRC 2005
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
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
MARS
Cave
MDM
Cave
NIMROD
Cave
Heavy Ion Guide
Light Ion Guide
K150 Beam Lines
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
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
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
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).
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
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
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?!
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)
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.
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.
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
decay study of pure RB samples
23Al - coincidence spectrum
5/2+
7/2+
IAS
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
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!
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
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.
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