Transcript Nuclear Physics for Astrophysics with Radioactive Beams

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,g) or (a, g) reactions - ANC
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(p and a) 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(El), Trojan Horse Method
(other) spectroscopic info: Jp, Eres, G
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to estimate direct terms: Jp, l, config mixings … variae
resonances (Jp, Eres, G’s) – variae, including resonant elastic scatt.
Need good, reliable data to make credible predictions:
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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,g)8B
Transfer or breakup vs proton capt in 8B
0.5
1.E+00
0.4
wave fct
in – scattering wf
0.3
transfer
1.E-01
0.1
0
1
10
100
1000
-0.1
-0.2
-0.3
-0.4
Bound state for r>RN
Snlj1/ 2 nlj (r )  Cnlj
wfct, probab
Pot (MeV)
0.2
Whittaker
pr capt
1.E-02
1.E-03
W ,l 1/ 2 (2r )
r
1.E-04
0
-0.5
10
radius (fm)
(T  Vcoul )Y (rˆ) (r )  Y (rˆ) (r )
20
30
radius (fm)
40
50
60
Direct Radiative proton capture
 M
[S ( E )  Ee2p ]
2
^
M is:
Integrate over ξ:
Low B.E.:
Find:
( )
M  A ( B , p , Bp ) O ( rBp ) B ( B ) p ( p ) i ( rBp )
M  I ( rBp ) O ( rBp ) (i ) ( rBp )
rB R N
I ( rBp )  C
A
Bp
^
A
Bp
A
Bp
A 2
capture ( C Bp
)
W  , l 1 ( 2 Bp rBp )
A
2
rBp
Proton Transfer Reactions
A
B(A+p)
p
a(b+p)
b
A+a->B+b
ANC’s measured using stable beams in MDM
+ 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
•
9Be
ANC’s at TAMU
from radioactive beams @ 10-12 MeV/nucleon
•
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]
RB in-flight production
1.5 105 pps
(p,xn), (p,pxn) reactions
in inverse kinematics
Transfer reactions for ANCs
10B(7Be,8B)9Be
14N(7Be,8B)13C
Beam spot ~F4 mm, Dq1.8deg, DE/E~1-1.5%
Scale (cm)
0
5
10
Reaction
Telescopes
“dream”?! Better beam!
1.5 mg/cm2
Melamine
1.7 mg/cm2
10
B Target
Beam Study
Detector
• Beam Study Detector: 1 mm Si strip detector
• Reaction Telescopes:
 105 mm Si strip detector
 1 mm Si detector
Better beams & sd-shell nuclei
17F
(10 MeV/n) on melamine; ORNL experiment
J. Blackmon et al, PRC 2005
Transfer reactions
Conclusions:
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Can extract ANC from proton transfer reactions -> (p,g) 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:
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Sp=Sn => ANCp=const*ANCn
Data further needed for:
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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
K150 Beam Lines
MARS
Cave
MDM
Cave
NIMROD
Cave
Light Ion Guide
Heavy Ion Guide
Nuclear Astrophysics with upgrade - III
Study sd-shell nuclei for rp-process
• 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)
One-nucleon removal can determine ANC (only!)
Proton (p)
p
b
Momentum distributions → nlj
Cross section → ANC
Gamma rays → config mixing
Need: Vp-target & Vcore-target
and reaction mechanism
Calc: F. Carstoiu; Data: see later
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
halo
2s1/2
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” m1.5fm (black points) and
Ray (red triangles).
S17 astrophysical factor (ours)
8B
S17 0 
New: S17(0) = 18.0  1.9 eVb
(G Tabacaru ea, 2004)
breakup
38.6 eV b
2
2
C

C

p
p
fm-1
3/ 2
1/ 2

For comparison:
 (7Be,8B) proton transfer at 12 MeV/u
A. Azhari e.a. – two targets:
10B S (0) = 18.4  2.5 eVb (PRL ’99)
17
14N S (0) = 16.9  1.9 eVb (PRC ’99)
17
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
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)
New average: S17(0) = 18.2  1.8 eVb
Published: LT et al.- PRC 69, 2004
22Mg(p,g)23Al
Gamma-ray space-based
telescopes to detect current (ongoing) nucleosynthesis
Astrophysical g-ray emitters
26Al, 44Ti, … and 22Na
Satellite observed g-rays from
26Al (T =7 ·105 y), 44Ti, etc.,
1/2
but not from 22Na (COMPTEL)
20Ne(p,g)21Na(p,g)22Mg(b,n)22Na
Depleted by 22Mg(p, g)23Al ?!
Dominated by direct and
resonant capture to first exc state
in 23Al
reaction
23Al
versus 23Ne
24Mg(7Li,8He)23Al
Structure of 23Al poorly
known: only 2 states, no Jp
Mirror 23Ne has Jp=5/2+ for
g.s. and Jp=1/2+ for 1-st exc
state (Ex=1.017 MeV)
NNDC says: Jp=3/2+
?
1/2+
5/2+
23Ne
23Al
23Al
halo nucleus; level inversion?!
J.X.Z.
Caggiano
Cai et al.,
etPhys
al., PRC
Rev C65,
65,025802
024610 (2001)
(2002)
22Mg(p,g)23Al astrophys S- factor
direct capture only
2s1/2 E1
1d5/2 E1
1d5/2 E1+E2
7.E+04
Poly. (1d5/2 E1+E2)
6.E+04
5.E+04
S-factor (eV b)
Calculating the astrophysical Sfactor in the 2 spin-parity
scenarios, if level inversion
occurs, the difference is dramatic
(upper figure)
The resulting reaction rate is 3050 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, g)23Al
Direct (2s1/2 or 1d5/2) and resonant
capture to first exc state in 23Al
(bottom figure).
reaction in novae
4.E+04
3.E+04
2.E+04
1.E+04
y = 62.815x2 + 1173x + 2016.6
0.E+00
0
0.5
1
1.5
2
2.5
3
Ep (MeV)
22
5/2+ direct
23
Mg(p,g) Al reaction rates
5/2+ - resonant
1/2+ direct
1.E+04
1.E+02
1.E+00
1.E-02
Rate (cm3/mole/s)
22Mg(p,g)23Al
1.E-04
1.E-06
1.E-08
1.E-10
1.E-12
1.E-14
1.E-16
1.E-18
1.E-20
1.E-22
0.01
0.1
T9
1
10
23Al
breakup experiment
Proposed to measure @GANIL:
Momentum distributions for
12C(23Al,22Mg) @50 MeV/u
Calculated 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 g-rays in coincidence with
22Mg to determine the core
excitation contributions.
Determine Jp from mom distrib
Determine 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,g) cross sections more complex. Need extra
work here.
MARS
In-flight RB production
24Mg
23Al
48A MeV
40A MeV
Primary beam 24Mg @ 48 MeV/A – K500 Cycl
Primary target LN2 cooled H2 gas p=1.6 atm
Secondary beam 23Al @ 39.5 MeV/A
(p,2n) reaction
Purity: 99%
Intensity: ~ 4000 pps
First time - very pure & intense 23Al
b decay study of pure RB samples
b-g coincidence spectrum
5/2+
7/2+
IAS
23Al
Tighe ea, LBL 1995
Perajarvi ea, JYFL 2000
5/2+
Proton br. total=1.1%
0.25%
√
1/2+
23Al
0.446(4)s
β+
Q22
ec=12240keV
Mg(p,g)23Al
β+
0.48%
9548
8456
8164
8003
7877
p
IAS: ft=2140 s +/-5%
7803 IAS 5/2+
7787 (5,7/2)+
0.38%
22Na
6985 5/2+
Qp=7580 keV
6575 5/2+
22Na(p,g)23Mg
resonances
2905 (3,5/2)+
2359 1/2+ NO!
2051 7/2+
Preliminary results!
Y Zhai thesis
VE Iacob, et al.
450 5/2+
0 3/2+
23Mg
Conclusions – “other methods”
Useful to have various methods/tools at hand
Medium size facilities useful:
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may get things done sooner and cheaper!
Valuable for (hands-on) education of students and postdocs!
Competition is healthy and necessary!
 Ga Gb 
 2p  2
 E
v  cont  
 exp  i 
  f  
 kT 
res 
 mkT 
Gtot  i
14O + p Resonant Elastic Scattering
3/ 2
– thick targets, inverse kinematics
Beam quality – crucial (no impurities)!
E < 10 MeV/nucleon
Will work on:
• a resonant elastic scattering
• (a,p) reactions, etc.
V. Goldberg, G. Tabacaru e.a. – Texas A&M Univ., PRC 2004
Nuclear physics for astrophysics. Summary
Indirect methods
transfer reactions (proton or neutron)
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5-10 MeV/nucleon
Better beams (energy resol, emittance)
Magnetic spectrometers at 0° – resolution, large acceptance, raytrace reconstr.
breakup
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~ 30-100 MeV/nucleon
Can neutron breakup be used for (n,g)?! (yes, but need n-nucleus potentials)
Spectroscopic info
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Jp , Eres, G, (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.