nuclear physics for astrophysics with radioactive beams livius trache texas a&m university...

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.