understanding r-process nuclei using the (d,p) reaction on exotic beams

Tuesday, October 24, 2006 HRIBF Astro Workshop

Kate Jones

Understanding r-process nuclei using the (d,p) reaction on exotic beams

Kate Jones

University of Tennessee

• N=50 and N=82 shell closures and the r-process

• 83Ge and 85Se: crossing the N=50 shell closure

• Shell model calculation of N=51 isotones

• First data from 132Sn(d,p)


Kate Jones

Important nuclear physics measurements for the r-process

Neutron magic-number nuclei are most important

Important measurements:• N ~ closed shell

Mass, t1/2

• N = closed shell + 1Sn (neutron separation energy)

neutron single-particle structure

(d,p) on closed shell nuclei

Close to shell closure

Low Q value for (n,)

Low level density

Small capture cross section

Statistical model not reliable

Direct capture important

HRIBF yields

N=82


Kate Jones

(d,p) reactions in inverse kinematics

132Sn beam (RIB)

Silicon detector

p

Unfavorable kinematics → Reduced Q-value Resolution

Rare Ion Beams (RIBs) are difficult and expensive to produce

Applicable to all isotopes which can be made into a beam

Recoil Detector133Sn recoil

CD2 target (deuteron)


Kate Jones

Crossing N=50: 83Ge and 85Se

* Winger, J.A. et al.,

Phys. Rev. C 38, 285 (1988)

Only known property of 83Ge is t1/2 *

?

Possible r-process line

83Ge 85Se 87Kr 89Sr 91Zr

1/2+

5/2+

Ex

(MeV

)

1

2

?from ENSDF www.nndc.bnl.gov

N=50


Kate Jones

82Ge(d,p)co

unts

/ 2

ns

0 1000 2000 3000 4000

430 μg/cm2 CD2 target

Ebeam = 330 MeV (4 MeV/u)

SIDAR in lampshade configuration covering θlab = 105°-150°

Ionization chamber at θlab = 0° filled with CF4

proton

recoil

coincidence timing between IC and SIDAR

TAC

silicon detector array

IC

ΔE

(ch

anne

ls)

E (channels)

Ge

Se


Kate Jones

83Ge results

0 1200 2400 3600 4800Ep (keV)

105°

127°

149°

θ lab

Q = 1.47 (0.02 stat., 0.07 sys.) MeV 1st Ex = 280 ( 20 stat.) keV

The large width of the first group (ΔEcm≈ 460 keV) and the absence of other levels below Ex = 1 MeV suggest two states.

Sn(83Ge) = 3.69 ± 0.07 MeV

Δ(83Ge) = – 61.25 ± 0.26 MeV

ΔEcm≈ 300 keV from the Se doublet

J.S.Thomas PRC 71 (2005) 021302


Kate Jones

83Ge results cont: Angular distributions

Results are consistent with:

l = 2 ground state (d5/2)

l = 0 1st excited state (s1/2) at Ex=280 keV

g.s. S = 0.48 ± 0.14

1st S = 0.50 ± 0.15

2H(82Ge,p)83Ge

Spectroscopic Factors

Measure single-particle nature of state


Kate Jones

85Se data

4 groups are populated, including g.s. and 1st excited

J.P. Omtvedt, et al., Z. Phys. A 339, 349 (1991).

Energy levels from β- decay

Angular distributions show l = 2 ground state and l = 0 1st excited state

g.s. S = 0.33 ± 0.09 (d5/2)

1st S = 0.30 ± 0.08 (s1/2)

0.00.0

461.9461.9

1114.91114.9

1437.61437.61444.01444.0

2136.82136.82145.82145.8

85Se Ex


Kate Jones

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Shell model calculations: N=51

83Ge 85Se 87Kr 89Sr 91Zr

Calculations by D. Dean, 2-body interaction M. Hjorth-Jensen

SPE’s from Andres Zucker .


Kate Jones

The Neutron-rich tin isotopes

16O

N = 82

Z = 50

124Sn132Sn

Stable Doubly magic

In

Sb

Double shell closure Z=50, N=82

132Sn(d,p) in progress, 130Sn(d,p) to follow


Kate Jones

Reaction Calculations

CCBA 132Sn(d,p) @ 630MeV

By Neil Summers


Kate Jones

132Sn(d,p) detectors

Plan View Beam View

ORRUBA 1000μm

ORRUBA telescopes

Beam

Beam

SIDAR

ORRUBA telescopes

5x5cm2 telescopes

ORRUBA telescopes

ORRUBA 1000μm

6 x ORRUBA 1000μm

5x5cm2 telescope


Kate Jones

132Sn(d,p) photo

ORRUBA detectorstectors

(back angles)

SIDAR detectorstectors

(back angles)


Kate Jones

132Sn(d,p) data

p (channels)

Ep(

chan

nels

)

• Forward telescope 2

• Energy and position from E detector

• Calculated energy loss added

• E = 63m

• TAC gated (MCP downstream)

PRELIMINARY


Kate Jones

132Sn(d,p) data + kinematics calculations

Ep(

chan

nels

)

p (channels)

(7/2-)

(3/2-)

(9/2-)

(5/2-)

(11/2-)

(1/2-)

3700

2004.6

1560.9

853.7

0.0 1.45s

1655.7

p1/2?

[1] P.Hoff PRL 77(1996)1020


Kate Jones

Q-value plot

VERY PRELIMINARY

EP (channels)

Ex

g.s


Kate Jones

Summary and Comments

•N=51Completed 82Ge(d,p) and 84Se(d,p)Measured Sn (mass) for 83GeMeasured angular distributionsExtracted spectroscopic factors

•132Sn(d,p)Measurement still in progressCan see at least 3 previously measured statesSee hint of p1/2, should be able to measure in final

analysis•130Sn(d,p) to come!


Kate Jones

Collaboration

• RIBENS / Center of Excellence collaboration ORNL D. Bardayan, J. Blackmon, M. Smith, C.Nesaraja, D. Shapira, F.

Liang ORAU M. Johnson UT KLJ, K. Chae, Z. Ma, B. Moazen Rutgers University J. Cizewski, S. Pain, R. Hatarik, P.O’Malley Tennessee Tech Ray Kozub, J.Shriner, S.Paulauskas, J.Howard,

D.Sissom University of Surrey J. Thomas, C.Harlin, N. Patterson Colorado School of Mines U.Greife, R. Livesay, L.Erikson Ohio University A. Adekola Furman A.Gaddis


Kate Jones

Shell model calculations: 83Ge

1/2+

Expt

0.5

1.0

1.5

Ex

(Me

V)

5/2+

Theory

Calculations from Alex Brown (private communication). Skyrme mean field, adjusted to reproduce the global single particle energies

Calculation of 83Ge [A. Brown, MSU] predicts stronger shell closure than seen in HRIBF 82Ge(d,p)83Ge experiment


Kate Jones

N=83 Systematics


Kate Jones

(n,) direct capture calculations

• G. Arbanas [ORNL] using the code Cupido (F.Dietrich) to calculate direct capture for 88Sr, 84Se and 82GeCupido (F.Dietrich) compared with TEDCA calculations

from T. RausherUsed SF from HRIBF measurementsKoning-Delaroche global optical potential

• E1 capture of p-wave neutrons dominates capture cross section into both 83Ge and 85Se.

• Semidirect capture through the GDR reduces cross section by ~10%

• Results show capture cross sections that are a factor of 10 down from that into 89Sr (stable case)


Kate Jones

Reaction Calculations 132Sn(d,p)133Sn[854]

By Neil Summers


Kate Jones

From (d,p)Q-value, Ex, ℓ-value,

Spec Factor

Calculate (n,γ) cross section

Use to modify residual interactions in nuclear structure (shell) model

Improve global masses for n-rich nuclei

Input into SupernovaCode

Nuclear data input into r-process calculations


Kate Jones

Other utility of (d,p) reactions - masses

• r-process involves thousands of (n,) reactions• Nuclear masses are needed

to calculate energy released in the r-process to calculate capture cross sections with a Statistical model for the “waiting point approximation” used in many r-

process calculations• (d,p) reactions can measure masses

Precision adequate for r-process studiesRequires reacceleration

r-process waiting point approximation


Kate Jones

New shell model calculations

• New effort by David Dean & M. Hjorth-Jensen to calculate all neutron-rich N=51 nuclei simultaneously

• Working with excitations built on a 78Ni core• Cannot currently reproduce measured spacing of 1st excited

state energies for n-rich N=51 nuclei• Appears necessary to activate g9/2 protons - which will

significantly enlarge model space• Very preliminary results - work in progress

understanding r-process nuclei using the (d,p) reaction on exotic beams

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