1. Characterising excited states in and around the semi-magic nucleus 68Ni using Coulomb excitation and one-neutron transfer
L. P. Gaffney1, F. Flavigny1, M. Zielińska2, K. Kolos4, A. N. Andreyev5, M. Axiotis6, D. L. Balabanski7, A. Blazhev8, J. Cederkäll9, T. E. Cocolios10, E. Clément11, T. Davinson12, G. De France11, H. De Witte1, D. Di Julio9, T. Duguet2, C. Fahlander9, S. J. Freeman10, G. Georgiev13, R. Gernhäuser14, A. Gillibert2, T. Grahn15, P. T. Greenlees15, L. Grente2, R. K. Grzywacz4,16, S. Harissopulos6, M. Huyse1, D. J. Jenkins5, J. Jolie8, R. Julin15, W. Korten2, Th. Kröll17, A. Lagoyannis6, C. Louchart2, T. J. Mertzimekis18, D. Miller19, D. Mücher14, P. Napiorkowski20, K. Nowak14, F. Nowacki21, A. Obertelli2, R. Orlandi1, J. Pakarinen15, P. Papadakis15, N. Patronis22, N. Pietralla17, P. Rahkila15, R. Raabe1, G. Rainovski17, E. Rapisarda3, P. Reiter8, M. D. Salsac2, M. Seidlitz8, B. Siebeck8, K. Sieja21, D. K. Sharp10, C. Sotty1, O. Sorlin11, J. Srebrny20, M. Taylor10, P. Van Duppen1, D. Voulot3, N. Warr8, R. Wadsworth5, F. Wenander3, K. Wimmer23, P. Woods12, K. Wrzosek-Lipska1
1KU Leuven, Belgium; 2CEA-Saclay, France; 3CERN-ISOLDE, Switzerland; 4University of Kentucky, U.S.; 5University of York, U.K.; 6NCSR-Demokritos, Greece; 7INRNE-BAS, Bulgaria; 8University of Köln, Germany; 9University of Lund, Sweden; 10Univeristy of Manchester, U.K.; 11GANIL, France; 12University of Edinburgh, U.K.; 13CSNSM, France; 14TU-München, Germany; 15University of Jyväskylä; Helsinki Institute of Physics, Finland; 16Oak Ridge National Laboratory, U.S.; 17TU Darmstadt, Germany; 18Univeristy of Athens, Greece; 19TRIUMF, Canada; 20HIL University of Warsaw, Poland; 21Universite de Strasbourg, France; 22University of Ioannina, Greece; 23Central Michigan University, U.S.

2. Characterising excited states in and around the semi-magic nucleus 68Ni using Coulomb excitation and one-neutron transfer
L. P. Gaffney1, F. Flavigny1, M. Zielińska2, K. Kolos4, A. N. Andreyev5, M. Axiotis6, D. L. Balabanski7, A. Blazhev8, J. Cederkäll9, T. E. Cocolios10, E. Clément11, T. Davinson12, G. De France11, H. De Witte1, D. Di Julio9, T. Duguet2, C. Fahlander9, S. J. Freeman10, G. Georgiev13, R. Gernhäuser14, A. Gillibert2, T. Grahn15, P. T. Greenlees15, L. Grente2, R. K. Grzywacz4,16, S. Harissopulos6, M. Huyse1, D. J. Jenkins5, J. Jolie8, R. Julin15, W. Korten2, Th. Kröll17, A. Lagoyannis6, C. Louchart2, T. J. Mertzimekis18, D. Miller19, D. Mücher14, P. Napiorkowski20, K. Nowak14, F. Nowacki21, A. Obertelli2, R. Orlandi1, J. Pakarinen15, P. Papadakis15, N. Patronis22, N. Pietralla17, P. Rahkila15, R. Raabe1, G. Rainovski17, E. Rapisarda3, P. Reiter8, M. D. Salsac2, M. Seidlitz8, B. Siebeck8, K. Sieja21, D. K. Sharp10, C. Sotty1, O. Sorlin11, J. Srebrny20, M. Taylor10, P. Van Duppen1, D. Voulot3, N. Warr8, R. Wadsworth5, F. Wenander3, K. Wimmer23, P. Woods12, K. Wrzosek-Lipska1
Coulomb excitation – 68Ni
68Ni 4.0, 4.5, 5.0 MeV/u
One-neutron transfer – 69Ni
70Ni 3.5 MeV/u Coulomb excitation – 70Ni
1KU Leuven, Belgium; 2CEA-Saclay, France; 3CERN-ISOLDE, Switzerland; 4University of Kentucky, U.S.; 5University of York, U.K.; 6NCSR-Demokritos, Greece; 7INRNE-BAS, Bulgaria; 8University of Köln, Germany; 9University of Lund, Sweden; 10Univeristy of Manchester, U.K.; 11GANIL, France; 12University of Edinburgh, U.K.; 13CSNSM, France; 14TU-München, Germany; 15University of Jyväskylä; Helsinki Institute of Physics, Finland; 16Oak Ridge National Laboratory, U.S.; 17TU Darmstadt, Germany; 18Univeristy of Athens, Greece; 19TRIUMF, Canada; 20HIL University of Warsaw, Poland; 21Universite de Strasbourg, France; 22University of Ioannina, Greece; 23Central Michigan University, U.S.

3. Monte Carlo Shell Model calculations
Y. Tsunoda JPG (2013), arXiv [nucl-th] v1

4. Excited states in 68Ni (Z=28; N=40)
Single-step Coulex
Multi-step Coulex
g-ray decays
B(E2; 0+1 -> 2+1) = 3.1(4) W.u. (b,c)
Re-measure B(E2; 0+1 -> 2+1) at safe energy and higher precision with respect to 196Pt target excitation.
Determine if higher-order transitions are of collective nature or not, using “clean” 208Pb target.
Y. Tsunoda J. Phys. G. (2013), arXiv [nucl-th] v1
O. Sorlin, et al., Phys. Rev. C 88, (2002) – Intermediate energy Coulomb excitation
N. Bree, et al., Phys. Rev. C 78, (2008)

5. 70Ni: A discrepancy RDDS: - - - = 2.7 W.u. ― = 10.0 W.u. x
Intermediate energy Coulex gives large B(E2) = 10.0 W.u.
Large B(E2) explained as proton-core polarisation (a)
New RDDS Lifetime gives B(E2) = 2.7 W.u. (b)
Consistent with latest shell-model calculations (c)
Reproduced from: O. Sorlin & M. Porquet, Prog. Part. Nucl. Phys. 61, 602 (2008). x
(b) D. Miller et al., Bull. Am. Phys. Soc. 55, DC (2010).
(c) Y. Tsunoda JPG (2013), arXiv [nucl-th] v1.
(b)
RDDS: = 2.7 W.u.
― = 10.0 W.u.
keV
(a)
(a) O. Perru et al., Phys. Rev. Lett. 96, (2006).

6. Coulex experiment and simulations
68Ni on 208Pb( MeV/u Ni Pb
Angles of detection for projectile/recoil in the T-REX setup
Software cut to make “safe”
T-REX + Miniball
Increasing multi-step probability
Front CD (150 mm thick) without barrels
Adjustable target CD-distance to optimise angles
Rear CD + rear barrels (not used for Coulex)

7. One-neutron transfer: 69Ni
Identification of 5/2+ -> info on N=50 shell gap.
Previous experiment fits two states; one “bump”
(a)
GANIL ~30 MeV/u
M. Moukaddam. Thesis: Évolution de la structure en couches dans les noyaux de masse moyenne: Recherche de l’orbitale 2d5/2 neutron dans le 69Ni. Strasbourg (2012)

8. One-neutron transfer: 69Ni
Identification of 5/2+ -> info on N=50 shell gap.
Previous experiment fits two states; one “bump”
New experiment better energy matched for l=2 transfer => large cross-section for 5/2+ state(s).
High resolution and efficiency of gamma-ray detection will give precise energy of 5/2+ states(s).
(b)
Q = 3.58 MeV
Q = 2.36 MeV
d(66Ni,67Ni)p
BCD
BBarrel
FCD (30 mm)
(b) J. Diriken. Thesis: Probing positive-parity states in 67Ni through one-neutron transfer reactions. KU Leuven (2013)

9. Total p+-g coincidences
Beam-time request: 68Ni
Beam rate
Coulex
300
871 5 25
>4; >0.019 W.u.
>17;
0.92 W.u.
68Ni beam – 2.1 x 105 Miniball
Primary yield – 1 x 106 ions/mC (estimated)
70Ni beam – 2 x 104 Miniball (assumed)
Primary yield – 2 x 105 ions/mC
68Ni
Transfer – 5.0 MeV/u
Target (thickness)
s (5/2+) [mb]
SF (5/2+)
Run time
CD2 (0.2 mg/cm2)
122
0.6
72 h
g-ray efficiency
Angular coverage
Total p+-g coincidences
2.5 MeV
~40%
840 (Si 5/2+i → g.s.)
196Pt ( MeV/u; 3 shifts
208Pb ( MeV/u; 15 shifts
+ regular ionisation chamber runs with laser ON/OFF to accurately monitor contamination + beam dump g rays
~50% 70Ga contamination = ~50% Laser OFF runs
If 2.7 W.u.; Ig(2+ -> 0 +) = 117 counts per day
Or 10 W.u.; Ig(2+ -> 0 +) = 407 counts per day
70Ni
196Pt (2.0 mg/cm2)
@ 3.5 MeV/u

10. +1 shift for setup of each beam
Summary
Coulomb excitation – 68Ni
68Ni 4.0, 4.5, 5.0 MeV/u
One-neutron transfer – 69Ni
70Ni 3.5 MeV/u Coulomb excitation – 70Ni
18 shifts
9 shifts
12 shifts
+1 shift for setup of each beam
41 shifts

11. 68Ni (Z=28, N=40) b-decay proposal : 100 (constant <E2>) 75 0.11
obtain precise gamma- and electron transition intensities between the 0+ and 2+ states
Experiment
Calculated transition properties
(2+) 2+ 0+
(2+) 2+ 0+
100 (constant <E2>) 75
0.11 44
1.2
100
Mueller PRC (2000), Flavigny (2013, IS467)

12. 69Ni (Level Scheme)

13. Beam contamination Ionisation chamber:
Mn/Fe (Z=25/26) previously separable(a)
Easy to separate Ni/Ga (Z=28/31)…
Advantage of direct beam measurement, high statistics quickly = short runs
(a) J. Van de Walle, et al., Eur. Phys. J 42, (2009).

14. Integrated cross section :
Gs = 3 mb
State at 2.5 MeV(d5/2) = 13 mb
Proton stopped in dE
BCD and Barrel for GS
BBarrel used alone for 2.5 MeV states
Integrated cross section (Barrel only) :
Gs = 3.5 mb
State at 2.5 MeV(d5/2) = 54 mb
RatioTREX(gs) = 6,5/17 *0,95 ~ 37%
RatioTREX(d5/2) = 67/122 *0,95 ~ 47%

15. d(66Ni,67Ni)p

16. 69Ni: updated motivation
N=50 gap size influences energy and strength distribution of 5/2+ states.
LNPS shell model calculations with 3 different assumed gaps.
~50/~50 distribution of 2 states at MeV consistent with observation.
Precise measurement will constrain calculations.
M. Moukaddam. Thesis: Évolution de la structure en couches dans les noyaux de masse moyenne: Recherche de l’orbitale 2d5/2 neutron dans le 69Ni. Strasbourg (2012)

17. 70Ni: updated motivation
Y. Tsunoda JPG (2013), arXiv [nucl-th] v1

18. Previous 68Ni Coulex at ISOLDE
B(E2; 0+1 -> 2+1) = x 102 e2 fm4

19. Total p+-g coincidences Most recent simulation
Transfer – 5.0 MeV/u
Scenario
Target (thickness)
s (5/2+) [mb]
SF (5/2+)
Run time
g-ray efficiency
Angular coverage
Total p+-g coincidences
Current
CD2 (0.2 mg/cm2)
122
0.6
72 h
2.5 MeV
~40%
840
Worst “
0.5
2.5 MeV
20%
280
Compensate
CD2 (1.0 mg/cm2)
1420
Most recent simulation
2.5 MeV
47%
5370
Eloss ~100 keV
Other states?
Negative parity states not 1n configuration, hence SF << 1.
Cross-section small regardless.

20. Miniball + TREX: Ge efficiency
Energy [keV]
Absolute efficiency

21. Beam rates Nucleus 68Ni (ions/mC) 70Ni (ions/mC) Requested yields
1 x 106
2 x 105
Database values
4 x 105
1 x 104
Recent measurements
8 x 105
N. Bree Coulex
~106