Coulomb excitation experiments at IPN Orsay
M. Zielińska1 , D. Doherty1 , M. Komorowska2 , I. Matea3 , G. Georgiev4 ,
P. Butler5 , K. Hadyńska-Klȩk6 , P.J. Napiorkowski2 , M. Wiedeking7 ,
K. Wrzosek-Lipska2 , R. Briselet1 , A. Drouart1 , L.P. Gaffney8 , A. Görgen6 ,
A. Gottardo4 , E.T. Gregor9 , M. Klintefjord6 , W. Korten1 , J. Ljungvall4 ,
P. Matuszczak1 , G. O’Neill5 , W. Pia̧tek2 , L. Próchniak2 , E. Rapisarda10 ,
M. Scheck9 , J. Srebrny2 , M. Thürauf11 ,
1
CEA Saclay, IRFU/SPhN, Gif-sur-Yvette, France; 2 Heavy Ion Laboratory, University of
Warsaw, Poland; 3 IPN Orsay, France; 4 CSNSM, Orsay, France; 5 University of Liverpool, UK;
6 University of Oslo, Norway; 7 iThemba LABS, South Africa; 8 KU Leuven, Belgium;
9 University of the West of Scotland, UK; 10 CERN-ISOLDE, Geneva, Switzerland
11 TU Darmstadt, Germany;
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 1/27
ALTO facility, IPN Orsay
ALTO (Accélérateur Linéaire et Tandem à Orsay)
•
•
•
stable beams from the 15 MV tandem accelerator
◦ gamma-ray spectroscopy: ORGAM
radioactive beams produced by photofission
◦ BEDO set-up: beta-decay studies
4700 hours of beam time per year
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 2/27
MINORCA campaign at IPN Orsay
•
MINORCA: MINiball and ORgam Campaign at the Tandem-ALTO
(June 2014-March 2015)
campaign managers: I. Matea, G. Georgiev
•
8 MINIBALL triple clusters + 15 ACS 70% Euroball Phase-I detectors
(GammaPool + French-UK LoanPool)
efficiency of 8% : 6.3% MINIBALL, 1.8% ORGAM
ancillary detectors: OUPS plunger, Si particle detector
LICORNE neutron source
•
•
•
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 3/27
Coulomb excitation experiments at IPN Orsay
•
two Coulomb excitation experiments in January 2015
◦ Shape coexistence in 74 Se
(NI-SI-68, M. Zielińska, K. Wrzosek-Lipska et al)
◦ Octupole collectivity in 146 Nd, 148 Sm
(NI-SI-69, P. Butler, M. Zielińska et al)
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 4/27
Experimental setup for Coulex experiments
•
DSSD detector (Lund University,
Sweden/RADCON, Russia):
•
0.52 mm thick
64 segments, 32 rings
85mm outer diameter
placed at backward angles
(120-169◦ )
•
•
•
•
•
•
OUPS plunger chamber
MINIBALL preamplifiers and cabling
hardware particle-gamma coincidence: MESYTEC STM-16+ amplifiers
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 5/27
Counts
Experimental setup for Coulex experiments
102
50000
40000
30000
10
20000
10000
1
0
500
74
1000
1500
2000
2500
3000
3500
4000
Energy [uncalibrated]
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
particle-gamma coincidence time
Se energy (one ring)
3
1800
2
1600
1400
1
1200
1000
0
800
−1
600
400
−2
200
−3
−3
Magda Zielińska, CEA Saclay
−2
−1
0
1
2
3
0
BRIX Workshop, Liege, 27-28 May 2015 - p. 6/27
Shape coexistence in 74 Se
NI-SI-68 experiment, 19/01-25/01/2015
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 7/27
Shape coexistence and evolution in light Se isotopes
• oblate shapes predicted for ground states
in 68,70,... Se
• calculations indicate shape coexistence
and considerable gamma softness in
68−74 Se
• quadrupole moments, transition rates and
deformation parameters are an excellent
test for theories
D1S 5D GCM(GOA): J.P Delaroche et al
N. Hinohara et al, PRC 82 (2010) 064313
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 8/27
Spectroscopy of 74 Se – missing pieces of information
•
•
two equally probable experimental values of Qs of 2+
1
recent conclusions of the beta-decay study (E. McCutchan et al.):
◦ 0+ has a beta-vibrational character
2
◦ 0+ and 2+ may form a strongly deformed band coexisting with gsb
3
3
◦ decay of 2+ strongly fragmented
4
L. Gaudefroyet al., PRC C 80, 064313 (2009)
Magda Zielińska, CEA Saclay
E McCutchan et al., PRC 87, 014307 (2013)
BRIX Workshop, Liege, 27-28 May 2015 - p. 9/27
Proposed measurement
• scattered projectiles detected by a DSSSD at backward angles (120-160◦ )
• MINORCA array in coincidence; low gamma-ray multiplicity, weak lines not on the Compton
+
background of 2+
→
0
1
1
• three targets used to exploit Z dependence of Coulomb excitation
Rate per day
Transition
Pb target
Sn target
Zr target
+
h2+
1 k E2 k03 i: 9 Wu
+
0+
3 → 21
1820
3440
1260
+
h2+
3 k E2 k03 i: 1 Wu
+
2+
3 → 02
1910
6330
1660
+
h2+
1 k E2 k03 i: 4 Wu
+
0+
3 → 21
650
1090
440
+
h2+
3 k E2 k03 i: 4 Wu
+
2+
3 → 02
1910
6290
1670
+
h2+
k
E2
k0
1
3 i: 2 Wu
+
0+
→
2
3
1
70
60
30
+
h2+
3 k E2 k03 i: 27 Wu
+
2+
3 → 02
1910
6010
1650
+
h2+
1 k E2 k03 i: 2 Wu
+
0+
3 → 21
190
950
120
+
h2+
3 k E2 k03 i: 70 Wu
+
2+
3 → 02
1910
5390
1560
+
+
→ It is possible to determine the h2+
3 k E2 k03 i matrix element without observing the 23 →
0+
3 decay!
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 10/27
74
energy of 74 Se ions backscattered on 120 Sn too low
to get a particle-gamma trigger
2+4 → 2+1 ?
2+4 → 0+2 ?
3
10
2+2 → 0+1
104
2+3 → 0+2
0+3 → 2+1, 1022 keV ?
5
10
6+1 → 4+1
4+1 → 2+1
6
10
two energies of 74 Se on 208 Pb used instead (233 MeV and 210 MeV)
2+1 → 0+1
+
+
22 → 2+1
Counts
◦
0+2 → 2+1
•
Se experiment
102
200
Magda Zielińska, CEA Saclay
400
600
800
1000
1200
1400
1600
1800
2000
Energy [keV]
BRIX Workshop, Liege, 27-28 May 2015 - p. 11/27
What can we determine?
•
•
+
lifetimes of 2+
3 , 24 states
(determined for the first time)
at least two quadrupole moments:
(precise lifetimes known)
2
6
2+
1 ,
4+
1
2
0
868
1460
1680
4
984
2
1023
•
+
k
E2
k0
h2+
3 i?
3
+
(if we can see the 0+
3 → 21 line)
729
635
0
220
1269
2
634
0
•
•
shape parameters hQ2 i (overall deformation) and hQ3 cos3δi (triaxiality)
for the ground state
shape parameters for other 0+ states?
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 12/27
Octupole collectivity in 146 Nd, 148 Sm
NI-SI-69 experiment, 26/01-01/02/2015
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 13/27
Regions of enhanced octupole collectivity
”Magic” numbers: 34, 56, 88, 134
L. M. Robledo, G. F. Bertsch: GCM (GOA)
Very high B(E3) in 152 Gd: 52(17) W.u. measured in (d,d’)
• How reliable is this value?
• Is there a peaking in octupole strength in the A∼150 region similar to what
is observed for Ra-Rn isotopes?
• Is it octupole vibration or static deformation?
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 14/27
How to measure octupole collectivity?
•
B(E3) transition probabilities are a sensitive probe of octupole collectivity
•
Decay of negative-parity states proceeds predominantly via E1 and E2
transitions; E3 branches are usually below observation limits
•
...but population of these states in Coulomb excitation proceeds via E3
transitions;
•
Coulex excitation cross sections can be related to B(E3)
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 15/27
E3 matrix elements: octupole vibration vs static deformation
H.J. Wollersheim et al, NP A556 (1993) 261
R. Ibbotson et al, PRL 71 (1993) 1990, NP A619 (1997) 213
rigid octupole shape: h4+ k E3 k1− i related to h0+ k E3 k3− i (226 Ra)
octupole vibration: h4+ k E3 k1− i equal to zero (148,150 Nd)
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 16/27
Experiment:
• 146 Nd, 148 Sm
-
3
10
11 → 0+1+ 2+2 → 0+1
-
104
0+2 → 2+1
11 → 2+1 + 2+2 → 2+1
S
Ni
6+1 → 4+1
58
31 → 2+1
4+1 → 2+1
10
targets of ∼1.5 mg/cm2
(104 MeV) and 58 Ni (182 MeV), 1pnA
32
5
Sm
2+1 → 0+1
Counts
• 32 S
148
102
200
400
Magda Zielińska, CEA Saclay
600
800
1000
1200
1400
1600
Energy [keV]
BRIX Workshop, Liege, 27-28 May 2015 - p. 17/27
Experiment:
• 146 Nd, 148 Sm
Nd
targets of ∼1.5 mg/cm2
(104 MeV) and 58 Ni (182 MeV), 1pnA
32
2+1 → 0+1
2+2 → 2+1
S
Ni
-
11 → 2+1
3
10
-
+ 0+2 → 2+1
104
4+2 → 31
4+1 → 2+1
5
10
58
4+2 → 4+1
31 → 2+1 + 6+1 → 4+1
Counts
• 32 S
146
102
400
Magda Zielińska, CEA Saclay
600
800
1000
1200
1400
1600
Energy [keV]
BRIX Workshop, Liege, 27-28 May 2015 - p. 18/27
Counts
Experiment: problem with 32 S datasets
146
Nd+32S
148
Sm+32S
102
800
1000
1200
1400
1600
Energy [keV]
fusion-evaporation on 16 O in the targets?
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 19/27
Outlook: Coulex experiments in PARIS@ALTO campaign
•
2-3 PARIS clusters (9 LaBr3:Ce (2x2x2 inches)
+ 9 NaI(Tl) (2x2x6 inches) crystals)
•
campaign likely to start in late November 2015
•
high efficiency: 3.5% at 6 MeV (two clusters)
•
24 Phase-I ACS HPGe detectors for
high-resolution gamma-ray spectroscopy
•
the same particle detector
•
two Coulomb excitation experiments accepted
◦ Superdeformation in 40 Ca (NI-SI-83, P. Napiorkowski et al)
◦ B(E2; 2+ → 0+ ) in 14 C (NI-SI-85, M. Wiedeking, K. Hadyńska et al)
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 20/27
Superdeformation in 42 Ca
NI-SI-83 experiment, P. Napiorkowski et al
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 21/27
Highly deformed structures in the A ∼ 40 region
36 Ar:
C. Svensson et al., PRL 85 (2000) 2693
38 Ar: D. Rudolph et al., PRC 65 (2002) 034305
40 Ar: E. Ideguchi et al., PLB 686 (2010) 18
40 Ca: E. Ideguchi et al., PRL 81 (2001) 222501
44 Ti: D. O’Leary et al., PRC 61 (2000) 064314
• B(E2; 4+ → 2+ ) = 170 Wu (β = 0.6) in 40 Ca
2
2
• moments of inertia in the side band very similar
for 40 Ca and 42 Ca
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 22/27
Superdeformation in 42 Ca confirmed by Coulex
• Coulomb excitation of 42 Ca on 208 Pb studied with AGATA at LNL Legnaro
• shape parameters determined using quadrupole sum rules
• high deformation in the side band, significant triaxiality of the ground state
K. Hadyńska-Klȩk, to be published
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 23/27
Coulex of 40 Ca
•
verification of lifetimes from DSAM and
determination of relative signs of intra-band E2
matrix elements
•
role of triaxiality?
•
decays of 0sd and 2sd states (4 and 5.6 MeV)
observed in PARIS detectors
•
transitions in the yrast band measured with
ORGAM
• 40 Ca
beam (168 MeV) on 208 Pb target (1mg/cm2 )
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 24/27
Collectivity of 14 C
NI-SI-85 experiment, M. Wiedeking, K. Hadyńska et al
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 25/27
Coulex of 14 C
•
•
•
short lifetime of the 2+ state: Coulex feasible but good efficiency
for 7 MeV gamma rays required
one measurement only (width in electron scattering 50.7(71) meV),
discrepancy with all theoretical calculations
B(E2)’s for 14−18 C similar although E(2+ ) differ
• 14 C
at 47 MeV, normalisation to the 208 Pb target
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 26/27
Summary
1) particle detector set-up for Coulex experiments at IPN Orsay validated
2) new opportunities for gamma-ray spectroscopy with stable beams!
Magda Zielińska, CEA Saclay
BRIX Workshop, Liege, 27-28 May 2015 - p. 27/27