1. Feeding of low-energy structures with different deformations by the GDR decay: the nuBall array coupled to PARIS
M. Kmiecik, A. Maj, B. Fornal, P. Bednarczyk et al.
IFJ PAN Kraków
for the PARIS collaboration
ALTO nu-ball hybrid spectrometer workshop 2016
Orsay, May 19-20, 2016

2. Plan
Motivation
Studying nuclear shapes by GDR measurements – examples of the method
Jacobi shape transitions
GDR feeding of superdeformed states
Nuclear deformation at highest spin studied using isomer gated GDR
Idea to apply described methods in experiments using nuBall + PARIS in regions of shape coexistence and shape isomer
link between deformation of hot compound nucleus and evaporation residues
population of states of different deformation by high-energy γ–rays from GDR decay
Outlook

3. Motivation link between deformation of hot compound nucleus
and deformation of cold evaporation residue n a
GDR g
GDR
GDR high energy gamma rays
- hot nucleus shape
low energy transitions - deformation of excited residue
Excitation energy [MeV]
Angular momentum [h]

4. GDR good probe for shape information
oblate G
prolate G
triaxial

5. GDR strengths for hot, rotating nuclei is more complicated
thermal shape fluctuations
Coriolis splitting
K. Mazurek – LSD calculations
potential energy calculated with LSD (Lublin-Strasbourg Drop) model: Dudek & Pomorski Phys. Rev. C67 (2003)
oblate
oblate
triaxial
triaxial
prolate
Jacobi shapes
Low energy component in GDR strength function

6. Examples of using the GDR to study nuclear shapes

7. a) Search for Jacobi shape transition in light nuclei: 46Ti
a) Search for Jacobi shape transition in light nuclei: 46Ti* decay to 42Ca
IRES:
105 MeV 18O + 28Si  46Ti*
Lmax  35 ,
E* = 88 MeV,
v/c  4.3%
Setup:
Euroball IV (26 clovers + 15 clusters)
HECTOR (8 big BaF2)
EUCLIDES (40 Si telscopes)

8. GDR gated on discrete transitions in 42Ca
MC Cascade
fit – 5-L
M. Lach et al., Eur Phys J. A12, 381 (2001)
A. Maj et al., Nucl. Phys. A731, 319c (2004)
Jacobi shape transition and seen for the first time Coriolis effect

9. b) GDR feeding of SD states
M. Kmiecik et al., Acta Phys. Pol. B36 (2005) 1169
sd / spher
nd / spher
sd / nd
feeding of the highly deformed states by the low energy GDR component
spher nd sd
M. Lach et al., Eur Phys J. A12, 381 (2001)

10. GDR feeding of SD states in 143Eu
LNL:
165 MeV 37Cl + 110Pd  147Eu*
G. Benzoni et al., Phys. Lett. 540B, 199 (2002)
Setup:
Euroball
HECTOR SD
feeding of the SD states in 143Eu by the low energy GDR component
spher ND

11. c) GDR decay to high-spin isomeric states
96 MeV 18O + 198Pt → 216Rn* E*=56MeV, Lmax=39h
gating on isomers
choosing nuclei
at highest spins
surviving fission
Setup:
Hector + Helena
Catcher Ge
BGO
isomer

12. Isomer gated GDR
high-energy γ-rays gated on isomer
gate on time
GDR width for 216Rn
small increase of deformation for highest spin - nucleus remains almost spherical up to the fission limit
M. Kmiecik et al. PR C70, (2005)

13. Idea – to apply described methods in experiments using nuBall + PARIS
Study:
GDR decay to states of different deformation in evaporation residues
Obtain information on:
feeding of these states by GDR
corelation between shape of hot nucleus and deformation of evaporation residues

14. Example 1 - shape coexistence
P. Möller et al., Phys. Rev. Lett. 103, (2009)
72-78Kr
prolate
oblate β=
38 ns
oblate
18.8 ns
prolate
oblate
prolate
prolate
oblate
E. Bouchez et al., Phys. Rev. Lett. 90, (2003)
11 ps
61 ps

15. Possible reactions
90 MeV on 66Zn,64Zn → 80Sr*,82Sr* → 76Kr, 78Kr
144 MeV on 46Ti → 78Sr* → 74Kr
32S

16. GDR gated on transitions between states of different deformation
E. Clement et al., Phys. Rev. C 75, (2007)
gating on low-energy γ-transitions
76Kr
oblate
prolate
result: GDR strength → nuclear shape

17. γ-transitions yield gated on GDR energy
E. Clement et al., Phys. Rev. C 75, (2007)
76Kr
gating on high-energy γ-rays
oblate
result: transitions yield as a function of GDR energy → GDR feeding of low energy structures
prolate

18. 74,78Kr isotopes 74Kr 78Kr oblate prolate oblate prolate
E. Clement et al., Phys. Rev. C 75, (2007)
74Kr
F. Becker et al., Nucl. Phys. A 770, 107 (2006)
78Kr
oblate
prolate
oblate
prolate

19. Example2 - shape isomer – 188Pt
S. Mukhopadhyay et al., Phys. Lett. B 739, 462 (2014)
188Pt
near prolate
triaxial
β =0.18and γ=−6°
β=0.16 and γ=−40°

20. Available reaction
176Yb 82 MeV, 4n) 188Pt

21. GDR decay to different deformation structures
GDR in CN (192Pt)
triaxial
β=0.16 γ=−40°
how the states of different deformation are populated by high energy gammas from GDR decay
near prolate
β =0.18and γ=−6°

22. gating on time
Example of time spectrum measured by FATIMA
gate on triaxial deformation
gate on (mostly) prolate deformation
result: GDR strength function delivering information on shape of hot nuclei decaying to given final deformation
oblate
triaxial
prolate

23. Experimental set-up measured: nu-ball array:
24 clover Ge detectors at 90 degrees ~4.5% efficiency at 1MeV
36 LaBr3 detectors from Fatima - 5% efficiency
PARIS clusters - 2% (at 23 cm) efficiency for 15 MeV gamma rays
measured:
low energy discrete transitions:
energy
time
multiplicity
high energy γ-rays

24. The PARIS PHOSWICH
10 ns risetime
Single pulses
HAMAMATSU
Mixed signal

25. First PARIS cluster – already used in the experiment at IPN Orsay

26. Conclusions
nuBall array together with PARIS clusters can be used for measurement of GDR high-energy gamma decay from compound nucleus in coincidence with low energy gamma transitions or/and with isomers
Possible regions of interest are: a) shape coexistence in Kr isotopes; and b) shape isomers around A≈190
Such experiments will allow us to:
trace shape evolution from hot nuclear system to specific cold nuclear structures
and study the feeding of states of different deformation by high-energy γ–rays from GDR decay

27. Deadlines:
Abstract submission: May 27, 2016
Registration closes: July 10, 2016