Study of nuclear fission barriers and fission yields of exotic nuclei using the advanced R 3B experimental apparatus at the GSI-FAIR facility

Study of nuclear fission barriers and fission yields of exotic
nuclei using the advanced R3
B experimental apparatus
at the GSI-FAIR facility
José Luis Rodríguez-Sánchez
University of Santiago de Compostela
9th
July 2021

2
Why still nuclear fission
A complicated process
- Largest scale colletive motion in nuclei
- Interplay between intrinsic (excitation energy) and collective (motion) degrees of freedom
- Dynamics governed by macroscopic and microscopic components of the nuclear potential
83 years after its discovery, the understanding of nuclear fission
still represents an important challenge in nuclear physics
A difficult experimental characterization
Identification of the two fission fragments in
atomic and mass number only reaches in
inverse kinematics using state-of-the-art
detectors
Lisa Meitner & Otto Hahn (1938)
J.L. Rodríguez-Sánchez

3
Main ingredients for modeling the fission process
● Nuclear densities
● Fission barriers
● Viscosity coefficients
● Nuclear potential energy
- Isospin dependence
- Excitation energy damping of shell and pairing effects
● Energy sharing between fission fragments
Why still nuclear fission
R. Bernard, S. A. Giuliani, and L. M. Robledo, Phys. Rev. C 99, 064301 (2019)
K.-H. Schmidt and B. Jurado, Phys. Rev. Lett. 104, 212501 (2010)
C. Schmitt et al., PRL 99, 042701 (2007)
P. Möller et al., PRC 79, 064304 (2009)
A.V. Ignatyuk et al., SJNP 21, 255 (1975)

4
Many applications
Nuclear structure
at large deformation
Dynamics of
nuclear matter
Nuclear astrophysics
Production of
radioactive ion beams
Hypernuclei
Medical radio-tracers
Production of energy
Nuclear fission
Reaction energy

5
Layout
✗ Experimental fission programme carried out at GSI
- State-of-the art experiments within the R3B collaboration
- Studies of nuclear structure and fission dynamics
✗ Future fission experiments at FAIR for r-process studies
- Fission barriers of exotic neutron-rich nuclei
- Evolution of fission yields with the excitation energy
- Phase-0 fission experiments at GSI
- Development of a new silicon tracker for the R3
B collaboration
✗ Conclusions and perspestives

6
Experimental fission programme at GSI
Charge distribution of ~100 exotic nuclei
covering elements from Hg to U at GDR
energies (E* ≈ 11 MeV)

7
State-of-the art experiments within the R3
B collaboration
Full identification in A, Z of both fission fragments and light-charged particles
J.L. Rodríguez-Sánchez et al.,
Phys. Rev. C 91, 064616 (2015)
E. Pellereau et al.,
Phys. Rev. C 95, 054603 (2017)
● Position resolution 250 µm
● ToF resolution 40 ps
● Magnetic field 2 Tm

8
B collaboration
208
Pb+p at 500A MeV
σ = 0.19
J.L. Rodríguez-Sánchez et al., Phys. Rev. C 91, 064616 (2015)

9
B collaboration
Nuclear structure
Evidence of a new fission mode from fission of Th isotopes
A. Chatillon et al., Phys. Rev. Lett. 102, 202502 (2020)

10
R3B
B collaboration
Nuclear dynamics at high excitation energies
Constraint of the nuclear viscosity coefficient and nuclear density parameterizations
J.L. Rodríguez-Sánchez et al., Phys. Rev. C 90, 064606 (2014) Phys. Rev. C 92, 044612 (2015)
Phys. Rev. C 91, 064616 (2015) Phys. Rev. C 94, 034605 (2016)
208
Pb+p at 500A MeV
E*

11
R3B
B collaboration
Nuclear dynamics at high excitation energies
Constraint of the nuclear viscosity coefficient at large deformations (saddle-scission dynamics)
J.L. Rodriguez-Sánchez et al., Phys. Rev. C 94, 061601(R) (2016) M. Feijoo, PhD thesis, University of Santiago de Compostela (2021)
236
U(650A MeV)+Al

12
R3B
Feijoo et al (2021)
B collaboration

13
Future fission experiments at FAIR
Fragmentation reactions
Super-FRS
SIS-100
Pre-separator (RIBs)
Main separator
Targets
R3B
Beam intensity 1×10 5
⁹ ×10¹¹
Transmission for U 55 % 98 %
Parameter GSI FAIR

14
238
U+Be at 1A GeV
H. Alvarez-Pol et al., PRC 82, 041602(R) (2010)
208
Pb+Be at 1A GeV
T. Kurtukian-Nieto et al., PRC 89, 024616 (2013)
Fragmentation reactions
242
Pu+Be
Rate/s
N=152
N=126

15
Future fission experiments at FAIR: r-process
● Fission barriers of neutron-rich nuclei still needed to constrain the theoretical models
Isospin dependence of fission barriers
Region covered by fragmentation reactions
P. Möller et al., Phys. Rev. C 79, 064304 (2009)
N=126
d
● Solar abundance fluctuations of 30% for r-process nuclei
S. A. Giuliani et al., Phys. Rev. C 102, 045804 (2020)

16
● Mass and charge distributions still needed to constrain the theoretical models that describe
the fission yields
S. Goriely et al., J. Phys. Conf. Series 665, 012052 (2016)
S. A. Giuliani et al., Phys. Rev. C 102, 045804 (2020)
J.-F. Lemaître et al., Phys. Rev. C 103, 025806 (2021)
J. Randrup et al., Phys. Rev. C 88, 064606 (2013)
● Solar abundance fluctuations of a factor 10 for r-process nuclei

17
● Excitation energy dependence of fission yields, in particular, between thermal fission and 40 MeV
● Solar abundance fluctuations up to 50% depending on the nuclear mass
N. Vassh et al., J. Phys. G: Nucl. Part. Phys. 46, 065202 (2019)

18
Fission induced by quasi-free (p,2p) reactions
The kinematic properties of the proton pair provide information
of the excitation energy of the residual nucleus by using
the four-momentum conservation
Invariant mass Rest mass
Exotic nuclei at 500A MeV
32
S(p,2p)31
P
C.C. Bojikob et al., J. Nucl. Phys.52, 5 (1990)
Excitation energy [MeV]

19
Phase-0 (p,2p)-fission experiment at GSI (March 2021)
● CALIFA and Si-tracker: Proton momenta and γ-rays
Energy res. protons(gamma) 1%(5.5% at 1.3 MeV), Position res. 70µm
● MUSIC, ToF wall and MWPC detectors: Fission fragments
∆Z~0.32 , ToF~40ps, Position res. 250µm (FWHM)
● NeuLand: Neutron multiplicities (max. 10)
Beam of 238
U at 560A MeV
● Magnetic field: 4Tm

20
R3B
Charge distribution of fission fragments and their correlations
238
U+p at 560A MeV

21
● Excitation energy of fissioning systems from the (p,2p) reactions with ∆E ~ 5 MeV
● Allowing to study the evolution of fission yields with the excitation energy
● Two PhD students working on the data analysis

22
High resolution pixel silicon detector
● Based on Monolithic Active Pixel Sensors
Two barrels surrounding the LH2
target
● 30 cm long
● 4-5 cm radius
● 363 silicon sensors
● Threshold of few eV per channel
● Azimuthal and polar angles: 0-360 and 8-80
Beam

23
(p,2p) event reconstruction
● Energy threshold for protons of 20 keV
● Vertex resolution better than 0.5 mm (FWHM)
● Angular resolutions better than 1 mrad (FWHM)
● Missing mass resolution of 2 MeV (FWHM)
LH2
target of 1.5cm
Thres = 20 keV

24
R3B
238
U
E*
● Measurement of fission barriers with an uncertainty of around 0.15 MeV
● Evolution of the fission yields with the excitation energy in steps of 2 MeV
Method: K.R. Kean et al., Phys. Rev. C 100, 014611 (2019)
Fission
Probability

25
R3B
Conclusions and perspectives
● The state-of-the art fission experiments carried out at GSI are providing valuable data to
study the nuclear structure and matter dynamics of exotic nuclei
- Discovery of new fission modes
- First constraints of nuclear dynamics at small and large deformations with spallation and
fragmentation reactions
● New fission experiments performed in March 2021 to study the fission process of exotic
nuclei in the Hg and Rn region and first (p,2p)-fission experiment to correlate the excitation
energy with the fission yields
● Development of a new silicon tracker for the R3
B collaboration to investigate fission
of neutron-rich nuclei in the U and Th region, which will provide data for:
- Fission barrier heights and fission yields around N=152
- Evolution of shell and pairing effects with the excitation energy
- Anisotropy of fission fragments as a function of the fission mode
- Gamma emission after the scission point
- Angular momentum gained during the scission stage as a function of the fission mode
- Neutron multiplicities and fission fragment correlations for nuclear reactors
- ...

26
collaboration
Sponsors:
Thank you for your attention!

28
First experiments at the fragment separator FRS
Exotic
nuclei
Identification of the two fission fragments in
atomic number for exotic nuclei
K.-H. Schmidt et al., NPA 665, 221 (2000)
Symmetric Asymmetric
First investigation of the evolution of
fission fragment charge distributions
with the isospin
Clear transition from symmetric to
asymmetric fission

Study of nuclear fission barriers and fission yields of exotic nuclei using the advanced R 3B experimental apparatus at the GSI-FAIR facility

Recommended

Recommended

More Related Content

Similar to Study of nuclear fission barriers and fission yields of exotic nuclei using the advanced R 3B experimental apparatus at the GSI-FAIR facility

Similar to Study of nuclear fission barriers and fission yields of exotic nuclei using the advanced R 3B experimental apparatus at the GSI-FAIR facility (20)

Recently uploaded

Recently uploaded (20)

Study of nuclear fission barriers and fission yields of exotic nuclei using the advanced R 3B experimental apparatus at the GSI-FAIR facility