clustering effects in ternary fission of heavy and ...€¦ · during the reaction between medium...
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CLUSTERING EFFECTS IN TERNARY FISSION OF
HEAVY AND SUPERHEAVY NUCLEAR SYSTEMSM. Ashaduzzaman1, E. Vardaci1, P. K. Rath1, D. Quero1, B. De Canditiis1, E. M. Kozulin2, G. N. Knyazheva2,
I.M. Itkis2 , K. Novikov2
1Dipartimento di Fisica “ Ettore Pancini ”, Università di Napoli “Federico II” and INFN Sezione di Napoli, Complesso Universitario di Monte
S. Angelo, Via Cintia - 80126, Napoli, Italy2Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research,(FLNR JINR), Dubna, Russia
1. ABSTRACT 2. ENERGY RELEASE IN FISSION
5. POTENTIAL ENERGY SURFACE 6. MCP BASED DETECTORS4. CLUSTER TRI-PARTITION
8. EXPERIMENTAL DATA 9. CONCLUSIONS7. EXPERIMENTAL TECHNIQUE
Clusterization, i.e., the process of forming compact pieces of
nuclear matter due to the shell effect inside the nucleus, plays
an important role in true ternary fission of super-heavy
nuclear systems [1]. Experimental investigations show that
during the reaction between medium mass nuclei and heavy
mass target, three body clusterization (ternary fission) occurs
into two heavy nuclei (doubly magic nuclei, i.e., 132Sn, 208Pb,
etc.) and one light nucleus [2]. In 238U + 238U composite
nuclear system, triple cluster decay is expected to occur
possibly creating two Pb-like fragments (Z = 82 and N = 126)
and a 60Ca which is highly exotic. Using this concept, we
have carried out a test experiment with the reaction between238U (with incident beam energy 6.2 MeV/u) and 238U
(target), in GANIL (Caen, France) with the CORSET [3]
setup by an international collaborations. The aim was to
measure the mass and energy distributions of the fragments
and their angular correlations by a TOF-TOF-E technique.
The data indicate mainly binary decay of fission fragments.
Besides, there are many events that can indicate ternary
decays. For the confirmation of two Pb-like and one 60Ca
nuclei, we have in progress further investigations.
[1] V. Zagrebaev, A. V. Karpov, W. Greiner, Phys. Rev. C, 81,
044608 (2010).
[2] I. M. Itkis et al., Phys. Rev. C, 83, 064613 (2011).
[3] E. M. Kozulin et al., Instruments and Experimental
Techniques, 51, 44 (2008).
[4] W.J. Swiatecki. 2nd un intern. conf. on the peaceful uses
of atomic energy. volume 15, page 248, Geneva (1958).
[5] G. Royer, J. Moignen. J. Phys. G: Nucl. Part. Phys.,
18:1781 (1992).
[6] Yu.V. Pyatkov et al., Eur. Phys. J. A, 45:29 (2010).
[7] M. Balasubramaniam et al., Pramana - J.Phys., 85:423
(2015).
252Cf
3 body decay occurs
when there is a shell closure
in the emerging fragments.
Beam
Target
Bea
m M
on
itors
Beam
Collimator
The potential energy surface of the three fragments for all
the possible ternary split-ups of the parent nucleus 252Cf [7].
Layout of the CORSET spectrometer
Energy release of an ideal, electrically charged, liquid drop vs.
the fissility parameter χ or Z2/A [4]. The parameter n gives the
number of equally sized fragments in the decay process.
Mass Distribution from Spontaneous fission of 252Cf [6].
10. REFERENCES
1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
VII (cm/ns)
V (
cm
/ns)
220 225 230 235 240 245 250 255 260
600
620
640
660
680
700
720
740
760
780
800
820
840
Fragment mass (u)
TK
E (
Me
V)
100 120 140 160 180 200 220 240 260 280 300
100
120
140
160
180
200
220
240
260
280
300
Mpost1
Mpo
st2
𝑽∥ < 𝑽𝒄.𝒎. ∶Sequential fission, detected fragments in the
backward (opposite to beam) direction.
𝑽∥ > 𝑽𝒄.𝒎. ∶Sequential fission, detected fragments in the
forward (beam) direction.
𝑽∥ = 𝑽𝒄.𝒎. ∶ Binary fission, full momentum transfer.
All previous studies on ternary fission proof that superheavy
systems can undergo 3 body decay. In this test experiment we
found the signature of sequential ternary fission case. The
physics of clusterization for which ternary fission occurs in
superheavy systems is a very important phenomena also for the
nucleogenesis in the r-process.
252Cf
Landscape of potential energy of three body
configurations formed in collision of 238U+238U [1].
χ = 0.611
Z2/A = 30.5 (208Bi)
More Energy from
binary
More Energy
from ternary
Z2/A : 30.5 to 43.3208Bi to 257Fm
BF
TF
3. FISSION BARRIER HEIGHT
A
For larger masses, both barriers reach gradually similar values.
Barrier heights (in MeV) for symmetric binary and ternary
fission as a function of temperature and mass number [5].
Binary
Fission
Ternary
Fission
A
Fis
sio
n B
arr
ier
Hei
gh
t
Fis
sio
n B
arr
ier
Hei
gh
t
The arrangement of four
alpha particle clusters in
the nucleus 16O
M1
M2
“CCT”
-Ternary
Cluster Decay252Cf
Thickness of Target:
1: 230 – 260 µg/cm2
2: 419 – 457 µg/cm2
3: 500 µg/cm2
Beam Energy: 6.2 MeV/A
2
3
4
238U
238U
197Au
Empty
1
Beam (238U) Beam
TOF Arm of CORSET With Start and Stop Detector.
8 Si-Detectors attached with Stop Detector.
Energy (arb. Units)
TO
F (a
rb. U
nit
s)
Mass-TKE Distributions