Heavy Element Research at Dubna (current status and future trends) Yuri Oganessian Flerov Laboratory of Nuclear Reactions Joint Institute for Nuclear Research Dubna, Moscow region, Russian Federation Talk at the CCAST Workshop on "Isospin Physics and Nuclear Liquid-Gas Phase Transtion" August 18-21, 2005, Beijing, China
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Heavy Element Research at Dubna (current status and future trends) Yuri Oganessian Flerov Laboratory of Nuclear Reactions Joint Institute for Nuclear Research.
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Heavy Element Research at Dubna (current status and future trends)
Yuri Oganessian
Flerov Laboratory of Nuclear ReactionsJoint Institute for Nuclear Research
Dubna, Moscow region, Russian Federation
Talk at the CCAST Workshop on "Isospin Physics and Nuclear Liquid-Gas Phase Transtion" August 18-21, 2005, Beijing, China
10m
0
Cyclotronk=550
Cyclotronk=600
MicrotronEe=25 MeV
Low energy RIB-line
4π-arrayFOBOS
FragmentseparatorCOMBAS
Mass-separatorMASHA
High resolutionRIB-line
Gas-filled recoilseparator
Energy selector of the recoiling nuclei + electron & γ-array
Also radiochemical Lab.and applied research Lab’s
Flerov Laboratory of Nuclear Reactionsof the Joint Institute for Nuclear ResearchFlerov Laboratory of Nuclear Reactions
of the Joint Institute for Nuclear Research
How many chemical elements can exist?
nucleus
electrons
Z
E. Rutherford (1932)According to QED such an atomic
structure is valid for very heavy atoms with Z~170 or even more
…but the limit of existence of elements is reached much earlier because of instability
Yu. Oganessian.. CCAST Workshop. August 19-21, 2005, Beijing, China
After all this is a theoretical hypothesis
- reactions of the SHE synthesis key problem
- what are we expecting to see in the experiment properties of SHE
- what we have already observed decay modes of SHE
- setting the experiments synthesis of elements 113 and 115
- Chemistry of SHE identification of atomic numbers of SHE
- overall picture of SHE nuclear shells and stability of the SHE
- the search for surviving SHE. Prospects
We shall try finding the answer to this question talking about:
90
100
110
120
b-
170 180 190150 160
- 3
- 3
- 5- 5
- 7
- 7
- 6
- 6
- 4
- 4
- 2
- 2
Pro
ton
num
ber
Neutron number
co ldfusion
ho tfusion
ca p t u ren e u t ro n
(t ,p ) an d tr an sf e r
r eac ti o n s
Reactions of Synthesis of the Heaviest Nuclei
SHE248Cm + 48Ca → 116
Here there are two questions:
What is the fusion probability for 48Ca and actinide nuclei?
What is the survival probability of the compound nucleus with
Z=114-118 at the excitation energy E*30 MeV?
fusion probability
Let us consider the fusion of the 48Са and 248Cm occurred and resulted in the formation of the compound nucleus 296116 with an excitation energy of about 40 MeV
Evidently, the dominant decay mode of such a nucleus would be fission into two fragments
Accordingly, one could attempt investigating the probability of formation of the compound nucleus by measuring its fission characteristics.
Target238U,244Pu
248Cm
F1
F248Ca
solid angle – 0.3 sr
angular resolution – 0.30
TOF-start detector
beam
position sensitivestop detector
x, y, E
mass resolution – 2 a.m.u
CORSET setup
TOF-start detector
Yu. Oganessian.. CCAST Workshop. August 19-21, 2005, Beijing, China
M. Itkis, Yu. Oganessian, et al., (2002)Fragment Energy and Mass Distributions in Cold and Hot Fusion Reactions
target-likebeam-like
150
100
200
250
30048 208Ca+ Pb
50 100 150 200 250Fragment mass number
TK
E (
MeV
)
DIC
E =18 MeVx
CNfission
CN
50 100 150 200 250Fragment mass number
150
100
200
250
300
TK
E (
MeV
)
58Fe
CNfission
DIC
58 208Fe+ Pb 14 MeV
CN
50 100 150 200 250Fragment mass number
150
100
200
250
300
TK
E (
MeV
)
48 244Ca+ Pu 33 MeVCNfission
quasi-fission
DIC
CN
Z=116
coldfusion
0
Potential energy surface
Z=116
Fusion probability 1 00
1 0-1
1 0-2
1 0-3
1 0-4
1 0-5
1 0-6
1 0-7
1 0 0 0 1 5 0 0 2 0 0 0
p ro je c tile s + P b 2 0 8
2 5 0 0Z .Z1 2
3 0 0 0
4 8 C a2 2 N e1 6 O
5 4 C r
5 0 T i
(1 2 )0
(11 4 )
(11 2 )
2 0 8 P b
5 8 F e
6 4 N i
7 0 Z n
7 6 G e
CN
/ ca
ptur
e
Z=116
hotfusion
Fusion probability 1 00
1 0-1
1 0-2
1 0-3
1 0-4
1 0-5
1 0-6
1 0-7
1 0 0 0 1 5 0 0 2 0 0 0
2 0 8
4 8
P b + p ro je c tile s h e a v ie r th a n C a
2 5 0 0Z .Z1 2
3 0 0 0
4 8 C a2 2 N e1 6 O
1 20
11 4
11 2
11 0
1 0 8
1 0 6
1 0 4
2 0 8 P b
CN
/ ca
ptur
e
A c t.- ta rg e ts + C a 4 8
11 2
11 811 4
Yu. Oganessian.. CCAST Workshop. August 19-21, 2005, Beijing, China
10 0 105 110 1 15 A to m ic nu m b er
1 05
1 04
1 03
1 02
1 01
1 00
1 0-1
1 0-2
Сro
ss s
ecti
ons
(pic
obar
ns)
Bf
Ex= 40 МeV
Ex= 0
neut
rons
γ-rays
fission
fission
σxn= (Γn / Γf)x; х – number of neutrons
(Γn / Γf) ~ exp [(Bf – Bn) / T] ~ 1/100
Bf = BfLD + ΔEShell
0
Survival probability
SHE
1001
8
7
6
5
4
3
2
Fis
sion
bar
rier
s (
MeV
)
1 5 2 1 6 2
h o tfu s io n
1 8 4
Survival probability
15 0 15 5 16 0 16 5 17 0 17 5 18 0 18 5 C N n e u tron nu m b er
1 05
1 04
1 03
1 02
1 01
1 00
1 0-1
1 0-2C
ross
sec
tions
(pb
)
the limit of theexp. sensitivity Superheavy
nuclei
The survivability of the compound nucleus is an independent evidence for the stabilizing effect
of the N=184 shell in the domain of SHE
beam tim e - 4000 h/y
beam intensity - 4 - 8 .10 /s
12
C onsum ption of m g/h 48 С а (68% ) - 0.5
Iso topes:
+U [233, 238], P u[242, 244],...,C f[249] Z = 112 - 118 48 C a