Superheavy Elements and Heavy Ion Fusion Reactions

Advanced Science Research Center, Japan Atomic Energy Agency
Research Fellow Katsuhisa Nishio

Nucleus
Electron e-Nucleus(Positivecharge)

Uranium235
235U
92 143

Neutron n(Electrically neutral)Proton p(Positive charge)

Including nuclei that can be synthesized artificially
There can be 6,000 different nuclei, including nucleithat can be artificially synthesized.
How many protons and neutrons can you pack?
Mass number Ａ = Number of protons Ｚ + Number of neutron N

Periodic Table of the Elements※For elementswith unstable
isotopes, the massof the most halflife isotope isshown inparentheses.

８ 119 120

Transuranium element
Actinides

Proton1935 Nuclear Chart
Uranium235，238U

LeadTinCalcium

Exists in nature
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Neutron

1958

1935

Nobelium：NoProton(Atomic number102)

1958

82
126

208Pb

50
82
2850

20820

22

828

48Ca

40Ca

Neutron

Maria G.-Mayer

Johannes H.D. Jensen

1963 Nobel prize

1935

2015

1958

114

Island of stability(Expanding the area
where nuclei exist)
Oganesson：Og(Atomic number118)

2015

184
82

126

Element 113, Niphonium(Synthesized at RIKEN)

50
82
28
2050

8202282878Ni

132Sn

Exists in nature
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ProtonCollapse
Spontaneous fission

(Experimental value) - (Droplet model mass formula)＝ Microscopic energy correction

Shell structure in nuclear masses
Atomic number 100 Up Heavy-ion fusion reaction(Currently reaching 118)
to Atomic Number 100
is produced(MeV)+50-5-1020+50-5-1020 28

Ni40

SnPbFm60 Proton80

10060100114 120 126 ?

中性子
4050

Neutron8280

120 126 MagicNumber

W.D.Myers and W.J. Swiatecki (1966).

Periodic Table of the Elements

Period 7Period 8

119

12090
Th

104
Rf

105
Db106
Sg

107
Bh

108
Hs

109
Mt

110
Ds

91
Pa

92
U93
Np

94
Pu

95
Am

96
Cm

97
Bk

111
Rg

98
Cf

112
Cn

99
Es

113
Nh100
Fm

114
Fl101
Md

115
Mc

102
No116
Lv

103
Lr

117
Ts118
Og

Synthesis of Element 113 in Japan
Eight years of experimentation and synthesis of threenihonium nuclei
209Bi
83

70Zn
30+＝278Nh
113

Transuranium
elementn+
NeutronKyushu University/RIKEN Mr. Morita

Pioneer of superheavy elements
FLNR (Russia)

G.N. Flerov

Fl (114)Mc (115)
Lv (116)Ts (117)
Og (118)
119,120
Synthesisplan

GSI (Germany)

P. Armbruster

RIKEN (Japan)

G. Münzenberg

Bh (107)
Hs (108)
Mt (109)
Ds (110)Rg (111)Cn (112)

Yu.Ts. Oganessian

S. Hofmann

Use 48Ca as a beam

Use 208Pb, 209Bi as atarget

K. Morita
Nh (113)119
synthesis
in progress

Number of protons = atomic number Z

Nuclei in the superheavy element region that havebeen synthesized so far.
120
115

48Ca + Actinide nucleus(Russia)
Og118

Reactions with Pb,BiTs(GSI, RIKEN, Germany) Mc Lv
NhFl110108 Bh105DsMtHs

Rg

Island of stability

114

113
NhCnspherical closed shell
184

Sg
Db

162

100
150

Cold fusion

Hot fusion

155

160

120

spherical closed shell

165

170

175

Neutron number

180

αCollapse
Spontaneous fission
EC / β+ Collapse
β- Collapse

185

Heavy-ion fusion reaction
Nuclei heavier than the 100th element have been synthesized by fusion
reactions using heavy ion beamsThe nuclei heavier than the 100th element
have been synthesized by a nuclear fusion reaction using heavy ion beams.
The reaction requires nuclei to collide with each other at kinetic energieshigher than the Coulomb repulsive forceCoulomb repulsive force between nuclei.

EnergyThreshold
Coulomb barrier
Distance between nuclei

Description of the Coulomb barrier- Coulomb repulsive force and attraction due to nuclear forces 16O ＋144Sm

Potential energy (MeV)

Repulsion

Attraction

Coulomb
Nuclear force

Total

Distance between nuclei

If the Coulomb barrier is
If the Coulomb barrier is
exceeded, fusion willautomatically fusion will occur(But in the case of a light
reaction system in the caseof light reactive systems)

When nuclei are deformed,fusion reactions occur even at
low energies.
→ This is also evidence thatthe 238U nucleus is deformed.

Fusion probability

Fusion Probability-Difference between spherical nuclei and deformed nuclei

Collision energy at the center of gravity system(MeV)

Coulomb barrier VB (MeV) when 208U is spherical (MeV)

K. Nishio et al., Phys. Rev. Lett., 93, 162701 (2004).

Cross section to synthesize superheavy elements
Cross-section
Cross-sectional
area (nb/ nbnano-Bahn)

Compound nucleus
103
102
101

Cold-fusion reaction (Pb,Bi)
Hot-fusion reaction (Actinide)GSI-SHIP Dubna

0

10Ca+238U 48Ca +238U,244Pu,
248
Cm,249Cf

48

10-1
10-2
10-3
10-4?

10-5
10-6
100

105

1 to 2 weeks
Experiments We
can generate one

110

115

1 pb
Pico Burn

120

ProtonAtomicnumber
number ofInjection nucleus

Target nucleus

nn

NeutronCompound nucleus
125nsuperheavy elements

RIKEN, Element 113

Evaporated residual nuclei(Superheavy elements!)

Why is it so difficult to make superheavy elements?
-Phenomena that occur in heavy reaction systems-

Three Steps of Superheavy Element Synthesis
34S
14+ 238
U92272Hs*108(1) Coulomb Barrier(2) Fusion process
Transcending ContactCompound268
Hs108+ 4 10n(3) Neutron evaporation

and Fission Competition

nucleus CN

6.6×1012

Quasifission

3.0×1011

Fusion then fission

6.3×1012

1 atom(Over a period of three weeks)~ 3×1011(1) Fusion is difficult in reactions between heavy nuclei.
(2) In superheavy elements, most of the compound nuclei are fissioned.
K. Nishio et al., Phys. Rev. C, 82, 024611 (2010).

Binding energy per nucleon
Binding energy of nucleus B (MeV/u)
Mass number of nucleus A-Mass model and actual nuclei-Bethe-Weizacker formula

N or Z is 20, 28, 50, 82, 126
The binding energies is large

Number of masses of nuclei A

Q-value of α collapse+=236U
92 144+
4He22232Th
14290

EnergyQ= + 4.5 MeV

Binding energy- 1766.4-B =-1790.2 MeV

4.5 MeV-28.3
4.5 MeV-1794.7

4He232Th

0.08 MeVQ-value of fission+=236U
92 14492Kr
36 56+
144Ba
5688

EnergyQ = +181.9 MeV(Where are you going?)
Binding energy- 782.1-1190.0-B =-1790.2 MeV100 MeV
92Kr

181.9 MeV

-1972.1

144Ba65 MeV

Nuclear fusion+70Zn
3040=+209Bi
83 126

Acceleration energy

261.4 MeV

Excitation energy

279Nh 16.5 MeV
113
166- 611.6-1639.6- 1989.8+261.4- 2251.2

16.5 MeV- 2006.5

Q= - 244.7 MeV

Practical experimentReactions learned in practiceTandem acceleration

Compound nucleus

nnn
34S + 169Tm = 203At
85
1669nnResidual nucleus

n199Atnn

Compoundnucleus

Key Points of the Experiment【 Experiments on fusion reactions 】（１）The same experimental apparatus and detectors are used to synthesize superheavy
elements. The experimental approach is also the same. The experimental concept is also thesame.
→ What equipment is needed?
（２）The experiment is conducted in an apparatus that is kept in an "ultra-high vacuum.
→ The injection beam, the device that initiates the fusion reaction, and the device that
separates the nuclei produced, where the produced nuclei are detected, and everything else.
（３）Data acquisition uses state-of-the-art digital electronics.
→ How does this differ from the conventional analog method?
（４）The method of data analysis is the same as in the superheavy element synthesis
experiment.
→ How do we identify the nuclides of the nuclei produced?
（５） It takes a long time to make superheavy elements, so we make lighter isotopes of theelements.
→ Creates the astatine isotope (At) with atomic number 85 (not found naturally).