Production of new neutron rich heavy and superheavy nuclei

Valeriy Zagrebaev, Mikhail Itkis, Alexander Karpov

for “SHE-2015”, March 31, 2015, A&M University, USA

JINR (Dubna)

•  Fusion reactions •  Elements 119 and 120 are on the way. What’s the next? •  Radioactive ion beams?

•  Multinucleon transfer reactions •  Shell effects in damped collisions of heavy ions? •  Production of new neutron rich SH nuclei in transfer reactions •  Production of new neutron rich Heavy nuclei in transfer reactions •  Separation of the products of transfer reaction (GALS setup)

We are still far from the Island of Stability

2

What is beyond 118 element?

Ø  Heavier projectiles (50Ti, 54Cr, 58Fe, 64Ni) Ø  Heavier targets (251Cf, 254Es -???); Ø  Symmetric reactions: 136Xe+136Xe, 136Xe+150Nd, 150Nd+150Nd; Ø  Multi–Nucleon–Exchange - Reactions with RIB (??, or colliders –

technique – (K4-K10)): Ø  Nucleon transfer reactions (136Xe+208Pb, 238U+248Cm).

Sufficient increasing of overall experiment efficiency is needed!

Heaviest target: 249Cf → Zmax= 118 ↓

New elements 119 and 120 are coming !

4

Mass-energy distributions of binary reaction fragments

Driving potentials are calculated with the NRV code (nrv.jinr.ru)

150

200

250

300

350

36S+238U→274Hs*

E*=46 MeV

Mass (u)

64Ni+238U→302120*

E*=31 MeV

48Ca+238U→286Cn*

E*=35 MeV

Yie

lds

(arb

.u.)

 

 

 

TK

E (

MeV

)

Z=28

 

 

 

 

 

 

50 100 150 200 250

1

2

3

Z=28

Z=82N=126N=50Z=28

Z=82N=126N=50

 

 

M=200 u M=208 u M=215 u

50 100 150 200 250

1

2

3

 

 

50 100 150 200 250

1

2

3

4

Z=82N=126N=50

 

210

220

230

240

250

260poten

tial energ

y (M

eV)

• G.N. Knyazheva, I. Itkis, E.M. Kozulin. The time scale of quasifission process in the reactions with heavy ions. International Symposium Entrance Channel Effect on the Reaction Mechanism in Heavy Ion Collisions, Messina (Italy) - November 6-8, 2013, Journal of Physics: Conference Series 515 (2014) 012009.

100

150

200

250

300

350

   

 

 

50 100 150 200 250100

150

200

250

300

35064Ni+238U→302120

 

 

Mass (u)

58Fe+244Pu→302120

0

1

2

3

4

 

   

50 100 150 200 2500123456  

   

Mass (u)

100

150

200

250

300

35048Ca+238U→286Cn

 

 

 

TK

E (

MeV

)

0.0

0.5

1.0

1.5

2.0

2.5  

 

 

Yie

ld (

arb. u

nit

s)

150 200 250 3000

100200300400500600700800

 

 

 

Co

un

ts

200 250 300 3500

20406080

100120  

 

 

200 250 300 3500

2

4

6

8

10  

 

TKE (MeV)

Y(ACN/2±20)=12%

Y(ACN/2±20)=8%

Y(ACN/2±20)=4%

1840

2444

2576

Zt Zp

34 u

22 u

11 u

70%

≤2%

≤0.2%

for ACN/2±20

E*CN≈45MeV

E.M. Kozulin et al., Dynamics of the 64Ni+238U reaction as a possible tool for synthesis of element with Z=120. Phys. Lett. B686, (2010), 227-232.

Influence of entrance channel

Z1Z2=980 1472 2132 2660

• E.M.Kozulin, G.N.Knyazheva, I.M.Itkis, E.M.Gazeeva, N.I.Kozulina, T.A.Loktev, K.V.Novikov, I.Harca. Shell effects in fission, quasi-fission and in multi-nucleon transfer reactions. International Symposium Entrance Channel Effect on the Reaction Mechanism in Heavy Ion Collisions, Messina (Italy) - November 6-8, 2013, Journal of Physics: Conference Series 515 (2014) 012010.

88Sr+176Yb: shell effects in damped collisions

170 175 180 185 190 195 200 20510-4

10-3

10-2

10-1

100

101

102

Z=82

Yie

ld (

mb

/(sr

u))

Fragment mass (u)

88Sr +176Yb

Z=28

60 80 100 120 140 160 180 2000102030405060708090100

Fragment mass (u)

Exci

tati

on

ener

gy (

MeV

)

40 60 80 100 120 140 160 180 200 220250

260

270

280

290

300

310

208Pb58Fe

N=50

Z=50N=82

N=126Z=82

Z=28

176Yb

Pote

nti

al ener

gy (

MeV

)

Fragment mass (u)

88Sr

140120100806040200-20-40-60

60 80 100 120 140 160 180 200

160180200220240260280300320340360

Fragmet mass (u)

TK

E (

MeV

)

100 3x100 101 3x101 102 3x102 103 3x103 104

TK

EL

(M

eV)

• E.M. Kozulin, G.N. Knyazheva, S.N. Dmitriev, I.M. Itkis, M.G. Itkis, T.A. Loktev, K.V. Novikov, A. Baranov, W.H. Trzaska, E. Vardaci, S. Heinz, O. Beliuskina, S.V.Khlebnikov. Shell effects in damped collisions of 88Sr with 176Yb at the Coulomb barrier energy. Phys. Rev. C89, 014614 (2014).

Fusion reactions with Radioactive Ion Beams for the production of neutron rich superheavy nuclei ?

No chances today and in the nearest future 9

Multinucleon transfer reactions for synthesis of heavy and

superheavy nuclei

Production of superheavies in multi-nucleon transfers (choice of reaction is very important)

11

Shell effects: Pb valley normal (symmetrizing) quasi-fission

inverse (anti-symmetrizing) quasi-fission

12

U-like beams give us more chances to produce neutron rich SH nuclei in “inverse quasi-fission” reactions

experiment is scheduled for March at GSI (we want to see Pb+x, then Pb+Ca+Pb) 13

238U + 248Cm. Primary fragments

14

Production of transfermium nuclei along the line of stability looks quite possible (only if there are shell effects!?)

Rather wide angular distribution of reaction fragments: a new kind of separators is needed

experiments on Au+Th and U+Th are currently going on in Texas (without separators) 15

Test (surrogate) reaction aimed on a search for the shell effects

in low-energy multi-nucleon transfer reactions

The experiment was performed (September 2014) at the Flerov Laboratory (Dubna)

New heavy nuclei in the region of N=126

“blank spot”

Test experiment on 136Xe + 208Pb collisions (Dubna, 2011)

18 Experiment with Z identification of PLF was performed in Legnaro last summer

136Xe+208Pb: productions of heavy neutron-rich nuclei in multinucleon transfer reaction

30 0

40 0

50 0

60 0

TK

E (

MeV

)

100 12 0 1 40 160 180 20 0 2 20 24010

-3

10-2

10-1

1 00

1 01

208Pb

Mass (u)

Yie

ld (

mb)

136Xe+208Pb(Ec.m.

=526 MeV)

136Xe 200 205 210 215 220 225 230

10-3

10-2

10-1

100

101

Z=88

Z=84

Z=86

136Xe+208Pb (Ec.m.=514MeV)

cro

ss s

ecti

on (

mb

)

Mass (u)

Cross  sec(on  for  210Po,  222Rn,  224Ra  (Ac(va(on  analysis)  

• E.M.Kozulin, E.Vardaci, G.N.Knyazheva, A.A.Bogachev, S.N.Dmitriev, I.M.Itkis, M.G.Itkis, A.G.Knyazev, T.A.Loktev, K.V.Novikov, E.A.Razinkov, O.V.Rudakov, S.V.Smirnov, W.Trzaska, V.I.Zagrebaev. Mass distributions of the 136Xe + 208Pb at laboratory energies around the Coulomb barrier: a candidate reactions for production neutron-rich nuclei at N=126. Phys. Rev. C86, 044611 (2012).

Production of new neutron rich heavy nuclei located along the last “waiting point” of astrophysical nucleosynthesis:

Choice of reaction ?

How to separate a given nucleus from all the other transfer reaction products ?

Fusion reactions

Transfer reactions

Available separators are not applicable !

New setup for selective laser ionization and separation of multi-nucleon transfer reaction products stopped in gas

(project GaLS, to be realized in Dubna in 2015)

New setup for selective laser

ionization (FLNR, Dubna)

two pumping lasers Nd: YAG and three DYE lasers (+ Ti: Sapphire laser)

Summary

•  Elements 119 and 120 can be really synthesized in the Ti and/or Cr fusion reactions with cross sections of about 0.05 - 0.02 pb.

•  Multi-nucleon transfer reactions can be really used for synthesis of neutron enriched long-living SH nuclei located along the beta-stability line. U-like beams are needed as well as new kind of separators.

•  Shell effects in production of trans-target nuclei (inverse quasi-fission) should be proved experimentally at last.

•  Transfer reactions give a unique possibility for synthesis of heavy neutron-rich nuclei with N=126 – the last “waiting point” of astrophysical nucleosynthesis.

•  Selective laser-ionization technique (GALS setup being developed at FLNR) is a powerful method of separation of the products of transfer reactions.

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