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Z>92 (Heaviest Element in Nature) and upto Z=100-101PowerPoint Presentation

Z>92 (Heaviest Element in Nature) and upto Z=100-101

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pocket

Search for Superheavy element and

Role of Fission Dynamics

- Z>92 (Heaviest Element in Nature) and upto Z=100-101
achieved by n irradiation or p, a, and d bombardment in

Cyclotron (1940-1955) (LBL)

- Z=102-106 by Light or Heavy-ion induced Fusion
-evaporation using heavy element targets (1958-1974)

Z=107-112 Heavy ion inuced fusion 208Pb,209Bi targets

(GSI)

Identified by recoil separation technique and connecting

to known daughter decay after implanting into Si strip

detectors.

- Z=112-116 48Ca+Pu,Am,Cm,Cf (JINR, Dubna)
Identified by gas filled separators and Si strip setectors

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Cross-section data and extrapolated values for cold-fusion

Reactions (1n -evaporation channel)

Cross-section increases with increasing isospin

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E*~33 MeV

E*~34-38 MeV

48Ca+244Pu->289114+3n

48Ca+244Pu->288114+4n

48Ca+242Pu->287114+3n

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48Ca+244Pu

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The flight time of the reaction products through SHIP is 2 ms.

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∙ Cold Fusion ms.208Pb and 209Bi targets bombarded by the following projectiles:

48Ca, 50Ti, 54Cr,58Fe, 62Ni, 64Ni, 70Zn, 76Ge, 82Se, and 86Kr.

∎ Hot Fusion 48Ca projectiles bombarded targets of 238U, 244Pu, 243Am,

245Cm, 248Cm, and 249Cf,

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Fission barrier calculations of Smolanzuk et al. ms.

106Sg has highest barrier with half life of 3 hrs

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For Z1Z2>1000 to 1650 depending ms.

on the value of the charge

asymmetry, Zp/ZT.

Extra push energies

Swiatecki

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No hindrance ms.

Onset of fusion limitation

Due to Extra push energies

Effective fissility : weighted mean of mono-nuclear and binary

With weight for binary taken as 1/3

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Difference in energy

Between touching

Point and saddle point

Small due to shell structure

Of Ca and Pb

Fusion area inside

Saddle point

All trajectories reaches fusion

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Brazilian Journal of

Physics, vol. 34, no. 3A,

September, 2004

The curve V (Z,L = 0) (for the value of R corresponding to

the pocket) has a few local minima, which reflect the shell

structure in the interacting nuclei.

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around 0.5 and then

relaxes quickly and

Trajectory move to main

48Ca+208Pb

EX=50 MeV

Aritomo and Ohta

Pre-print

Nuclear Physics A 744 (2004) 3–14

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Critical stage ms.

For FF mass

Asymmetries

large

Turning stage

For QF neck develops

and speeds up fission

keeping mass asymm.

For deep QF mass asymm

Relaxed in sub-pocket

At TS

48Ca+244Pu

Ex=50 MeV

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The smaller formation probability due to inhibition of fusion by competing mechanism:DIC,QF,FF,PEFAsymmetric channels: higher E*

and unfavourable for survival

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Transition from fusion by competing mechanism:

FF to QF

Mass distribution for

FF is asymmetric in shape

With peak around 132

QF

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Measurements at LNL,Legnaro (Italy) fusion by competing mechanism:

470-630 MeV 80Se + 208Pb

372 MeV 56Fe+232Th

288116

470-630 MeV

312124

80Se + 232Th

Measurement of fragment mass and kinetic energy

and neutron correlations

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Schematics of the setup for Se+Pb,Th experiment fusion by competing mechanism:

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80 fusion by competing mechanism:Se+208Pb

470 MeV

80Se+232Th

470 MeV

DIC dominates but significant events around symmetry

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Se+Pb more asymmetric compared to Se+Th fusion by competing mechanism:

QF is expected to be more for Se+Th

80Se+208Pb

470 MeV

80Se+232Th

470 MeV

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80 fusion by competing mechanism:Se+208Pb

288116

80Se+232Th

312124

ν sftot=10±2 for Se+Pb

12±1 for Fe+Th

=17±2 for Se+Th

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on average of about 0.6 neutron per unit Z fusion by competing mechanism:

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an increase of about 0.54 neutron per unit Z fusion by competing mechanism:

excitation energy gained by the system in its transition from the saddle to the

scission point (the term ΔEx by Hilscher) that is known to show a strong mass

and Z dependence.

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JINR,Dubna fusion by competing mechanism:

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41 detectors of DEMON at Dubna fusion by competing mechanism:

T. Materna et al. Nuclear Physics A734

(2004) 184-l 87

208±20

QF

FF

A/2±30

The pre-scission neutron multiplicity distribution simulated

using backtracing procedure show two components for Ca+Pu

Whereas for Ca+Pb only one component is seen

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Survival probability fusion by competing mechanism:

Depends on fissiondelay

And speed of cooling

Mainly by neutron

evaporation

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Expected intensities fusion by competing mechanism:s-1for neutron-rich radioactive beams

SPIRAL 24Ne 7 x 107

HI based 44Ar 5 x107

PIAFE 78Zn 108

84Ge 2 x108

94Kr 2 x 109

Reactor based

Region beyond Z= 114 needs beam intensities in excess of 1014 s-1.

With MAFF and spallation facility with 100μA proton of 1GeV

Intensities may go up by 3 to 4 orders of magnitude

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SERC Course fusion by competing mechanism:

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