z>92 (heaviest element in nature) and upto z=100-101

March, 2006 SERC Course 1

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

Search for Superheavy element and Role of Fission Dynamics


Cross-section data and extrapolated values for cold-fusionReactions (1n -evaporation channel)

Cross-section increases with increasing isospin


48Ca+242Pu->287114+3n 48Ca+244Pu-

>288114+4n

48Ca+244Pu->289114+3n

E*~33 MeVE*~34-38 MeV


Yury Ts. OganessianPure Appl. Chem., Vol. 76, No. 9, pp. 1715–1734, 2004.


48Ca+244Pu


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


∙ Cold Fusion 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,


BLDf gradually disappears

Spherical

Deformed


Fission barrier calculations of Smolanzuk et al.

106Sg has highest barrier with half life of 3 hrs


Extra push energies Swiatecki

For Z1Z2>1000 to 1650 depending on the value of the charge asymmetry, Zp/ZT.


Onset of fusion limitationDue to Extra push energies

No hindrance

Effective fissility : weighted mean of mono-nuclear and binaryWith weight for binary taken as 1/3


Injection direction

Fusion area inside Saddle point

Difference in energyBetween touchingPoint and saddle pointSmall due to shell structureOf Ca and Pb

All trajectories reaches fusion


Quasi-fission isdominant

Extra pocket in massSymmetric region Deep

Quasi-fission


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.

Evgeni A. CherepanovBrazilian Journal of Physics, vol. 34, no. 3A, September, 2004


48Ca+208PbEX=50 MeV

Aritomo and OhtaPre-print

Nuclear Physics A 744 (2004) 3–14

Mass asymm fluctuatesaround 0.5 and then relaxes quickly andTrajectory move to main pocket

March, 2006 SERC Course 2748Ca+244PuEx=50 MeV

Critical stage

Turning stage

For FF massAsymmetrieslarge

For QF neck developsand speeds up fissionkeeping mass asymm.

For deep QF mass asymmRelaxed in sub-pocketAt TS


The smaller formation probability due to inhibition of fusion by competing mechanism:DIC,QF,FF,PEF Asymmetric channels: higher E* and unfavourable for survival


Transition fromFF to QF

QF

Mass distribution forFF is asymmetric in shapeWith peak around 132


Measurements at LNL,Legnaro (Italy)Measurements at LNL,Legnaro (Italy)

470-630 MeV 80Se + 208Pb

372 MeV 56Fe+232Th

288116

Measurement of fragment mass and kinetic energy and neutron correlations

80Se + 232Th 312124470-630 MeV


Schematics of the setup for Se+Pb,Th experiment


80Se+232Th 470 MeV80Se+208Pb 470 MeV

DIC dominates but significant events around symmetry


Mass (amu)

50 100 150 200 25010-1

100

101

102

103470 MeV510 MeV550 MeV630 MeV

Z = 50 N = 82

Mass (amu)

50 100 150 200 250101

102

103

Z = 50 N = 82

d/d

M (a

rb. u

nits

)

80Se+232Th 470 MeV80Se+208Pb 470 MeV

Se+Pb more asymmetric compared to Se+Th

QF is expected to be more for Se+Th

March, 2006 SERC Course 35Ecm-VB (MeV)

0 20 40 60 80 100 120 140 160 180 200

cros

s se

ctio

nsX

Ecm

(arb

. un

its)

0

2000

4000

6000

8000

80Se+208Pb (gated region)80Se+232Th (gated region)Fit to Se+Pb dataFit to Se+Th data

higher extra-push energyin the case of 80Se+232Th


80Se+208Pb 288116

ExCN (MeV)

0 50 100 150 200 250

tot

0

10

20

30

40

50

80Se+232Th 312124

ExCN (MeV)

0 50 100 150 200 250

tot

0

10

20

30

40

50

ν sf tot =10±2 for Se+Pb

12±1 for Fe+Th

=17±2 for Se+Th


on average of about 0.6 neutron per unit Z


an increase of about 0.54 neutron per unit Z

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.


JINR,Dubna


41 detectors of DEMON at DubnaT. Materna et al. Nuclear Physics A734 (2004) 184-l 87

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

FF

QF

A/2±30

208±20


??

Connectecd withknown species

Self-consistent


Change fromHot fusion toCold fusionFor higher N-Z


Survival probability Depends on fissionfission delaydelayAnd speed of coolingMainly by neutron neutron evaporationevaporation


Expected intensities s-1 for neutron-rich radioactive beams

SPIRAL 24Ne 7 x 107

HI based 44Ar 5 x 107

PIAFE 78Zn 108

84Ge 2 x 108

94Kr 2 x 109

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

Reactor based

With MAFF and spallation facility with 100μA proton of 1GeVIntensities may go up by 3 to 4 orders of magnitude

z>92 (heaviest element in nature) and upto z=100-101

Documents

fusion evaporation

serc coursebldf

serc coursemeasurements

inhibition of fusion

hot fusion

heavy element targets

heavy ion inuced fusion

upto z