The Synthesis of Super Heavy Elements

The Synthesis of Super Heavy Elements (SHE)

D. Ackermann, University of Mainz/GSI

Future of Gamma Spectroscopy at LNL: GASP and CLARA Arrays

GAMMA2004

March 3rd 2004

• requirements for the synthesis of SHE

• reaction mechanism studies• fusion/fission excitation function → SHIP, MAIALE+CORSET…• the CN spin distribution → GASP+inner ball, GAMMASPHERE…

• nuclear structure of the SHE: spectroscopy tools • in beam (RDT + γ-γ) → RITU, FMA, PRISMA(gas filled)+CLARA…• ER-α-α/-α-γ(-γ) after separation → SHIP, RITU+GREAT, PRISMA(gas filled)…

• an interesting example: 270Ds

• the basic technical requirement: beam intensity

• CW accelerator• UNILAC upgrade – a first step

208Pb

region der spherically shell stabilised nuclei(„island of stability“)

region of deformed shell stabilised nuclei around Z=108 and N=162

at GSI: Elements 107-112first synthesisedand unambiguouslyidentified

107 – Bh108 – Hs109 – Mt

Shell Correction Energies Eshell in the Region of Superheavy Elements

P. Möller et al.

element 110 recently named

Darmstadtium – Ds

• IUPAC decision - August 2003

• Baptized - December 2003

All Chains with Z ≥ 110

JINR/FLNRDubna, Russia

GSI

RIKENTokyo, Japan

The 2-step process Fusion - Evaporation

220.0 230.0 240.0 250.0 260.010

-9

10-7

10-5

10-3

10-1

101

Elab [MeV]

σ[m

bar

n]

50Ti + 208Pb ⇒ 258Rf*(HIVAP calculations)

fusion

fission

3n1n 2n

evaporation residues

≈5-7 orders of magnitude

1. CN formation• entrance channel

properties (nuclear structure, deformation…)

2. ER formation• survival • fission competition • vibration-rotation

probes: • Fusion-fission

excitation function (fission and ER-production)

• -distribution...

F.P. Heßberger

Fusion Dynamics and the Spin Distribution

fusionevaporation

fusionfissioncompetition

σ

range of barriers

3n

1n2n

ER

survival via“rotationalstabilisation”?fission ( +1)

Erot( )=2µRb

2

2

Fusion Dynamics and the Spin Distribution

Vb = VCoulomb + VNucl + V

( +1)Erot( )=

2µRb2

0 < < crit

0

crit

Eshell´ = crit < ´crit

compound system entrance channel

r

Vb

2

1 GASP – inner ball (80 BGO-crystals)

CN = (Mγ - Mγs)∆ γ + Mγs∆ γs + iMi∆ i + ∆ gs/m ; i = p, n, α

γ-ray fold

GASP response function

2 GASP – high resolution Ge-detectors

Eγ

3 statistical model(codes like PACE, EVAP,

HIVAP…)

evaporation parameters

Mγ

ER identification spin removed by particles and statistical

γ-rays

Experimental Approach to the Spin Distribution with GASP

Reactions with deformed targets leading to CN in Z = 82 Region

36S+180Hf → 216Ra*34S+168,170Er → 202,204Po*

32S+164Dy → 196Pb*

48Ti+150Nd → 198Pb*

48Ca+150Nd → 198Hg*

→Features to investigate via fusion/fission excitation function and spin distribution

• can rotation stabilize the compound system?σl• the competition of fission and evaporationσfus/fis+σl• the role of deformation for heavy CNσfus/fis+σl• the effect of the shell Z=82 on fusionσfus/fis+σl

48Ca+168Er → 216Ra*48Ca+164Dy → 212Rn*

48Ca+144,154Sm → 192,202Pb*

Fold Distributions with GASP for 64Ni+100Mo

260 MeV

3n

5n

6n

4n

∆fold ≈ 9

246 MeV

2n

4n3n

∆fold ≈ 18

D.Ackermann et al., J. Phys. G 23 (1997)

64Ni+100MoANL/Notre Dame BGO array

260MeV246MeV

∆ ≈ 20

∆ ≈ 10

Fold Distributions with GASP for 34s+170Er → 204Po*

0,0

2,0x104

4,0x104

6,0x104

0,0

5,0x104

1,0x105

1,5x105

2,0x105

0 5 10 15 20 250,0

5,0x104

1,0x105

1,5x105

2,0x105

144 MeV

168 MeV

158 MeV

Yie

ld

3n 4n

34S+170Er

3n 4n 5n

5n 6n

γ ray fold

GASP – inner ball (80 BGO-crystals)

Collaboration for Spin-Distribution Measurements

GSI:S. HofmannF.P. HeßbergerG. Münzenberg (Uni Mainz)M. RuanD. A. (Uni Mainz)

M.G. ItkisG.N. KniajevaE.M. KozulinYu.Ts. OganessianR.N. Sagaidak

FLNR, JINR, Dubna

INFN PadovaD. BazzaccoS. BeghiniE. FarneaR. MenegazzoC. Rossi-AlvarezC. Ur

Univ. Padova

G. MontagnoliF. Scarlassara

Comenius Univ. Bratislava

S. AntalicG. Berek

LNLM. AxiotisL. CorradiG. De AngelisA. GadeaV. KumarA. LatinaN. MargineanT. MartinezA.M. StefaniniS. SzilnerM. Trotta

ER-α-γ Spectroscopy behind SHIP

Nuclear Structure of the Heaviest Nuclei I: ER-α-α Coincidences: 251No

F.P. Heßberger et al., submitted to EPJ A

Nuclear Structure of the Heaviest Nuclei II: ER-α-α Coincidences: 257DbF.P. Heßberger et al., Eur. Phys. J. A 12, 57-67 (2001)

S. Cwiok, S. HofmannAnd W. NazarewiczNPA A575 (1994)

Experiment:α-α-coincidences

Nuclear Structure of the Heaviest Nuclei III:ER-α-γ Coincidences: 255Rf/253No

F.P. Heßberger, Symposium on Nuclear Clusters, Rauischholzhausen Germany, August 2002

270Ds

266Hs

262Sg

The even-even isotope 270Ds

The even-even Isotope 270110 and its decay products 266Hs und 262Sg

8 decay chains:• 2 types with different τα(270110): 0.15ms and 8.6 ms• 3 out of 4 chains complete of the typ:

α-α-fission• 1 γ-ray (218 keV) coincident to the mother decay in chain #7• 7 days of irradiation ⇒ σ = (13±5) pbarn

(for comparison σ(269110) = 15 pbarn)

S. Hofmann et al., Eur. Phys. J. A 10, 2001

k-isomer and Tentative Decay Scheme for 270110

S. Ćwiok and P.-H. Heenen

162

ν[725]11/2-

ν[615]9/2+

ν[613]7/2+

1.34 MeV∆I = 10-

162

ν[725]11/2-

ν[615]9/2+

ν[613]7/2+

1.31 MeV∆I = 9-

Fermi

level

neutrons

tentative decay scheme

270110

266Hs

S. Hofmann et al., Eur. Phys. J. A 10, 2001

Project for a superconducting CW-linacU.Ratzinger et al., University of Frankfurt

• dc beam• 1 < A/q < 7• Ebeam: 4-7.5 MeV/u• ∆Ebeam < ± 3keV/u

Intensity gain:

• Duty cycle 30%→100% 3.5• 28 GHz ECR-source 5-10increased stability (65% → 85)% 1.3• shorter shutdowns (107 d/y → 47 d/y) 1.2

Total gain 25-55

0 5 10 15 20

Z / m

EnergyMeV/u

1.8 2.4 3.3 4.2 5.2 6.1 7.1

CH DTL, supercond.324 MHz 108 MHz

DebuncherIH DTL,108 MHz

1.40.30.003

25 30

RFQ,108 MHz

ECR source

QWR Cavities

normalconducting

superconducting

superconducting

New 28 GHZ ECR Ion SourceGoals : Increasing the average beam intensity on target

Higher intensity in high charge statesHigher duty factor in linac

Semi-empirical scaling law: I(Aq+) ∼ ωECR2

➨ increase of microwave frequency➨ higher magnetic flux density (superconducting)

20 25 30 35 40 45 500,1

1

10

100

1000

inte

nsity

(eµA

)

Xe charge state

28 GHz SC-ECRIS (2007)(extrapolated)

14 GHz GSI-CAPRICE II (1990)

New Front-end for the High Charge State Injector

New RFQ-structure:• gain of the duty factor• higher injection energy• increased acceptance

Additional 28 GHz-ion-source:• intensity gain of factor two• higher charge states for increased duty factor

LEBT – Laminated magnets:• redundance for ion sources• preparation for future pulse to pulse operation with different ion-species

50% duty factor → intensity-gain factor x2

High Duty Cycle RF-Operation of the GSI- High Charge State Injector (HLI) and the Alvarez-accelerator

Rebuncher

Alvarez

Presently:duty factor (beam)= 25 % (rf: 35 %),A/ξ ≤ 8

Upgrade:(new RFQ-structure, higher charge state from 28 GHz-ECR)

A/ξ ≤ 6.5, duty factor = 50 % (rf: 60 %)

Performance of all rf-tube-amplifiers ([email protected] MW, IH+RFQ+Single Gap@200 kW, Rebuncher@ 4 kW) is sufficient to meet the requirements

Rebuncher

The SHIP group

GSI: The collaboration

JINR-FLNR Dubna, Russia:

A.G. PopekoA.V. Yeremin

University Bratislava, Slovakia

Š. ŠaroS. Antalic (Ph.D. student)G. Berek (Ph.D. student)B. Streicher (Ph.D. student)

University Jyväskylä, Finland:

M. LeinoJ. Uusitalo

S. HofmannF.P. HeßbergerR. MannG. Münzenberg (Univ. Mainz)P. Kuusiniemi (Postdoc)B. Sulignano (Ph.D. student)D. A. (Univ. Mainz)

B. Lommel (targetlab)B. Kindler (targetlab)

H.-G. Burkhard (mechanics)H.-J. Schött (elektronics)