EURISOL Workshop 16-20 Jan 2006EURISOL Workshop 16-20 Jan 2006 R-D HerzbergR-D Herzberg

Opportunities for Opportunities for Spectroscopy of super heavy Spectroscopy of super heavy

elementselements

OverviewOverview

In-beam Spectroscopy of SHE is a In-beam Spectroscopy of SHE is a very successful techniquevery successful technique

Complementary to Decay StudiesComplementary to Decay Studies

Optical Studies Optical Studies

Scientific GoalsScientific Goals Single Particle structure of SHESingle Particle structure of SHE

Detailled in-beam spectroscopy of nuclei Detailled in-beam spectroscopy of nuclei

from Cf to Ds and beyondfrom Cf to Ds and beyond

Anchor “floating” chainsAnchor “floating” chains

Ideally follow the stability line…Ideally follow the stability line…

… … or at least stay as close to it as possible.or at least stay as close to it as possible.

Deformation brings strongly downsloping orbitals from above the next spherical shell gap close to the Fermi surface.

Nobelium region is ideal for this:

“Large” Cross sect.

f5/2 - f7/2 probed

Systematics possible

Why study Why study transfermiums?transfermiums?

Magic ShellsMagic Shells

M Bender et al, PLB

Decay StudiesDecay Studies Important for ground state properties:Important for ground state properties:

Mass (Mass (≠ ≠ Q-value)Q-value) Spin + ParitySpin + Parity Decay modesDecay modes LifetimeLifetime ShapeShape

Confirmation of chainsConfirmation of chains Unambiguous (Z,N) identificationUnambiguous (Z,N) identification

S. Hofmann, Nucl. Phys. News Intl

108110

112

114

120

109 RIB on Pb/Bi

3·109 132Sn onvarious targets

The SHE reach of MAFF

S. Hofmann, Nucl. Phys. News 14, 5 (2004)

108110

112

114

120

109 RIB on Pb/Bi

3·109 132Sn onvarious targets

The SHE reach of MAFF

S. Hofmann, Nucl. Phys. News 14, 5 (2004)

108110

112

114

120

109 RIB on Pb/Bi

3·109 132Sn onvarious targets

The SHE reach of MAFF

S. Hofmann, Nucl. Phys. News 14, 5 (2004)

108110

112

114

120

109 RIB on Pb/Bi

3·109 132Sn onvarious targets

The SHE reach of MAFF

S. Hofmann, Nucl. Phys. News 14, 5 (2004)

108110

112

114

120

-7 MeV

-6 MeV

-5 MeV

-4 MeV

-3 MeV

Shell-CorrectionEnergies

R. Smolanczuk et al.,Phys. Rev. C 52, 1872(1995)

R. Smolanczuk and A. Sobiczewski,Proc. XV Nucl. Phys. Div. Conf., Singapore (1995), p. 313

3·109 132Sn onvarious targets

In-beam StudiesIn-beam Studies

Experience with gamma and CE studiesExperience with gamma and CE studies Unique set of problemsUnique set of problems Main challenge is Fission Main challenge is Fission

251251MdMd

B(M1)/B(E2) B(M1)/B(E2) K K22(g(gKK-g-gRR))22/Q/Q0022

gK ~ 0.7 Mainly E2[514]7-

2

7 -

2

1 -

2

[521] 1-

2a ~ 0.9:

Mainly E2

7 +

2

[633]7+

2gK ~ 1.3 Mainly M1

E2

M1

C. Theisen priv comm.

251251MdMd

First rotationalFirst rotational

band firmly band firmly

establishedestablished

in an odd in an odd

transfermiumtransfermium

nucleusnucleus

C. Theisen/A Chatillon priv comm.

MoI 2MoI 2

A. Afanasiev, PRC 67, 24309, (2002)

IsomersIsomers

Provide information on quasiparticle Provide information on quasiparticle statesstates

Indirect evidence for isomer in Indirect evidence for isomer in 254254NoNo

seen in the 1970sseen in the 1970s

A. Ghiorso et al, PRC 7 (1973) 2032A. Ghiorso et al, PRC 7 (1973) 2032

Several searches in JYFL and ANLSeveral searches in JYFL and ANL

Isomer TaggingIsomer Tagging

γ

α

γγ

Jurogam Array

Target Chamber

DSSD Pixel

e

Prompt Gammas

Isomer decay

Followed by

Alpha decay

•Use the DSSD as a calorimeter! GD Jones, NIM A488, 471 (2002)

InterpretationInterpretation

1.4 266 ms

(8-)

0+

2.6 184 ms

Experiment

Which Cases?Which Cases?

Neutron Number

Pro

ton N

um

ber

Already Done

PotentiallyDoable

Feasibility dependsOn the specifics in

Each and every case!

How to get there?How to get there?

Available Targets:Available Targets: 208208Pb, Pb, 209209Bi (Cold fusion)Bi (Cold fusion) 232232Th, Th, 238238U, U, 243243Am, Am, 248248CmCm (Hot Fusion) (Hot Fusion)

Beams: Far out.Beams: Far out.

Up, up and awayUp, up and away

Picture from S. Hofmann

53K

59Sc

63V

67Mn

73Co

208Pb + X

72Fe

66Cr

62Ti

58Ca

52Ar

209Bi + X

45Cl

39P

35Al

31Na

25F

238U + X

Start from the beam: Start from the beam: 132132SnSnX + 132Sn

N=82

PromisingPromising

The combination of N=82 targets and The combination of N=82 targets and doubly magic doubly magic 132132Sn should be Sn should be favourable.favourable.

Unfortunately they have the highest Unfortunately they have the highest Coulomb barriers Coulomb barriers

Lots of angular momentum Lots of angular momentum

Egido & Robledo PRL 85 1198

92Kr + 164Dy 256No*

Ex = 24 MeV

High spin states in High spin states in SHESHE

48Ca + 208Pb 256No*

Ex = 21 MeV

Nuclear IdentificationNuclear Identification

Alpha tagging Alpha tagging Easy, uniqueEasy, unique

Beta TaggingBeta Tagging Tricky, need gammaTricky, need gamma

Fission TaggingFission Tagging Easy, not uniqueEasy, not unique

Isomer TaggingIsomer Tagging Low Efficiency, Low Efficiency, UniqueUnique

EquipmentEquipment

Target Target High beam quality neededHigh beam quality needed Prompt Spectrometer capable of high ratePrompt Spectrometer capable of high rate

EXOGAM, AGATAEXOGAM, AGATA Separator with large transmissionSeparator with large transmission

gas-filled Separator needed for EURISOLgas-filled Separator needed for EURISOL Excellent Recoil IDExcellent Recoil ID DAQ capable of high rate: DAQ capable of high rate: Triggerless, Digital Triggerless, Digital

Gamma Ray SpectrometerGamma Ray Spectrometer

Dominant channel is constant ~0.1 - 1b Dominant channel is constant ~0.1 - 1b Fission. This limits Ge rate!Fission. This limits Ge rate!

Target wheel spokes need beam Target wheel spokes need beam sweepingsweeping

High granularity and large distance to High granularity and large distance to keep individual rates low keep individual rates low (AGATA!)(AGATA!)

Background from entrance windows etc.Background from entrance windows etc. Need windowless system!Need windowless system!

AGATAAGATA((AAdvanced dvanced GAGAmma mma TTracking racking AArray)rray)

4 4 -array -array for Nuclear Physics Experiments at European for Nuclear Physics Experiments at European accelerators providing radioactive and high-intensity stable accelerators providing radioactive and high-intensity stable

beamsbeams

Main features of AGATA

Efficiency: 40% (M =1) 25% (M =30)today’s arrays ~10% (gain ~4) 5% (gain ~1000)

Peak/Total: 55% (M=1) 45%

(M=30)today ~55% 40%

Angular Resolution: ~1º FWHM (1 MeV, v/c=50%) ~ 6 keV !!!today ~40 keV

Rates: 3 MHz (M=1) 300 kHz (M

=30)today 1 MHz 20 kHz

• 180 large volume 36-fold segmented Ge crystals in 60 triple-clusters • Digital electronics and sophisticated Pulse Shape Analysis algorithms allow• Operation of Ge detectors in position sensitive mode -ray tracking

Electron SpectrometerElectron Spectrometer

Fission does not readily produce CEFission does not readily produce CE SHE produce more CE than Gamma SHE produce more CE than Gamma

Delta electrons require HV barrierDelta electrons require HV barrier Generally difficultGenerally difficult Rate concentrated near field axisRate concentrated near field axis Baseline dirty -> need digital cardsBaseline dirty -> need digital cards

SACREDSACRED

At present, electron experimentsUse 20% of the beam current of Gamma experiments.

Rate adjustable with HV barrier.

Targets need to be thinner (0.25 mg/cm2)

P.A. Butler et al., NIM A 381, 433 (1996)

H. Kankanpaa et al., NIM A 534, 503 (2004)

SAGESAGE

Fermium Wins Heavyweight Title

IP

E [cm-1]

Excimer

Laser

l=351 +

353 nmDye Laser

l=398 nm0

52400

25100

ScanRegion

5I6o

3H6o

5G5o

3G5o

3I7o

J =

• Observation and Assignment of Atomic Levels without any Previous Knowledge of the Atomic Structure

• Demonstrated with a Sample of 1010 Atoms 255Fm, t1/2= 20.1 h, Produced at the HFIR, Oak Ridge

• Based on State-of-the-Art MCDF Calculations

25 April 2003

MCDF Calculation

Experiment

Laser

SHIPZ=102

Resonance Ionization Spectroscopyat Trans-Fermium Elements

BufferGasCell

GSIMAFF

@

Sewtz et al., Phys. Rev. Lett., 90 (2003) 163002-1

o

oDetermination of

• the Valence Electron Configuration by Ion Mobility Measurements ~ eV

• Atomic Levels / Ionization Potentials by Optical Spectroscopy ~ meV

@ MLLTRAPSHIPTRAP

Determination of the Atomic Structure of the Heaviest Elements M. Sewtz, et al.

Relativistic Effects :

• Contraction of the s1/2, p1/2 Orbitals

• Expansion of the d,f Orbitals

Variations in Atomic and Chemical Properties

J.P. Desclaux At. Data Nucl. Data Tables 12, 311 (1973)

Sewtz et al., Spectrochim. Acta B 58, 1077 (2003) ( )

ConclusionsConclusions

In-beam studies will need to be assessed In-beam studies will need to be assessed individually but will be possibleindividually but will be possible

Decay Spectroscopy is vital Decay Spectroscopy is vital

Optical Spectroscopy provides Optical Spectroscopy provides complementary informationcomplementary information

Exciting Times!Exciting Times!