Measuring octupole collectivity in 221Rn using Coulomb excitation at MINIBALL, & SPEDE

George O’Neill

Octupole collectivityCertain nucleon configurations have reflection asymmetry

Enhanced Schiff moments due to nearly degenerate parity doublets

Induce atomic electric-dipole moments

Octupole moment measured through E3 transition

[1] ‘Octupole collectivity in 220Rn and 224Ra’, L. Gaffney, PhD thesis, 2012

221-RadonParity doublet splitting only possible in odd mass systems [2]

Theoretically, asymmetry strongest @ Z=88, N=134

Good beam achievable at ISOLDE

Internal conversion dominates some transitions vs gamma decay

221Rn, 1x105 ion/s48 hour beam time120Sn target, 2 mg/cm2

REX-ISOLDERadioactive ion beam – Radioactive beam EXperiment at ISOLDE

Protons incident on UCX target

Accelerates up to 3.0 MeV/u

MINIBALLCoulomb excitation

Gamma detector array with DSSSD

144 segments of encapsulated Ge

Currently offline for HIE-ISOLDE upgrade

Results so far

201.0 ↓

223.5 ↓

289.3 ↓

Kβ1

↓

Kα1, Kα2

↓

221Rn, 6x103 ion/s30 hour beam time120Sn target, 2 mg/cm2

Results so far

201.0 ↓

223.5 ↓

289.3 ↓

Kβ1

↓

Kα1, Kα2

↓

7/2+, 0 keV

223.5 keV

22.5 keV7/2+, 0 keV

201.0 keV 223.5 keV

SPEDE - motivationSPectrometer for Electron DEtection

Si detector in backwards geometry

Allows full picture

Can also be used for other useful physics

SPEDE – where we areBeam time applied for at JYFL

Detector ordered

Preamplifiers tested

On track for installation Q4 2014

SummarySome initial results for 221Rn

SPEDE will enhance knowledge of nucleus

Should have first results by 2015

1. ‘Octupole collectivity in 220Rn and 224Ra’, L. Gaffney, PhD thesis, 2012

2. ‘Reflection-asymmetric shapes in odd-A actinide nuclei’, Nucl. Phys. A529 (1991), S. Ćwiok, W. Nazarewicz

3. ‘Combined in–beam γ–ray and conversion electron spectroscopy with radioactive ion beams’, P. Papadakis, J. Pakarinen (JYFL proposal)

221Rn CollaborationCEA

Dr Marie-Delphine Salsac, Dr Magda Zielinska

Technischen Universität DarmstadtProf Thorsten Kröll, Dr Marcus Scheck, Sabine Bönig, Michael Thürauf

University of FloridaProf C.Y. Wu

University of JyväskyläDr Tuomas Grahn, Joonas Konki, Sanna Stolze

University of CologneDr Nigel Warr, Lars Lewandowski, Burkhard Siebeck, Tim Steinbach, Andreas Vogt

KVI GroningenDr Lorenz Willman

KU LeuvenDr Liam Gaffney, Dr Kasia Wrzosek-Lipska, Tim De Coster, Nele Kesteloot

University of LiverpoolProf Peter Butler, George O'Neill

University of MichiganProf Tim Chupp

Yale UniversityDr Christian Bernards

SummarySome initial results for 221Rn

SPEDE will enhance knowledge of nucleus

Should have first results by 2015

1. ‘Octupole collectivity in 220Rn and 224Ra’, L. Gaffney, PhD thesis, 2012

2. ‘Reflection-asymmetric shapes in odd-A actinide nuclei’, Nucl. Phys. A529 (1991), S. Ćwiok, W. Nazarewicz

3. ‘Combined in–beam γ–ray and conversion electron spectroscopy with radioactive ion beams’, P. Papadakis, J. Pakarinen (JYFL proposal)