On octupole nuclei and the status of SPEDE George O’Neill g.g.oneill@liv.ac.uk.

On octupole nuclei and the status of SPEDE

George O’Neillg.g.oneill@liv.ac.uk

Certain nucleon configurations have reflection asymmetry

(N, j, l) intruder orbitals interact with (N – 1, j – 3, l – 3) natural states

‘Octupole magic numbers’ ≈ 34, 56, 88 and 134

Can measure B(E3) transitions

Octupoles

220Rn results220Rn, 3x105 ion/s

2.82 MeV/A

224Ra results224Ra, 7x105 ion/s

2.83 MeV/A

220Rn 224Ra

220Rn 224Ra interpretation

Studies of pear-shaped nuclei using accelerated radioactive beams Nature

497, 199–204

Odd octupolesOdd nucleon couples with core

(almost) Degenerate parity doublets

Enhanced Schiff moment (~3 orders of magnitude)

Improves limits on EDM

Internal conversionInternal conversion coefficient, α = N(ɣ)/N(e-)

ICC increases as Z, λ →∞, Etrans→0

Internal conversion dominates some transitions vs. gamma decay

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

221Rn results

201100% ↓

22471% ↓ 287

23% ↓

Kβ 56% ↓

Kα 324% ↓

221Rn, 6x103 ion/s30 hour, 2.85 MeV/u120Sn target, 2 mg/cm2

27315% ↓

221Rn results

221Rn results

Electron spectrometersSemi-conductors; silicon

Segmented

Need to control δ–e- flux

Now used in-beam with γ–ray spectrometers

SPEDESPectrometer for Electron DEtection

Will be situated at MINIBALL

Si detector in backwards geometry

Can be used for many areas of nuclear structure

SPEDEChanges will result in new chamber

Similar to T-REX

Easy access to both detectors

SPEDE – numbersPCB ø – 12 cm, Detector ø – 5 cm (0.5 mm thick)

24 segments

Depletion voltage ~50V

Cooled to -30 C∘Simulated FWHM: 9.2 keV @ 678 keV

SPEDE – where we areDetector & PCB ready – mechanical design finalised in coming days

Preamplifiers tested

In-beam testing and commissioning at JYFL – spring 2014

On track for installation when HIE-ISOLDE comes online

SummarySimulation of 221Rn configuration on-going

Combined e--γ ray spectroscopy unlocking secrets of nuclei

SPEDE will enhance experiments for all users of MINIBALL

Should have first results from it 2015

CollaborationCEA

Marie-Delphine Salsac, Magda Zielinska

Technischen Universität DarmstadtThorsten Kröll, Marcus Scheck, Sabine Bönig, Michael Thürauf

University of FloridaC.Y. Wu

University of JyväskyläTuomas Grahn, Janne Pakarinen, Philippos Papadakis, Joonas Konki, Sanna Stolze

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

KVI GroningenLorenz Willman

KU LeuvenLiam Gaffney, Kasia Wrzosek-Lipska, Tim De Coster, Nele Kesteloot

University of LiverpoolPeter Butler, Rolf-Dietmar Herzberg, George O'Neill, Jim Thornhill

University of MichiganTim Chupp

Yale UniversityChristian Bernards

SummarySimulation of 221Rn configuration on-going

Combined e--γ ray spectroscopy unlocking secrets of nuclei

SPEDE will enhance experiments for all users of MINIBALL

Should have first results from it 2015