On octupole nuclei and the status of SPEDE

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 134Can 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 doubletsEnhanced 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→0Internal 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; siliconSegmentedNeed to control δ–e- fluxNow used in-beam with γ–ray spectrometers

SPEDESPectrometer for Electron DEtectionWill be situated at MINIBALLSi detector in backwards geometryCan be used for many areas of nuclear structure

SPEDEChanges will result in new chamberSimilar to T-REXEasy access to both detectors

SPEDE – numbersPCB ø – 12 cm, Detector ø – 5 cm (0.5 mm thick)24 segmentsDepletion voltage ~50VCooled to -30 C∘Simulated FWHM: 9.2 keV @ 678 keV

SPEDE – where we areDetector & PCB ready – mechanical design finalised in coming daysPreamplifiers testedIn-beam testing and commissioning at JYFL – spring 2014On track for installation when HIE-ISOLDE comes online

SummarySimulation of 221Rn configuration on-goingCombined e--γ ray spectroscopy unlocking secrets of nucleiSPEDE will enhance experiments for all users of MINIBALLShould 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-goingCombined e--γ ray spectroscopy unlocking secrets of nucleiSPEDE will enhance experiments for all users of MINIBALLShould have first results from it 2015