On octupole nuclei and the status of SPEDE

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

2. Octupoles • 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

3. 220Rn results 220Rn, 3x105ion/s2.82 MeV/A

4. 224Ra results 224Ra, 7x105 ion/s2.83 MeV/A

5. 220Rn 224Ra

6. 220Rn 224Ra interpretation

7. Studies of pear-shaped nuclei using accelerated radioactive beamsNature497, 199–204

8. Odd octupoles • Odd nucleon couples with core • (almost) Degenerate parity doublets • Enhanced Schiff moment (~3 orders of magnitude) • Improves limits on EDM

9. Internal conversion • Internal 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 time 120Sn target, 2 mg/cm2

10. 221Rn results Kα 324% ↓ 221Rn, 6x103ion/s30 hour, 2.85 MeV/u120Sn target, 2 mg/cm2 22471% ↓ Kβ56% ↓ 201100% ↓ 28723% ↓ 27315% ↓

11. 221Rn results

12. 221Rn results

13. Electron spectrometers • Semi-conductors; silicon • Segmented • Need to control δ–e- flux • Now used in-beam with γ–ray spectrometers

14. SPEDE • SPectrometer for Electron DEtection • Will be situated at MINIBALL • Si detector in backwards geometry • Can be used for many areas of nuclear structure

15. SPEDE • Changes will result in new chamber • Similar to T-REX • Easy access to both detectors

16. SPEDE – numbers • PCB 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

17. SPEDE – where we are • Detector & 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

18. Summary • Simulation 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

19. Collaboration • CEA Marie-DelphineSalsac, Magda Zielinska • TechnischenUniversität Darmstadt Thorsten Kröll, Marcus Scheck, Sabine Bönig, Michael Thürauf • University of Florida C.Y. Wu • University of Jyväskylä TuomasGrahn, JannePakarinen, PhilipposPapadakis, JoonasKonki, SannaStolze • University of Cologne Nigel Warr, Lars Lewandowski, BurkhardSiebeck, Tim Steinbach, Andreas Vogt • KVI Groningen Lorenz Willman • KU Leuven Liam Gaffney, KasiaWrzosek-Lipska, Tim De Coster, NeleKesteloot • University of Liverpool Peter Butler, Rolf-Dietmar Herzberg, George O'Neill, Jim Thornhill • University of Michigan Tim Chupp • Yale University Christian Bernards

20. Summary • Simulation 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