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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
