35 Ca decay beta-delayed 1- and 2-proton - PowerPoint PPT Presentation

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35 Ca decay beta-delayed 1- and 2-proton

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  1. 35Ca decay beta-delayed 1- and 2-proton spokespersons: J. Giovinazzo (CENBG), O. Tengblab (CSIC) institutions: Centre d’Etudes Nucléaires (Bordeaux) – CNRS / univ. Bordeaux – France Istituto de Estructura de la Materia (Madrid) – CSIC – Spain Dep. of Physics and Astronomy (Aarhus) – univ. Aarhus – Denmark PH department CERN (Geneva) – Switzerland beta delayed proton(s) emission program 31Ar studied at ISOLDE previous decay studies Berkeley, J. Aystö et al. (1985) GANIL, W. Trinder et al. (1999)

  2. Previous experiments 1985 Berkeley, J. Aystö et al., PRL 55 (1985) 1384 40Ca(3He,a4n) reaction, helium-jet technique small angle proton-proton coincidences with DE-E silicon telescope - only b-2p measurement (sequential) - first decay scheme logft(IAS) = 3.09 T1/2 = 50 ± 30 ms Dm = 4463 ± 60 keV (IMME) 1999 GANIL, W. Trinder et al., PLB 459 (1999) 67 40Ca fragmentation, LISE implantation / decay experiment gamma: 3 Ge (70%) and 2 NaI detectors - 19 b-p(g) transitions  B(GT) (weaker quenching than sd shell) - no b-g - no b-2p to excited state in 33Cl logft(IAS) = 4.1  missed strength ? T1/2 = 25.7 ± 0.2 ms Dm = 4530 ± 66 keV (IMME)

  3. 31Ar and 35Ca at ISOLDE current proposal is continuation of b-p and b-2p decay studies at ISOLDE 31Ar experiment : Phys. Rev. C87, 055808 (2013) G. T. Koldste, H.O.U. Fynbo, et al. mainly study of 30S resonances (b-p)  nucleosynthesis  b-p(g) and b-2p  new experimental method for Gp / Gg estimate

  4. purpose of the experiment (I) rich decay scheme beta-gamma beta-proton(-gamma) beta-2proton(-gamma) 1/2+ QEC T = 5/2 35Ca 1/2+ IAS 1/2+ 3/2+ 2+ 33Cl + 2p 0+ 34Ar+p 3/2+ 0 35P decay spectroscopy a unique access to drip-line nuclei

  5. purpose of the experiment (II) 1/2+ QEC T = 5/2 35Ca 1/2+ IAS b/CE 1/2+ 3/2+ 2+ 33Cl + 2p  beta-gamma coincidences not observed in previous experiments unexpected low B(F) strength g 0+ 34Ar + p 3/2+ 0 35P


  6. purpose of the experiment (III)  beta-proton unresolved proton groups (GANIL)  improved resol. B(GT) distribution (including b-g ?) 1/2+ QEC T = 5/2 35Ca 1/2+ IAS b/CE p 1/2+ 3/2+ 2+ 33Cl + 2p g 0+ proton emission from IAS is isospin forbidden T(35PIAS) = 1/2 T(34Args) = ½ proton vs gamma emission  isospin mixing 34Ar + p 3/2+ 0 35P

  7. purpose of the experiment (IV) 1/2+ QEC T = 5/2  beta-proton-gamma vs beta-2-proton gamma / proton widths in 34Ar rp-process: 33Cl(p,g)34Ar reaction 35Ca 1/2+ IAS b/CE p 1/2+ g 3/2+ 2+ 33Cl + 2p 0+ 34Ar + p 3/2+ 0 35P

  8. purpose of the experiment (V) 1/2+ QEC T = 5/2 35Ca 1/2+ IAS b/CE p p 2p? 1/2+ 3/2+ 2+ 33Cl + 2p 0+ 34Ar + p 3/2+ 0  beta-2-proton feeding of excited state in 33Cl ? (seen at Berkeley, not at GANIL) search for a direct 2-proton branch (never evidenced in b2p) 35P

  9. purpose of the experiment (summary)  beta-proton high resol. spectro. B(GT) distribution 1/2+ QEC T = 5/2  gamma / proton widths, rp process 35Ca  beta-(1-/2-)proton E(IAS), masses (IMME) 1/2+ IAS 1/2+ 3/2+ 2+ 33Cl + 2p  beta-gamma and B(F) strength (and B(GT) ? ) 0+ 34Ar+p 3/2+ 0  beta-2-proton 33Cl states feeding and direct 2p 35P  detailed decay scheme 

  10. detection set-up (I): charged particles “Silicon-cube” device 6 DSSSD for protons  high granularity (2p emission angles)  detection efficiency ~60% for 1 proton  energy FWHM ~ 25 keV (low noise P.A.) back-detectors - beta suppression - high-energy protons ions deposited on a thinmylar catcher back-plane DSSSD catcher

  11. detection set-up (II): gamma-rays Germanium detectors 2 Ge-clusters (si-cube originally designed for 3 Ge-clovers) (31Ar experiment with 2 MINIBALL clusters) - high resolution - efficiency ~10-15% (at 1 MeV) close geometry (~8 cm)

  12. beam-time request production with TiC targets (under tests, unknown count rates) measurements: cycles (T1/2) ~ 1 shift (~20% “duty cycle”) continuous production (100%) experiment “duty cycle” ~75 % detection efficiency 1 proton ~50 % 2 protons ~25 % daily count rates bp b2p total b2p direct with 0.135Ca / s 3000 60 0.6 ? beam-time request - Beam and separator tuning 3 shifts - Set-up tuning and calibration (37,36Ca…) 3 shifts - Experiment (35Ca beam) 24 shifts - Total 30 shifts

  13. 35Ca decay beta-delayed 1- and 2-proton spokespersons: J. Giovinazzo (CENBG), O. Tengblab (CSIC) institutions: Centre d’Etudes Nucléaires (Bordeaux) – CNRS / univ. Bordeaux – France Istituto de Estructura de la Materia (Madrid) – CSIC – Spain Dep. of Physics and Astronomy (Aarhus) – univ. Aarhus – Denmark PH department CERN (Geneva) – Switzerland thank you for your attention…