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Isospin Symmetry Workshop: Precision Half-Life Determination of Superallowed 0+→0+ β+-Emitters

This workshop focuses on the precise determination of half-lives in superallowed 0+→0+ β+-emitters such as 42Ti, 38Ca, and 30S, as well as mirror β transitions of 39Ca, 31S, and 29P. Experimental setups, measurements, detection systems, and data analyses are discussed to achieve a relative precision of ~10-3. Error budgets, experimental conditions, and analysis techniques are scrutinized to ensure accurate results. Various parameters affecting half-life determination are explored, along with the importance of mirror transitions and branching ratios. The text highlights the required measurements, setup details, and calibration programs for successful research in nuclear structure studies.

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Isospin Symmetry Workshop: Precision Half-Life Determination of Superallowed 0+→0+ β+-Emitters

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  1. Precision half-life determination of the superallowed 0+→0+β+-emmiters 42Ti,38Ca,30S and the mirror β transitions of 39Ca, 31S and 29P Workshop of ESNT: Isospin symmetry and its breaking in nuclear structure CEA/SPhN-Saclay, April 29th 2011

  2. Experimental ft measurements 0+ • Precision measurements required: • QEC → mass measurements: f ~ Q5 • T1/2, BR →b-decay studies: t = T1/2 / BR T1/2 QEC BR 0+ to test Ft value  requiredrelative precision ~10-3 Super Allowed Fermi 0+ → 0+ Mirror Transitions T=1/2

  3. Half-life measurements: Experimental details • typical setup: • - beam purification system: traps • - beta detector • - gamma detectors • JYFL – IGISOL •  ISOLDE / CERN

  4. Typical setup: JYFL – IGISOL JYFLTRAP b detector Ge detectors Tape transport system

  5. Typical setup: JYFL – IGISOL detection setup - b plastic scintillator - g germanium tape transport system

  6. Typical setup: ISOLDE/ CERN detection - b gas counter - g germanium radioactive ions GSI tape system

  7. Half-life measurements: Experimental details measurement principle cycles - isotope accumulation - purification - transport - decay measurement - remaining activity evacuation • different fixed dead times: • 2 ms, 8 ms, 100ms • different detector high-voltages • different detection thresholds

  8. Half-life measurements: Experimental details • Data analysis: • cycle selection: no beam, detector sparking… • half-life cuts: test of dead time correction • half-life as a function of background, of rate, of detector settings •  Is there any dependence of the half-life of these parameters? •  error budget

  9. Super Allowed Fermi 0+ → 0+

  10. Error budget all nuclei of interest • Experimental quantities: • Q values: traps, high precision “easily” reachable • half-lives: feasible • branching ratios: hard part…

  11. Super Allowed Fermi 0+ → 0+: 42Ti

  12. Beam purification: JYFLTRAP

  13. Typical spectrum: one run

  14. Implantation on the tape?

  15. Dead time correction: part 1 2ms 8ms 100ms

  16. Dead time correction: part 2  test of dead time correction

  17. Different experimental conditions: thresholds and high-voltages

  18. Error budget • counting statistics: 0.45 • dead time correction: 0.01 • experimental parameters (threshold, HV): 0.00 • T1/2 as function of background: 0.00 • T1/2 as function of counting rate: 0.00 • “wrong” implantation: 0.00 • -------------------------------------------------------------------- • Total: 0.45 •   T1/2(42Ti) = 208.14 ± 0.45 ms

  19. Half-life of 42Ti: JYFL 2008 42Ti T1/2 = 208.14 ± 0.45 ms (2.16 ‰) 611 keV BR = 48.2(15)% T. Kurtukian Nieto et al., PRC80 (2009) 035502 Ft = 3114(79)

  20. Half-life of 42Ti:

  21. Super Allowed Fermi 0+ → 0+: 38Ca

  22. Half-life of 38Ca: ISOLDE 2007 38Ca T1/2 = 443.8 ± 1.9 ms Blank et al., EPJ A 44,363 (2010)

  23. Half-life of 38Ca:

  24. Super Allowed Fermi 0+ → 0+: 30S

  25. Half-life measurements : 30S JYFL 2009

  26. Half-life measurements : 30S 30P (T1/2 = 148.88 ± 0.24 s)  as contamination  as daughter need to characterize both contributions - filiation of 30S no additional parameter - production (mass separator) background constraint required example run 30S T1/2 = 1175.9 ± 1.7 ms (1.45 ‰) Souin, et al., EPJA (2011)

  27. Half-life measurements : 30S

  28. Error budget 2007 2011 sensitive improvement for half-lives some difficult work to do for branching ratios

  29. Mirror b decay

  30. Mirror b decay • Measurements required: • b-decay Q value • super-allowed branching ratio • b-decay half-life • b-n angular correlation coefficient N. Severijns, O. Naviliat-Cuncic

  31. Status in 2009 • Experimental quantities: • half-lives: feasible

  32. Mirror transitions: Half-lives of 39Ca Blank et al., EPJ A 44,363 (2010)

  33. Mirror transitions: Half-life of 31S: JYFL 2009 T. Kurtukian Nieto, A. Bacquias et al. T1/2 = 2546.4(18) ms

  34. Mirror transitions: Half-life of 29P: JYFL 2009 T. Kurtukian Nieto, A. Bacquias et al. preliminary

  35. Error budget 2009 2011

  36. Branching Ratio Measurements

  37. Capot Al Ge • Need to know the efficiency with a precision of 0.1% • calibration programme of a • monocristal detector: • - source measurements • - MC simulations Detector scheme J. Souin

  38. RX of the detector Scanning done with a collimated 137Cs (CSNSM Orsay) HPGe 137Cs collimated (477MBq) X-Y table J. Souin

  39. Scanning done with collimated 137Cs source Determination of the germanium active volumen Length of the hole (13.6mm larger than expected) Front cap J. Souin

  40. Calibration programme at Bordeaux Gamma sources (with BR know with high precition) done at ISOLDE: 75Se, 27Mg, 24Na, 66Ga, 56Co 133Ba,60Co,207Bi,137Ce, 152Eu,88Y, 85Sr,51Cr,54Mn,57Co

  41. Summary : 0+->0+ 2007 2011

  42. Summary Mirror Transitions 2009 2011

  43. The End

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