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The polar experience: IGISOL proposal I77, study of the beta decay of 102,104,105 Tc by means of the total absorption technique A. Algora IFIC-Univ. Valencia. Contents. Motivations, original plans Experimental setup, preparation Experimental problems Techniques of analysis

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  1. The polar experience: IGISOL proposal I77, study of the beta decay of 102,104,105Tc by means of the total absorption techniqueA. AlgoraIFIC-Univ. Valencia

  2. Contents • Motivations, original plans • Experimental setup, preparation • Experimental problems • Techniques of analysis • Monte Carlo simulations of the setup • Some spectra, first steps • Future

  3. Some definitions Decay energy of the nucleus i Decay constant of the nucleus i Number of nuclei i at the cooling time t

  4. Motivations, original plans 239Pu example The main motivation of this work was the study of Yoshida and coworkers (Journ. of Nucl. Sc. and Tech. 36 (1999) 135) See 239Pu example, similar situation for 235,238U

  5. Motivations, original plans Solution: underestimation of the E energy of some nuclides with half lives in the range of 1000s Assuming some decay chains with appropriate characteristics, the discrepancy is solved X chain (released E=1.5 MeV) X1(T1/2=200 s)→X2(T1/2=800 s) Our motivation was to measure the beta decay of the proposed nuclei using the total absorption technique.

  6. Motivations, original plans In their work (detective work) Yoshida et al. identified some nuclei that may be responsible for the under-estimation of the E component. Possible nuclei that may be blamed for the anomaly were 102,104,105Tc Explanation: not correctly measured, certainly suffer from the Pandemonium effect, their half lives are in the range, and their fission yields are also the required to solve the discrepancy

  7. Experimental setup, preparation

  8. Experimental setup, preparation

  9. Experimental setup, preparation

  10. Experimental setup, preparation

  11. Experimental setup Si det. TAS det (Det 1 & det 2). Rad. beam . Ge det. Tape station

  12. Experimental problems, solutions ZAN b- ZAN Z+1AN-1+ e- +  for b- ZAN Z-1AN+1+ e+ +  for b+ Z+1AN-1 ZAN+ e- Z-1AN+1+  + xray EC • The problem of the contaminations: • T1/2, laser ionization scheme, trap • In this case the β delayed neutron emission is not a problem

  13. Experiment preparation G. Lhersonneau et al., Eur. Phys. J A 9 (2000) 385

  14. The ion guide technique Generic ion guide: the nuclear reaction products are stopped in a gas and are transported through a differential pumping system into the accelerator stage of the mass separator. The process is fast enough for the ions to survive as single charged ions. The system is chemically insensitive and very fast (sub-ms).

  15. The IGISOL technique Fission ion guide: 2700 ions/s per mb, eff. of 1.6x10-4 relative to the production in the target Details of our experiment: Beam: 30 MeV proton (5microA) Target: natural U Target thickness: 15 mg/cm2 Target dimensions: 10x50 mm, tilted 7 degrees Yield of 112Rh: 3500 atoms/microC Tight collimation scheme to avoid contamination of neighbour mases (losses of 25%)

  16. Cycles for 104Tc (T1/2= 18.3m) Beam gate 30 m Measuring time 1 h Tape movement T1/2 of possible contaminants: 104Mo (60 s), 104Rh(42 s), 105Tc(7.6m)

  17. Cycles for 105Tc (T1/2= 7.6m) Beam gate 8 m Measuring time 12 m Tape movement T1/2 of possible contaminants: 105Mo (35.6 s), 105Rh(4.44 h), 104Mo(60 s), 104Tc(18.3 m),

  18. 104Tc TAS spectrum Last known level: 4268 keV Qβ=5600 keV

  19. 105Tc TAS spectrum Last known level: 2404 keV Qβ=3640 keV

  20. Techniques of analysis • We use the methods of analysis developed by the Valencia group. In particular the Expectation Maximization (EM) method • First step: the implementation of the geometry of the setup for the Monte Carlo simulations and to test it with sources • Calculation of the response function, and then the analysis itself

  21. Monte Carlo simulations of the setup: geometry

  22. Monte Carlo simulations of the setup The Monte Carlo simulations require the implementation of the geometry in full detail Example: details of the Si holder and the rollers

  23. Monte Carlo simulations of the setup

  24. Monte Carlo simulations of the setup

  25. Monte Carlo simulations of the setup

  26. Expectation Maximization (EM) method: • modify knowledge on causes from effects Algorithm: Analysis of 104Tc Some details: Known levels up to: 1515 keV excitation From that level up to the Qβvalue we use an statistical model (Back Shifted Fermi formula for the level density with parameters taken from the RIPL database (102Ru,106Pd) Branching ratios

  27. Results of the analysis for 104Tc

  28. Future • 102Tc case, 100Tc case • We need to develop a better tape station system • There are new possibilities using laser ionization schemes • ???

  29. The people involved in the “polar” project J.L. Tain, B. Rubio, E. Nácher, L. Caballero, J. Agramunt, A. B. Perez, W. Gelletly, L. Batist, A. Garcia, J. Äystö, H. Penttilä, I. Moore, P. Karvonen, A. Jokinen, S. Rinta-Antila, A. Kankainen, T. Eronen, U. Hager, T. Sonoda, J. Hakala, I. N. Izosimov, T. Yoshida, F. Storrer, A. L. Nichols, G. Lhersonneau, K. Burkard, W. Huller, A. Krasznahorkay, A. Vitéz, J. Gulyás, M. D. Hunyadi, A. Algora

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