1. 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

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 Number of nuclei i at the cooling time t Decay constant of the nucleus i

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

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) X 1 (T 1/2 =200 s)→X 2 (T 1/2 =800 s ) Our motivation was to measure the beta decay of the proposed nuclei using the total absorption technique.

6. 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 102,104,105 Tc 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 Motivations, original plans

7. Experimental setup, preparation

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

12. Experimental problems, solutions Z A N  Z+1 A N-1 + e - + for  Z A N  Z-1 A N+1 + e + + for  + Z A N + e -  Z-1 A N+1 + + x ray EC ZANZAN Z+1 A N-1 -- The problem of the contaminations: T 1/2, laser ionization scheme, trap In this case the β delayed neutron emission is not a problem

13. Experiment preparation Nucleus T 1/2 Cross Sec. 104Zr 1.2s 0.360611 104Nb 4.8s 8.846785 104Mo 60s28.197895 104Tc18.3m11.677034 104Rustable 0.628251 104Rh 42s 0.004392 104Pdstable 0.000004 Nucleus T 1/2 Cross Sec. 105Nb 2.95s 3.113171 105Mo 35.6s20.985006 105Tc 7.6m18.378065 105Ru4.44h 2.091102 105Rh35.36h 0.030913 105Pdstable 0.000059 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 Details of our experiment: Beam: 30 MeV proton (5microA) Target: natural U Target thickness: 15 mg/cm 2 Target dimensions: 10x50 mm, tilted 7 degrees Yield of 112 Rh: 3500 atoms/microC Tight collimation scheme to avoid contamination of neighbour mases (losses of 25%) Fission ion guide: 2700 ions/s per mb, eff. of 1.6x10 -4 relative to the production in the target

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

17. Cycles for 105 Tc (T 1/2 = 7.6m) Beam gate Measuring time Tape movement 12 m 8 m T 1/2 of possible contaminants: 105 Mo (35.6 s), 105 Rh(4.44 h), 104 Mo(60 s), 104 Tc(18.3 m),

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

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

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

27. Results of the analysis for 104 Tc

28. Future 102 Tc case, 100 Tc 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