1. Beta decay studies using total absorption gamma spectroscopy technique A. Algora, M. Csatlós, L. Csige, J. Gulyás, M. Hunyadi, A. Krasznahorkay Institute of Nuclear Research of the Hungarian Acad. of Sciences Debrecen, Hungary For the Valencia, Debrecen, GSI, Warsaw, St. Petersburg, Madrid, Strasbourg, Surrey, Jyväskylä collaboration

2. Z A N  Z-1 A N+1 + e + + for  + Z A N  Z+1 A N-1 + e - + for  ++ ZANZAN Z-1 A N+1 In principle a good description of  i and  f  good B(GT) Z A N + e -  Z-1 A N+1 + + x ray EC Basic relations

3. How to measure the B(GT) Theoretical quantity Strength function Relationship Beta feeding Half life of parent Fermi function

4. The problem of measuring the  - feeding  ZANZAN We use Ge detectors to construct the level scheme populated in the decay From the  intensity balance we deduce the  -feeding What happens if we miss some gamma intensity??? ZANZAN  Z-1 A N+1 Apparent situation Real situation   

5. Experimental difficulties: Pandemonium Effect Introduced by the work of Hardy et al (Phys. Lett 71B (1977) 307). Their study questions the possibility of building correctly a level scheme from a beta decay experiment using conventional techniques. Several factors can contribute to this problem: if the feeding occurs at a place where there is a high density of levels, there is a large fragmentation of the strength among different levels and there is a large number of decay paths, which makes the detection of the weak gamma rays difficult we can have gamma rays of high energy, which are hard to detect

6. Solution Since the gamma detection is the only reasonable way to solve the problem, we need a highly efficient device: A TOTAL ABSORTION SPECTROMETER 11 22 NaI

7. Analysis d = R(B)  f Response (R): It is calculated for  -s and  -s using Monte Carlo techniques (GEANT3,GEANT4) Introduce branching ratios (guess, or from statistical nuclear theory) Possible methods for the solution of the inverse problem: Peel off Regularization methods Bayesian progresive learning Maximum entropy method See: Cano et al. NIM A 430 (1999) 333; 488,Cano PhD thesis, J. L. Tain et al. NIM A 571 (2007) 719, 728

8. Example of the Pandemonium effect, measurements performed at GSI On-line Mass-separator Clustercube 6 cluster detectors in close geometry TAS

9. The decay of 150 Ho 2 - isomer High resolution results (cluster cube) No. total of  : ~ 1064 No. total of levels:~295 Sharp resonance ~ 4.4 MeV B(GT) is approx. 47 % of the TAS result. Algora et al. PRC 68 (2003) 034301

10. The decay of 150 Ho 2 - isomer : comparison with the TAS result

11. Lucrecia, Total Absorption Gamma Spectrometer at ISOLDE (CERN) A large NaI cylindrical crystal 38 cm Ø, 38cm length An X-ray detector (Ge) A  detector Collection point inside the crystal

12. The N  Z region around mass70  Drastic shape changes depending on the occupancy of orbitals.  Oblate to prolate transition and shape coexistence are predicted. [A. Petrovici et al. N P. A708 (2002) 190 and ref. therein]. Free neutron orbitals with same quantum numbers than the valence protons:  Gamow-Teller decay allowed.  Large part of the GT strength accesible inside the Q EC window Theoretical calculations predict different B(GT) distributions on the daughter nucleus depending on the shape of the ground state of the parent (oblate, prolate or spherical). [I. Hamamoto et al., Z. Phys. A353 (1995) 145] [P. Sarriguren et al., Nuc. Phys. A635 (1999) 13]

13. E. Nácher et al. PRL 92 (2004) 232501 The 76 Sr and 74 Kr β-decays Ground state of 76 Sr prolate (β 2  0.4) as indicated in Lister et al., PRC 42 (1990) R1191 E. Poirier et al. PRC 69 (2004) 034307 Ground state of 74Kr:(60±8)% oblate, in agreement with other exp results and with theoretical calculations (A. Petrovici et al.)

14. IGISOL proposals I77 and I116, study of the beta decay of nuclei that are important contributors to the reactor decay heat Studies of the heat (decay heat) in the cool (weather)

15. Fission: the released energy Kinetic energy of fission products (FP) and neutrons Prompt  radiation from FP  and β decay energy through the natural decay of fission products

16. Decay heat: definition Decay energy of the nucleus i (gamma, beta or both) Number of nuclei i at the cooling time t Decay constant of the nucleus i Requirements for the calculations: large databases that contain all the required information (nuclides, lifetimes, mean  - and β-energy released in the decay, n-capture cross sections, fission yields, etc, etc …

17. The main motivation of this work was the study of Yoshida and co-workers (Journ. of Nucl. Sc. and Tech. 36 (1999) 135) See 239 Pu example, similar situation for 235,238 U 239 Pu example (  component of the decay heat ) I77: measurement of the beta decay of 104,105 Tc

18. 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: certainly suffer from the Pandemonium effect, their half lives are in the range needed, and their fission yields are also correlated in the way required to solve the discrepancy Motivations, original plans

19. Results of the analysis for 104 Tc (preliminary)

20. Impact of the results on the decay heat summations ( 104,105 Tc) NuclideEnergy Type ENDF/B VII (& Jeff 3.1) TAS Experiment 104 TcELP1595 (75) 915 (35) EEM1890 (30)3263 (65) 105 TcELP1310 (173) 805 (35) EEM 668 (19) 1736 (70) ΔE(  )= 1373 104 +1068 105 = 2441 keV; ΔE(e-)= -680 104 -505 105 =-1185 keV

21. Impact of the results for 239 Pu

22. Beta-decay still offers a very interesting field of research. The utilization of new devices and recently developed analysis techniques opens new possibilities for the understanding of nuclear structure. We have discussed here a method to measure the B(GT) in beta decay, which can be considered more reliable. The limitations on these kind of studies are determined by nature (we can only reach states inside the Q energy window) The method is Total Absorption Spectroscopy A very interesting physics programme running, mainly devoted to cases on the proton rich side (ground state shape determination, conf. mixing, p-n pairing,..). We are also involved in studies of neutron rich side which are also important, but for other reasons (decay heat) and that will allow us to gain experience for the future FAIR Conclusions