Measurement of β - delayed neutrons around the third r-process peak at GSI

1. Measurement of β-delayed neutrons around the third r-process peak at GSI ROGER CABALLERO FOLCH, Barcelona, 9th November 2011

2. Introduction Proposal GSI facility & setup Preliminary analysis Contents Introduction: Theoretical concepts Experiment proposal GSI facility and experimental setup Preliminary analysis 2/16

3. Introduction Proposal GSI facility & setup Preliminary analysis Introduction UPC Neutron detector (Beta delayed neutron, BELEN) Neutron detector designed and constructed by UPC GRETER research group. The detection of the neutron is based on the detection of products of the following reaction of the neutron with 3He counters 3He + n → 3H + 1H + 765 keV Spectra obtained for each 3He counter Polyethylene moderator Noise Full energy deposited 765 keV n n Edge effect 191 keV Proportional 3He counter Ion beam Silicon β decay detector n 3/16

4. Introduction Proposal GSI facility & setup Preliminary analysis Introduction Neutron emission after β- decay scheme To measure neutron emission probabilities after beta decay of neutron rich isotopes with relevance in basic nuclear physics, astrophysics and nuclear technology. 4/16

5. Introduction Proposal GSI facility & setup Preliminary analysis Introduction Example of β-delayed neutron emission neutron BETA 5/16

6. Introduction Proposal GSI facility & setup Preliminary analysis Introduction Relevance Nuclear structure knowledge: study different aspects of the decay of these nuclei. Half lives and neutron emission probabilities provide information about their decay mechanism and structure. Astrophysics (r-process): β- decay studies near the r-process path. Pn values, together with decay half lives, are the main ingredients for the study of heavy elements nucleosynthesis via the r-process. The exact place for the r-process has not been identified yet. 6/16

7. Introduction Proposal GSI facility & setup Preliminary analysis Introduction Proposal Experiment objectives S410: “Beta-decay measurements of new isotopes near the third r-process peak” Has been performed at GSI in September 2011 with a week beam time. To measure half lives and beta delayed neutron emission probability of isotopes near the third abundance peak of the r-process (N≈126). The measurements were centered on isotopes 215Tl, 211Hg. Some isotopes around have already been identified. We expect to identify 211-214Hg 213-216Tl 208-211Au 208,209Pt 205,206Ir 7/16

8. t1/2 exists identified Introduction Proposal GSI facility & setup Preliminary analysis Proposal Status of the art Centered N=126 Area of interest Pn (%) QRPA Bn= 2-3 MeV 8/16

9. Introduction Proposal GSI facility & setup Preliminary analysis Proposal Explosive nucleosynthesis and the r-process around the third abundance peak Focus of present proposal r-path Effect of half-lives “Ignorance”-Curve The Astr. Jour., 579 (2002), H. Schatz et al. Proc. CGS-13 (2009), G. Martinez-Pinedo 9/16

10. DF3 + QRPA +FRDM + QRPA Exp. T. Kurtukian et al. Introduction Proposal GSI facility & setup Preliminary analysis Proposal Difficult to calculate/predict half-live and Pn-values of the nuclei in this region: FRDM + QRPA K.-L. Kratz, (private communication) K.-L. Kratz, (private communication) (I.Borzov, et al. 2003) (P.Moeller, et al. 2003) T. Kurtukian-Nieto, et al., Phys. Lett. B (Submitted) 10/16

11. Introduction Proposal GSI facility & setup Preliminary analysis Proposal GSI facility & setup GSI facility. Fragment separator spectrometer (FRS) Beam characteristics 238U beam 1GeV/n 2x109 ions/s intensity 1.6 g/cm2 Be target 11/16

12. Introduction Proposal GSI facility & setup Preliminary analysis GSI facility & setup S410 experiment setup Polyethylene shielding Neutron detector SIMBA 12/16

13. Introduction Proposal GSI facility & setup Preliminary analysis GSI facility & setup S410 experiment setup Neutron shielding FRS detectors BELEN neutron detector 12/16

14. Introduction Proposal GSI facility & setup Preliminary analysis GSI facility & setup Silicon Implantation Detector and Beta Absorber (SIMBA) Multilayer silicon detector It allowed us to measure both ion implants and β-decays. Decay events can be correlated in time with the detection of neutrons. SIMBA detector Tracking layers XY (60 segm.) 60x60 mm2 (0.3mm thick) 2 SSSD (7 segm.) 60x40 mm2 (1mm thick) 3 DSSD (implantation area, 60x40 segm.): 60x40 mm2 (0.7mm thick) 2 SSSD (7 segm.) 60x40 mm2 (1mm thick) 13/16

15. Introduction Proposal GSI facility & setup Preliminary analysis GSI facility & setup Neutron detector for FRS-GSI S410 experiment 30 3He counters: · 20 with 20 atm pressure · 10 with 10 atm pressure 14/16

16. Introduction Proposal GSI facility & setup Preliminar analysis Preliminary analysis GSI facility & setup Data analysis method based in Go4 & root Z Po Bi Pb Tl Tracking signals FRS detectors Hg A/Q Identification plot 15/16

17. Introduction Proposal GSI facility & setup Preliminary analysis Preliminary analysis Data analysis method based in Go4 & root Calibration files for Z and AoQ (ID): 205Bi & 216Po Gamma rays of Isomers Z Counts keV 205Bi 286 Counts 698 881 796 keV A/Q 15/16

18. Introduction Proposal GSI facility & setup Preliminar analysis Preliminary analysis Data analysis method based in Go4 & root Noise Counts Implantation Beta decay Location on silicon layer detector (SIMBA) Energy deposited (ch) 16/16

19. Introduction Proposal GSI facility & setup Preliminar analysis Preliminary analysis Data analysis method based in Go4 & root n β- β- n Counts Implants keV Beta disintegrations Neutron signal Noise Pulser Energy (ch) β- decays calibrations will be performed with a 137Cs source β- decay curves will provide half lives values 252Cf for BELEN efficiency Ch 16/16

20. The end! www-w2k.gsi.de/frs-setup GRETER research group - Nuclear Engineering Section (SEN) Thanks to the fellowship of the Càtedra ARGOS