1 / 17

Study of multi-neutron emission in the b -decay of 11 Li

Study of multi-neutron emission in the b -decay of 11 Li. Towards 2-neutron correlation studies. Spokespersons F. Delaunay (LPC Caen), D. Cano-Ott (CIEMAT Madrid) Collaboration LPC Caen CIEMAT Madrid IEM, CSIC, Madrid Chalmers University, Göteborg IFIC, Valencia UPC, Barcelona

harper
Download Presentation

Study of multi-neutron emission in the b -decay of 11 Li

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Study of multi-neutron emission in the b-decay of 11Li Towards 2-neutron correlation studies Spokespersons F. Delaunay (LPC Caen), D. Cano-Ott (CIEMAT Madrid) Collaboration LPC Caen CIEMAT Madrid IEM, CSIC, Madrid Chalmers University, Göteborg IFIC, Valencia UPC, Barcelona University of Aarhus IPN Orsay CEA/DAM/DIF, Bruyères-le-Châtel CERN INTC-P-307

  2. Motivation • b-decay of 11Li: • Qb = 20.6 MeV • Weakly bound daughter 11Be •  Variety of delayed particle emissions • Delayed 2-neutron emission: • P2n = 4.2 % • No measurement of 2-neutron kinematics (correlations?) • Tentative 2-neutron decay paths from 1-neutron transitions • Delayed 1-neutron emission still unclear: • Unresolved weak transitions, uncertain branching ratios… CERN INTC-P-307

  3. Previous studies: b-1n Latest study: Hirayama et al., PLB 611 (2005) 239 20 40 60 80 100 120 140 TOF (ns) CERN INTC-P-307

  4. Previous studies: b-2n Detection of 2 neutrons in coincidence  energies and angles F.M. Marqués et al., TONNERRE plastic array, GANIL/LISE3 b-m-m b-n-m No particle discrimination  Data dominated by random coincidences involving b-rays, ambient g-rays, cosmic rays (80-90 %...) CERN INTC-P-307

  5. Goals of the experiment • Measure directly for the 1st time 2 delayed neutrons in coincidence • Use an array of liquid scintillator modules • Granularity  Angular resolution • Neutron TOF  Energy • Liquid  n-g discrimination  suppression of background (g, m…) • Digital signal processing  improved discrimination  lower En threshold • Feasibility of correlation studies between delayed neutrons • Sequential or simultaneous emission? • Correlated or uncorrelated neutrons? • Possible insight into configuration of neutrons in the decaying state • + Improved picture of single neutron emission CERN INTC-P-307

  6. Near array (30 det’s) Experimental setup • 40 liquid modules: • 20 cm in diameter, 5 cm thick • ~40 % intrinsic efficiency • n-g discrimination • Near array: d = 1.5 m • solid angle : 3.3 % of 4p • dE=70 keV at 1 MeV • n-n coincidences • Far array: d = 3 m • dE=35 keV at 1 MeV • solid angle : 0.3 % of 4p • Precise tagging of 1 of the 2 n • Improved 1n data Modules characterised with monoenergetic neutrons HPGe 11Li beam • Plastic • b • TOF start Far array (10 det’s) + Digital electronics & DAQ CERN INTC-P-307

  7. Count-rate estimates • 11Li rate: ~1000 ions/s • (Ta foil target + W surface ionisation source) • 2-neutron coincidences: • Assuming 50 % of the 2-neutron intensity detectable (threshold En~500 keV) • 10 events/h in near array • 1 event/h between near and far array 1-neutron emission: for a transition with 1 % intensity • 380 events/h in near array • 30 events/h in far array b-n-g coincidences(b-1n to excited states of 10Be): Assuming 2 % photopeak efficiency, 1 % 1n-line, 1 g-ray in 10Be • 8 events/h in near array • 0.7 event/h in far array CERN INTC-P-307

  8. Beamtime request For ~1000 2n events in near array: 15 shifts • 15 shifts will also give: • For a 1 % 1n transition: • 46000 events in near array  ~10 times Hirayama’s statistics • 3800 events in far array with E resolution twice as good as Hirayama’s • b-n-g coincidences: • 1 % 1n transition, 2 % g-efficiency, 1 g-ray in 10Be • 900 events involving near array • 80 events involving far array CERN INTC-P-307

  9. Summary of beamtime request • 11Li, ~1000 ions/s: 15 shifts • Test & calibration beam: 49K (P1n = 86 %), ~500 ions/s • 2 shifts • Electronics & DAQ tuning: 1 shift • 49K-11Li beam changeover: 1 shift Total beamtime request: 19 shifts CERN INTC-P-307

  10. Collaboration LPCCaen : N.L. Achouri, F. Delaunay,J. Gibelin, F.M. Marqués, N.A. Orr, M. Parlog, M. Sénoville CIEMAT, Madrid : D. Cano-Ott, A. Garcia Rios, T. Martinez, M. Mendoza, C. Santos IEM, CSIC, Madrid : M.J.G. Borge, E. Nacher, A. Perea, O. Tengblad Chalmers University, Göteborg : A. Heinz, B. Jonson, T. Nilsson, G. Nyman IFIC, Valencia : A. Algora, C. Domingo, B. Rubio, J.L. Tain UPC, Barcelona : R. Baeturia, F. Calvino, B. Gomez University of Aarhus : H.O.U. Fynbo, K. Riisager IPN Orsay : M. Assié, N. de Séréville CEA/DAM/DIF, Bruyères-le-Châtel : B. Laurent, X. Ledoux CERN INTC-P-307

  11. CERN INTC-P-307

  12. 11Li decay scheme Hirayama et al., PLB 611 (2005) 239 CERN INTC-P-307

  13. Simulated TOF spectra Near array 46000 counts for a 1% 1-n line Far array 3800 counts for a 1% 1-n line M. Sénoville CERN INTC-P-307

  14. bnm + bmm + b2n Previous studies: 11Li b-2n with TONNERRE F.M. Marqués CERN INTC-P-307

  15. TOF response to monoenergetic neutrons Tests at CEA Bruyères-le-Châtel Liquid cell (CIEMAT) 20 cm diameter, 5 cm thick En=1.2 MeV, Threshold ~500 keV TONNERRE plastic bar 160 x 20 x 4 cm3 En=1 MeV, Threshold ~750 keV Preliminary S. Pietri, LPC, PhD thesis, 2003 23-28 Oct. 2011 CERN INTC-P-307

  16. A Cross-talk probability measurement Target 51° 86 cm CEA Bruyères-le-Châtel 23-28 Oct. 2011 Shield B 1.5 MeV neutrons Cross-talk Threshold ~ 500 keV NAB/NA ~ 10-4 Simulations: NAB/NA ~ 1.5 x 10-4 Preliminary M. Sénoville N.L. Achouri CERN INTC-P-307

  17. Neutron-g discrimination d + d →3He + n(4.3 MeV) Qslow / Qtot Neutrons g Threshold = 100 keVee  En~500 keV CERN INTC-P-307

More Related