Department of Physics

Beta-¬‐delayed neutron spectroscopy with trapped fission products

Date • Time

Tuesday, August 29, 2017 - 14:00


30 BB 03


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Open to: Staff

Speaker: Agnieszka Czeszumska (Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, USA, Department of Nuclear Engineering, University of California, Berkeley, California 94720, USA)

For decays  where  β−  decay  populates  excitation  energies  above  the  neutron  separation  energy,  the  daughter  nucleus  may  de-¬‐excite  by  emitting  a  neutron,  a  process  referred  to  as  β-¬‐delayed neutron  emission  (βn).  

This  decay  mode  influences  abundances  calculated  in  r-¬‐process  nucleosynthesis  models,  affects  nuclear  reactor  safety  analysis  calculations,  and  can  illuminate  aspects  of  nuclear  structure.  However,  existing  data  for  neutron-¬‐rich  nuclei  are  often  incomplete  or  discrepant.  A  newly  developed  recoil-¬‐ion  detection  technique  allows  for  high-¬‐precision  βn  branching  ratio  and  neutron  energy  measurements,  without  the  difficulties  associated  with  direct  neutron  detection.  In  this  approach,  ions  are  trapped  using  a  Beta-¬‐Paul  trap  surrounded  by  an  array  of  detectors.  Upon  decay,  recoiling  daughter  nuclei  and  emitted  particles  emerge  from  the  center  of  the  trap  with  minimal  scattering.  The  neutron  energy  can  be  determined  from  the  time-¬‐of-¬‐flight,  and  hence  momentum,  of  the  recoiling  ions.  In  this  talk,  I  will  summarize  the  latest  results  from  the  experiment  conducted  at  CARIBU.  

This  material  is  based  upon  work  supported  by  the  Department  of  Energy,  National  Nuclear  Security  Administration,  under  Award  Numbers  DE-¬‐NA0000979  (NSSC),  

DE-¬‐AC52-¬‐07NA27344  (LLNL);  Office  of  Nuclear  Physics  Contract  DE-¬‐AC02-¬‐

06CH11357  (ANL),  and  grants  DE-¬‐FG02-¬‐94ER40834  (University  of  Maryland),  DE-¬‐FG02-¬‐98ER41086  (Northwestern  University);  NSERC,  Canada,  under  Application  No.  216974;  and  the  Department  of  Homeland  Security.  A.  Czeszumska  acknowledges  support  from  the  Lawrence  Scholar  Program  at  LLNL.

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