1. Steven W. Yates Research at UKAL: Lessons Learned and New Adventures www.pa.uky.edu/accelerator/

2. E* E** gs   Excited Nucleus Incident Neutron Target Nucleus Inelastic Neutron Scattering inelastically scattered neutron (n,n'  ) reaction E** gs E* Cooled Nucleus

3. n  Neutron Production 3 H(p,n) 3 He Q = -1 MeV 2 H(d,n) 3 He Q = 3 MeV Neutron Energies (Accelerator Voltage: 1.5 – 7.0 MV) 3 H(p,n) 0.5 < E n < 6 MeV 2 H(d,n) 4.5 < E n < 10 MeV 2 H or 3 H gas Pulsed p or d beam from VdG accelerator Target

4. Beam  γ (n,n'  ) singles

5. (n,n'  ) Singles Measurements scattering sample gas cell HPGe BGO Beam

6. (n,n'  ) Singles Measurements scattering sample gas cell Beam Gas Handling System

7. 94 Zr ( n,n  ) Compton suppressed TOF Gating

9. 94 Zr ( n,n  ) Angular Distribution W(  ) = 1 + a 2 P 2 (cos  ) + a 4 P 4 (cos  ) Comparison with statistical model calculations (CINDY) → multipole mixing ratio (  and spins

10. Detector Doppler-Shift Attenuation Method v E(  ) = E  (1 + v/c cos  ) The nucleus is recoiling into a viscous medium. v  v(t) = F(t)v max E(  ) = E  (1 + F(  ) v/c cos  )  

11. Level Lifetimes: Doppler-Shift Attenuation Method (DSAM) T. Belgya, G. Molnár, and S.W. Yates, Nucl. Phys. A607, 43 (1996). E.E. Peters et al., Phys. Rev. C 88, 024317 (2013). Scattered neutron causes the nucleus to recoil. Emitted γ rays experience a Doppler shift. Level lifetimes in the femtosecond region can be determined. γ γ 0°180° τ = 7.6(9) fs τ = 76(7) fs

12. DSAM Not Doppler- shifted Completely Doppler- shifted Calculated curve F(  ) exp  τ = 76(7) fs K.B. Winterbon, Nucl. Phys. A246, 293 (1975). T. Belgya, G. Molnár, and S. W. Yates, Nucl. Phys. A607, 43 (1996).

13. Paraffin-Filled Shielding Lithium Carbonate Loaded Paraffin Beam  Gas Cell Scattering Sample HPGe Kentucky Gamma-ray Spectrometer KEGS

14. gas cell Beam

15. “Monoenergetic” Neutron Production  Scattering Sample 3 H(p,n) 3 He n Neutron energy at center of the gas cell 1.75 MeV3.19 MeV Straggling in 3.3-μm Mo entrance foil (keV) 3231 dE/dgas, 3-cm tritium cell at 1 atm (keV) 8155 dE/d , outgoing neutron energy deviation over the sample (keV) 2340 Diagnostic MCNPX calculations of neutron production in gas cell Gas cell with Mo foil window

16. Inelastic Neutron Scattering with Accelerator-Produced Neutrons  No Coulomb barrier/variable neutron energies  Excellent energy resolution (  rays detected)  Nonselective, but limited by angular momentum  Lifetimes by Doppler-shift attenuation method (DSAM)  T. Belgya, G. Molnár, and S.W. Yates, Nucl. Phys. A607, 43 (1996)  E.E. Peters et al., Phys. Rev. C 88, 024317 (2013).  Gamma-gamma coincidence measurements  C.A. McGrath et al., Nucl. Instrum. Meth. A421, 458 (1999)  E. Elhami et al., Phys. Rev. C 78, 064303 (2008)  Limited to stable nuclei  Large amounts of enriched isotopes required

17.  Fast neutron physics  Nuclear shell structure and shape transitions  Nuclear level lifetime determinations with the Doppler-shift attenuation method  Nuclear structure relevant to double-β decay  Precision fast neutron reaction cross sections  Corporate and homeland security applications  Neutron detector development (with collaborators) www.pa.uky.edu/accelerator/ Current and Future Research Directions at UKAL

18.  Fast neutron physics  Nuclear shell structure and shape transitions  Nuclear level lifetime determinations with the Doppler-shift attenuation method  Nuclear structure relevant to double-β decay  Precision fast neutron reaction cross sections  Corporate and homeland security applications  Neutron detector development (with collaborators) www.pa.uky.edu/accelerator/ Current and Future Research Directions at UKAL

19. 2νββ 0 νββ? 52 53 54 55 56 57 58 59 Z BE -- -- 136 Te 136 I 136 Xe 136 Cs -- 136 Ba EC 136 Ce 136 La 136 Pr Is the neutrino its own antiparticle? What is the mass of the neutrino? EC

20. M. Auger et al., PRL 109, 032505 (2012) Pictures from R. Neilson TIPP 2011 and http://www-project.slac.stanford.edu/exo/ EXO-200: 200 kg of Xe (l) 80.6% enriched in 136 Xe (remaining 19.4% is 134 Xe) Q-value: 2457.83 ± 0.37 keV 1000 2000 E(keV) Counts

21. EXO Resolution 228 Th 2615 keV FWHM ≈ 100 keV M. Auger et al., PRL 109, 032505 (2012)

22. Neutron Backgrounds from Radioactive Decay Fig. 1. Neutron energy spectrum from U and Th traces in rock as calculated with modified SOURCES. Contributions from 60 ppb U (filled squares and lower curve), 300 ppb Th (open circles and middle curve) and the sum of the two (filled circles and upper curve) are shown. M.J. Carson et al., Astroparticle Phys. 21, 667 (2004).

23. Fig. 7. Energy spectra of muon-induced neutrons at various boundaries: (a) filled circles–– neutrons at the salt/cavern boundary, open circles––neutrons after the lead shielding; (b) filled circles––neutrons at the salt/cavern boundary (the same as in (a)), open circles–– neutrons after the lead and hydrocarbon shielding. Neutron Backgrounds from Cosmic-ray Muons M.J. Carson et al., Astroparticle Phys. 21, 667 (2004).

24. UKAL Experiments Inelastic neutron scattering  Monoenergetic neutrons via 3 H(p,n) 3 He  Allows determination of : Level scheme Transition multipolarities Multipole mixing ratios Level lifetimes Transition probabilities Solid XeF 2 samples of 130 Xe, 132 Xe, 134 Xe, 136 Xe  Highly enriched, solid targets not used previously XeF 2 in Teflon vial

25. New Level: 2485 keV 134 Xe 1614 847 2485 0.200.480.32

26. New Level: 2485 keV 87116382485

27. 2485-keV Transition bg σ Measurement Q-value: 2458 keV

28. Other New Levels 847 2502 2440 1593 1655

29.  Fast neutron physics  Nuclear shell structure and shape transitions  Nuclear level lifetime determinations with the Doppler-shift attenuation method  Nuclear structure relevant to double-β decay  Precision fast neutron reaction cross sections  Corporate and homeland security applications  Neutron detector development (with collaborators) www.pa.uky.edu/accelerator/ Current and Future Research Directions at UKAL

30. S. F. Hicks University of Dallas, Irving, TX J. R. Vanhoy US Naval Academy, Annapolis, MD M. T. McEllistrem and S. W. Yates University of Kentucky, Lexington, KY Applied Science with Monoenergetic Pulsed Neutrons from the University of Kentucky Accelerator Laboratory

31.  Critical need for high-precision and accurate elastic and inelastic neutron scattering data on materials important for fission reactor technology  Critical need for trained individuals (NEUP initiative) Part of the Advanced Fuel Cycle Initiative (AFCI) to develop safe, clean, and affordable energy sources http://www.gen-4.org/Technology/evolution.htm Goals of Gen IV: i)Safer ii)Sustainable iii)Economical iv)Physically Secure

32. “A Technology Roadmap for Generation IV Nuclear Energy Systems,” Generation IV International Forum, December 2002. One of the Six Generation IV Nuclear Energy Systems Inelastic Neutron Scattering Energy Loss Mechanism Fe * Neutron elastic and inelastic scattering cross sections are needed from structural materials such as Fe and coolants such as Na.

33. Forward monitor Long counter Neutron detector Gas cell Beam line Copper shielding (n,n') TOF > 2-meter deep scattering pit

34. Typical adjustment of wedge with cell and sample Tungsten wedge Na sample Gas cell Beam line Neutron detector 3H(p,n) Q=  0.76 MeV 2H(d,n) Q= 3.3 MeV 3H(d,n) Q= 17.6 MeV

35. Flight paths to about 4 m can be used for neutron scattering. Angles between 30 and 145 degrees are accessible with the Na and Fe samples. Neutrons are detected by a deuterated benzene liquid scintillation detector (1  x5.5  ). Pulse Shape Discrimination Neutron Detection: Main Understanding background generation in TOF spectra

36. 23 Na Inelastic cross sections to a given final state can be measured directly via (n,n’) or derived from  -ray excitation functions. Angular distributions of (n,n’) provide the best information on the reaction mechanism. Gamma-ray measurements provide the best information on the partition of reaction strength. Inelastic Cross Sections --Two Techniques (n,n') (n,n' γ )

38. EVALUATIONS EXPERIMENTAL DATA

39.  Fast neutron physics  Nuclear shell structure and shape transitions  Nuclear level lifetime determinations with the Doppler-shift attenuation method  Nuclear structure relevant to double-β decay  Precision fast neutron reaction cross sections  Corporate and homeland security applications  Neutron detector development (with collaborators) www.pa.uky.edu/accelerator/ Current and Future Research Directions at UKAL

40. Glodo-IEEETransNuclSci.60.864.2012 http://www.rmdinc.com/ SCINTILLATOR DEVELOPMENT Multi-radiation detectors – CLYC: Cs 2 LiYCl 6 – CNYC: Cs 2 NaYCl 6 – CLLC: Cs 2 LiLaCl 6 – CLLB: Cs 2 LiLaBr 6 Measured detector response for E n = 0.5 - 22 MeV ~7 scintillators in 36 hours.

41. http://atguelph.uoguelph.ca/2011/11/guelph-physicist-leads-project-at-triumf-lab/ http://www.physics.uoguelph.ca/Nucweb/tigress.html DETECTOR DESIGN & CHARACTERIZATION Neutron Detectors – Efficiency(E n ) – Pulse Shape Discrimination – Amplitude Distribution e n n D  DEuterated SCintillator Array for Neutron Tagging @ TRIUMF scintillator fluid C 6 D 6 Different recoiling ions excite the atomic/molecular structure differently, and exhibit different characteristic decay times.

42. http://atguelph.uoguelph.ca/2011/11/guelph-physicist-leads-project-at-triumf-lab/ https://www.facebook.com/photo.php?fbid=645033412191460&set=pb.114964 088531731.-2207520000.1373380138.&type=3&theater http://www.physics.uoguelph.ca/Nucweb/tigress.html DESCANT neutron detector array TIGRESS  -ray detector array

43. Our Colleagues University of Dallas U.S. Naval Academy University of Guelph University of Wisconsin at Lacrosse Georgia Institute of Technology University of Notre Dame Radiation Monitoring Devices University of Cologne HI  S at TUNL Yale University Technical University Darmstadt University of the West of Scotland University of the Western Cape (South Africa) iThemba Labs TRIUMF ANU