From Notre Dame to National Labs: Cross sections at no charge!

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1 From Notre Dame to National Labs: Cross sections at no charge! NSL 80 th Anniversary Celebration A. Couture 8 April 2018 Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA

2 A Highly Personal History of Notre Dame Collaborations for Neutron-Induced Reactions But really neutrons? Prehistory: Neutron Measurements at Forschungszentrum Karlsruhe The Dark Ages: ntof at CERN Present History: Making Neutrons in the desert (LANSCE) Future History: Neutron Production at Notre Dame 4/3/18 2

3 Synthesis of the heavy elements relies on neutroninduced reactions Stellar H, He, C, O, Si Burning Stars, Novae, Supernovae s-process He Shell burning in AGB stars Core and shell burning in massive stars r-process Site unknown NS mergers? CCSN? p-process Abundances and Attribution from Anders & Grevasse, 1989 And Käppeler and Wisshak, 1989 Heavy element synthesis dominated by neutron capture NSL capabilities have focused on charged particle beams Knowledge of neutron capture reveals information about stellar evolution, neutron densities, and galactic history 4/3/18 3

4 Prehistory: Traveling to Forschungszentrum Karlsruhe to work with Lolita and Franz The Machine The Working Model 4/3/18 4

5 But we managed to make some measurements 600 Figure 3 Energy Spectra versus Emission Angle Neutron Yield per Energy Interval (Normalized for Solid Angle, arb units) o 5 o 10 o 15 o 20 o 25 o 30 o 35 o 40 o 45 o 50 o 55 o 60 o 65 o Energy (kev) Figure 5 Total Neutron Spectrum Neutrons from 7 Li(p,n) Integrated Neutron Spectrum (normalized, arb units) Monte Carlo Simulation of Spectrum seen by Target Experimental Spectrum form 7 Li(p,n) at E p =1936 kev Maxwellian fit, kt=26.0 kev Energy (kev) 4/3/18 5

6 And we managed to publish some results (much later ) This helped address the question as to the existence of a strong s-process It turns out that the heaviest s-process elements are made in low-metallicity AGB stars Ratzel et al. PRC 70 (2004). 4/3/18 6

7 The Dark Ages: Geneva and Time-of-Flight at CERN n_tof was a new facility at the time Used the 20 GeV proton beam from the PS at CERN Energy dependence of the neutron cross section was becoming more important Planned PhD work Swiss mountains, French wines, and all I have is a Leatherman 4/3/18 7

8 Best laid plans run awry, but more physics came out 4/3/18 8

9 Present History: Making Neutrons in the Desert at LANSCE Some seeds get planted early Capture Gamma Symposium Santa Fe, NM Sept /3/18 9

10 Present History: Making Neutrons in the Desert at LANSCE 4/3/18 10

11 LANSCE at Los Alamos opens the door to many new measurements N/cm**2/eV/sec 1.E+08 1.E+06 1.E+04 1.E+02 1.E+00 1.E-02 Lujan Center (DANCE, Fission) 20 m Flight Path 100 microamperes Down-scattered neutrons LANSCE Neutron sources LSDS (Fission) 1 microampere WNR (GEANIE, FIGARO, Fission) 10 m Flight Path 1.8 microamperes 1.E-04 Fusion neutrons 1.E-06 Fission neutrons 1.E-01 1.E+01 1.E+03 1.E+05 1.E+07 1.E+09 E n (ev) 800 MeV linear accelerator: H+ beams for isotope production and H- beams to drive two neutron beam facilities Lujan center: moderated spallation source, three flight paths devoted to nuclear science sub-thermal En 500 kev WNR: unmoderated spallation target, generating neutrons with 100 kev En 600 MeV 4/3/18 11

12 The Detector for Advanced Neutron Capture Experiments offers the benefits of both ntof and Karlsruhe Proton Bunch Collimator White Neutron Bunch DANCE Target 1 Water Moderator ~20 m E p = 800 MeV ν p =20 Hz 10 mev < E n < 500 kev φ n = n/s/cm 2 /decade 4/3/18 12

13 Once again, Students do the work. LSU Collaborations with universities are essential in maximizing the science output from LANSCE 13 student theses are in progress or have been completed with DANCE 4/3/18 13

14 Again, improved capabilities offer physics advances Weigand et al. PRC 92 (2015) High efficiency of DANCE coupled with intense neutron source at LANSCE allow measurement on small, radioactive samples 63 Ni is one such case Increases in the neutron capture cross section bypass 63 Cu production, which is a calibration for the weak s-process 63 Ni(n,γ) 4/3/18 14

15 Surprisingly, even stable isotopes offer challenges Past measurements suffered from poorly understood neutron backgrounds known cross sections have changed by factors of 2 This has a large impact on nucleosynthesis from iron through zirconium K. Macon, PhD Thesis (2016) These Zn results tend to indicate that the weak s- process may be more efficient than previously accounted This impacts both direct production and CCSN seeds 4/3/18 15

16 Future History: Neutron Production at Notre Dame? Despite their intensity and versatility, white neutron sources struggle in extreme capture:scatter measurements Activation offers alternate systematics Neutrons here? There are opportunities to pursue neutron production with the Notre Dame 5U pelletron This opens the possibility of new measurements on light isotopes (A<40) that are not otherwise possible Nuclear astrophysics Nuclear energy Advances in targetry allow high intensity and variable spectra 4/3/18 16

17 Conclusions The NSL has a rich history of collaboration with national lab capabilities I have illustrated this through neutron work, but this is only a small sampling of the 80 year history of Notre Dame s NSL While we are here today talking about history, the reason we are here is because of the future The NSL offers insightful science, critical education, and world-class facilities 4/3/18 17

18 Thank you! 4/3/18 18