Anti-neutrinos Spectra from Nuclear Reactors Alejandro Sonzogni National Nuclear Data Center ENDF/B VII.1 Decay Data Sub-Library Most recent … • Q values -- Audi 2011 mass update • ENSDF data (when complete) else Wallet Cards (2011) • Atomic data -- Evaluated Atomic Data Library (LLNL) – includes X-rays and Auger electrons • TAGS data • Electron conversion -- BrIcc • Theoretical calculations for neutron-rich nuclei using beta-strength functions (Moller) and CGM (Kawano) More details in Nuclear Data Sheets 112, 2887 (2011). Anti-neutrinos #2 - Alejandro Sonzogni ENDF VII.I Decay Data Sub Library A transformation of all relevant data into computer “friendly” files What’s in there… 3817 “materials” g.s. and isomers Wallet Cards Theory (CGM) ENSDF New ENSDF What’s it good for … • Decay heat • Antineutrino spectra • Delayed nu-bars (reactor operation) • Astrophysics ? • ???? Antineutrino Experiments Decay of fission fragments More than 800 nuclides produced in the fission of 235U Antineutrino Spectrum: S (E) =S Yi x Si(E) Yi: cumulative fission yields Si(E): individual spectrum - decay from Level i to level k Jipi Ik Z,N Nucleus Jkpk Ek Z+1,N-1Nucleus a: normalization, d: shape factor, F: Fermi function. The sum spectrum is obtained as: b: branching ratios All nuclear decay data from ENDF/B-VII.1 (December 2011) Anti-neutrinos #8 - Alejandro Sonzogni Example, 137Cs Anti-neutrinos #9 - Alejandro Sonzogni How to calculate anti-neutrino rates The nuclei in the core form a decay/processing network: - (n,g) Neglect processing as Fns << l and consider an equilibrium situation: (n,g) - Then the anti-neutrino rate per fission is: Used by Vogel et al, 1981, ENDF/B-V We’ll repeat the calculations using the fission yields from ENDF/B-VII.1 Anti-neutrinos #10 - Alejandro Sonzogni 235U at thermal energies Anti-neutrinos #11 - Alejandro Sonzogni Anti-neutrinos from reactors Flux Principal Contributors 235U, 238U, 239Pu, 241Pu Detection through inverse decay on proton Reaction threshold : ~1.8 MeV NNDC calculations on the Daya signal shape Anti-neutrinos #13 - Alejandro Sonzogni 235U(thermal n,f) main contributors to antineutrino spectra Nucleus % at 3 MeV Nucleus 54-Xe-137 3.519 55-Cs-139 Nucleus % at 5 MeV 41-Nb-100 4.872 37-Rb- 92 9.171 3.259 37-Rb- 92 3.694 39-Y - 96 7.475 39-Y - 94 3.120 39-Y - 96 3.545 41-Nb-100 6.592 40-Zr- 99 3.010 52-Te-135 2.994 55-Cs-142 4.585 41-Nb-100 2.916 39-Y - 94 2.897 55-Cs-140 4.153 41-Nb- 98 2.830 55-CS-140 2.780 52-Te-135 3.636 39-Y - 92 2.812 39-Y - 95 2.646 39-Y - 99 3.460 54-Xe-139 2.606 38-Sr- 95 3.435 41-Nb-101 2.654 % at 4 MeV With TAGS: 140Cs. 96Y seems is good shape. We’ll look at some of the other nuclides and if available, compare it to Rudstam data. Anti-neutrinos #14 - Alejandro Sonzogni One small nucleus, one big effect 92Rb a) 2000 ENSDF 51(18) % g.s. 92Rb b) Update with new data 95(5) % g.s. Effects of Valencia TAGS data Anti-neutrinos #16 - Alejandro Sonzogni Anti-neutrinos for Applied Purposes 235,238U and 239Pu produce a different signal, in shape, maxima and multiplicity Anti-neutrinos #17 - Alejandro Sonzogni 100Nb, CFY=5.89E-2, DCFY=16.883 % The GS to GS transition is not well determined. It could be up to 75%. BNL plans to submit a proposal to CARIBU. Would include other Nb nuclides Anti-neutrinos #18 - Alejandro Sonzogni 142Cs, CFY=2.71E-2, DCFY=2.803 % Anti-neutrinos #19 - Alejandro Sonzogni 92Rb, CFY=4.82E-2, DCFY=1.398 % Anti-neutrinos #20 - Alejandro Sonzogni 92Rb, comparison to Rudstam data Anti-neutrinos #21 - Alejandro Sonzogni 92Rb, comparison to Rudstam data Anti-neutrinos #22 - Alejandro Sonzogni Summary The next generation of experiments using anti-neutrinos from nuclear reactors have just published their first results. More to come in the next few years. There is a close link between basic nuclear structure research and the calculation of anti-neutrino spectra. Anti-neutrinos #23 - Alejandro Sonzogni Why nuclear reactors? Nearly 1,000 different fission fragments (materials) are produced in the fission of an actinide nuclide. Most of them are neutron rich, undergoing betaminus decay: Nucleus(Z,A) Nucleus(Z+1,A) + e- + anti-neutrino In an equilibrium situation, we obtain about 6 antineutrinos/second per fission, or ~1020 anti-neutrinos per reactor. Anti-neutrinos interact through weak interaction, very small cross sections, s ~ 5x10-19 barns Anti-neutrinos #24 - Alejandro Sonzogni Some history In - decay, the electron energy is a continuum distribution linking two nuclear levels (quantum). Another particle must be involved n p + e- + anti-neutrino (Fermi, 1934) First detection in 1956 by Cowan and Reines (LANL) using neutrinos from a nuclear reactor in SRS: anti-neutrino + p n +e+ The positron created two 511 keV gammas and the neutron was captured in Cd, releasing a gamma cascade Anti-neutrinos #25 - Alejandro Sonzogni More history In 1962, Leon Lederman and collaborators (BNL) discovered the muon neutrinos: Finally, in 1975 the Tau lepton and in 2000 the Tau neutrino were discovered. In the late 1960’s Ray Davies (BNL) measured the flux of neutrinos coming from the Sun, observing a deficit. Neutrino oscillations were formalized to explain this problem. Anti-neutrinos #26 - Alejandro Sonzogni 239Pu at thermal energies Anti-neutrinos #27 - Alejandro Sonzogni 238U at fast energies Anti-neutrinos #28 - Alejandro Sonzogni 252Cf spontaneous fission Anti-neutrinos #29 - Alejandro Sonzogni 235U - spectra ratios The published ILL data is binned at 250 keV. Could we get the 50 keV data? Anti-neutrinos #30 - Alejandro Sonzogni 239Pu - spectra ratios Anti-neutrinos #31 - Alejandro Sonzogni 238U - spectra ratios Anti-neutrinos #32 - Alejandro Sonzogni 252Cf - spectra ratios More theory needed, but better agreement with higher statistics, cleaner data Anti-neutrinos #33 - Alejandro Sonzogni 3 near neutrino detectors and 3 far neutrino detectors anti-neutrino + proton (water) positron + neutron Captured in Gd Two 511 keV gammas Anti-neutrinos #34 - Alejandro Sonzogni High energy gamma signal Anti-neutrino Signal Use the anti-neutrino capture on proton: Reaction has a 1.8 MeV threshold Anti-neutrinos #35 - Alejandro Sonzogni Daya Bay Results Anti-neutrinos #36 - Alejandro Sonzogni Some recent experiments Daya Bay Experiment in China, 6 nuclear power reactors. Ref: F.P. An et al, Physical Rev. Lett. 108, 171803 (2012) Anti-neutrinos #37 - Alejandro Sonzogni