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Coincidence method

Coincidence method. Detection of the 2 fission fragments High level of rejection of alphas and high energy reactions (>10 MeV) Very thin target backing and detectors. Parallel plate avalanche counters. Very thin detectors : Reduction of scattered neutrons No correction for self absorption

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Coincidence method

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  1. Coincidence method • Detection of the 2 fission fragments • High level of rejection of alphas and high energy reactions (>10 MeV) • Very thin target backing and detectors Parallel plate avalanche counters • Very thin detectors : • Reduction of scattered neutrons • No correction for self absorption • No background generated for capture measurements • Fast timing : 0.5 ns in accuracy • Localisation spatial dependence of the flux

  2. Coincidence method Targets on thin backing Thin detectors

  3. Measured isotopes • Minor actinide : 237Np • Thorium cycle : 233U, 234U, 232Th • Spallation target : 209Bi, natPb • Reference isotopes : 235U, 238U

  4. Flux from 235U and 238U (JENDL above 20 MeV)

  5. Flux from 235U and 238U

  6. 234U Previous data (IRMM report) Better energy resolution achieved at nTOF

  7. α activity fission 234U Limited targets 233U 209Bi natPb Extended targets

  8. Angular distribution Reference Side peaking Fit with P(cosθ)=Reference(cosθ)*(1+Bcos2θ)

  9. Dependence of anisotropy with energy 232Th 234U

  10. CONCLUSION • Fission cross section have been measured by detecting the 2 fission fragments in coincidence • This allows measurements up to 1 GeV • Measurements for 234U, 233U, 232Th, 237Np, and 209Bi, natPb • 235U and 238U used as reference materials • Need to correct for the angular acceptance

  11. 232Th case : comparison to others

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