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Preliminary Results of (n,f) Measurements at CERN n_TOF with FIC0 and FIC1 Detectors

Preliminary Results of (n,f) Measurements at CERN n_TOF with FIC0 and FIC1 Detectors. P.Cennini 1 , A.Goverdovski 2 , W.Furman 3 , V.Ketlerov 2,1 , V.Konovalov 3,1 , V.Vlachoudis 1 1 CERN, 2 IPPE, 3 JINR and n_TOF Collaboration. With a lot of help of:. A.Doroshenko 2 S.Girod 1

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Preliminary Results of (n,f) Measurements at CERN n_TOF with FIC0 and FIC1 Detectors

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  1. Preliminary Results of (n,f) Measurements at CERN n_TOF with FIC0 and FIC1 Detectors P.Cennini1, A.Goverdovski2, W.Furman3, V.Ketlerov2,1, V.Konovalov3,1, V.Vlachoudis1 1CERN, 2IPPE, 3JINR and n_TOF Collaboration

  2. With a lot of help of: A.Doroshenko2 S.Girod1 D.Kolokolov2 V.Mitrofanov2 B.Samylin2 M.Sedysheva3 1CERN, 2IPPE, 3JINR

  3. Motivation n_TOF Collaboration scientific program Nuclear data for ADS: fission cross-section measurements Fundamental nuclear physics: study of vibrational fission resonances

  4. Fast Ionization Chamber Design • Gas – Ar 90%+CF4 10% • Pressure – 600 mbar • Distance – 5 mm • HV – 300 V • 17 targets in the beam • “noise” electrode • 2 targets out of the beam

  5. FIC1 Photo

  6. FIC1 and FIC0 Photo

  7. Inside FIC1 Photo 1

  8. Inside FIC1 Photo 2

  9. FIC0 Main Electronics

  10. Basic Equations For single channel i of given isotope X TDC data Flash ADC data If there is some impurity nucleus Y

  11. Extraction of cross-section Flash ADC data Kiis obtained from MC simulation is calculated with accounting for dead time and from an analysis of pulse-height histogram is really measured (see below for more detail) From reference 235U channel one can extract F(E(t)) So it is possible to extract fission cross-section from counting rate of each (X,i) channel

  12. Isotopic Dilution Method Definitions: m5 , m6 – masses of 235U and 236U targets  - content of 235U in 236U target 5, 6 – fission cross-sections 5, 6– registration efficiencies of FF (6 is valid for FF from 235U admixture to 236U target!) n5, n6 – count rates

  13. Isotopic Dilution Method • Master equation • R = n6 / n5 = (6/5)(m66 +  m65)/ (m55) • Around resolved resonances En=8 – 20 eV 5 is very high • (up to 710 b) while 6 = 0, then • R0 =  (m66)/( m55 ) • For other energies where 5 << 6 and due to  << 1 • R(En) = R0 (6 / 5 )/  • There are no 6,5 or m6 , m5 ratios. We have only  and count rates. •  = 0.00047 ± 0.00002 – measured by mass-spectrograph

  14. Isotopic Dilution Method U-235, 0.047%

  15. List of Targets ----FIC0---- 235U - 47mg (3 targets) 238U - 110mg (3 targets) 232Th - 80mg (2 targets) 236U - 20mg (2 targets) 237Np - 10mg (1 target) 234U - 34mg (6 targets) ----FIC1---- 235U - 30mg (1 targets) 238U - 90mg (2 targets) 241Am - 2mg (4 targets) 243Am - 10mg (4 targets) 245Cm - 2mg (2 target) 233U - 20mg (2 targets)

  16. Targets Backing - 100 microns aluminum foil Substance is painted on both sides Spot diameter is 80mm Thickness from 5mkg/cm2 to 450mkg/cm2 Number of painted layers 100-200 Uniformity is 5% - 10%

  17. Painting Technique

  18. Target analysis For mass, impurities, uniformity with Ionization chamber with Frisch grid For low radioactive targets 232Th, 238U, 235U, 237Np, 236U Si detector For high radioactive targets 233U, 245Cm, 243Am, 241Am

  19. Ionization Chamber

  20. Alpha Spectrum of 235U

  21. Alpha Spectrum of 232Th

  22. Si Detector S = 1 cm2

  23. Alpha Spectrum of 241Am

  24. Alpha Spectrum of 243Am (2.6%)

  25. Alpha Spectrum of 245Cm

  26. Alpha Spectrum of 237Np

  27. 235U Contamination Even impurity of 10e-5 – 10e-4 which is impossible to determine by a-analysis is essential for neutron induced fission experiments

  28. 235U Contamination of 236U and 238U 1e-5 of 235U 238U 236U 4e-4 of 235U 235U

  29. Noise Filtering 238U

  30. Noise Filtering 237Np

  31. Noise Filtering (Low Energy)

  32. Noise Filtering 237Np (res)

  33. Neural Network Filtering

  34. Pulse Height Histogram 236U

  35. T-E Calibration from Capture

  36. 235U Resonances

  37. T-E Calibration from Fission

  38. Energy Resolution 234U

  39. Preliminary Results Below 1MeV 234U, 236U 237Np, 245Cm

  40. 237Np Resonances 1

  41. 237Np Resonances 2

  42. 237Np Resonances 3

  43. 237Np Resonances 4 present ENDF pointwise

  44. 237Np Resonances 5

  45. 245Cm with a-background

  46. 245Cm

  47. 245Cm Resonances 1

  48. 245Cm Resonances 2

  49. 245Cm Resonances 3

  50. 234U Resonances 1

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