Isotopic distribution and dependency to fission product kinetic energy for 241 Pu thermal neutron-induced fission Collaboration : S. Julien-Laferrière 1 , A Chebboubi 1 , O. Serot 1 , D. Bernard 1 , O. Litaize 1 , N. Terranova 1 G. Kessedjian 2 , O. Meplan 2 , C. Sage 2 A. Blanc 3 , H. Faust 3 , U. Köster 3 , P. Mutti 3 , A. Letourneau 4 , T. Materna 4 , S. Panebianco 4 , M. Rapala 4 Sylvain Julien-Laferrière 1 CEA DEN, DER, SPRC, Cadarache, LEPh, Saint-Paul-lès- CEA, DEN, DER, SPRC, Cadarache, LEPh, Saint-Paul-lès-Durance Durance LPSC, Université Grenoble-Alpes, CNRS/IN2P3, Grenoble 2 LPSC, Université Grenoble-Alpes, CNRS/IN2P3, Grenoble 3 Institut Laue-Langevin, Grenoble 4 CEA, DRF, IRFU, Saclay, SPhN, Gif-sur-Yvette PhD supervisors: O. Serot - LEPh G. Kessedjian - LPSC 6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei | PAGE 1
THE LOHENGRIN MASS SPECTROMETER Experimental position 1 (straight unfocused beam) Target Experimental position 2 position (refocused beam) Reactor Reactor core wall Main magnet Light water pool Refocusing magnet Condenser 1 m 2 x 380 kV ILL reactor thermal neutron flux at target ~ 5 . 10 14 n/s/cm² Experimental positions Lohengrin mass spectrometer at the ILL, Grenoble Select an ion beam according to the ion mass A , Two experimental setups: kinetic energy E k and ionic charge q • Ionisation chamber : measure of N(A,E k ,q) • A / q through the magnetic field • Germanium detectors: measure of N(A,Z,E k ,q) • E k / q through the electric field (A 1 ,E 1 ,q 1 )≡ (A 2 ,E 2 ,q 2 ) ≡(A 3 ,E 3 ,q 3 ) 6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei | PAGE 2
GAMMA SPECTRA ANALYSIS – EXAMPLE FOR MASS 140 Count Rate for each γ -ray of 𝟔𝟓 𝟐𝟓𝟏 𝒀𝒇 Count (Arbitrary Unit) Mass 140 41 18 Ar 16000 𝒓 = 𝟑𝟑 140 53 I 𝑭 𝒍 = 𝟕𝟓 MeV 14000 140 55 Cs 12000 140 𝑌𝑓 54 10000 40 19 K 8000 140 140 𝑌𝑓 55 Cs 54 6000 4000 2000 Ionic Charge 0 140 𝑌𝑓 b - 400 600 800 1000 1200 1400 54 g -ray energy [keV] g 2 b - 140 𝐽 ⟹ 140 𝑌𝑓 ⟹ 140 𝐷𝑡 ⟹ 140 𝐶𝑏 53 54 55 56 g 1 𝑈 Τ 1 2 = 0.86 𝑡 𝑈 Τ 1 2 = 13.6 𝑡 140 𝐷𝑡 54 𝑈 Τ 1 2 = 63.7𝑡 6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei | PAGE 3 𝑈 Τ 1 2 = 12.8 𝑒
ISOTOPIC YIELD COMPUTATION PRINCIPLE Bateman equations 𝑂 𝐵, 𝑎 𝑗 , 𝑟 𝐹 𝑙 = 𝑂 𝑠𝑏𝑥 𝐵, 𝑎 𝑗 , 𝑟 𝐹 𝑙 σ 𝑟 𝑂 𝐵, 𝑎 𝑗 , 𝑟 𝐹 𝑙 𝜁 𝛿 ∙ 𝐽 𝛿 ∙ 𝐶𝑉(𝑟) − 𝐶𝑑𝑙(𝐵, 𝑎 𝑗 , 𝑟, 𝐹 𝑙 ) 𝑄 𝑎 𝑗 |𝐵 𝐹 𝑙 = σ 𝑘,𝑙 𝑂 𝐵, 𝑎 𝑘 , 𝑟 𝑙 𝐹 𝑙 With: 𝑂 𝐵, 𝑎 𝑗 , 𝑟 𝐹 𝑙 the isotopic count rate 𝑂 𝑠𝑏𝑥 𝐵, 𝑎 𝑗 , 𝑟 𝐹 𝑙 the γ pic integral Detector Efficiency BU – N(A=136) (Arbitrary Unit) (Arbitrary Unit) Energy (keV) Time (min) Example of the time evolution of the fissile material quantity. Detector efficiency – results from a MCNP computation Fit: 𝑔𝑗𝑠𝑡𝑢 𝑝𝑠𝑒𝑓𝑠 𝑞𝑝𝑚𝑧𝑜𝑝𝑛𝑗𝑏𝑚 + 𝑓𝑦𝑞𝑝𝑜𝑓𝑜𝑢𝑗𝑏𝑚 6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei | PAGE 4
ISOTOPIC RELATIVE YIELD RESULTS : P(Z|A=140|E k ) Isomeric Ratio for 138 Cs: 𝑱𝑺 = 𝒁(𝑫𝒕 𝒏 ) (𝒁(𝑫𝒕 𝒏 ) + 𝒁(𝑫𝒕 𝑯𝑻 )) Τ 2,5 JEFF-3.1.1 2 JENDL Our work 1,5 1 0,5 0 -0,5 -1 I Xe Cs Y(140,I) < 𝑎(A) > and 𝜏 𝑎 (A) can be extracted from a Correlation matrix Gaussian fit for the masses investigated: 137 to 141 Y(140,Xe) for the relative yields of mass 140 Y(140,Cs) 6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei | PAGE 5
CHARGE POLARIZATION <Z> From the relative isotopic yields: compute < 𝑎 > and 𝜏 𝑎 for the measured masses: 137 to 141 56 Compute the charge polarization for the pre-neutron mass 55 A’ corresponding to the post-neutron mass A Δ𝑎 𝐵′ = < 𝑎 𝐵 > − 𝑎 𝑉𝐷𝐸 (𝐵′) Δ Z 54 Δ Z Schillebeeckx w. 1 Fifrelin sawtooth 0,8 <Z> - our work ΔZ exp w. Fifrelin 0,6 53 <Z> - JEFF-3.1.1 sawtooth 0,4 ΔZ JEFF -3.1.1 w. <Z> - Fifrelin Fifrelin sawtooth 0,2 <Z> - GEF 52 0 135 140 145 -0,2 Post-neutron mass A -0,4 -0,6 -0,8 The pre-neutron mass A ’ corresponding to the -1 post-neutron mass A is estimated from the Fifrelin 95 105 115 125 135 145 155 or GEF average neutron multiplicity, so-called Pre-neutron mass A’ sawtooth 6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei | PAGE 6
ISOTOPIC DISTRIBUTION DEPENDENCY TO E K mass 139 P(Z = 53 | A = 139) 139 I Kinetic Energy (MeV) Kinetic Energy (MeV) Evolution over kinetic energy of the relative total count Evolution over kinetic energy of the relative total rate of I for mass 139 count rate of Ba over Xe for mass 139 Clear dependency to kinetic energy, constant hypothesis is rejected: p-values << 1 • Correlation matrices have also been computed • 6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei | PAGE 7
CONCLUSIONS AND PROSPECTS • Determine the relative isotopic yield for masses 137 to 141 along with the correlation matrix → picture of the analysis, mandatory in order to interpret and use the data • Absolute isotopic yield achievable with absolute mass yield measurement Y(A) : 𝑍 𝐵, 𝑎 = 𝑍 𝐵 ∙ 𝑄(𝑎|𝐵) → Y(A) obtained from IC measurements on the entire heavy peak: work in progress. • Isomeric ratios are interesting data to constrain the spin probability distribution at scission. This work can be done via the Fifrelin code. More isomeric ratio for the masses 130, 132 and 136 are still to be evaluated. • Kinetic energy dependency of the relative isotopic yield investigated → for the masses 92, 138 and 139 : a clear dependency is observed 6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei | PAGE 8
Collaboration : Thank you for your attention, S. Julien-Laferrière 1 , A Chebboubi 1 , O. Serot 1 , 3 minutes for questions! D. Bernard 1 , O. Litaize 1 , N. Terranova 1 G. Kessedjian 2 , O. Meplan 2 , C. Sage 2 A. Blanc 3 , H. Faust 3 , U. Köster 3 , P. Mutti 3 , A. Letourneau 4 , T. Materna 4 , S. Panebianco 4 , M. Rapala 4 1 CEA DEN, DER, SPRC, Cadarache, LEPh, Saint-Paul-lès- Durance 2 LPSC, Université Grenoble-Alpes, CNRS/IN2P3, Grenoble 3 Institut Laue-Langevin, Grenoble 4 CEA, DRF, IRFU, Saclay, SPhN, Gif-sur-Yvette | PAGE 9 Commissariat à l’énergie atomique et aux énergies alternatives Direction DEN 6th Workshop on Nuclear Fission and Centre de Cadarache | 13108 Saint Paul lez Durance Cedex Département DER Spectroscopy of Neutron-Rich Nuclei Service SPRC Etablissement public à caractère industriel et commercial | RCS Paris B 775 685 019
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