Isotopic distribution and dependency to fission product kinetic - - PowerPoint PPT Presentation

6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei | PAGE 1

Isotopic distribution and dependency to fission product kinetic energy for 241Pu thermal neutron-induced fission Sylvain Julien-Laferrière

CEA, DEN, DER, SPRC, Cadarache, LEPh, Saint-Paul-lès-Durance LPSC, Université Grenoble-Alpes, CNRS/IN2P3, Grenoble

PhD supervisors:

• O. Serot - LEPh
• G. Kessedjian - LPSC

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

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

THE LOHENGRIN MASS SPECTROMETER

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Lohengrin mass spectrometer at the ILL, Grenoble Select an ion beam according to the ion mass A, kinetic energy Ek and ionic charge q

• A/q through the magnetic field
• Ek/q through the electric field

Two experimental setups:

• Ionisation chamber : measure of N(A,Ek,q)
• Germanium detectors: measure of N(A,Z,Ek,q)

Experimental position 1 (straight unfocused beam) Experimental position 2 (refocused beam) Refocusing magnet Condenser 2 x 380 kV Main magnet 1 m Reactor wall Target position Reactor core Light water pool ILL reactor thermal neutron flux at target ~ 5 . 1014 n/s/cm²

Experimental positions (A1,E1,q1)≡ (A2,E2,q2) ≡(A3,E3,q3)

Ionic Charge Count Rate for each γ-ray of 𝟔𝟓

𝟐𝟓𝟏𝒀𝒇

(Arbitrary Unit)

GAMMA SPECTRA ANALYSIS – EXAMPLE FOR MASS 140

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54 140𝑌𝑓

b- g1 g2

400 600 800 1000 1200 1400 2000 4000 6000 8000 10000 12000 14000 16000

40 19K 41 18Ar

140 55 Cs 140 55 Cs 140 53 I

g-ray energy [keV]

Mass 140 𝒓 = 𝟑𝟑 𝑭𝒍 = 𝟕𝟓 MeV

53 140𝐽 ⟹ 54 140𝑌𝑓 ⟹ 55 140𝐷𝑡 ⟹ 56 140𝐶𝑏

𝑈 Τ

1 2 = 12.8 𝑒

𝑈 Τ

1 2 = 13.6 𝑡

𝑈 Τ

1 2 = 63.7𝑡

𝑈 Τ

1 2 = 0.86 𝑡

54 140𝐷𝑡

b-

Count

54 140𝑌𝑓 54 140𝑌𝑓

Time (min)

ISOTOPIC YIELD COMPUTATION PRINCIPLE

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Example of the time evolution of the fissile material quantity. Fit: 𝑔𝑗𝑠𝑡𝑢 𝑝𝑠𝑒𝑓𝑠 𝑞𝑝𝑚𝑧𝑜𝑝𝑛𝑗𝑏𝑚 + 𝑓𝑦𝑞𝑝𝑜𝑓𝑜𝑢𝑗𝑏𝑚

𝑂 𝐵, 𝑎𝑗, 𝑟 𝐹𝑙 = 𝑂𝑠𝑏𝑥 𝐵, 𝑎𝑗, 𝑟 𝐹𝑙 𝜁𝛿 ∙ 𝐽𝛿 ∙ 𝐶𝑉(𝑟) − 𝐶𝑑𝑙(𝐵, 𝑎𝑗, 𝑟, 𝐹𝑙)

Detector efficiency – results from a MCNP computation Energy (keV) Detector Efficiency (Arbitrary Unit)

𝑄 𝑎𝑗|𝐵 𝐹𝑙 = σ𝑟 𝑂 𝐵, 𝑎𝑗, 𝑟 𝐹𝑙 σ𝑘,𝑙 𝑂 𝐵, 𝑎

𝑘, 𝑟𝑙 𝐹𝑙

Bateman equations BU – N(A=136) (Arbitrary Unit) With: 𝑂 𝐵, 𝑎𝑗, 𝑟 𝐹𝑙 the isotopic count rate 𝑂𝑠𝑏𝑥 𝐵, 𝑎𝑗, 𝑟 𝐹𝑙 the γ pic integral

ISOTOPIC RELATIVE YIELD RESULTS

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Isomeric Ratio for 138Cs: 𝑱𝑺 = Τ 𝒁(𝑫𝒕𝒏) (𝒁(𝑫𝒕𝒏) + 𝒁(𝑫𝒕𝑯𝑻))

I Xe Cs

< 𝑎(A) > and 𝜏𝑎(A) can be extracted from a Gaussian fit for the masses investigated: 137 to 141 Correlation matrix for the relative yields of mass 140

Y(140,I) Y(140,Cs) Y(140,Xe)

: P(Z|A=140|Ek)

• 1
• 0,5

0,5 1 1,5 2 2,5 JEFF-3.1.1 JENDL Our work

CHARGE POLARIZATION

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From the relative isotopic yields: compute < 𝑎 > and 𝜏𝑎 for the measured masses: 137 to 141 Compute the charge polarization for the pre-neutron mass A’ corresponding to the post-neutron mass A Δ𝑎 𝐵′ = < 𝑎 𝐵 > − 𝑎𝑉𝐷𝐸(𝐵′)

52 53 54 55 56 135 140 145 <Z> - our work <Z> - JEFF-3.1.1 <Z> - Fifrelin <Z> - GEF

Post-neutron mass A Pre-neutron mass A’ The pre-neutron mass A’ corresponding to the post-neutron mass A is estimated from the Fifrelin

• r GEF average neutron multiplicity, so-called

sawtooth ΔZ <Z>

• 1
• 0,8
• 0,6
• 0,4
• 0,2

0,2 0,4 0,6 0,8 1 95 105 115 125 135 145 155 ΔZ Schillebeeckx w. Fifrelin sawtooth ΔZ exp w. Fifrelin sawtooth ΔZ JEFF-3.1.1 w. Fifrelin sawtooth

ISOTOPIC DISTRIBUTION DEPENDENCY TO EK

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Evolution over kinetic energy of the relative total count rate of I for mass 139 Evolution over kinetic energy of the relative total 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

Kinetic Energy (MeV) Kinetic Energy (MeV)

P(Z = 53 | A = 139) 139I mass 139

CONCLUSIONS AND PROSPECTS

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• 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

Direction DEN Département DER Service SPRC Commissariat à l’énergie atomique et aux énergies alternatives Centre de Cadarache | 13108 Saint Paul lez Durance Cedex

Etablissement public à caractère industriel et commercial | RCS Paris B 775 685 019

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

1 CEA DEN, DER, SPRC, Cadarache, LEPh, Saint-Paul-lès-

Durance

2

LPSC, Université Grenoble-Alpes, CNRS/IN2P3, Grenoble

3 Institut Laue-Langevin, Grenoble 4CEA, DRF, IRFU, Saclay, SPhN, Gif-sur-Yvette

Thank you for your attention, 3 minutes for questions!

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