Measurement of the fission mass yields of Am242 at the Lohengrin - PowerPoint PPT Presentation

Measurement of the fission mass yields of Am242 at the Lohengrin Spectrometer Charlotte AMOUROUX 1 A. Bidaud 2 , N. Capellan 2 , S. Chabod 2 , H. Faust 3 , G. Kessedjian 2 , U. Köster 3 , A. Letourneau 1 , F. Martin 2 , T. Materna 1 , S. Panebianco 1 , Ch. Sage 2 , O. Serot 4 1 CEA, DSM ‐ Saclay, France 2 LPSC Grenoble, CNRS/IN2P3, France 3 Institut Laue Langevin, France 4 CEA, DEN ‐ Cadarache, France

242 Am(Z=95) � 241 Am : 90% of the radiotoxicity of the nuclear waste (without plutonium) between 200 and 1000 years ‐ > Transmutation of 241 Am FP1 n+ 241 Am 242 Am FP2 � 242 Am : two long ‐ lived states Z=95 (odd charge) 5 ‐ 141 Y 48.6 keV 1 ‐ 16.02 H Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 2/12

PLAN • Experimental Set ‐ up & Analysis Method • Energy and Charge Distributions • Uncertainties Determination • Results Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 3/17

Experimental setup � High neutron flux Reactor � Target � Magnet: Selection A/q � Condenser: Selection: E/q � Detector: E Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 4/17

How do we measure the energy of the fragment ? � Δ E ‐ E Ionisation Chamber * A.Bail thesis E ‐ > E/q ‐ >A/q ‐ >A =>Y(A,E,q) Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 5/17

How to calculate the fission yields ? � Energy Distribution for a given q � Charge Distribution for a given E N(A,q,E) according to q and E Valid if no correlation between E and q In reality we have a correlation but its influence on Y(A) in less than 3% Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 6/17

Q ‐ Distribution � Example of Q ‐ distribution : two differents cases � Measured Charge is determined at the last crossed material (Nickel) Nickel Foil Nickel Foil Q~21 ‐ 22 Q~24 ‐ 25 Target Target Magnet Magnet A=105 A=136 Without nanosecond isomer With nanosecond isomer Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 7/17

E ‐ Distribution A=105 Q=21 � 0.6 MeV for determination of KE � 0.6 MeV for (q,E) correlation Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 8/17

Kinetic energy as a fonction of the fragment mass Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 9/17

E ‐ Distribution � Statistic errors: � Systematics errors: ‐ ~ 1% ‐ 1,5% low energy part ‐ 1,0% high energy part A=105 Q=21 ~0,8% of the Amplitude [a.u] total area _ ~1,5% of the maximal total area fluctuation of _ 1,0 % maximal between 2 E ‐ fluctuation of distribution 1,5 % between 2 E ‐ distribution Energy [MeV] 10/17 Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012

Determination of the systematic error This point is known twice For the same mass as a function of time: For all masses: σ ~ 3% Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 11/17

Sources of relative uncertainties and their respective contributions . Source Contribution Statistical ~1 % Extrapolation of the low part 1.5 % of the energy distribution Extrapolation of the high part 1% of the energy distribution Discrepancies between the two measurements of the 3% common point ? Normalisation Total of the systematic error 3.5% Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012

Fission Yields of Am ‐ 242 � Objectives of the experiment : ‐ Fission Mass Yields from Am ‐ 241(2n,f) ‐ Is there any difference between the fission yields of Am ‐ 242(n,f) and Am ‐ 242m(n,f) ? σ fission =6856(±656)barn* 242m Am Y (141 y) 8,6% Y=Y’ ? n+ 241 Am σ fission =2644(±281)barn* 91,4% 242 Y’ Am (16h) * G.Fioni et al,Nucl Phys.A693(2001) 546 O.Bringer,Ph.D Thesis,INP Grenoble, October 2007 Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 13/17

How do we proceed to observe a possible difference ? Shut ‐ down of the reactor B A A: Strong evolution of the properties B: vaccum problem of the target (large energy shift) Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 14/17

What is the maximum possible difference ? 242m Am n+ 241 Am 242 Am Hypothesis: X=0. General case : Γ ~1 for X’=0 (0,04 for all σ Y and 0,07 for σ Ym ) Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 15/17

Conclusions Normalisation Y 105 =6,5% � No difference between the yields: quantification on ‐ going. � If you assume they are equal … Only statistical error Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 16/17

Future � Isotopic fission yields * A.Bail Thesis * Meeting GEDEPEON Jan 2011 G.Kessedjian (F.Martin thesis (on ‐ going)) 235 U 239 Pu 233 U Thank you 241 Pu 242 Am for your attention … Charlotte AMOUROUX ‐ WONDER ‐ 25/09/2012 17/17

Back ‐ up 18

Comparaison with the GEF code(June 2012) 19

Number of fissions 20

Evolution of the kinetic energy as a function of time 21

FWHM of the energy distribution as a function of time 22