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

Charlotte AMOUROUX1

Measurement of the fission mass yields of Am242 at the Lohengrin Spectrometer

• A. Bidaud2, N. Capellan2, S. Chabod2,
• H. Faust3, G. Kessedjian2, U. Köster3,
• A. Letourneau1, F. Martin2, T. Materna1,
• S. Panebianco1, Ch. Sage2, O. Serot4

1CEA, DSM‐Saclay, France 2LPSC Grenoble, CNRS/IN2P3, France 3Institut Laue Langevin, France 4CEA, DEN‐Cadarache, France

242Am(Z=95)

241Am : 90% of the radiotoxicity of the nuclear waste (without plutonium) between 200 and 1000 years ‐> Transmutation of 241Am

n+ 241 Am

242 Am

FP1 FP2 242Am : two long‐lived states Z=95 (odd charge)

2/12

Charlotte AMOUROUX‐WONDER ‐25/09/2012

141 Y 16.02 H

1‐ 5‐ 48.6 keV

PLAN

• Experimental Set‐up & Analysis Method
• Energy and Charge Distributions
• Uncertainties Determination
• Results

Charlotte AMOUROUX‐WONDER ‐25/09/2012

3/17

High neutron flux Reactor Target Magnet: Selection A/q Condenser: Selection: E/q Detector: E

Experimental setup

4/17

Charlotte AMOUROUX‐WONDER ‐25/09/2012

How do we measure the energy of the fragment ?

E‐> E/q‐>A/q‐>A

* A.Bail thesis

=>Y(A,E,q)

Charlotte AMOUROUX‐WONDER ‐25/09/2012

ΔE‐E Ionisation Chamber

5/17

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

How to calculate the fission yields ?

In reality we have a correlation but its influence on Y(A) in less than 3%

6/17

Charlotte AMOUROUX‐WONDER ‐25/09/2012

Example of Q‐distribution : two differents cases Measured Charge is determined at the last crossed material (Nickel)

With nanosecond isomer Without nanosecond isomer

Q‐Distribution

A=105 A=136

Target Target Nickel Foil Nickel Foil

Magnet Magnet

Q~21‐22 Q~24‐25

7/17

Charlotte AMOUROUX‐WONDER ‐25/09/2012

E‐Distribution

A=105 Q=21

8/17

Charlotte AMOUROUX‐WONDER ‐25/09/2012

0.6 MeV for determination of KE 0.6 MeV for (q,E) correlation

Kinetic energy as a fonction of the fragment mass

9/17

Charlotte AMOUROUX‐WONDER ‐25/09/2012

E‐Distribution

Statistic errors: ‐ ~ 1% Amplitude [a.u] Energy [MeV]

~1,5% of the total area _ maximal fluctuation of 1,5 % between 2 E‐ distribution ~0,8% of the total area _ maximal fluctuation of 1,0 % between 2 E‐ distribution

A=105 Q=21 Systematics errors: ‐ 1,5% low energy part ‐ 1,0% high energy part

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%

11/17

Charlotte AMOUROUX‐WONDER ‐25/09/2012

Source Contribution Statistical ~1 % Extrapolation of the low part

• f the energy distribution

1.5 % Extrapolation of the high part

• f the energy distribution

1% Discrepancies between the two measurements of the common point 3% Normalisation ? Total of the systematic error 3.5%

Sources of relative uncertainties and their respective contributions.

Charlotte AMOUROUX‐WONDER ‐25/09/2012

n+ 241 Am

242m Am 242

Am

Y Y’

σfission=2644(±281)barn*

91,4% 8,6% Y=Y’ ? 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) ?

Fission Yields of Am‐242

(141 y) (16h)

σfission=6856(±656)barn*

* G.Fioni et al,Nucl Phys.A693(2001) 546 O.Bringer,Ph.D Thesis,INP Grenoble, October 2007

13/17

Charlotte AMOUROUX‐WONDER ‐25/09/2012

How do we proceed to observe a possible difference ?

B: vaccum problem A: Strong evolution of the properties

• f the target (large energy shift)

A

Shut‐down of the reactor

B

14/17

Charlotte AMOUROUX‐WONDER ‐25/09/2012

Hypothesis: X=0. for X’=0 (0,04 for all σY and 0,07 for σYm ) General case : Γ~1

What is the maximum possible difference ?

n+ 241 Am

242m Am 242

Am

15/17

Charlotte AMOUROUX‐WONDER ‐25/09/2012

Conclusions

No difference between the yields: quantification on‐going. If you assume they are equal … Normalisation Y105=6,5% Only statistical error

16/17

Charlotte AMOUROUX‐WONDER ‐25/09/2012

17/17

Charlotte AMOUROUX‐WONDER ‐25/09/2012

Isotopic fission yields

Future

239Pu 233U * A.Bail Thesis * Meeting GEDEPEON Jan 2011 G.Kessedjian (F.Martin thesis (on‐going)) 241Pu

…

242Am

Thank you for your attention

235U

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