page 1 cross-sections of neutron threshold reactions studied by activation method anne larédo...

Page 1

Cross-sections of Neutron Threshold Reactions studied

by activation methodAnne Larédo

Supervisor: Dr. Vladimír Wagner

Nuclear Physics Institute, Academy of Sciences of Czech RepublicÉcole des Mines de Nantes (France)

Page 2

Plan

Introduction

Uppsala experiment

Spectrum analysis

Cross section measurements

Incertainty calculation

Correction calculation

Page 3

Introduction

Threshold reactions on Au, Al, Bi, In, Ta, Ni, Zn, Y, I

Up to now almost no experimental cross-section data for high energy neutron reaction (E>20MeV)

The Uppsala experiment enable new cross-section measurements for high energy neutrons (62 to 93 MeV).

My work consists in analysing the gamma spectrum resulting from the experiment to obtain experimental cross-sections.

Page 4

Uppsala experiment (1/2)

Took place in February 2010 in Uppsala, Sweden

Neutron source : • quasi-monoenergetic• based on reaction 7Li(p,n)7Be• energy range 11-175 MeV

Proton beam energies : 62, 70, 80, and 93 MeV

Page 5

Uppsala experiment (2/2)

Threshold reactions on Au, Al, Bi, In, Ta, Ni, Zn, Y, I

Al Au Bi Co In Ta

Experimental disposition

Page 6

Spectrum analysis(1/5)

Gamma spectrum peak analysis using DEIMOS32 software

Page 7

Spectrum analysis(2/5)

Gamma spectrum for different neutron energy and different time

MeV File Treal [s]62 S6RBiP21 3787

S6RBiP22 7224S6RBiP23 37749

65 S62BiP11 4207S62BiP12 37288S62BiP13 85038

70 S70BiP21 3869S70BiP22 7214S70BiP23 24597

80 S80BiP21 3654S80BiP22 7246S80BiP23 21830

93 S93BiP21 3410S93BiP22 23916

Page 8

Spectrum analysis(3/5)

Possible reactions and isotopes producted by these reaction enable to know what we are looking for.

Page 9

Spectrum analysis(4/5)

Determination of present isotopes using the result tables from DEIMOS32 compare to data base (decay data search) on gamma radiations.

..\ANALYSIS\Bi analysis - 4.xlsx

energy609.341661.331663.686670.542791.292802.949820.181824.982847.027880.860897.180899.119910.444911.707912.831918.113983.846

Page 10

Spectrum analysis(5/5)

10 isotopes found from (n,2n) to (n,9n) reactions

Isotope1 201Bi2 202Bi3 203Bi4 204Bi5 205Bi6 206Bi7 207Bi8 208Bi9 201Pb

10 203Pb

Page 11

Cross-section measurement(1/4)

Determination of Nyield

)()(

)(

11

1

)(

)( 0

irrreal tirr

t

t

foillive

real

areaP

aabspyield e

t

e

e

mt

t

CCoiEI

BECSN

Peak area Self-absorption correction

Beam correction

Dead time correction Decay during cooling and measurement

γline intensity

Detector efficiency

Correction for coincidences

Square-emitter correction

Weight normalization

Decay during irradiation

Page 12

Cross-section measurement(2/4)

First approximation of Nyield

)()(

)(

11)(

0

irrreal tirr

t

t

live

real

P

pyield e

t

e

e

t

t

EI

SN

))).(ln()).(ln())².(ln()ln(.exp()( 43 EeEdEcEbaEP

• Detector efficiency determination

080924654,0

127329,2

834704,20

083642,89

19554,144

e

d

c

b

a

Page 13

Cross-section measurement(3/4)

)()(

)(

11)(

0

irrreal tirr

t

t

live

real

P

pyield e

t

e

e

t

t

EI

SN

Peak area Sp : given by DEIMOS for each peak

γline intensity Iγ : from decay data search

treal : data from experiment

tlive : data from experiment

Decay constant λ :

T1/2 : data from libreries as decay data search

t0 = Beam end – start of measurement

tirr : time of irradiation

2/1

)2ln(

T

Page 14

Cross-section measurement(4/4)

Afoiln

yield

NmN

ASN

..

..

Nyield : previously calculate

Nn : number of neutrons in peak (per cm²)For experiment condition and energies

MeV Nn

65 2,9820E+0970 5,3165E+0980 6,3691E+0993 7,6936E+09

Foil mass mfoil (given data from experiment)

Foil size S : (2,5)² cm² = 6,25 cm²

Relative mass A : 208,98 [g.mol-1]

Avogadro’s number NA = 6,022.1023

Page 15

Incertainty determination(1/4)

i

NN i

averageyield _

First approximation :

Nyield_average : mean of Nyield for a same neutron energy

Ni : Nyield for a neutron energy

Precise analysis :

n

i i

n

i i

i

averageyield

N

N

N

N

12

12

_ 1

Page 16

Incertainty determination(2/4)

With :

ideimosi NaerrN .

aerrdeimos : incertainty on the peak area from the software Deimos32

n

i i

averageyield

N

N

12

_1

1

Then :

Page 17

Incertainty determination(3/4)

Next step :

)1(1

2

2_

2

nn

N

NN

X

n

i i

iaverageyield

If:

2_

2 .yincertaint1 XNX averageyieldElse :

averageyieldNX _2 yincertaint1

..\ANALYSIS\Bi analysis - 4.xlsx

Page 18

Incertainty determination(4/4)

Last step :

 combinaison of the relative uncertainty (from the Deimos data) with the uncertainty from intensity, neutron spectra, detector uncertainty :

ΔNyield_average : Deimos uncertainty 10% : Beam intensity uncertainty 10% : neutron spectra uncertainty 3 % : detector efficiency uncertainty

Finally:

2222_. etectoreutroneamaverageield DNBN

..\Results - Cross-section graphs\XS Bi vysledne srovnani.xls

Page 19

Results (1/7)

Bi207 : The results for this isotope are for

now out range. Current work : using

spectrum from after and before irradiation

to soustract the gammas which are not from

the irradiation we are interrested in but

from previous one.

Page 20

Results (2/7)

Bi206 : very small incertainty

Page 21

Results (3/7)

Bi205 :

Page 22

Results (4/7)

Bi204 :

Page 23

Results (5/7)

Bi203 :

Page 24

Results (6/7)

Bi202 :

Page 25

Results (7/7)

Bi201 :

Page 26

Correction calculation

COI : correction for coincidences between severals gamma rays of an isotope.

..\COI\COI calculation.xlsx

Ba : Beam correction

..\beamcorr-Upps2010.xls

CS-A : Self absorption correction

..\Self-absorption\Self-absorption correction

.xlsx

Background correction..\ANALYSIS\Bi analysis - 4.xlsx

Dabs e

DC

.1

.

Page 27

Conclusion

Now the first result for the cross section are calculated.

We compared experimental datas to theorical model.

Most importants correction have been added