Cross-sections of Neutron Threshold Reactions studied by activation method
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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)
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Plan
Introduction Uppsala experiment Spectrum analysis Cross section measurements Incertainty calculation Correction calculation
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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.
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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
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Uppsala experiment (2/2)
Threshold reactions on Au, Al, Bi, In, Ta, Ni, Zn, Y, I
Al Au Bi Co In Ta
Experimental disposition
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Spectrum analysis(1/5)
Gamma spectrum peak analysis using DEIMOS32 software
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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
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Spectrum analysis(3/5) Possible reactions and isotopes producted by these reaction enable to know what we are looking for.
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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
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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
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Cross-section measurement(1/4)
Determination of Nyield
)()(
)(
111
)()( 0
irrreal tirr
t
t
foillive
real
areaP
aabspyield e
tee
mtt
CCoiEIBECS
N
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
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Cross-section measurement(2/4)
First approximation of Nyield
)()(
)(
11)(
0
irrreal tirr
t
t
live
real
P
pyield e
tee
tt
EIS
N
))).(ln()).(ln())².(ln()ln(.exp()( 43 EeEdEcEbaEP
• Detector efficiency determination
080924654,0127329,2834704,20083642,8919554,144
edcba
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Cross-section measurement(3/4)
)()(
)(
11)(
0
irrreal tirr
t
t
live
real
P
pyield e
tee
tt
EIS
N
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
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Cross-section measurement(4/4)
Afoiln
yield
NmNASN....
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
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Incertainty determination(1/4)
iNN 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
NN
N
12
12
_ 1
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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 :
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Incertainty determination(3/4)
Next step :
)1(1
2
2_
2
nnN
NN
X
n
i i
iaverageyield
If:
2_
2 .yincertaint1 XNX averageyieldElse :
averageyieldNX _2 yincertaint1
..\ANALYSIS\Bi analysis - 4.xlsx
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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
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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.
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Results (2/7) Bi206 : very small incertainty
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Results (3/7) Bi205 :
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Results (4/7) Bi204 :
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Results (5/7) Bi203 :
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Results (6/7) Bi202 :
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Results (7/7) Bi201 :
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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 eDC .1.
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Conclusion
Now the first result for the cross section are calculated.
We compared experimental datas to theorical model.
Most importants correction have been added