determination of experimental cross-sections by activation method pierre-jean viellenave tutor: dr....
TRANSCRIPT
Determination of experimental cross-sections by activation
method
Pierre-Jean Viellenave Tutor: Dr. Vladimir Wagner
Nuclear Physics Institute, Academy of Sciences of Czech Republic
Contents
Introduction
Spectrum analysis with DEIMOS32
Cross-sections calculation
Statistical analysis (incertainty calculation)
Results
Introduction
My work consists:
In analysing gamma spectrums from experiment with DEIMOS32…
Experiment = measurement of radioactive sample (activated by activation method in a cyclotron) with different configurations
…To get experimental cross-sections
Spectrum analysis with
DEIMOS32Gamma lines peak analysis with the software DEIMOS 32
Spectrum analysis with
DEIMOS32We’re able to plan possible reactions and isotopes produced
Spectrum analysis with
DEIMOS32Comparison between the result tables from DEIMOS 32 analysis and the internet data base (decay data search) on gamma lines to identify the isotopes
Spectrum analysis with
DEIMOS324 isotopes found from (n,2n) to (n,4n) reactions and 1 isotope (198Au) found from (n,gamma) reaction.
Cross-sections calculation
Nyield calculation:
)()(
)(
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
Cross-sections calculation
Detector efficiency (given):
Nyield approximation:
173815,0
18474,3
3295,18
6493,36
d
c
b
a
)()(
)(
11)(
0
irrreal tirr
t
t
live
real
P
pyield e
t
e
e
t
t
EI
SN
Cross-sections calculation
Nyield calculation:
)()(
)(
11)(
0
irrreal tirr
t
t
live
real
P
pyield e
t
e
e
t
t
EI
SN
Sp: peak areaIγ: gamma line intensity (in %)Treal & Tlive: datas from exp.λ: decay constant
Tirr: irradiation timeT0: beam end – start of measurement
2/1
)2ln(
T
Cross-sections calculation
Cross-section calculation:
Nn: neutrons number (depends on experiment) mfoil: foil massS: foil size (in cm2)
A: mass number (197 for Au)NA: Avogadro’s number (6,022.1023 {mol-1})
Afoiln
yield
NmN
ASN
..
..
Statistical analysis
N yield_average calculation for each isotope => to increase the precision:
n
i i
n
i i
i
averageyield
N
N
N
N
12
12
_ 1 ideimosi NaerrN .
Aerr: incertainty of peak area (data from DEIMOS)
So =>
n
i i
averageyield
N
N
12
_1
1
Statistical analysis
N yield_average calculation for each isotope => to increase the precision:
n
i i
n
i i
i
averageyield
N
N
N
N
12
12
_ 1 ideimosi NaerrN .
Aerr: incertainty of peak area (data from DEIMOS)
So =>
n
i i
averageyield
N
N
12
_1
1
Statistical analysis
Finally:
)1(1
2
2_
2
n
N
NN
X
n
i i
averageyieldi
averageyieldNX _2 yincertaint1
2_
2 .yincertaint1 XNX averageyield
With:
Results
0 2 4 6 8 10 12 1417800
18000
18200
18400
18600
18800
332,983 keV
Series1Series5Series7Series9
Measurement
Num
ber
of
nucle
i
197Au (n, 2n) 196Au
0 2 4 6 8 10 12 1418200
18400
18600
18800
19000
19200
19400
355,684 keV
Series1Series5Series7Series9
Measurement
Num
ber
of
nucle
i (1
0^
6)
Results197Au (n, 4n) 194Au
0 2 4 6 8 10 12 1412450
12500
12550
12600
12650
12700
12750
12800
194Au (328 keV)Series5Series7Series9
Measurement
Nu
mb
er o
f ra
dio
acti
ve
nu
clei
0 2 4 6 8 10 12 1411300
11400
11500
11600
11700
11800
11900
12000
12100
194 Au (293 keV
Series5
Series7
Series9
Measurement
nu
mb
er o
f ra
dio
nu
clid
e [1
0^6]
Results197Au (n, 2n) 196m2Au
0 2 4 6 8 10 12 141000
1100
1200
1300
1400
1500
1600
147,81 keV
Series1Series5Series7Series9
Measurement
Num
ber o
f nuc
lei (
10^6
)
0 2 4 6 8 10 12 14800900
100011001200130014001500
188,27 keV
Series1Series5Series7Series9
Measurement
Num
ber
of
nucle
i
Results
Comments:
Fluctuations are purely systematical
Nyield-average isn’t depending on the configuration
But the difference of Nyield-average (calculated for each gamma line and isotope) is bigger than the uncertainty of weighted average. It comes from the systematic uncertainty of efficiency determination.
Thank you for your attention !!!