Experimental Determination
of
Neutron Cross
Sections
of
Yttrium
by
Activation
Method
by
Barbara Geier
Supervisors:
Assoc
. Prof Dr. Wolfgang Sprengel
RNDr
.
Vladimír
Wagner
Csc
.
Ing.
Ondřej
Svoboda
Internship
at
the
Nuclear
Spectroscopy
Department
of
Nuclear
Physics
Internship
Organized
by
IAESTE Graz
6
weeks
Departement
of
Nuclear
Spectroscopy
in
Řež
Summary
1.
Irradiation of the yttrium foil by neutrons
to
produce
radioactive isotopes
2.
Analysing
of the gamma
emission
of the
daughter
nuclei
by a germanium
semiconductor
detector
3.
Determination
of the area of a gamma
peak
with
the program DEIMOS32
4.
Determination
of the
number
of
produced
nuclei
N
yield
out of the
peak
area
5.
Determination
of the cross section for the
single isotopes out of
N
yield
Introduction
Cross
section
:
probability
of
nuclear
reaction
Depends
on
the
neutron
energy
–
excitation
function
Example
:
Activation
Method
Reaction
of
a
neutron
beam
with
nuclei
to
produce
radioactive
isotopes
Daughter
nuclei
start
to
decay
by
gamma
emission
Semiconductor
detector
(
for
analysing
gamma
emission
)
◦
Compton
scattering
◦
Photoeffect
◦
Production
of
electron
-
positron
pairs
Experiment:
Production
of
the
Neutron Beam
E
Protons
: 35
MeV
Reaction
:
7
Li(
p,n
)
7
Be
E
Neutrons
: ~32
MeV
Yttrium sample was
irradiated
for
22 h
Quasi
-
monoenergetic
neutron
spectrum
for
a
7
Li(
p,n
)
7
Be
reaction
,
with
protons
at
an
energy
of
35
MeV
Experiment
Gamma
emission
of
yttrium
sample was
measured
in a
germanium
semiconductor
detector
for
different
distances
: 15, 23, 53, 70,
93, 173 mm
Evaluation
of
measured
gamma
spectrum
with
Deimos32
Determination
of
area
and
uncertainty
of
area
for
gamma
peaks
Corrections
N
yield
:
Number
of
produced
nuclei
in a
given
foil
Corrections
Weighted
average
:
Uncertainty
of
weighted
average
:
2
–
test
:
Possible
Reactions
Radioactive
potassium
isotope
40
K
Gamma
peak
at
an
energy
of
1460
keV
Analysed
for
reference
to
see
if
the
measurement
went
smoothly
The
ratio
between
the
area
of
the
gamma
peak
and
the
life
time
of
the
detector
should
be
constant
Number
of
produced
nuclei
N
yield
for
the
isotope
88
Y
Reaction
:
89
Y(n,2n)
88
Y
Half liveT
1/2
= 106.95 d
Comparison
between
the
different
measurements
of
the
23 mm
distance
between
sample
and
detector
for
the
gamma
line
at
an
energy
of
898.0
keV
898.0
keV
1836
keV
Number
of
produced
nuclei
N
yield
for
the
isotope
88
Y
The sample was
turned
to
the
other
side
after
each
measurement
.
There
is
a
slight
influence
on
the
results
between
side
(a) (
left
)
and
side
(b)
(
right
)
of
the
sample.
N
yield
for
the
isotope
88
Y
Comparison
between
the
different
measurements
at
different
distances
for
the
898.0
keV
gamma
line
:
N
yield
for
the
isotope
87
Y
Reaction
:
89
Y(n,3n)
87
Y
Half liveT
1/2
= 79.8 h
388.5
keV
484.8
keV
Comparison
between
the
different
measurements
of
23 mm
distance
between
sample
and
detector
for
the
gamma
line
at
an
energy
of
388.5
keV
N
yield
for
the
isotope
87
Y
Nearly
100%
decays
from
the
isomeric
state
87m
Y
to
87
Y
The
equation
for
the
change
of
radioactive
nuclei
after
irradiation
for
87
Y
is
:
Cross
section
Cross
section
for
88
Y
1
barn
= 10
-
28
m
2
Cross
section
for
the
89
Y(n,2n)
88
Y
reaction
:
(0.41
±
0.05)
barn
Cross
section
for
87m
Y
Cross
section
for
the
89
Y(n,3n)
87m
Y
reaction
:
(0.56
±
0.07)
barn
Cross
section
for
87
Y +
87m
Y
Cross
section
for
the
89
Y(n,3n)
87
Y +
89
Y(n,3n)
87m
Y
reaction
:
(0.77
±
0.08)
barn
Cross
section
for
87
Y
Cross
section
for
the
89
Y(n,3n)
87
Y
reaction
:
(0.21
±
0.03)
barn
Thank
you
for
your
attention
!
Questions
?
Calculation
of
the
peak
efficiency
correction
factor
for
the
distance
of
173 mm
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