Formation of mixed X,n-radiation field at an electron accelerator
For conducting photonuclear programs with the use of a high-intensity photon source the latter is ordinary obtained by transformation of an electron beam into X-ray radiation. Such a process is performed using an intermediate target-converter maid from a high-Z material. The (γ,n) reactions take pla...
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irk-123456789-1957872023-12-07T12:14:45Z Formation of mixed X,n-radiation field at an electron accelerator Zakharchenko, A.A. Uvarov, V.L. Malets, Eu.B. Linear charged-particle accelerators For conducting photonuclear programs with the use of a high-intensity photon source the latter is ordinary obtained by transformation of an electron beam into X-ray radiation. Such a process is performed using an intermediate target-converter maid from a high-Z material. The (γ,n) reactions take place in the converter under the action of high-energy bremsstrahlung photons. As a result, a quasi-isotropic neutron flux escapes the converter jointly with the photon beam directed forward. The parameters of the both types of radiation, as well as the ratio of their intensities play the important role depending on a program under way. In work, the spatial radiant characteristics of the mixed X,n-radiation generated with the electron beam in the converter located together with an isotopic target in the middle of a neutron moderator in the electron energy range 40…95 MeV and various size of the moderator are studied by computer simulations with the use of a GEANT4 transport code. Для виконання фотоядерних програм з використанням джерела фотонів великої інтенсивності останнє зазвичай одержують шляхом трансформації пучка електронів у гальмівне випромінення. Цей процес здійснюють за допомогою проміжної мішені-конвертера, який виготовляють з матеріалу з великим Z. Під дією високоенергетичних гальмівних фотонів у конвертері відбуваються (γ,n)-реакції. Як результат, з нього, крім спрямованого уперед потоку фотонів, виходить також квазіізоторопний потік нейтронів. Параметри обох видів випромінення, так само як і співвідношення їх інтенсивностей, грають важливу роль залежно від програми, що виконується. У роботі методом комп’ютерного моделювання з використанням транспортного коду GEANT4 досліджено просторово-енергетичні характеристики мішаного X,n-випромінення, яке генерується електронним пучком у конвертері з танталу, що розміщений разом з ізотопною мішенню у середині модератора нейтронів, при енергії електронів у діапазоні 40…95 МеВ і різному розмірі модератора. 2022 Article Formation of mixed X,n-radiation field at an electron accelerator / A.A. Zakharchenko, V.L. Uvarov, Eu.B. Malets // Problems of Atomic Science and Technology. — 2022. — № 5. — С. 68-72. — Бібліогр.: 10 назв. — англ. 1562-6016 PACS: 87.56.bd; 41.50.+h;81.40.Wx; 87.53Bn DOI: https://doi.org/10.46813/2022-141-068 http://dspace.nbuv.gov.ua/handle/123456789/195787 en Problems of Atomic Science and Technology Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Linear charged-particle accelerators Linear charged-particle accelerators Zakharchenko, A.A. Uvarov, V.L. Malets, Eu.B. Formation of mixed X,n-radiation field at an electron accelerator Problems of Atomic Science and Technology |
| description |
For conducting photonuclear programs with the use of a high-intensity photon source the latter is ordinary obtained by transformation of an electron beam into X-ray radiation. Such a process is performed using an intermediate target-converter maid from a high-Z material. The (γ,n) reactions take place in the converter under the action of high-energy bremsstrahlung photons. As a result, a quasi-isotropic neutron flux escapes the converter jointly with the photon beam directed forward. The parameters of the both types of radiation, as well as the ratio of their intensities play the important role depending on a program under way. In work, the spatial radiant characteristics of the mixed X,n-radiation generated with the electron beam in the converter located together with an isotopic target in the middle of a neutron moderator in the electron energy range 40…95 MeV and various size of the moderator are studied by computer simulations with the use of a GEANT4 transport code. |
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Zakharchenko, A.A. Uvarov, V.L. Malets, Eu.B. |
| author_facet |
Zakharchenko, A.A. Uvarov, V.L. Malets, Eu.B. |
| author_sort |
Zakharchenko, A.A. |
| title |
Formation of mixed X,n-radiation field at an electron accelerator |
| title_short |
Formation of mixed X,n-radiation field at an electron accelerator |
| title_full |
Formation of mixed X,n-radiation field at an electron accelerator |
| title_fullStr |
Formation of mixed X,n-radiation field at an electron accelerator |
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Formation of mixed X,n-radiation field at an electron accelerator |
| title_sort |
formation of mixed x,n-radiation field at an electron accelerator |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2022 |
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Linear charged-particle accelerators |
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http://dspace.nbuv.gov.ua/handle/123456789/195787 |
| citation_txt |
Formation of mixed X,n-radiation field at an electron accelerator / A.A. Zakharchenko, V.L. Uvarov, Eu.B. Malets // Problems of Atomic Science and Technology. — 2022. — № 5. — С. 68-72. — Бібліогр.: 10 назв. — англ. |
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2025-07-16T23:58:50Z |
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| fulltext |
68 ISSN 1562-6016. Problems of Atomic Science and Technology. 2022. №5(141)
https://doi.org/10.46813/2022-141-068
FORMATION OF MIXED X,n-RADIATION FIELD
AT AN ELECTRON ACCELERATOR
A.A. Zakharchenko
1
, V.L. Uvarov
1
, Eu.B. Malets
2
1
National Science Center “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine;
2
H.S. Skovoroda Kharkiv National Pedagogical University, Kharkiv, Ukraine
E-mail: uvarov@kipt.kharkov.ua
For conducting photonuclear programs with the use of a high-intensity photon source the latter is ordinary ob-
tained by transformation of an electron beam into X-ray radiation. Such a process is performed using an intermedi-
ate target-converter maid from a high-Z material. The (,n) reactions take place in the converter under the action of
high-energy bremsstrahlung photons. As a result, a quasi-isotropic neutron flux escapes the converter jointly with
the photon beam directed forward. The parameters of the both types of radiation, as well as the ratio of their intensi-
ties play the important role depending on a program under way. In work, the spatial radiant characteristics of the
mixed X,n-radiation generated with the electron beam in the converter located together with an isotopic target in the
middle of a neutron moderator in the electron energy range 40…95 MeV and various size of the moderator are stud-
ied by computer simulations with the use of a GEANT4 transport code.
PACS: 87.56.bd; 41.50.+h;81.40.Wx; 87.53Bn
INTRODUCTION
Pulse neuron sources on the basis of electron accel-
erator provide the possibility to measure the cross section
of the neutron-capture reactions at neutron energy in the
range from thermal one until tens MeV using a time-of-
flight technique. The most widespread way to obtain such
radiation field is the neutron generation by (,sn) reaction
in a converter of the bremsstrahlung (X-ray) radiation
exposed to an electron beam. A specially developed
moderator is commonly applied to increase the yield of
the low-energy neutrons (see e.g. [1]).
A promise area of application of the mixed
Х,n-radiation with the thermalized spectrum of the neu-
tron component is photonuclear technology of isotope
production, in particular, of medical assignment [2]. In
work, the possibility to control the radiation flux density
and neutron spectrum at an isotopic target by moderator
size and electron beam energy is studied by computer
simulation on the basis of a GEANT4 code [3].
1. SIMULATION CONDITIONS
1.1. In the research of processes of the neutron gen-
eration and moderation, a device outlined in Fig. 1 was
considered as the basis. It comprises a branch tube from
aluminum 1, which axes coincides with the axes of the
electron beam. At the tube centre, the bremsstrahlung
converter K and isotopic target M are positioned. The
converter consists of four tantalum plates each by 1mm
in thickness separated with the same gaps for cooling.
For measuring the isotope yield under joint acting of
X-rays and thermalized neutrons, the tube with the con-
verter and target were located in the middle of the mod-
erator. Detail description of the latter is given in the
work. A channel for placement of neutron activation
detectors was preliminary maid in the moderator body.
1.2. At the beginning of the research, the data on the
cross section of the
181
Ta(,sn)
181-s
Ta reactions that pro-
vide the photoneutron generation in the Ta converter
were checked. Their excitation functions calculated by a
TALYS-1.95 package [4] and used in simulations were
compared with those obtained experimentally (Fig. 2).
Fig. 1. Target station with the neutron moderator
10 15 20 25 30 35 40 45
0
100
200
300
400
500
C
ro
ss
-s
ec
ti
o
n
,
m
b
E , MeV
talys
Ta181(g,n)Ta180
Ta181(g,2n)Ta179
Ta181(g,3n)Ta178
Total neutron production
Experiment
Ta-180, [5]
Ta-180, [6]
Ta-179, [7]
Ta-179, [8]
Fig. 2. Cross section of the Ta
181
(,sn)Ta
181-s
reactions
(TALYS + experiment)
For comparison the cross sections of the neutron
photogeneration in tantalum computed by TALYS and
GEANT4 codes respectively are represented in Fig. 3. It
is seen that in the area of giant dipole resonance (GDR)
both presentations of the excitation function are in good
agreement. For calculation of the neutron yield from the
converter into the front and back half-space relative to
the electron beam, and also energy distribution of the
neutrons, the circuit given in Fig. 4, was used.
mailto:uvarov@kipt.kharkov.ua
ISSN 1562-6016. Problems of Atomic Science and Technology. 2022. №5(141) 69
10 20 30 40 50 60 70 80 90 100
0
100
200
300
400
500
600
C
ro
ss
-s
ec
ti
o
n
,
m
b
E , MeV
Ta-181(g,n)
talys
geant4 LEND
Fig. 3. Cross section of the Ta
181
(,sn)Ta
181-s
reaction
(TALYS + GEANT4 LEND)
Fig. 4. Geometry of calculation of the photoneutron
yield from the converter
2. RESULTS
2.1. In Figs. 5, 6 the results of modeling of the neu-
tron reduced yield, spectrum and output angle from the
converter at an electron beam energy of 40 MeV are
given.
0 1 2 3 4 5 6 7 8 9 10
10-7
10-6
10-5
10-4
n
i /
N
b
ea
m
,
n
eu
tr
o
n
s
p
er
e
le
ct
ro
n
E , MeV
plusZ
minus0Z
sphere40
Fig. 5. Energy distribution of neutrons:
plusZ – towards Z axis (the plain A(+));
minus0Z – against Z axis (the plain B(–));
sphere40 – the total yield into sphere 4
0 10 20 30 40 50 60 70
0,00
0,01
0,02
0,03
n
i /
S
n
i
Q, degree
plus0Z
minus0Z
Fig. 6. Neutron distribution vs output angle
from the converter
The results of simulation of the photoneutron spectra
in the electron energy range that provides a LU-40m
accelerator of NSC KIPT [9] are presented in Fig. 7 and
Table 1. For speedup, the calculations were carried out
with step 0.1 MeV. It is evident that the major part of
neutrons has the energy less than 2.5 MeV.
0 5 10 15 20 25
10-7
10-6
10-5
10-4
n
i /
N
e
,
n
eu
tr
o
n
s
p
er
e
le
ct
ro
n
E , MeV
40 MeV
60 MeV
95 MeV
Fig. 7. Photoneutron spectra
at various electron beam energy
Table 1
Asymmetry of the neutron escape from the converter
when the simulation geometry given in Fig. 4
E, MeV nA(+)/nB(–)*
40 1.170
60 1.167
95 1.168
*nA(+)/nB(–) – is the asymmetry coefficient (the ra-
tio of the neutron yield into the A plain to their yield
into the B plain).
2.2. For the study of the moderator size impact on
the spectrum and flux of the photoneutrons at the target,
the devices were used, which layout is given in Fig. 8.
In particular a moderator measuring 20×20, 30×30, and
40×40 cm was considered. The results of simulations
are presented in Tabs. 2–6 and in Figs. 9–11. The ob-
tained characteristics of the X-ray flux on the target as
well as the data on the relative yield of the photons and
photoneutrons are displayed in Figs. 12–14.
70 ISSN 1562-6016. Problems of Atomic Science and Technology. 2022. №5(141)
Table 2
Characteristics of the total neutron yield from the converter at various electron beam energy
Ee, MeV Simulated tracks Neutron yield
Neutron per
electron (n/e)
nS/e/cm
2
* nS/100 A
40 1.67E+08 250588 1.50E-03 1.49E-05 9.27E+09
60 1.64E+08 309814 1.89E-03 1.87E-05 1.17E+10
95 1.58E+08 346973 2.20E-03 2.17E-05 1.36E+10
*Mean density of the neutron flux on a sphere by 2.835 cm in radius, nS – reduced total neutron yield
a
b
Fig. 8. Geometry of simulation of the neutron flux in region of the isotopic target:
а – without moderator (1 – accelerator’s exit window; 2 – tantalum converter with the virtual spherical neutron
counter 3); b – with moderator (4 – paraffin-graphite moderator; 5 – channel for the neutron activation detectors
(the virtual spherical neutron counter is placed in the depth of the channel))
Table 3
Characteristics of the neutron flux in the target region (without converter)
Ee, MeV Nbeam n converter n target target/conv ntarg/e
ntarg/e/cm
2
40 1.14×10
8
164301 17923 0.109 1.57×10
–4
1.68×10
–6
Table 4
Characteristics of the neutron flux in the target region (with converter)
Ee, MeV Nbeam n converter n target target/conv ntarg/e
ntarg/e/cm
2
20×20 сm
40 1.31×10
8
189928 41403 0.218 3.16×10
–4
3.38×10
–6
30×30 сm
40 2.3×10
8
334008 76540 0.229 3.33×10
–4
3.56×10
–6
40×40 сm
40 1.27×10
8
184742 42682 0.231 3.36×10
–4
3.6×10
–6
Table 5
Characteristics of the neutron flux in the activation detectors region
Ee, MeV Nbeam n converter n detect detect/conv ndet/e
ndet/e/cm
2
ndet/s/cm
2
for
100 A
20×20 сm
40 1.31×10
8
189928 1955 0.01 1.49×10
–5
2.11×10
–6
1.32×10
9
30×30 сm
40 2.3×10
8
334008 4118 0.012 1.79×10
–5
2.54×10
–6
1.58×10
9
40×40 сm
40 1.27×10
8
184742 2341 0.013 1.84×10
–5
2.61×10
–6
1.63×10
9
ISSN 1562-6016. Problems of Atomic Science and Technology. 2022. №5(141) 71
Table 6
Yield of neutrons with energy less than 100 keV (without moderator and at its different size)
Ee, MeV Nbeam n (En < 0.1 MeV) n0.1/Nbeam
No moderator
40 1.14×10
8
1308 8.72×10
–6
20×20 сm
40 1.31×10
8
19692 1.50×10
–4
30×30 сm
40 2.3×10
8
38259 1.66×10
–4
40×40 сm
40 1.27×10
8
21720 1.71×10
–4
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0
10-7
10-6
10-5
10-4
n
/e
,
n
eu
tr
o
n
p
er
e
le
ct
ro
n
E , MeV
Ebeam = 40 MeV
no
moderator
Fig. 9. Photoneutron spectrum in the target region
depending on presence of the 30×30 cm moderator
(40 MeV beam energy)
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0
10-7
10-6
10-5
10-4
n
/e
,
n
eu
tr
o
n
p
er
e
le
ct
ro
n
En , MeV
Ebeam = 40 MeV
20ґ20 cm
30ґ30 cm
40ґ40 cm
Fig. 10. Photoneutron spectra in the target region
depending on moderator size
(40 MeV beam energy)
10-3 10-2 10-1
10-7
10-6
N
th
er
m
al
/
N
be
am
En , meV
30ґ30 cm
40 MeV
60 MeV
95 MeV
Fig. 11. Spectra of the thermalized neutrons
at the target region
10 20 30 40 50 60 70 80 90
0.0
2.0x10-2
4.0x10-2
6.0x10-2
8.0x10-2
1.0x10-1
1.2x10-1
N
/
N
b
ea
m
/
D
E
,
1
/M
eV
E , MeV
30ґ30 cm
40 MeV
60 MeV
95 MeV
Fig. 12. Spectrum of the bremsstrahlung photons
on the target
35 40 45 50 55 60 65 70 75 80 85 90 95 100
10-5
10-4
10-3
10-2
10-1
100
30ґ30 cm
Total neutrons
Thermal neutrons
Bremsstrahlung photons
P
ar
ti
cl
es
p
er
e
le
ct
ro
n
Ee , MeV
Fig. 13. Comparative yield of photoneutrons
and bremsstrahlung photons
35 40 45 50 55 60 65 70 75 80 85 90 95 100
1.0x10-4
2.0x10-4
3.0x10-4
4.0x10-4
5.0x10-4
6.0x10-4
30ґ30 cm
Total neutrons
Thermal neutrons
N
eu
tr
o
n
p
er
p
h
o
to
n
Ee , MeV
Fig. 14. Photoneutron yield per one
above-threshold photon (Eth = 8.02 MeV)
Еn , MeV
72 ISSN 1562-6016. Problems of Atomic Science and Technology. 2022. №5(141)
CONCLUSIONS
1. The obtained results of the simulations on the
yield of photoneutrons from the tantalum converter at
the presence of the neutron moderator and without it are
in satisfactory agreement with the data of measurements
conducted earlier with the use of rhenium neutron detec-
tors activated by the reaction
187
Re (n,)
188
Re [10].
2. The neutron distribution over the output angle
from the converter is characterized by asymmetry with
preference along the electron beam direction. The
asymmetry coefficient is about 1.17 and doesn’t depend
on the electron energy in range 40…95 MeV.
3. The size of paraffin-graphite moderator of
30×30 cm seems being close to optimal as its expansion
to 40×40 cm provides the gain in the thermalized neu-
tron yield not higher than 1%.
4. The total yield of photoneutrons from the brems-
strahlung converter makes about of 10
–4
of the yield of
the above-threshold photons. The latter doesn‘t depend
virtually on the presence of a moderator.
REFERENCES
1. K. Devan, A. Meaze, Guinyun Kim, et al. Photo-
Neutrons Produced at the Pohang Neutron Facility
Based on an Electron Linac // J. of Korean Phys.
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2. A.N. Dovbnya, Yu.V. Rogov, V.A. Shevchenko, et al.
A Study of
192
Ir Production Conditions at an Elec-
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v. 11, № 5, p. 691-694.
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developments in Geant4 // NIM. 2016, A835, p. 186-
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4. TALYS-1.95,
https://tendl.web.psi.ch/tendl_2019/talys.
htmlhttps://tendl.web.psi.ch/tendl_2019/talys.html.
5. H. Utsunomiya, H. Akimune, S. Goko, et al. Cross
section measurements of the
181
Ta(,n)
180
Ta reaction
near threshold and the p-process nucleosynthesis //
Phys. Rev., Part C, Nucl. Phys. 2003, v. 67,
p. 015807.
6. S. Goko, H. Utsunomiya, S. Goriely, et al. Partial
photoneutron cross sections for the isomeric state
180
Ta-m // Phys. Rev. Letts. 2006, v. 96, p. 192501.
7. G.P. Antropov, I.E. Mitrofanov, B.S. Russkikh. Pho-
toneutron reactions on Al, S, Ta, and Bi // Izv. Rossi-
iskoi Akademii Nauk, Ser. Fiz. 1967, v. 31, p. 336 (in
Russian).
8. R.L. Bramblett, J.T. Caldwell, G.F. Auchampaugh,
S.C. Fultz. Photoneutron cross sections of Ta
181
and
Ho
165
// Phys. Rev. 1963, v. 129, p. 2723.
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Physics Complex with Energy of Electrons up to
100 MeV // Problems of Atomic Science and Tech-
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Article received 19.07.2022
ФОРМУВАННЯ ПОЛЯ МІШАНОГО X,n-ВИПРОМІНЕННЯ НА ПРИСКОРЮВАЧІ ЕЛЕКТРОНІВ
О.О. Захарченко, В.Л. Уваров, Ю.В. Малец
Для виконання фотоядерних програм з використанням джерела фотонів великої інтенсивності останнє
зазвичай одержують шляхом трансформації пучка електронів у гальмівне випромінення. Цей процес здійс-
нюють за допомогою проміжної мішені-конвертера, який виготовляють з матеріалу з великим Z. Під дією
високоенергетичних гальмівних фотонів у конвертері відбуваються (,n)-реакції. Як результат, з нього, крім
спрямованого уперед потоку фотонів, виходить також квазіізоторопний потік нейтронів. Параметри обох
видів випромінення, так само як і співвідношення їх інтенсивностей, грають важливу роль залежно від про-
грами, що виконується. У роботі методом комп´ютерного моделювання з використанням транспортного ко-
ду GEANT4 досліджено просторово-енергетичні характеристики мішаного X,n-випромінення, яке генеру-
ється електронним пучком у конвертері з танталу, що розміщений разом з ізотопною мішенню у середині
модератора нейтронів, при енергії електронів у діапазоні 40…95 МеВ і різному розмірі модератора.
https://tendl.web.psi.ch/tendl_2019/talys.%20html
https://tendl.web.psi.ch/tendl_2019/talys.%20html
https://tendl.web.psi.ch/tendl_2019/talys.html
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