Producing the planar multiphoton sources by photonuclear technique: 1. A model of gamma-fluorescent source
The possibility is shown to produce the planar -sources with the two and more spectral bands in the photon energy range up to ~100 keV by activating K-lines of the characteristic -ray radiation in the thin layers of the elementary substances by an external single-photon -source. A one-dimensional mo...
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Uvarov, V.L. 2017-04-04T05:51:41Z 2017-04-04T05:51:41Z 2016 Producing the planar multiphoton sources by photonuclear technique: 1. a model of gamma-fluorescent source / V.L. Uvarov // Вопросы атомной науки и техники. — 2016. — № 3. — С. 139-143. — Бібліогр.: 18 назв. — англ. 1562-6016 PACS: 07.05.Tr; 41.50.+h; 41.75.Fr; 78.70.En https://nasplib.isofts.kiev.ua/handle/123456789/115394 The possibility is shown to produce the planar -sources with the two and more spectral bands in the photon energy range up to ~100 keV by activating K-lines of the characteristic -ray radiation in the thin layers of the elementary substances by an external single-photon -source. A one-dimensional model of a combined planar source in the form of a stack of foils from the inactive and active materials has been developed. The model enables the analysis and optimisation of a source against its intensity and spectral composition. A variant of a production target for manufacturing at an electron accelerator the planar -sources on the basis of the isotopes ⁵⁷Со and ¹⁷⁹Та is offered and investigated by computer simulation. It is shown, that from the viewpoint of yield of the isotopes, suitable for the use in absorptiometry, the photonuclear method is competitive as compared with the reactor and cyclotron technologies. Показана возможность получения планарных -источников с двумя и более спектральными полосами в диапазоне энергий фотонов до ~100 кэВ путѐм активации К-линий характеристического рентгеновского излучения в тонких слоях простых веществ внешним однофотонным -источником. Разработана одномерная модель комбинированного планарного источника в виде набора тонких слоѐв из неактивных и активных материалов. Модель обеспечивает возможность анализа и оптимизации источника в отношении интенсивности и спектрального состава излучения. Предложен и исследован методом компьютерного моделирования вариант технологической мишени для наработки на ускорителе электронов планарных -источников на основе изотопов ⁵⁷Со и ¹⁷⁹Та. Показано, что в отношении выхода изотопов, пригодных для использования в абсорбциометрии, фотоядерный метод является конкурентоспособным по сравнению с реакторными и циклотронными технологиями. Показана можливість одержання планарних -джерел з двома і більше спектральними смугами в діапазоні енергій фотонів до ~100 кеВ шляхом активації К-ліній характеристичного рентгенівського випромінювання в тонких шарах простих речовин зовнішнім однофотонним -джерелом. Розроблена одномірна модель комбінованого планарного джерела у вигляді набору тонких шарів неактивних та активних матеріалів. Модель забезпечує можливість аналізу та оптимізації джерела щодо інтенсивності та спектрального складу випромінювання. Запропоновано та досліджено методом комп'ютерного моделювання варіант технологічної мішені для напрацювання на прискорювачі електронів планарных -джерел на основі ізотопів ⁵⁷Со і ¹⁷⁹Та. Показано, що відносно виходу ізотопів, придатних для використання в абсорбціометрії, фотоядерний метод є конкурентоспроможним у порівнянні з реакторними і циклотронними технологіями. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Экспериментальные методы и обработка данных Producing the planar multiphoton sources by photonuclear technique: 1. A model of gamma-fluorescent source Получение планарных мультифотонных источников фотоядерным методом: 1. модель гамма-флуоресцентного источника Одержання планарних мультифотонних джерел фотоядерним методом: 1. модель гамма-флуоресцентного джерела Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Producing the planar multiphoton sources by photonuclear technique: 1. A model of gamma-fluorescent source |
| spellingShingle |
Producing the planar multiphoton sources by photonuclear technique: 1. A model of gamma-fluorescent source Uvarov, V.L. Экспериментальные методы и обработка данных |
| title_short |
Producing the planar multiphoton sources by photonuclear technique: 1. A model of gamma-fluorescent source |
| title_full |
Producing the planar multiphoton sources by photonuclear technique: 1. A model of gamma-fluorescent source |
| title_fullStr |
Producing the planar multiphoton sources by photonuclear technique: 1. A model of gamma-fluorescent source |
| title_full_unstemmed |
Producing the planar multiphoton sources by photonuclear technique: 1. A model of gamma-fluorescent source |
| title_sort |
producing the planar multiphoton sources by photonuclear technique: 1. a model of gamma-fluorescent source |
| author |
Uvarov, V.L. |
| author_facet |
Uvarov, V.L. |
| topic |
Экспериментальные методы и обработка данных |
| topic_facet |
Экспериментальные методы и обработка данных |
| publishDate |
2016 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Получение планарных мультифотонных источников фотоядерным методом: 1. модель гамма-флуоресцентного источника Одержання планарних мультифотонних джерел фотоядерним методом: 1. модель гамма-флуоресцентного джерела |
| description |
The possibility is shown to produce the planar -sources with the two and more spectral bands in the photon energy range up to ~100 keV by activating K-lines of the characteristic -ray radiation in the thin layers of the elementary substances by an external single-photon -source. A one-dimensional model of a combined planar source in the form of a stack of foils from the inactive and active materials has been developed. The model enables the analysis and optimisation of a source against its intensity and spectral composition. A variant of a production target for manufacturing at an electron accelerator the planar -sources on the basis of the isotopes ⁵⁷Со and ¹⁷⁹Та is offered and investigated by computer simulation. It is shown, that from the viewpoint of yield of the isotopes, suitable for the use in absorptiometry, the photonuclear method is competitive as compared with the reactor and cyclotron technologies.
Показана возможность получения планарных -источников с двумя и более спектральными полосами в
диапазоне энергий фотонов до ~100 кэВ путѐм активации К-линий характеристического рентгеновского излучения в тонких слоях простых веществ внешним однофотонным -источником. Разработана одномерная
модель комбинированного планарного источника в виде набора тонких слоѐв из неактивных и активных
материалов. Модель обеспечивает возможность анализа и оптимизации источника в отношении интенсивности и спектрального состава излучения. Предложен и исследован методом компьютерного моделирования
вариант технологической мишени для наработки на ускорителе электронов планарных -источников на основе изотопов ⁵⁷Со и ¹⁷⁹Та. Показано, что в отношении выхода изотопов, пригодных для использования в
абсорбциометрии, фотоядерный метод является конкурентоспособным по сравнению с реакторными и циклотронными технологиями.
Показана можливість одержання планарних -джерел з двома і більше спектральними смугами в діапазоні енергій фотонів до ~100 кеВ шляхом активації К-ліній характеристичного рентгенівського випромінювання в тонких шарах простих речовин зовнішнім однофотонним -джерелом. Розроблена одномірна модель
комбінованого планарного джерела у вигляді набору тонких шарів неактивних та активних матеріалів. Модель забезпечує можливість аналізу та оптимізації джерела щодо інтенсивності та спектрального складу випромінювання. Запропоновано та досліджено методом комп'ютерного моделювання варіант технологічної
мішені для напрацювання на прискорювачі електронів планарных -джерел на основі ізотопів ⁵⁷Со і ¹⁷⁹Та.
Показано, що відносно виходу ізотопів, придатних для використання в абсорбціометрії, фотоядерний метод
є конкурентоспроможним у порівнянні з реакторними і циклотронними технологіями.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/115394 |
| citation_txt |
Producing the planar multiphoton sources by photonuclear technique: 1. a model of gamma-fluorescent source / V.L. Uvarov // Вопросы атомной науки и техники. — 2016. — № 3. — С. 139-143. — Бібліогр.: 18 назв. — англ. |
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ISSN 1562-6016. ВАНТ. 2016. №3(103) 139
PRODUCING THE PLANAR MULTIPHOTON SOURCES
BY PHOTONUCLEAR TECHNIQUE:
1. A MODEL OF GAMMA-FLUORESCENT SOURCE
V.L. Uvarov
National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
E-mail: uvarov@kipt.kharkov.ua
The possibility is shown to produce the planar -sources with the two and more spectral bands in the photon en-
ergy range up to ~100 keV by activating K-lines of the characteristic x-ray radiation in the thin layers of the elemen-
tary substances by an external single-photon -source. A one-dimensional model of a combined planar source in the
form of a stack of foils from the inactive and active materials has been developed. The model enables the analysis
and optimisation of a source against its intensity and spectral composition. A variant of a production target for man-
ufacturing at an electron accelerator the planar -sources on the basis of the isotopes 57Со and 179Та is offered and
investigated by computer simulation. It is shown, that from the viewpoint of yield of the isotopes, suitable for the
use in absorptiometry, the photonuclear method is competitive as compared with the reactor and cyclotron technolo-
gies.
PACS: 07.05.Tr; 41.50.+h; 41.75.Fr; 78.70.En
INTRODUCTION
Single- and multi-photon -sources are widely used
in up-to-date medical and industrial diagnostics, inspec-
tion check-up, spectrometry, etc. (see, e.g. [1, 2]). For
instance, the diagnostics of the osteoporosis, the most
widespread age-specific illness of the bone tissue, is
based on measuring its mineral density by single- and
dual- photon absorptiometry. As it was preliminary
specified, the radiation with photon energy in the range
30…60 keV provides the most contrast differentiation
between the soft and bone tissues in an introscopic im-
age. So initially for the single photon absorptiometry,
the 125I isotope (T1/2=59.4 day) having the most inten-
sive spectral line 27.5 keV has been chosen, as well as
153Gd (42 and 99 keV; 240.4 day) is used in the more
accurate dual photon diagnostics [3, 4]. The both iso-
topes are produced by radiochemical extraction from the
targets irradiated in reactor [5]. To obtain a sealed -
source, a separated isotope product is hermetically en-
capsulated.
In the sequel, a method of dual absorptiometry based
on the use of the X-ray tubes (DEXA-technique) has
been developed (see, e.g. [4]). This time the spectrum of
radiation is formed with specially chosen filters to pro-
vide the intensity maximum in the specified region. In
turn, the peripheral quantitative computed tomography
(pQCT) appears to be more informative [6]. That meth-
od uses the movable X-ray tubes with the filters, provid-
ing the spectral maximum near 60 keV. At the same
time, obtaining in such a way the dual photon sources
with the adequate operation life, high stability and uni-
formity of the radiation field, and also with the narrow
spectral bands is rather knotty problem. In particular,
this circumstance impedes realization of the dual photon
variant of pQCT, which is promising for early recogni-
tion of the illness.
As known, the radionuclides decaying via the elec-
tron capture emit Auger electrons and photons of the
characteristic X-ray radiation. Its high-energy part cor-
responds to the transitions of the orbital electrons on an
empty K-state. The X-ray radiation is generated also at
interaction of gammas with the bound atomic electrons
as a result of photoeffect (see, e.g. [7]). Thus one can
obtain a high-energy X-ray source either by selecting an
appropriate radionuclide or by acting on an inactive
(cold) material with the photons having energy higher
than the K-line energy of that material. Their values lay
in the range from 13 eV (hydrogen) to ~120 keV (urani-
um), i.e. just cover the range suitable for medical intros-
copy. The proton-redundant nuclei, decaying through
the K-capture, can be generated in the photonuclear
reactions realized at an comparatively inexpensive and
safe electron accelerator. In this work, the conditions are
studied for manufacturing the planar -sources with the
specified two and more spectral bands by combining
the layers of the cold materials and planar
-sources produced by a photonuclear technique.
1. MAIN REACTIONS
57Со (Е =122.1 and 136.5 кeV; Т1/2=271.3 day) is
one of the most suitable -activator of the characteristic
X-radiation. Therefore it is used in the form of quasi-
point sources in the fluorescence elemental analysis [8].
The planar sources on the basis of this isotope with ac-
tivity up to 740 MBq and measuring up to 700 500 mm
(the flood sources) are applied in medicine for calibrat-
ing the gamma-ray chambers (see, e.g. [9]).
Commonly, 57Со is produced on cyclotrons by the
reactions 56Fe(d,n)57Co and 58Ni(p,2p)57Co [10]. This
radionuclide can be generated also by a photonuclear
technique in a target from nickel via the two channels
simultaneously [11]:
58Ni( ,p)57Co,
58Ni( ,n)57Ni 35h
57Co.
The first reaction has the threshold 8.2 MeV at a
maximum of the cross section of about 60 mb, the
second 12.2 MeV and 23 mb, respectively [12].
A beam of the high-energy photons can be obtained
at an electron accelerator as secondary bremsstrahlung
radiation. For this, an intermediate target-converter from
high-Z material is used. The radiation has a continuous
spectrum with end-point photon energy corresponding
to the electron energy Е0.
mailto:uvarov@kipt.kharkov.ua
ISSN 1562-6016. ВАНТ. 2016. №3(103) 140
At the 57Со photonuclear production with the use of
a target from natural nickel (the 58Ni abundance is
68.27%) and electron beam with energy higher than
20 MeV, the channels of the hot admixtures production
are also revealed. Besides, the photoneutrons, generat-
ing as a result of the ( ,xn) processes in the elements of
the accelerator exit devices, can also effect on a produc-
tion target. The main reactions of the hot by-product
generation in natural nickel are
58Ni( ,2n)56Ni 5.9 day
56Co
77.3day
56Festab;
58Ni( ,np)56Co 77.3day 56Festab;
58Ni(n,p)58Co 70.8day
58Festab;
60Ni( ,np)58Co 70.8day
58Festab.
Those admixtures have considerably lesser half-life
than 57Со. So by proper target cooling, their relative
contribution to the target activity can be reduced to the
tolerable value.
179Та (Т1/2=665 day) is the one more isotope promis-
ing for medical diagnostics. Its principal К-lines are
54.07 keV (21.9%), 54.61 keV (12.6%), 62.98 keV
(2.4%), 63.24 keV (4.7%), and 64.9 keV (1.6%) – [13].
This isotope can be produced by the reaction
181Та( , 2n)179Та with maximum of the cross section
180 mb and threshold 14.2 MeV. A target from natural
tantalum (the 181Та abundance makes 99.99%) can be
utilized – [14]. At the same time, 180Та is generated also
under those conditions as the most active admixture via
the reaction 181Та( ,n)180Та with threshold 7.6 MeV. As
a result of the decay (Т1/2=8.15 h), 180Та is transformed
into the stable isotopes 180Hf (86%) and 180W (14%).
The reaction 181Та(n, )182Та 114.4day
182Wstab is
induced also in tantalum by photoneutrons.
2. PHOTONUCLEAR ISOTOPE YIELD
The expression for the target activity A(t), produced
by the end of the irradiation period t, can be presented in
the form
0
1( ) ( ) ,
I
A t y tD t
e
(1)
where y1 – is the yield of the new nuclei normalized to
the one beam electron, – is their decay constant, I0 – is
the average electron beam current, D( t) – is the coeffi-
cient of the target deactivation during exposure,
1 exp( )
( ) .
t
D t
t
(2)
In case of a channel with the formation of an inter-
mediate nucleus, its contribution A (t) to the activity of
the target isotope by EOB can be determined from the
expression
0
1
'''( ) [ ( ) ( ' )] ,
'
I
A t y t D t D t
e
(3)
where
1
'y – is the normalized yield of the intermediate
isotope, – is its decay constant. So at a period of the
nickel activation of t >>35 h, the contribution of the
channel 58Ni( ,n)57Ni 57Co to the total yield of 57Со
can reach 24%.
The analytical expression for the normalized photo-
nuclear yield of an isotope y1 in a thick production target
is presented in Ref. [15]. In particular, it is shown, that
the effective isotope generation is provided at a target
thickness of about free range ( )iR E of the photons
with energy iE , corresponding to the maximum of the
cross section of i reaction, where
1
( ) ( )i iR E E ,
( )iE is the mass attenuation coefficient of photons
in the target material. So the volumetric distribution of
the generated nuclei along the bremsstrahlung axes in a
target layer of lesser thickness can be considered as
quasi-homogeneous. Commonly,
iE corresponds to
the region of the giant dipole resonance and makes
~20 MeV. Thus in case of a target from nickel ( )iR E
~1 сm.
3. GAMMA-FLUORESCENCE
Consider the type of radiation sources obtained by
stacking the thin layers of the cold elementary substanc-
es and planar -sources with homogeneous volumetric
distribution of the hot nuclei.
As known, the principal process of interaction of the
gammas having energy up to 100 keV with substance is
the photoeffect on bound electrons of the atoms, which
probability increases with the grows the of binding en-
ergy [7]. The excitation of the atoms is removed by
emission of characteristic X-ray (fluorescence), in
which the relative contribution of K-lines makes from
84% (indium) to practically 100% (uranium) [8]. Un-
der such conditions, the yield of K-lines can be consid-
ered as proportional to the mass attenuation coefficient
of gammas, given by the formula
( , ) σ ( , ) ,A
ph
Z
N
E Z E Z
A
(4)
where ph – the cross section of the photoeffect, NA – is
the Avogadro number, АZ – is the average atomic
number of the substance.
Hereinafter, we will call the cold elements of a com-
bined source, fluorescent under external irradiation, as
radiators, while its hot elements as activators. We will
identify also the combined radiation sources by the ex-
pressions like L+M*+…, where L, M,… are the
names of the chemical elements of materials in the order
of their positioning relative to a radiation detector, while
the mark * denotes the presence of -activity at the cor-
responding component of the source.
3.1. TWO-COMPONENT SOURCE
Let us consider a source of the L+M* type, com-
prising a radiator L and activator M* with thicknesses
d1 and
*
2d , respectively. Taking into account, that the
lateral dimension of each element of the source consid-
erably exceeds its thickness (the condition of planarity),
the analysis of excitation and transfer of the radiation is
being conducted using the one-dimensional approxima-
tion. Such an approach seems to be substantiated at least
ISSN 1562-6016. ВАНТ. 2016. №3(103) 141
at a source thickness of less or about the photon free
range. So at a total activator’s activity of А*, the flux of
its gammas acting on the radiator L with due regard to
the homogeneous depth distribution of hot nuclei, as
well as to the self-absorption of their radiation, is de-
fined by the expression
*
1,2 2 2*
2 2
( ) *
( ) 1 exp ( ) ,
2 ( )
I E A
Ф E E d
E d
(5)
where I(E ) – is the quantum yield of the photons with
energy E , 2(E ) – is the mass attenuation coefficient of
photons in the activator material. The subscript 1, 2 de-
notes the boundary between the first and second (L and
M*) elements of the source. The analysis of the formula
(5) shows, that in case of a planar activator, its optimum
thickness, taking into account the self-absorption of
radiation, makes ~ [ 2(E )]-1. That corresponds to the
free range of the photons with energy Е . Their flux
Ф(Е ), leaving the radiator sideway the detector (a high-
energy band of the source spectrum), amounts
1,2 1 1( ) ( ) exp ( ) ,Ф E Ф E E d (6)
where 1(E ) – is the mass attenuation coefficient of
activating gammas in the radiator material.
In turn, the flux Ф1,2(Е ), acting on the radiator, ex-
cites in its volume characteristic X-rays with photon
energy Ех1.The yield of the X-radiation from the source
Ф(Ех1), considering self-absorption in the radiator both
activating gammas and induced fluorescent photons,
makes
1 1 1 1 1 1
1 1,2
1 1 1
( ) exp ( ) exp ( )
( ) ( ) ,
2 ( ) ( )
x
x
x
E E d E d
Ф E Ф E
E E
(7)
where 1(Eх1) – is the mass attenuation coefficient of
the fluorescent photons, induced in the radiator, in its
material.
As it follows from the expression (7), the maximum
yield of the fluorescence provides a radiator with thick-
ness
1
max 1 1
1 1 1 1
1
( )
( ) ( ) ln .
( )
x
x
E
d E E
E
(8)
The formula (8) gives the value of
max
1d , that lays
between the values of free range of the activating and
fluorescent photons in the radiator material. This cir-
cumstance corroborates the validity of the developed
model at the conditions of practical interest. At the same
time, the formula (7) can overestimate the value of the
X-ray yield beyond that region, since the offered one-
dimensional model does not take into consideration the
effects of photon scattering at a radiator thickness ex-
ceeding the value of their free range.
3.2. THREE-COMPONENT SOURCE
Now we will analyze a source of the L+M*+N type,
including the two radiators: the main radiator of d1
thickness and a complementary one, N, d3 thick as well
as an activator M* by
*
2d in thickness, placed between
them. The fluxes of the activator radiation in both sides
are equal, or Ф2,3(Е )=Ф1,2(Е ). The radiators can be
manufactured either from the same material (to increase
a low-energy band in a two-photon variant of the
source) or from the different materials (if there is the
necessity to create a third band in the spectrum).
Firstly, we will study the second variant as more
general. In this case, the X-radiation with photon energy
Ех3 will be induced in the complementary radiator N. To
reduce its self-absorption in the source, we will set a
thin activator, that meets the condition
*
2d << [ 2(Eх3)]
1,
where 2(Eх3) – is the mass attenuation coefficient of
photons with energy Eх3 in the activator material. The
flux of the X-radiation at the boundary with activator,
Ф2,3(Ех3), considering the absorption in this radiator
both activating and fluorescent photons, makes
3 3 3 3 3
2,3 3 2,3
3 3 3
( ) 1 exp ( ) ( )
( ) ( ) ,
2 ( ) ( )
x
x
x
E E E d
Ф E Ф E
E E
(9)
where 3(E ) and 3(Eх3) – are the mass attenuation co-
efficients of photons with energy E and Eх3 in the mate-
rial of the second radiator, respectively. The flux of this
X-radiation from the source after its consecutive attenu-
ation in the activator and L-radiator, amounts
*
3 2 3 2 1 3 1 2,3 3( ) exp ( ) ( ) ( ) ,x x x xФ E E d E d Ф E
(10)
where 1(Eх3) and 2(Eх3) – are the mass attenuation
coefficients of photons with energy Eх3 in the materials
of the first radiator and activator, respectively. In case
of high-thick complementary radiator,
d3 >> [ 3(Eх3)+ 3(E )]-1, the intensity of the third band
in the spectrum is maximal, namely,
*
3 2 3 2 1 3 1max
3 2,3
3 3 3
( ) exp ( ) ( )
( ) ( ) .
2 ( ) ( )
x x
x
x
E E d E d
Ф E Ф E
E E
(11)
If the both radiators have been fabricated from simi-
lar material ( 1 3), the relative gain of the low-energy
band, as compared with the two-component variant,
makes
*
2 1 2 1 1 1 1 1 1 31 1 11
1 1 1 1 1 1 1 1 1
exp ( ) ( ) 1 exp ( ) ( )( ) ( )( )
.
( ) ( ) ( ) exp ( ) exp ( )
x x xxx
x x x
E d E d E E dE EФ E
Ф E E E E d E d
(12)
If the second radiator is thick (d3>> [ 1(Eх1)+ 1(E )]-1,
its contribution to the radiation of the source is maxi-
mal. So in a system Та+Ni*+Ta at a thickness of the
two first elements of 0.1 mm the addition of the second
radiator can increase the yield of the tantalum fluores-
cence up to 64%.
The sources with the greater number of components
and their various sequence can be analyzed in the same
way. The value of the mass attenuation coefficient of
the photons with any energy in various materials can be
calculated, e.g., using a package ХМuDat [16].
ISSN 1562-6016. ВАНТ. 2016. №3(103) 142
4. DESIGN OF PRODUCTION TARGET
In the report [17], a technique for joint production of
the planar 179Та and 57Со sources is described. The fea-
ture of a proposed target device lays in the usage of the
tantalum simultaneously as a converter of the brems-
strahlung radiation and a target for generation
179
Та, as
well as for photonuclear activating the nickel resulting
in the 57Со generation.
It should be noted, that the free range of photons
with energy above the reaction threshold of 14.2 MeV
in tantalum makes ~1 cm. This is by two orders of val-
ues higher than the free range of the Ta characteristic
photons. As it was shown above, the latter value determi-
nates the optimal thickness of the source-see formula (8).
The geometry of the accelerator exit device provid-
ing the maximal yield of both the target isotopes and
minimal self-absorption of their radiation in the ob-
tained -sources was determined by means of computer
simulation. The target device corresponds a two-layer
cylinder with the central passage for cooling water. A
tape from tantalum 0.1mm thick by 180 cm in length
and coiled into a roll by 23.5 mm in outward diameter
forms an outside of the cylinder. A similar tape from
nickel, coiled also into a roll, forms an inner layer of the
cylinder. To provide even distribution of the surface
activity and absorbed dose, the electron beam is scanned
along the moving line of the target-cylinder with its
simultaneous rotation about the axis of the target. For a
comparison, the data on productivity of the known tech-
nologies for manufacturing isotopes used in the absorp-
tiometry as well as the results of calculation of joint
179Та and 57Со capacity on the basis of an electron ac-
celerator are given in Table. It is seen, that photonuclear
technology realized even at an accelerator with rather
ordinary parameters (40 МeV; 250 µА) is competitive.
Capacity of various techniques of isotope production (100 h irradiation run)
Isotope Installation Parameters Reaction Yield,
GBq
Refe-
rence
125I Reactor 5 1013 n/сm2 s 124Xe(n, )125Xe 125I 14.0 [5]
153Gd Reactor 6 1013 n/сm2 s 152Gd(n, )153Gd 0.13 [5]
57Co Cyclotron
20 15 МeV
250 µА
58Ni(p,2p)57Co 10 [18]
+
179Ta
57Co
Electron
accelerator
40 МeV
250 µА
181Ta( ,2n)179Ta
58Ni( ,p)57Co
58Ni( ,n)57Ni 57Co
+
3.7
8.2
[17]
CONCLUSIONS
A model has been developed for analysis of the mul-
ti-photon sources obtained by mixing the radiation of
the thin -active foils, produced at an electron accelera-
tor, and the induced characteristic X-radiation in the
thin layers of the cold elementary substances, contacting
with the active foils. The model makes it possible to
calculate the intensity of the bands of the combine
sources as well as their optimization with regard to the
intensity and spectral composition using the available
data on the mass attenuation coefficients of gammas in
the materials of the source components.
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Article received 03.03.2016
http://www.nndc.bnl.gov/nudat2/
ISSN 1562-6016. ВАНТ. 2016. №3(103) 143
ПОЛУЧЕНИЕ ПЛАНАРНЫХ МУЛЬТИФОТОННЫХ ИСТОЧНИКОВ ФОТОЯДЕРНЫМ
МЕТОДОМ: 1. МОДЕЛЬ ГАММА-ФЛУОРЕСЦЕНТНОГО ИСТОЧНИКА
В.Л. Уваров
Показана возможность получения планарных -источников с двумя и более спектральными полосами в
диапазоне энергий фотонов до ~100 кэВ путѐм активации К-линий характеристического рентгеновского из-
лучения в тонких слоях простых веществ внешним однофотонным -источником. Разработана одномерная
модель комбинированного планарного источника в виде набора тонких слоѐв из неактивных и активных
материалов. Модель обеспечивает возможность анализа и оптимизации источника в отношении интенсив-
ности и спектрального состава излучения. Предложен и исследован методом компьютерного моделирования
вариант технологической мишени для наработки на ускорителе электронов планарных -источников на ос-
нове изотопов 57Со и 179Та. Показано, что в отношении выхода изотопов, пригодных для использования в
абсорбциометрии, фотоядерный метод является конкурентоспособным по сравнению с реакторными и цик-
лотронными технологиями.
ОДЕРЖАННЯ ПЛАНАРНИХ МУЛЬТИФОТОННИХ ДЖЕРЕЛ ФОТОЯДЕРНИМ МЕТОДОМ:
1. МОДЕЛЬ ГАММА-ФЛУОРЕСЦЕНТНОГО ДЖЕРЕЛА
В.Л. Уваров
Показана можливість одержання планарних -джерел з двома і більше спектральними смугами в діапазо-
ні енергій фотонів до ~100 кеВ шляхом активації К-ліній характеристичного рентгенівського випроміню-
вання в тонких шарах простих речовин зовнішнім однофотонним -джерелом. Розроблена одномірна модель
комбінованого планарного джерела у вигляді набору тонких шарів неактивних та активних матеріалів. Мо-
дель забезпечує можливість аналізу та оптимізації джерела щодо інтенсивності та спектрального складу ви-
промінювання. Запропоновано та досліджено методом комп'ютерного моделювання варіант технологічної
мішені для напрацювання на прискорювачі електронів планарных -джерел на основі ізотопів 57Со і 179Та..
Показано, що відносно виходу ізотопів, придатних для використання в абсорбціометрії, фотоядерний метод
є конкурентоспроможним у порівнянні з реакторними і циклотронними технологіями.
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