Сomparison of GEANT4 with EGSnrc for simulation of gamma-radiation detectors based on semi-insulating materials
We considered GEANT4 version 4.9.4 with different Electromagnetic Physics Package for calculation of response functions of detectors based on semi-insulating materials. Computer simulations with GEANT4 packages were run in order to determine the energy deposition of gamma-quanta in detectors of spec...
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Skrypnyk, A.I. Zakharchenko, A.A. Khazhmuradov, M.A. 2017-01-10T11:46:02Z 2017-01-10T11:46:02Z 2011 Сomparison of GEANT4 with EGSnrc for simulation of gamma-radiation detectors based on semi-insulating materials / A.I. Skrypnyk, A.A. Zakharchenko, M.A. Khazhmuradov // Вопросы атомной науки и техники. — 2011. — № 5. — С. 93-100. — Бібліогр.: 19 назв. — англ. 1562-6016 PACS: 29.40.Wk, 85.30De https://nasplib.isofts.kiev.ua/handle/123456789/111466 We considered GEANT4 version 4.9.4 with different Electromagnetic Physics Package for calculation of response functions of detectors based on semi-insulating materials. Computer simulations with GEANT4 packages were run in order to determine the energy deposition of gamma-quanta in detectors of specified composition (HgI2 and TlBr) at various energies from 0.026 to 3 MeV. The uncertainty in these predictions is estimated by comparison of their results with EGSnrc simulations. A general good agreement is found for EGSnrc and GEANT4 with Penelope 2008 model of LowEnergy Electromagnetic package. Досліджено можливості різних моделей електромагнітної взаємодії гамма-квантів у GEANT4 v.4.9.4 для розрахунку функцій відгуку детекторів на основі напівізолюючих матеріалів. GEANT4 використано для визначення втрат енергії гамма-квантами в детекторах з HgI2 і TlBr в діапазоні енергій від 0,026 до 3 МеВ. Похибки розрахунків GEANT4 було оцінено шляхом порівняння з даними моделювання EGSnrc. Виявлено добру відповідність між розрахунками EGSnrc та GEANT4 при використанні моделі електромагнітної взаємодії Penelope 2008. Исследованы особенности различных моделей электромагнитных взаимодействий гамма-квантов в GEANT4 v.4.9.4 для расчета функций отклика детекторов на основе полуизолирующих материалов. GEANT4 использован для определения потерь энергии гамма-квантов в детекторах из HgI2 и TlBr в диапазоне энергий от 0,026 до 3 МэВ. Погрешности расчетов GEANT4 оценивались при сравнении с данными моделирования EGSnrc. Хорошее согласие обнаружено между расчетами EGSnrc и GEANT4 при использовании модели электромагнитных взаимодействий Penelope 2008. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Вычислительные и модельные системы Сomparison of GEANT4 with EGSnrc for simulation of gamma-radiation detectors based on semi-insulating materials Порiвняння можливостей GEANT4 та EGSnrc для моделювання детекторiв гамма-випромiнювання на основi напiвiзоляторiв Сравнение возможностей GEANT4 и EGSnrc для моделирования детекторов гамма-излучения на основе полуизоляторов Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| title |
Сomparison of GEANT4 with EGSnrc for simulation of gamma-radiation detectors based on semi-insulating materials |
| spellingShingle |
Сomparison of GEANT4 with EGSnrc for simulation of gamma-radiation detectors based on semi-insulating materials Skrypnyk, A.I. Zakharchenko, A.A. Khazhmuradov, M.A. Вычислительные и модельные системы |
| title_short |
Сomparison of GEANT4 with EGSnrc for simulation of gamma-radiation detectors based on semi-insulating materials |
| title_full |
Сomparison of GEANT4 with EGSnrc for simulation of gamma-radiation detectors based on semi-insulating materials |
| title_fullStr |
Сomparison of GEANT4 with EGSnrc for simulation of gamma-radiation detectors based on semi-insulating materials |
| title_full_unstemmed |
Сomparison of GEANT4 with EGSnrc for simulation of gamma-radiation detectors based on semi-insulating materials |
| title_sort |
сomparison of geant4 with egsnrc for simulation of gamma-radiation detectors based on semi-insulating materials |
| author |
Skrypnyk, A.I. Zakharchenko, A.A. Khazhmuradov, M.A. |
| author_facet |
Skrypnyk, A.I. Zakharchenko, A.A. Khazhmuradov, M.A. |
| topic |
Вычислительные и модельные системы |
| topic_facet |
Вычислительные и модельные системы |
| publishDate |
2011 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Порiвняння можливостей GEANT4 та EGSnrc для моделювання детекторiв гамма-випромiнювання на основi напiвiзоляторiв Сравнение возможностей GEANT4 и EGSnrc для моделирования детекторов гамма-излучения на основе полуизоляторов |
| description |
We considered GEANT4 version 4.9.4 with different Electromagnetic Physics Package for calculation of response functions of detectors based on semi-insulating materials. Computer simulations with GEANT4 packages were run in order to determine the energy deposition of gamma-quanta in detectors of specified composition (HgI2 and TlBr) at various energies from 0.026 to 3 MeV. The uncertainty in these predictions is estimated by comparison of their results with EGSnrc simulations. A general good agreement is found for EGSnrc and GEANT4 with Penelope 2008 model of LowEnergy Electromagnetic package.
Досліджено можливості різних моделей електромагнітної взаємодії гамма-квантів у GEANT4 v.4.9.4 для розрахунку функцій відгуку детекторів на основі напівізолюючих матеріалів. GEANT4 використано для визначення втрат енергії гамма-квантами в детекторах з HgI2 і TlBr в діапазоні енергій від 0,026 до 3 МеВ. Похибки розрахунків GEANT4 було оцінено шляхом порівняння з даними моделювання EGSnrc. Виявлено добру відповідність між розрахунками EGSnrc та GEANT4 при використанні моделі електромагнітної взаємодії Penelope 2008.
Исследованы особенности различных моделей электромагнитных взаимодействий гамма-квантов в GEANT4 v.4.9.4 для расчета функций отклика детекторов на основе полуизолирующих материалов. GEANT4 использован для определения потерь энергии гамма-квантов в детекторах из HgI2 и TlBr в диапазоне энергий от 0,026 до 3 МэВ. Погрешности расчетов GEANT4 оценивались при сравнении с данными моделирования EGSnrc. Хорошее согласие обнаружено между расчетами EGSnrc и GEANT4 при использовании модели электромагнитных взаимодействий Penelope 2008.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/111466 |
| citation_txt |
Сomparison of GEANT4 with EGSnrc for simulation of gamma-radiation detectors based on semi-insulating materials / A.I. Skrypnyk, A.A. Zakharchenko, M.A. Khazhmuradov // Вопросы атомной науки и техники. — 2011. — № 5. — С. 93-100. — Бібліогр.: 19 назв. — англ. |
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COMPUTING AND MODELLING SYSTEMS
COMPARISON OF GEANT4 WITH EGSnrc FOR SIMULATION
OF GAMMA-RADIATION DETECTORS BASED ON
SEMI-INSULATING MATERIALS
A.I. Skrypnyk∗, A.A. Zakharchenko, M.A. Khazhmuradov
National Science Center ”Kharkov Institute of Physics and Technology”, 61108, Kharkov, Ukraine
(Received August 1 , 2011)
We considered GEANT4 version 4.9.4 with different Electromagnetic Physics Package for calculation of response
functions of detectors based on semi-insulating materials. Computer simulations with GEANT4 packages were run
in order to determine the energy deposition of gamma-quanta in detectors of specified composition (HgI2 and TlBr)
at various energies from 0.026 to 3 MeV. The uncertainty in these predictions is estimated by comparison of their
results with EGSnrc simulations. A general good agreement is found for EGSnrc and GEANT4 with Penelope 2008
model of LowEnergy Electromagnetic package.
PACS: 29.40.Wk, 85.30De
1. INTRODUCTION
The variety of electrophysical characteristics (spe-
cific resistance, product of mobility µ and mean
drift time τ for holes and electrons – (µτ)h,e) is
a serious disadvantage of semi-insulating materials
(wide band-gap semiconductor with high resistivity).
Now this is a main cause that the semi-insulator
gamma-radiation detectors could not be mass pro-
duced. Wide band-gap semiconductor detectors have
considerable spread of (µτ)h,e values (in order of mag-
nitude and more) [1] even if they are produced from
one ingot. As result the same size detectors biased
to the same voltage U b have a different charge collec-
tion efficiency (CCE ). It results in non-uniformity of
serial devices response and in necessity of individual
setup parameters selection.
Also the material non-uniformities are a serious
obstacle to comparison of detector characteristics
measured in different studies. Computer simulation
is an optimal method to overcome the material non-
uniformity problem. Simulation may be useful both
to research of wide band-gap detector behavior and
designing of device based on them [2].
Previously we have developed the model of
the planar wide band-gap semiconducting gamma-
radiation detectors where EGSnrc Monte-Carlo
(MC) simulation package was used for determina-
tion of the energy deposition of gamma-quanta and
charged particles [3]. This model was tested on the
several groups of CdTe and CdZnTe detectors [4].
The observed difference between model and experi-
mentally measured amplitude distributions of radia-
tion sources 137Cs and 152Eu was explained in process
of this model verification [2]. However, by this now
all factors defining such important gamma-radiation
detector characteristics as sensitivity δ and charge
collection efficiency CCE are not determined even
for the most researched semi-insulating materials as
CdTe and CdZnTe. By-turn it does not permit to
define exhaustive set of the control parameters of the
wide band-gap detector model. The determination
of these parameters would allow calculating the most
realistic response of the gamma-radiation detector.
The model [4] enabled to obtain a good agree-
ment between calculated and experimental response
functions of CdTe (CdZnTe) gamma-radiation de-
tectors in the most cases analyzed. However EGSnrc
package possibilities are restricted only by a simula-
tion of photon, electron and positron transport. It
does not allow using the above mentioned model [4]
for analysis of the charge collection efficiency experi-
ments with the wide band-gap detectors when proton
and α-particle beams are used [5]. Also the model
[4] is unsuitable for researching of actual problems of
radiation resistance of semi-insulators in mixed radi-
ation fields (charged particles and/or neutrons and
gamma-quanta) [6].
Geant4 [7] is an actively developing toolkit for
the simulation of the passage of charged particles,
neutrons and gamma-quanta through matter. This
MC package offers a set of physical process mod-
els to describe the interaction of charged and neu-
tral particles with matter in the wide energy range.
Geant4 provides various models of the same electro-
magnetic processes (EM packages) [8]. To implement
the model [4] on Geant4 platform properly it is nec-
essary to define EM package which provides better
agreement with EGSnrc simulation results.
In the present work statistical characteristics of
∗Corresponding author E-mail address: belkas@kipt.kharkov.ua
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2011, N5.
Series: Nuclear Physics Investigations (56), p.93-100.
93
the EGSnrc-calculated response functions of planar
wide band-gap detectors based on
HgI2 and TlBr to gamma-quanta with energies
between 0.026 and 3 MeV is compared with the
results of Geant4 simulation. The same radiation
source and detector geometry parameters are used to
calculate the photon and charged particle transport
in EGSnrc and Geant4 simulations. A good agree-
ment between results of EGSnrc and Geant4 simu-
lations is obtained with using Penelope − 2008 EM
package Geant4 v.4.9.4 [9].
2. THE GEANT4 AND EGSnrc
ELECTROMAGNETIC MODELS
Geant4 includes three EM packages, which use differ-
ent models for cross-sections of photons and charged
particles interactions with the matter and different
models for final state sampling algorithms. These are
Standard EM model and two models for low energy
region identified as Livermore and Penelope EM
model. All models describe the photoelectric effect,
the Compton scattering and the gamma conversion.
The model processes of the induced emission and
scattering e−–e− and e−–e+ are available for elec-
trons and positrons.
In the recent years many articles were published
where Geant4 simulation results are compared with
yield of ¿referenceÀ MC codes EGSnrc and MCNP
[7–10]. EGSnrc and MCNP packages have longer
application history in radiation physics and nuclear
medicine in comparison with Geant4. As a result of
often modifications of Geant4 code and fixation of al-
gorithm bugs the comparison of different Geant4 ver-
sion simulations with other Monte-Carlo codes and
experimental data can show the differing results. In
the present work Geant4 v.4.9.3 and v.4.9.4 simula-
tions are compared with results of EGSnrc version
4r2.3.1.
The Standard model uses an analytical approach
to describe the electromagnetic interactions in the
range from 1 keV up to about 100 TeV. An analytical
approach combines numerical databases with analyt-
ical cross-section models assuming quasi-free atomic
electrons while the atomic nucleus is fixed. Trans-
port of X- and gamma rays takes into account Comp-
ton scattering using the free-electron approximation,
gamma conversion into electron-positron pair, and
photoelectric effect. Bremsstrahlung and ionization
are the available processes for electrons and positrons.
The binding energy of atomic electrons is taken into
account only at the photoelectric effect simulation.
The simplified computational algorithm of the nu-
clear radiation transport through the matter pro-
vides the most calculating efficiency for the Standard
model in comparison with other models. However,
coherent (Rayleigh) scattering and atomic relaxation
processes are not included for this package.
Atomic and shell ionization effects are included
in the Livermore model. The lower energy threshold
of the simulation interactions is decreased down to
250 eV. The available physical processes are Rayleigh
and Compton scattering, photo-electric effect, pair
production, bremsstrahlung, and ionization. The flu-
orescence and Auger emission in excited atoms are
also considered. This package describes the electro-
magnetic interactions of electrons and photons tak-
ing into account subshell integrated cross sections for
photoelectric effect, ionization, and electron binding
energies for all subshells. Cross-sections of particle
interactions with matter are calculated from evalu-
ated data libraries from Lawrence Livermore National
Laboratory – EPDL97 for photons [11], EEDL for
electrons [12] and EADL for fluorescence and Auger
effects [13].
The physical model which originally was devel-
oped for Penelope MC code [9] combines analytical
approach for computation of cross-section of the dif-
ferent interactions with data from cross-section data-
bases calculated in Seltzer and Berger work [14]. Al-
gorithm Penelope 2008 is used in Geant4 beginning
with version v.4.9.3. This model is applicable to in-
teractions in range from about 200 eV up to 1 GeV.
Now PenelopeEM Package is still tested.
NIST data [14, 15] with empirical correction fac-
tors for set of elements [16] are employed for compu-
tation of bremsstrahlung loss in the EGSnrc model
of the electromagnetic interactions. Cross-sections of
the photoelectric effect, pair and triplet generation
and coherent scattering cross-sections are determined
from EDPL [11] and XCOM [17] estimations. The
Klein-Nishina method allowing for Doppler broaden-
ing correction and correction for chemical bond ef-
fects is used to calculate the incoherent (Compton)
scattering cross-sections. Parameters of atom relax-
ation are determined for every atomic subshell.
Contribution of the atom relaxation processes can
be appreciable during registration of gamma-quanta
with energies up to about 1 MeV. They are not
described in the Geant4 Standard Electromagnetic
Model. Thus it is possible to expect the largest dif-
ference between simulation data received with using
Standard EM Package and EGSnrc simulation re-
sults.
3. RESULTS OF SIMULATIONS
Functions of gamma-quantum energy loss distrib-
ution (response functions) were computed for pla-
nar detectors based on two wide band-gap semi-
conducting compounds: mercuric (II) iodide (HgI2)
and thallium bromide (TlBr). HgI2 detectors are
investigated over a long period of time [18] while
TlBr is a comparatively new material for nuclear
radiation detection [19]. Initial energy of gamma-
quantum beam was chosen in the range from 0.026 up
to 3 MeV. Simulations were run for all three Geant4
packages of electromagnetic interactions. Geometric
sizes of detectors and gamma-quantum beam parame-
ters were identical for all Geant4 and EGSnrc mod-
els.
Since the thickness of investigated detectors was
about 1 mm the minimal run length of Geant4-
94
simulated particles (cutForElectron) and gamma-
quanta (cutForGamma) in detector material was set
equal to 0.01 mm. It corresponds to the minimal en-
ergy 3.21 keV for gamma-quanta and 43.23 keV for
electrons in HgI2. The minimal energy of Geant4-
simulated gamma-quanta in TlBr is 3.85 keV and
48.14 keV for electrons. The similar energy thresh-
olds PCUT = 2 keV (gamma-quanta) and ECUT =
20 keV (electrons) were set for both materials during
EGSnrc simulations.
In the present work we do not consider the energy
loss of fast electrons due to the excitation of lattice
vibrations. Statistical moments: average energy loss,
variance and asymmetry coefficient were computed
for every function of distribution of energy loss. Re-
ceived dependences of the statistical moments against
initial energy of gamma-quantum beam allow reveal-
ing and describing in detail systematical differences
between results of Geant4 and EGSnrc simulation.
3.1. Mercuric (II) Iodide
Mercuric (II) iodine (HgI2) belongs to the group
of AIIBV I semiconductor compounds. The functions
of distribution of gamma-quantum energy loss were
computed for the planar HgI2 detector with size of
5×5×1 mm3. The parallel monoenergetic gamma-
quantum beam was uniformly scanned on the detec-
tor area. The beam incidence angle was equal to
90◦. At the first stage of the pesent work we used
Geant4 v.4.9.3-p01 for comparison with EGSnrc
simulations. 106 gamma-quantum histories were sim-
ulated for every energy. The statistical moments of
the response functions were calculated on their base.
Fig. 1 shows the dependence of average en-
ergy losses <E> of gamma-quanta (the first mo-
ment) against initial beam energy in the investi-
gated HgI2 detector. Calculated energy losses are
practically equal for all investigated models in the
energy range less than Eγ < 0.4 MeV. The en-
ergy losses calculated from Standard and Livermore
simulation data are stably lower than results of
EGSnrc simulations in region Eγ > 0.4 MeV.
Fig.1. The dependence of average energy losses of
gamma-quanta in HgI2 vs initial beam energy
The predicted mean energy losses of gamma-
quanta received from Standard and Livermore mod-
els practically coincides in the range between 0.4
and 2 MeV. But the Geant4 v.4.9.3-p01 simulation
demonstrates abrupt increase of the mean losses for
Livermore model relative to Standard model data
for gamma-quantum energies above Eγ > 2 MeV
(Fig. 1). The quick increase of the electron-positron
pair production cross-section is a single essential fea-
ture of the gamma-quantum interaction with HgI2
in energy range above Eγ > 2 MeV. Consequently
observed difference (Fig. 1) may be concerned with
Geant4 v.4.9.3-p01 errors of the positron trajectory
simulation.
The repeated simulation of the HgI2-detector re-
sponse functions using Geant4 v.4.9.4-p02 (release
from 24-06-2011) showed that these bugs have been
fixed by authors. Moreover, as Fig. 1 shows the
difference between Penelope model data in version
4.9.4-p02 and result of EGSnrc simulation consid-
erably decreased. That is why, except where noted,
for further study we use results received from Geant4
v.4.9.4-p02 simulations.
To reveal the most essential differences between
simulation results received with different Geant4 EM
packages it is necessary the detailed analysis of the
investigated HgI2-detector response functions in the
energy range of gamma-quanta where different phys-
ical processes are dominated.
Fig. 2 shows the computed distributions of
gamma-quantum energy losses for initial beam en-
ergy Eγ = 0.08 MeV. At this energy the photoelec-
tric effect is a dominating process of the gamma-
radiation interaction with HgI2. The amount of
absorbed photons (on the Fig. 2 and further these
events correspond to energy Eγ) for all models
insignificantly differs (Table 1). It confirms that
similar values of photoelectric effect cross-sections
for Hg and I are used in all models. Atomic re-
laxation processes are not taken into account in
the Standard model. Therefore the photoelectric
effect event quantity is maximal for this model.
Fig.2. Energy losses of gamma-quanta with energy
Eγ = 0.08 MeV in HgI2-detector
95
Table 1 and follow-up data show that the total ef-
ficiency of registration of gamma-quanta of investi-
gated detectors is almost the same for all models.
The fine structure of escape peaks is reconstructed
from the results of EGSnrc simulations in the most
detail. As Fig. 2 demonstrates the used energy bin
(1 keV) allows separating KX - and LX -series of char-
acteristic photons for both elements (Hg and I).
Table 1. The amount of photoelectric effect events
and total efficiency for gamma-quanta with
Eγ = 0.08 MeV
EM model Photoeffect Efficiency, HgI2
Standard 804176 0.818
Livermore 784069 0.822
Penelope 788043 0.822
EGSnrc 765231 0.819
In low-loss energy region of HgI2-detector response
functions computed with using Livermore and
PenelopeEM models show good agreement with
EGSnrc simulation data. According to Fig. 2 these
three models have an almost equal distribution of the
energy losses in the region up to 0.04. . . 0.045 MeV.
In the energy loss region above 0.045 MeV the bet-
ter agreement with EGSnrc data is observed for
LivermoreEM model.
All EM models lead to the similar distribution
of the Compton tail in the gamma-quantum en-
ergy region where Compton scattering is prevailed
(Fig. 3). Computations with Penelope EM model
allow obtaining the better agreement with EGSnrc
simulation in the Compton valley whereas Standard
and Livermore results exceed EGSnrc data. At
the same time the amount of absorbed gamma-
quanta for the Livermore model is equal about
two thirds of the same as other models (Table 2).
Fig.3. Energy losses of gamma-quanta with energy
Eγ = 0.6 MeV in HgI2-detector
As follows Fig. 4 and Table 3 data the Livermore and
Standard EM models employ cross-sections of pho-
toelectric interaction with HgI2 for gamma-quanta
with energy Eγ = 1.28 MeV which values are much
less compared with the same in the Penelope EM
model and EGSnrc. It is confirmed by the lack
of photopeaks for the response functions simulated
with using these models. Moreover the disappear-
ing of the Compton edges on the Fig. 4 indicates
that the Livermore and Standard models employ
smaller probabilities of the gamma-quantum Comp-
ton scattering angels above 135◦ in comparison with
the Penelope model and EGSnrc.
Table 2. The amount of photoelectric effect events
and total efficiency for gamma-quanta with
Eγ=0.6 MeV
EM model Photoeffect Efficiency, HgI2
Standard 12602 0.058
Livermore 7418 0.057
Penelope 13488 0.058
EGSnrc 11312 0.058
If gamma-quantum energy is enough for electron-
positron pair production (gamma-conversion) (for ex-
ample Eγ = 1.28 MeV , Fig. 4) a double-escape
peak of annihilation gamma-quanta becomes appre-
ciable in the Geant4 simulations (Table 3). On
the Fig. 4 these events correspond to the energy
equal to 0.259 MeV. According to EGSnrc sim-
ulation of response function of investigated HgI2-
detector at energy Eγ = 1.28 MeV the dou-
ble escape peak is not yet observed (Table 3).
Fig.4. Energy losses of gamma-quanta with energy
Eγ = 1.28 MeV in HgI2-detector
Table 3. The amount of the photoelectric effect and
double escape events for gamma-quanta with
Eγ = 1.28 MeV (HgI2)
EM model Photoeffect Double-escape
Standard 39 234
Livermore 18 209
Penelope 1700 201
EGSnrc 1083 37
Above results show that there is good agreement be-
tween the response functions of the investigated HgI2-
detector received with the Penelope and EGSnrc
model apart from double-escape peak of the anni-
hilation gamma-quanta.
96
Finally, the computation of the HgI2-detector re-
sponse function based on the 107 simulation trajec-
tories of gamma-quanta with energy Eγ = 3 MeV
shows a good agreement between results of the
PenelopeEM model and EGSnrc (Fig. 5). Plots
corresponding to results of the Livermore and
Standard models are located appreciably lower.
The escape peaks in that models are absent (Ta-
ble 4 and Fig. 5). This indicates that values
of cross-section of the electron-positron pair pro-
duction employed by the Livermore and Stan-
dard models are smaller as compared with the
same of the PenelopeEM model and EGSnrc.
Fig.5. Energy losses of gamma-quanta with energy
Eγ = 3 MeV in HgI2-detector
Table 4. The amount of event of the escape and
double escape of annihilation gamma-quanta (HgI2),
Eγ = 3 MeV
EM model Escape Double-escape
Standard 1 74
Livermore 0 59
Penelope 65 3366
EGSnrc 121 7152
Fig. 5 shows that the response functions of the
HgI2-detector received with the Geant4 v4.9.4-p02
Livermore and Standard models practically coin-
cide. So average energy losses of gamma-quanta with
energy 3 MeV also coincide (Fig. 1). It confirms
our supposition about the incorrect computation of
the HgI2-detector response functions when Geant4
v.4.9.3-p01 Livermore and Standard models have
been used (Fig. 1).
Other statistical characteristics of response func-
tions of the investigated HgI2-detector – variance
(Fig. 6) and skewness coefficient (Fig. 7) – also
demonstrate a good agreement between results of
Geant4 v4.9.4-p02 Penelope EM package simula-
tions and EGSnrc data.
From Fig. 1, Fig. 6 and Fig. 7 it follows that
main differences of all statistical characteristics of
the HgI2-detector response functions between Geant4
v4.9.3-p01 and v4.9.4-p02 simulation data correspond
to the electron-positron pair production region (Eγ
> 1.022 MeV). In the gamma-quantum energy re-
gion where positrons are not generated the response
functions received with different Geant4 versions
coincide. Therefore the cause of anomalous simu-
lation results is incorrect values of specific ioniza-
tion energy losses of positrons in HgI2 those used
by Geant4 v4.9.3-p01. The differences between re-
sponse functions of the investigated TlBr-detector re-
ceived using of both Geant4 versions are insignificant.
Fig.6. The dependence of variance of the HgI2-
detector response functions vs gamma-quantum
energy
Fig.7. The dependence of skewness coefficient of the
HgI2-detector response functions vs gamma-quantum
energy
3.2. Thallium Bromide
Thallium bromide (TlBr) belongs to the group of
AIIIBV I semiconductor compounds. Quality differ-
ences between the linear gamma-ray attenuation co-
efficients of TlBr and HgI2 are negligible. These dif-
ferences are characteristic for the energy region where
photoelectric effect is dominated (Fig. 8). At the
same time the TlBr linear gamma-ray attenuation
coefficient exceeds the same of HgI2 about 10% be-
ginning from gamma-ray energy Eγ = 0.1 MeV. As
follows we can expect that average losses of gamma-
97
quanta energy in TlBr will be higher than in HgI2 at
the same detector thickness.
Distributions of the gamma-quantum energy
losses were calculated for the planar TlBr-detector
with size of 3.142 mm2 × 0.8 mm. The parallel mono-
energetic beam of gamma-quanta was uniformly dis-
tributed on the detector area. The beam incidence
angle was equal to 90◦. 106 histories were simulated
for each gamma-ray energy. Statistical moments of
response functions were calculated using these histo-
ries (Fig. 9 and Fig. 10).
The data plotted on the Fig. 9 – 12 are received
from the Geant4 v4.9.4-p02 simulations. Response
functions of the investigated TlBr-detector obtained
using version v.4.9.3 coincide with version v.4.9.4
calculations within the scope of statistical uncertain-
ties. It gives grounds for affirmation that the reason
of above-mentioned anomalous simulation results for
HgI2-detector is not the errors of the positron trajec-
tory simulation algorithm. As we think these anom-
alous results are consequence of incorrect values of
the specific ionization energy losses of positrons in
HgI2. Similarly the case of HgI2-detector the better
coincidence between EGSnrc and Geant4 simulation
data is observed when the Penelope model of elec-
tromagnetic interactions has been used (Fig. 9 and
10).
Fig.8. The linear gamma-ray attenuation coefficient
for HgI2 and TlBr [17]
The analysis of simulated TlBr-detector response
functions for gamma-ray photons with energy Eγ =
0.6 MeV (Fig.11) shows the presence of escape peaks
of characteristic photons of Tl and Br KX-series in
all models apart from the Standard EM model. The
Compton tail is identically reconstructed in all sim-
ulations. As for the Compton valley region that
the better agreement with EGSnrc data is obtained
for the Geant4 PenelopeEM package simulation.
The amount of the absorbed gamma-quanta with the
energy 0.6 MeV for the LivermoreEM model sim-
ulation is about 30% less in comparison with other
models (Table 5).
The response function of the investigated TlBr-
detector for rather high energy gamma-quanta (Eγ
= 3 MeV, Fig. 12) received with using EGSnrc MC
package shows a good agreement only with the results
of the Geant4 Penelope model simulation. For the
Livermore and Standard models the escape peak of
the annihilation gamma-quanta is almost absent and
amplitude of the double escape peak is more than
an order of magnitude less as compared with other
simulations (Table 6).
Fig.9. The dependence of average energy losses of
gamma-quanta in TlBr vs the initial energy beam
Fig.10. The dependence of variance of TlBr-
detector response functions vs the gamma-quantum
energy
Fig.11. The energy losses of gamma-quanta with
the energy Eγ = 0.6 MeV in TlBr-detector
98
Table 5. The amount of photoelectric effect events
and total efficiency for gamma-quanta with
Eγ = 0.6 MeV
EM model Photoeffect Efficiency, TlBr
Standard 14288 0.061
Livermore 9231 0.060
Penelope 15652 0.060
EGSnrc 16804 0.064
Fig.12. The energy losses of gamma-quanta with
the energy Eγ = 3 MeV in TlBr-detector
Table 6. The amount of event of the escape and
double escape of annihilation gamma-quanta
(TlBr), Eγ = 3 MeV
EM model Escape Double-escape
Standard 13 435
Livermore 5 395
Penelope 235 5881
EGSnrc 577 13433
4. CONCLUSIONS
The comparison of the response functions of the HgI2
and TlBr gamma-radiation detectors computed for
all models of the electromagnetic interactions of the
Geant4 package and EGSnrc has been made in this
work. In the energy region of gamma-quanta up
to 0.4 MeV there is a good agreement between re-
sponse functions of the investigated detectors cal-
culated with using EGSnrc and both Livermore
and Penelope models of the Geant4 package. For
wider gamma-quantum energy region between 0.026
and 3 MeV statistical parameters of the response
functions simulated with EGSnrc and Geant4 pack-
ages have a good agreement only when the Penelope
model of electromagnetic interactions has been used.
By the HgI2-detector example it is shown that the
comparison of the response functions received with
using different simulation packages allow removing
incorrect results and explaining the reason of their
appearance.
References
1. G. Sato, A. Parsons, D. Hullinger, et al. Develop-
ment of a spectral model based on charge trans-
port for the Swift/BAT 32K CdZnTe detector
array // Nucl. Instr. and Meth. A. 2005, v.541,
p.372-384.
2. A.A. Zakharchenko, M.A. Khazhmuradov. Inves-
tigation of the properties of semiconductor de-
tectors of nuclear radiation by the Monte Carlo
method. Part 1: Semiconductor detectors of
gamma radiation: Preprint. NASU, NSC KIPT:
Review, 2011, p.1-48 (in Russian).
3. I. Kawrakow, E. Mainegra-Hing, D. Rogers.
EGSnrcMP, the new multi-platform version of
EGSnrc // Med. Phys. 2004, v.31, p.1731.
4. A.A. Zakharchenko, A.A. Veryovkin, V.E. Kutny,
A.V.Rybka, M.A. Khazhmuradov. Simulation
of response function of CdZnTe detectors for
gamma-radiation dosimetry // The Journal of
Kharkov National University. Physical series:
”Nuclei, Particles, Fields”. 2008, N832, issue
4(40), p.71-76 (in Russian).
5. M.Breese, E. Vittone, G. Vizkelethy, P. Sellin.
A review of ion beam induced charge microscopy
// Nucl. Instr. and Meth. B. 2007, v.264, p.345-
360.
6. A.Cavallini, B. Fraboni, W.Dusi, et al. Radia-
tion effects on II–VI compound-based detectors
// Nucl. Instr. and Meth. A. 2002, v.476, p.770–
778.
7. K.Amako, S.Guatelli, V. Ivanchencko, et al.
Geant4 and its validation // Nuclear Physics. B.
(Proc. Suppl.) 2006, v.150, p.44-49.
8. G.Cirrone, G. Cuttone, F. Di Rosa, et al. Valida-
tion of the Geant4 electromagnetic photon cross-
sections for elements and compounds // Nucl. In-
str. and Meth. A. 2010, v.618, p.315-322.
9. J. Sempau, J. Fernandez-Varea, E. Acosta,
F. Salvat. Experimental benchmarks of the
Monte-Carlo code PENELOPE // Nucl. Instr.
and Meth. B. 2003, v.207, p. 107-123.
10. H.Yoriyaz, M.Moralles, P. Siqueira, et al. Physi-
cal models, cross sections, and numerical approx-
imations used in MCNP and GEANT4 Monte
Carlo codes for photon and electron absorbed
fraction calculation // Med. Phys. 2009, v.36
(11), p.5198-5213.
11. D.Cullen, J. Hubbell, L.Kissel. EPDL97:
The Evaluated Photon Data Library ‘97 Version
LLNL: UCRL-50400, v.6, rev.5, 1997; http://
www-nds.iaea.org/epdl97/document/epdl97.pdf
99
12. S. Perkins, D.Cullen, S. Seltzer. Tables and
graphs of electron-interaction cross-sections from
10 eV to 100 GeV derived from the LLNL eval-
uated electron data library (EEDL), Z=1-100
LLNL: Report UCRL-50400, v.31, 1991.
13. S. Perkins, M.Chen, D. Cullen, et al. Tables and
graphs of atomic subshell and relaxation data de-
rived from the LLNL evaluated atomic data li-
brary (EADL), Z=1–100. LLNL: Report UCRL-
50400, v.30, 1992.
14. S. Seltzer, and M.Berger. Bremsstrahlung Spec-
tra from Electron Interactions with Screened
Atomic Nuclei and Orbital Electrons // Nucl. In-
str. and Meth. B. 1985, v.12, p.95-134.
15. S. Seltzer, and M. Berger. Bremmstrahlung En-
ergy Spectra from Electrons with Kinetic Energy
from 1 keV to 10 GeV Incident on Screened Nu-
clei and Orbital Electrons of Neutral Atoms with
Z = 1-100 // Atomic Data and Nuclear Data Ta-
bles. 1986, v.35, p.345-418.
16. C.Myers, B. Kirk, L. Leal. Comparative analysis
of nuclear cross sections in Monte Carlo meth-
ods for medical physics applications // Computa-
tional Medical Physics Working Group Workshop
II, Sep 30-Oct 3, 2007 // http:
cmpwg.ans.org/oct2007/Presentations/T203.pdf
17. XCOM: Photon Cross Sections Database, Natio-
nal Institute of Standards and Technology 1998;
http://www.nist.gov/pml/data/xcom/index.cfm
18. H.Malm. A Mercuric Iodide Gamma-Ray Spec-
trometer // IEEE Trans. Nucl. Sci. 1972, v.19,
p.263-265.
19. K.Hitomi, O. Muroi, T. Shoji, et al. Room tem-
perature X- and gamma-ray detectors using thal-
lium bromide crystals // Nucl. Instr. and Meth.
A. 1999, v.436, p.160-164.
СРАВНЕНИЕ ВОЗМОЖНОСТЕЙ GEANT4 И EGSnrc ДЛЯ МОДЕЛИРОВАНИЯ
ДЕТЕКТОРОВ ГАММА-ИЗЛУЧЕНИЯ НА ОСНОВЕ ПОЛУИЗОЛЯТОРОВ
А.И. Скрыпник, А.А. Захарченко, М.А. Хажмурадов
Исследованы особенности различных моделей электромагнитных взаимодействий гамма-квантов в
GEANT4 v.4.9.4 для расчета функций отклика детекторов на основе полуизолирующих материалов.
GEANT4 использован для определения потерь энергии гамма-квантов в детекторах из HgI2 и TlBr
в диапазоне энергий от 0,026 до 3 МэВ. Погрешности расчетов GEANT4 оценивались при сравне-
нии с данными моделирования EGSnrc. Хорошее согласие обнаружено между расчетами EGSnrc и
GEANT4 при использовании модели электромагнитных взаимодействий Penelope 2008.
ПОРIВНЯННЯ МОЖЛИВОСТЕЙ GEANT4 ТА EGSnrc ДЛЯ МОДЕЛЮВАННЯ
ДЕТЕКТОРIВ ГАММА-ВИПРОМIНЮВАННЯ НА ОСНОВI НАПIВIЗОЛЯТОРIВ
А.I. Скрипник, О.О. Захарченко, М.А. Хажмурадов
Дослiджено можливостi рiзних моделей електромагнiтної взаємодiї гамма-квантiв у GEANT4 v.4.9.4
для розрахунку функцiй вiдгуку детекторiв на основi напiвiзолюючих матерiалiв. GEANT4 викори-
стано для визначення втрат енергiї гамма-квантами в детекторах з HgI2 i TlBr в дiапазонi енергiй вiд
0,026 до 3 МеВ. Похибки розрахункiв GEANT4 було оцiнено шляхом порiвняння з даними моделюван-
ня EGSnrc. Виявлено добру вiдповiднiсть мiж розрахунками EGSnrc та GEANT4 при використаннi
моделi електромагнiтної взаємодiї Penelope 2008.
100
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