Linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal
We present the results of the polarization and intensity measurements versus photon energy Eg=5-35 MeV for the photon beam produced by the electrons with the energies 1.2 and 1.5 GeV moving in the silicon crystal 500 and 290 mm thick along the (110) plane. The comparison with results of another rese...
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| Published in: | Вопросы атомной науки и техники |
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| Date: | 2001 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2001
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| Cite this: | Linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal / V.V. Denyak, V.M. Khvastunov, V.P. Likhachev, S.A. Paschuk, H.R. Schelin // Вопросы атомной науки и техники. — 2001. — № 1. — С. 60-62. — Бібліогр.: 8 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859659710831001600 |
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| author | Denyak, V.V. Khvastunov, V.M. Likhachev, V.P. Paschuk, S.A. Schelin, H.R. |
| author_facet | Denyak, V.V. Khvastunov, V.M. Likhachev, V.P. Paschuk, S.A. Schelin, H.R. |
| citation_txt | Linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal / V.V. Denyak, V.M. Khvastunov, V.P. Likhachev, S.A. Paschuk, H.R. Schelin // Вопросы атомной науки и техники. — 2001. — № 1. — С. 60-62. — Бібліогр.: 8 назв. — англ. |
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| container_title | Вопросы атомной науки и техники |
| description | We present the results of the polarization and intensity measurements versus photon energy Eg=5-35 MeV for the photon beam produced by the electrons with the energies 1.2 and 1.5 GeV moving in the silicon crystal 500 and 290 mm thick along the (110) plane. The comparison with results of another research group and theoretical calculation indicates the qualitative agreement. The correlation in the shape of the radiation intensity spectrum and its polarization energy dependence is observed.
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| first_indexed | 2025-11-30T09:20:57Z |
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LINEAR POLARIZATION OF PHOTONS PRODUCED BY THE
ELECTRONS MOVING ALONG THE CRYSTALLOGRAPHIC PLANE IN
A SILICON CRYSTAL
V.V. Denyak a, V.M. Khvastunov a, V.P. Likhachev b,
S.A. Paschuk c, H.R. Schelin c
a - National Scientific Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
b - University of São Paulo, São Paulo, Brazil
c - Federal Center of Technological Education, CEFET-PR, Curitiba, PR, Brazil
We present the results of the polarization and intensity measurements versus photon energy Eγ=5-35 MeV for the
photon beam produced by the electrons with the energies 1.2 and 1.5 GeV moving in the silicon crystal 500 and
290 µm thick along the (110) plane. The comparison with results of another research group and theoretical
calculation indicates the qualitative agreement. The correlation in the shape of the radiation intensity spectrum and
its polarization energy dependence is observed.
PACS: 29.27.Fh, 29.27.Hj, 41.60.-m, 07.85.Fv.
INTRODUCTION
There are relatively small numbers of methods of
polarized photon production in the energy range of 1-
100 MeV. Not far ago the high polarisation degree was
found for photon beam produced by high-energy
electrons moving along crystallographic plane in crystal
[1]. High intensity and polarization degree make such
photon beam very suitable for the study of atomic
nuclear structure as well as dynamic characteristics of
nuclear reactions induced by polarized photons.
The intensity of such beams was actively
investigated by the theoreticians and experimentalists
during the last years. But, the studying of photon
polarization has been started recently. Only some first
experiments were devoted to the measurements of
photon beam polarization [2,3]. The high polarization
degree Pγ=0.6-0.9 near the characteristic maximum was
observed in these investigations.
The theoretical investigation of the photon
polarization is also at the very beginning now. The
authors of work [2] give two possible methods of such
calculations. But, as they mentioned, their results should
be considered only as an illustration of some general
approach.
Recently, rather interesting results were achieved in
the theoretical calculation of the photon polarization on
the base of “thermal-layer” model [3] that gave very
good agreement with experimental data on diamond
target. At the same time, similar analysis [4] performed
for the silicon crystal does not give correct description
of experimental polarization spectrum of [2].
The objective of our work was the experimental
investigation of the soft part of linear polarization
energy spectrum of photons emitted by high-energy
electrons in the silicon crystal. It is very important to
increase the quantity of experimental information in the
energy region where it was observed disagreement with
theory [4].
Moreover, it was supposed to carry out
simultaneously the measurements of photon intensity
spectrum. Such measurements were not performed in
previous investigations. At the same time, the
information about the intensity spectrum is very
important to test the theoretical models. The
experimental conditions of measurements have some
parameters, such as initial electron beam
monochromaticity, divergence, photon beam
collimation etc., should be taken into account in the
computation. Since the theoretical methods for intensity
spectrum calculation were developed quite well even for
thick crystals, these spectra may be used as test of
correctness of experimental parameters accounting.
Some preliminary results were already represented
in a previous paper [5].
EXPERIMENTAL TECHNIQUE
The experiments have been performed using the
electron beam of 2 GeV LINAC of the National
Scientific Center Kharkov Institute of Physics and
Technology (NSC KhIPT). The experimental setup is
shown in Fig. 1.
Fig. 1. Experimental setup: 1 - the goniometer with
the target of a silicon single crystal, 2 - the deflecting
magnet, 3 - the concrete shelding, 4 - the photon beam
collimator, 5 - the cleaning magnet, 6 - the deuterium
polarimeter, 7 - the ionization chamber, 8 - the
quantometer
The photon beam was generated by electrons
moving in (110) plane of Si crystal. The electron energy
(Ee) was 1200 MeV and 1500 MeV for 500 µm
and 290 µm crystal thick correspondingly. The electron
beam parameters at the crystal target location were:
60 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2001, № 1.
Series: Nuclear Physics Investigations (37), p. 60-62.
monochromaticity ~1 %, divergence ~10-4 rad. The
photon beam angular collimation was Θ~10-4 rad.
The polarimeter operation [6] is based on the
measurement of the proton yield asymmetry (A) of the
deuterium photodisintegration:
A=PΣ,
where Р is the photon polarization degree and Σ is the
asymmetry of the reaction γ+d=n+p.
The photon spectra, corresponding to the amorphous
target, were measured with the same crystal.
EXPERIMENTAL RESULTS
As the result of the measurements, the proton energy
spectra for three different crystal orientations
corresponding to the direction of the photon polarization
vector: the parallel (N||) and perpendicular (N⊥) to the
reaction plane as well as for the disoriented crystal (No)
were obtained. The registered protons were considered
as a result of direct photodisintegration of the deuteron.
Thus, we were able to restore the photon energy spectra
according the reaction kinematics. The possible
contribution of protons generated at Eγ above the meson
production threshold is small mainly due to the slope
character of the photon intensity spectra (~1/Eγ) and it
does not exceed a few percents.
The photon beam polarization had been restored
according to the formula:
Pγ=A/Σ=(N|| - N⊥)/(Σ (N|| + N⊥)).
For the photon energy region above 10 MeV the
deuteron photodisintegration asymmetry (Σ) values
were taken from the experimental paper [7]. For lower
energies Eγ, we used the results of the reaction
asymmetry calculations based on the covariant gauge-
invariant model with a Paris potential [8]. In this work,
the interaction in the final state was considered in the
form of re-scattering in the 1S0 state, and it was obtained
that deuteron photodisintegration asymmetry within the
range Еγ=4-10 MeV is constant and equal to 0.99.
Our results are shown at Fig. 2 together with
experimental data [2] obtained under the conditions
very close to our measurements (silicon crystal 400 µm
thick, (110) plane, and electron beam with the energy
900 MeV).
The upper part of Fig. 2 shows the radiation
intensity extracted from our experimental data on the
oriented crystal and normalized by the disoriented
crystal case as following:
β= (N|| + N⊥)/2No.
The beam polarization is represented at the down part of
Fig. 2. In spite of the fact that polarization
measurements of [2] were carried out with another
experimental technique (Compton polarimeter), they are
in qualitative agreement with ours measurements at
initial electron energy Ee=1200MeV. However one can
see that our experiment gave bigger polarization degree
which could be attributed to more high Ee leading to the
shift of the radiation maximum to higher Eγ (~Ee
3/2).
Comparison of our results for Ee=1200 MeV
(Fig. 2,a and Fig. 2,c) with theoretical calculations of
work [2] (Fig. 2,e) shows that continuous model gives
more correct description of polarization energy
dependence. It should have a broad maximum at Eγ=5-
10 MeV with a flattening out at Eγ=20-30 MeV.
At Fig. 2,a and Fig. 2,c the results of theoretical
calculations on the base of “thermal-layer” model are
shown. Despite the fact that the authors performed this
analysis using the parameters very close to ours for
electron beam initial energy 1200 MeV, their
calculation agree with our experimental data only
qualitatively. As it is seen from intensity, this
calculation overestimated the coherent effect (i.e.
theoretical intensity spectrum is higher than
experimental). That, of course, leads to higher
polarization, since the polarization value should depend
from a number of electrons involved in channeling
motion (i.e. in coherent radiation).
The characteristic feature of obtained results is that
the beam polarization energy dependence is very similar
to intensity energy dependence. To check this
suggestion, the polarization in the coherent part of the
spectrum was calculated from experimental data
according to the formula:
Pc=((N|| -No) - (N⊥ -No))/(((N|| -No) + (N⊥ -No))Σ).
The results of these calculations are given at Fig. 3.
It is seen that polarization in the coherent part of the
spectrum changes weakly with displacement from
maximum of intensity energy spectrum, which proves
out conclusion mentioned above.
CONCLUSIONS
Investigated low energy photon beam spectrum,
produced by electrons moving in silicon crystal along
the crystallographic plane, possesses the peak with the
high polarization degree ~80 % whose intensity exceeds
approximately in 5-6 times the amorphous level. The
“thermal-layer” model, that gives good theoretical
description of the experiments with diamond,
overestimate the polarization for silicon crystal. The
characteristic feature of radiation is that the beam
polarization, as a function of photon energy, reflects the
behavior of the radiation intensity spectrum itself.
ACKNOWLEDGEMENTS
The authors are very thankful to Kasilov V.I.,
Sanin V.M, and Shcherbak S.F. for their significant help
in photon beam production.
61
0 10 20 30 40
0
2
4
6
8
10
Eγ ,MeV
a) β
0 10 20 30 40
0
2
4
6
8
10
Eγ ,MeV
b)
β
0 10 20 30 40
0.0
0.2
0.4
0.6
0.8
1.0 Pγ
Eγ ,MeV
с)
0 10 20 30 40
0.0
0.2
0.4
0.6
0.8
1.0 Pγ
Eγ ,MeV
d)
0 10 20 30 40
0.0
0.2
0.4
0.6
0.8
1.0
2
1
Eγ ,MeV
Pγ
e)
Fig. 2. Relative intensity and polarization degree of the photon beam.a),c) - Ee=1200 MeV, t=500 µm,
curves – results of work [4];b),d) - Ee=1500 MeV, t=290 µm;e) - data of paper [2]: Ee=900 MeV,
t=400 µm, (1) - modeling and (2) - continuous model
Fig. 3. Polarization in the coherent part of the spectrum at Ee=1500 MeV, t=290 µm
REFERENCES
1. Yu.N. Adishchev et al. Detection of Linear
Polarization of Gamma Radiation at Electron Plane
Channeling in Diamond // JETP Letters, 1981, v. 33,
p. 462-465.
2. S.A. Vorobyov et al. Experimental and Theoretic
Investigation of Radiation Linear Polarization of
Relativistic Electrons at Plane Channeling // J. of
Exp. and Theor. Phys., 1988, v. 94, p. 38-48.
3. V.B. Ganenko et al. Investigation of Linear
Polarization of Radiation Emitted by Planar
Channeling Relativistic Electrons in Diamond
Crystal // Phys. of Atom. Nuclei, 1997, v. 60, p. 165-
171.
4. I.N. Mondrus et al. Spectral and Polarization
Characteristics of Radiation at Plane Channeling //
Poverkhnost', Fizika, khimiya, mekhanika. 1995,
v. 5, p. 76-78 (in Russian).
5. V.V. Denyak et al. Linear Polarization of
Bremsstrahlung Radiation at Plane Falling of
Electrons on Silicon Crystal // Proceeding of XXI
All Union Workshop on Physics of Charged
Particles Interaction with Crystals. Moscow:
Moscow University, 1991, p. 76 (in Russian).
6. Yu.V. Vladimirov et al. Polarimeter on the Base of
Gas Deuterium Target and Semiconductor
Detectors. Preprint KhIPT, 88-60, 1988 (in
Russian).
7. W. Del Bianko et al. Neutron asymmetry
measurement in the deuteron photodisintegration
between 10 and 70 MeV // Phys. Rev. Lett. 1981,
v. 47, p. 1118-1120.
8. A.Yu. Buki et al. Photodisintegration of Deuteron by
Linearly Polarized Photons Near Threshold // Sov. J.
of Nucl. Phys., 1990, v. 51, p. 769-770.
62
PACS: 29.27.Fh, 29.27.Hj, 41.60.-m, 07.85.Fv.
Introduction
A=P,
Experimental results
Conclusions
ACKNOWLEDGEMENTS
REFERENCES
|
| id | nasplib_isofts_kiev_ua-123456789-78448 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-30T09:20:57Z |
| publishDate | 2001 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Denyak, V.V. Khvastunov, V.M. Likhachev, V.P. Paschuk, S.A. Schelin, H.R. 2015-03-17T12:12:09Z 2015-03-17T12:12:09Z 2001 Linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal / V.V. Denyak, V.M. Khvastunov, V.P. Likhachev, S.A. Paschuk, H.R. Schelin // Вопросы атомной науки и техники. — 2001. — № 1. — С. 60-62. — Бібліогр.: 8 назв. — англ. 1562-6016 PACS: 29.27.Fh, 29.27.Hj, 41.60.-m, 07.85.Fv. https://nasplib.isofts.kiev.ua/handle/123456789/78448 We present the results of the polarization and intensity measurements versus photon energy Eg=5-35 MeV for the photon beam produced by the electrons with the energies 1.2 and 1.5 GeV moving in the silicon crystal 500 and 290 mm thick along the (110) plane. The comparison with results of another research group and theoretical calculation indicates the qualitative agreement. The correlation in the shape of the radiation intensity spectrum and its polarization energy dependence is observed. The authors are very thankful to Kasilov V.I., Sanin V.M, and Shcherbak S.F. for their significant help in photon beam production. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Nuclear reactions Linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal Линейная поляризация фотонов, полученных при движении электронов вдоль кристаллографической плоскости в кристалле кремния Article published earlier |
| spellingShingle | Linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal Denyak, V.V. Khvastunov, V.M. Likhachev, V.P. Paschuk, S.A. Schelin, H.R. Nuclear reactions |
| title | Linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal |
| title_alt | Линейная поляризация фотонов, полученных при движении электронов вдоль кристаллографической плоскости в кристалле кремния |
| title_full | Linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal |
| title_fullStr | Linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal |
| title_full_unstemmed | Linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal |
| title_short | Linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal |
| title_sort | linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal |
| topic | Nuclear reactions |
| topic_facet | Nuclear reactions |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/78448 |
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