Expected coherent bremsstrahlung photon beam parameters at the S-DALINAC
Expected spectra and polarization of the coherent bremsstrahlung photon beam that can be created at S-DALINAC was calculated using the Uberall-Diambrini theory. Photon beam parameters are convenient for carrying out experiments on photon scattering and nuclear photodisintegration in the giant resona...
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| Zitieren: | Expected coherent bremsstrahlung photon beam parameters at the S-DALINAC / V.B. Ganenko, D.S. Lyasotskiy, V.L. Morokhovskii, A.V. Solodovnikov // Вопросы атомной науки и техники. — 2000. — № 2. — С. 48-50. — Бібліогр.: 8 назв. — рос. |
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| author | Ganenko, V.B. Lyasotskiy, D.S. Morokhovskii, V.L. Solodovnikov, A.V. |
| author_facet | Ganenko, V.B. Lyasotskiy, D.S. Morokhovskii, V.L. Solodovnikov, A.V. |
| citation_txt | Expected coherent bremsstrahlung photon beam parameters at the S-DALINAC / V.B. Ganenko, D.S. Lyasotskiy, V.L. Morokhovskii, A.V. Solodovnikov // Вопросы атомной науки и техники. — 2000. — № 2. — С. 48-50. — Бібліогр.: 8 назв. — рос. |
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| container_title | Вопросы атомной науки и техники |
| description | Expected spectra and polarization of the coherent bremsstrahlung photon beam that can be created at S-DALINAC was calculated using the Uberall-Diambrini theory. Photon beam parameters are convenient for carrying out experiments on photon scattering and nuclear photodisintegration in the giant resonance region with polarized photons.
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EXPECTED COHERENT BREMSSTRAHLUNG PHOTON BEAM
PARAMETERS AT THE S-DALINAC
V.B. Ganenko, D.S. Lyasotskiy, V.L. Morokhovskii, A.V. Solodovnikov
National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
Expected spectra and polarization of the coherent bremsstrahlung photon beam that can be created at S-
DALINAC was calculated using the Uberall-Diambrini theory. Photon beam parameters are convenient for carrying
out experiments on photon scattering and nuclear photodisintegration in the giant resonance region with polarized
photons.
PACS: 29.27.Hj; 25.20.-x.
1. INTRODUCTION
Coherent bremsstrahlung radiation (CB) generated by
relativistic electrons in monocrystal photon targets made
from diamond crystals, having a high Debay
temperature, perfect crystal lattice and small atomic
number, offer the most high operating parameters, and
due to this they findwide use in experiments of nuclear
physics and elementary particles [1]. In consequence of
the periodicity of atom location in the crystal lattice,
when relativistic electrons fall onto the crystal at a small
angle ψ relative to the crystal axes, (but exceeding
substantially a critical angle of axial channeling,
ψ>>ψc,) in the CB spectra the interference maxima
appear. The radiation intensity in these maxima
substantially exceeds the electron radiation intensity in
an amorphous material and the radiation in the
maximum possesses a significant linear polarization.
The spectrum and polarization of CB are well described
by the theory based on the Born approximation [2-4].
According to [2-4] the CB cross section can be
presented in the form of a sum:
dσkti=dσint+dσam,
where dσint is the interference part of CB cross section
depending on the crystal orientation relatively to the
electron beam; dσam is the non-coherent part of cross
section, which does not depend on the crystal orientation
and presents itself a cross section of usual
bremsstrahlung in the amorphous substance. Thus CB
spectrum consists of two parts: coherent part with
interference maximuma and usual bremsstrahlung. The
interference peak has a sharp upper border and is
reduced slowly in the low-energy area. The radiation
intensity in the interference peak falls with increasing
angle ψ, and the peak itself is displaced in the higher
energy range and at larger ψ it is not observed.
CB beams on the base of diamond crystal were
obtained practically at all electron accelerators with a
beam energy of Е0~1 GeV and higher [1]. However,
there are sufficient number of accelerators at which is
conducted studies of nuclear structure and mechanisms
of photonuclear reactions in the low-energy range
(before the threshold of pion production) and with the
significantly lower energy, Е0~100 MeV. Photonuclear
studies on such setups, as a rule, are conducted on
nonpolarized beams of bremsstrahlung or tagged
photons, while the presence of radiation polarization
often opens more possibilities for investigations. Great
advantages of accelerators of such a class are unique
electron beam parameters, first of all the high intensity
that allows conducting precise experiments.
We have studied a possibility of making the beam of
linear polarized photons on the base of CB electrons in
the diamond crystal at the accelerator with the initial
electron energy Е0=100 MeV suitable for investigations
in the area of giant dipole resonance. As an example
considered the beam parameters, which can be get at the
accelerator S-DALINAC [5], which have such main
electron beam parameters:
-electron energy Е0=20-100 MeV;
-maximal intensity of the electron beam –20 µA;
-duty factor –100%.
2. RESULTS
For evaluation of the CB beam quality and possibility
to use it in experimental studies, of deciding importance
are two main characteristics: intensity of coherent part
of the beam and value of polarization in the radiation
maximum Pγ. Usually, the intensity of coherent part Iint is
evaluated by the excess of radiation intensity in the CB
maximum over the intensity of non-coherent part of
radiation Iam(coherent effect β):
β=(dσint+dσam)/dσam=(Iint+Iam)/Iam.
For getting a beam suited to experimental investigations
it is necessary to provide values of coherent effect and
polarization not less than ∼1.4 and ∼20%, respectively.
Concrete values of these parameters substantially
depend on real conditions of getting and forming the CB
beam.
We have performed calculations of CB spectra and
polarization for the initial electron energy Е0=100 MeV
and diamond crystals of a thickness 0.01 and 0.03 cm
with taking into account real experimental conditions:
angle of multiple scattering and divergence of electron
beam, collimation of gamma radiation. Crystals of such
thickness are most optimal for obtaining high beam
polarization. The calculations were performed for the
crystal orientation, when a main contribution to the CB
cross section is given only from one point of the
reciprocal lattice (2,2,0). The given orientation ensures
the highest value of polarization.
Fig. 1 presents the calculation results for spectrum
and polarization of CB electrons of the initial energy
48 ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2000, № 2.
Серия: Ядерно-физические исследования (36), с. 48-50.
.
Е0=100 MeV in the diamond crystal of the thickness
0.01 cm at the energy of interference maximum
Eγ
р=20 MeV (relative energy Х=Еγ/Е0=0.2) for values of
radiation collimation angle in the interval θс=0.25-2θγ
(θγ=mc2/E0, m-electron mass). It is seen that for the
initial electron energy Е0=100 MeV the spectrum and
polarization keep yet all particularities inherent to CB,
observed under the higher energy Е0≥1 GeV. Results of
the calculation show that both a coherent effect and
polarization in the CB maximum substantially depend
on the angle of radiation collimation and can reach
sufficiently high values.
0 10 20 30 40 50 60 70 80 90 100
0,8
0,9
1,0
1,1
1,2
1,3
1,4
1,5
1,6
1,7
1,8
1,9
2,0
a
6
5
4
3
2
1
β
E , MeV
0 10 20 30 40 50 60 70 80
-15
-10
-5
0
5
10
15
20
25
30
35
40
45
b
6
5
4
3
2
1
Po
lar
iza
tio
n,
%
E , MeV
Fig. 1. Spectra (a) and polarization (b) of CB
electrons with Е0=100 MeV in the crystal of the
thickness 0.01 cm at energy interference maximum
Eγ
р=20 MeV and radiation angles collimation (1)-0.25,
(2)-0.5, (3)-0.75, (4)-1, (5)-1.5, (6)- 2θγ.
In Fig. 2 the value of coherent effect and polarization
in the CB maximum is shown as a function of radiation
collimation for crystals of the thickness 0.01 and
0.03 cm. The value of coherent effect decreases from β≈
1.85 to β≈1.34 at collimation angle changing from θ
c=0.25θγ to 2θγ, the polarization at that decreases from P
γ≈40% to 14%. During further increasing the collimation
angle the coherent effect and polarization practically do
not change. For the crystal of the thickness 0.03 cm the
values of coherent effect and polarization decrease
within 2-10%. The calculations results allow to conclude
that for getting a CB beam suitable for use in
experimental investigations at accelerators with the
initial energy Е0∼100 MeV, a very strong radiation
collimation within θc≈0.25-0.5θγ is required. Decreasing
of intensity of the gamma beam may be in some cases
compensated by increasing the photon target thickness.
0,0 0,5 1,0 1,5 2,0
0,5
0,8
1,0
1,3
1,5
1,8
2,0
2,3
a
2
1
β
collimation angle, θ γ
0,0 0,5 1,0 1,5 2,0
10
15
20
25
30
35
40 b
2
1
po
la
riz
at
io
n,
%
collimation angle, θ γ
Fig. 2. The value of coherent effect (a) and
polarization (b) versus radiation collimation for Eγ
р=20 MeV and crystals thickness 0.01 cm (1) and
0.03 cm (2).
In Fig. 3 the results of calculation of the energy
dependence of coherent effect and polarization are given
at collimation angles θc=0.5θγ for the crystal of
thickness 0.01 cm. It is seen that the values of coherent
effect and polarization increase to β≈2.2 and Pγ≈45% at
Eγ=10 MeV and decrease to β≈1.4 and Pγ≈20% at
Eγ=35 MeV so the collimation provides acceptable
parameters of CB beam for photonuclear investigations
within the photon energy range from 5 to 35 MeV. At
the collimation angle θc≈θγ this range decreases to
20 MeV.
To evaluate the intensity of CB radiation at the given
collimation we calculated the intensity of a usual
bremsstrahlung under these conditions (electron energy
Е0=100 MeV, thickness of diamond 0.01 cm,
49
collimation angle θc=0.5θγ), which practically is
equivalent to non-coherent part of CB. At the electron
current of 1 µA the expected flux of bremsstrahlung
gamma-quanta of the energy Eγ=20 MeV is about dN/dE
γ≈8.9⋅107 γ/MeV/s. Taking into account the coherent
effect (β≈1.7) the CB intensity of the given energy and
current increase up to dN/dEγ≈1.5⋅108 γ/MeV/s. If the
electron current at the accelerator S-DALIINAC reach
value 20 μA thus, it is hoped for getting intensive beams
of linear polarized CB photons up to dN/dEγ≈3⋅
109 γ/MeV/s at Eγ=20 MeV with which one can carry
out investigations of widespread
0 5 10 15 20 25 30 35 40
1,0
1,2
1,4
1,6
1,8
2,0
2,2
2,4
1
2
β
E, MeV
a
0 5 10 15 20 25 30 35 40
0
5
10
15
20
25
30
35
40
45
50
b
2
1
P
o
l a
r
i z
a
t
i o
n
,
%
E , M e V
Fig. 3. Energy dependence of coherent effect (a)
and polarization (b) of CB for the crystal of the
thickness 0.01 cm at radiation collimation angles
θс=0.5θγ (1) and θc=θγ (2).
photonuclear reactions in the range of the giant dipole
resonance (GDR), in particular on the elastic and non-
elastic photon scattering on nuclei. Cross sections of
these processes in the GDR region are sufficiently great.
So, the cross section of the elastic scattering on 28Si for
the scattering angle 1350 in the interval Eγ=18-22 MeV
is ~14 μb so tagged photon beam may be used [6,7].
With the increase of atomic number an elastic scattering
cross section increases and, for example, for 208Pb at
Eγ=20 MeV and at the scattering angle 1200 is already
200 μb [8]. The great cross sections do such
investigations quite real. The expected reaction yield for
experimental conditions provided in works [7,8] with
the use of polarized CB photons at the electron current
10 μA equals ~27 count/s for [6] and ~9 count/s for [7].
More precise estimations should be made for each
concrete experiment.
REFERENCES
1. G.D. Kovalenko, L.Ya. Kolesnikov, A.L. Rubashkin.
Topics in Current Physics 38. Coherent Radiation
Sources. Coherent Bremsstrachlung-Experiment.
P. 33-60. Springer-Verlag Berlin Heidelerg, 1985.
2. G. Diamrini. High-energy bremsstrachlung and
electron pair production thin crystals // Rev. Mod.
Phys. 1968, v. 40, p. 611-623.
3. U. Timm. Coherent bremsstrahlung of electrons in
crystals. Preprint DESY, 69/14, 1969.
4. M.L Ter-Mickaelyan. Influence of a medium on
electromagnetic processes at high energies.
Yerevan: Izd. AS Arm. SSR. 1969, 457 p. (in
Russian).
5. H. Genz, H.-D. Graf, J. Horn, K.D. Hummel,
M. Knirsch, C. Luttge, A. Richter, T. Rietdorf,
K. Ruhl, P. Schardt, E. Spamer, A. Stiller,
F. Thomas, O. Titze, J. Topper, H. Weise.
Operational experience and results from the S-
DALINAC. Proceedings of the third European
particle accelerator conference, EPAC 92, Berlin,
24-28 March, 1992, v. 1, p. 49-51.
6. S.F. LeBrun, A. M.Nathan,, S.D. Hoblit. Photon
scattering in giant dipole resonance region of 16O.
University of Illinois at Urbana champaing nuclear
physics laboratory department of physics. Preprint
P/87/2/28.
7. R. Alarkon, A. M.Nathan, S.F. LeBrun, S.D. Hoblit.
Photon scattering in giant resonance region of
24Mg, 28Si and 32S. University of Illinois at Urbana
champaing nuclear physics laboratory department of
physics. Preprint P/88/9/130.
8. K.P. Schelhaas, J.M. Henneberg, M. Sanzone-
Arenhover, N. Wieloch-Laufenberg, U. Zurmuhl,
B. Ziegler, M. Schumacher and F. Wolf Nuclear
photon scattering by 208Pb // Nucl. Phys. 1988,
v. A489, p. 189-224.
16 ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2000, № 2.
Серия: Ядерно-физические исследования (36), с. 48-50.
.
V.B. Ganenko, D.S. Lyasotskiy, V.L. Morokhovskii, A.V. Solodovnikov
National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
1. INTRODUCTION
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| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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| spelling | Ganenko, V.B. Lyasotskiy, D.S. Morokhovskii, V.L. Solodovnikov, A.V. 2015-05-27T12:22:04Z 2015-05-27T12:22:04Z 2000 Expected coherent bremsstrahlung photon beam parameters at the S-DALINAC / V.B. Ganenko, D.S. Lyasotskiy, V.L. Morokhovskii, A.V. Solodovnikov // Вопросы атомной науки и техники. — 2000. — № 2. — С. 48-50. — Бібліогр.: 8 назв. — рос. 1562-6016 PACS: 29.27.Hj; 25.20.-x. https://nasplib.isofts.kiev.ua/handle/123456789/82269 Expected spectra and polarization of the coherent bremsstrahlung photon beam that can be created at S-DALINAC was calculated using the Uberall-Diambrini theory. Photon beam parameters are convenient for carrying out experiments on photon scattering and nuclear photodisintegration in the giant resonance region with polarized photons. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Еxperimental methods Expected coherent bremsstrahlung photon beam parameters at the S-DALINAC Ожидаемые параметры поляризованного тормозного пучка фотонов на ускорителе S-DALINAC Article published earlier |
| spellingShingle | Expected coherent bremsstrahlung photon beam parameters at the S-DALINAC Ganenko, V.B. Lyasotskiy, D.S. Morokhovskii, V.L. Solodovnikov, A.V. Еxperimental methods |
| title | Expected coherent bremsstrahlung photon beam parameters at the S-DALINAC |
| title_alt | Ожидаемые параметры поляризованного тормозного пучка фотонов на ускорителе S-DALINAC |
| title_full | Expected coherent bremsstrahlung photon beam parameters at the S-DALINAC |
| title_fullStr | Expected coherent bremsstrahlung photon beam parameters at the S-DALINAC |
| title_full_unstemmed | Expected coherent bremsstrahlung photon beam parameters at the S-DALINAC |
| title_short | Expected coherent bremsstrahlung photon beam parameters at the S-DALINAC |
| title_sort | expected coherent bremsstrahlung photon beam parameters at the s-dalinac |
| topic | Еxperimental methods |
| topic_facet | Еxperimental methods |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/82269 |
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