Special features of ultrarelativistic electron radiation in a thin layer of matter
The condition and specific features of non-dipole regime of radiation is discussed in connection with the results of the recent CERN experiment NA63 on measurement of the radiation power spectrum of 149 GeV electrons in thin tantalum targets. The first experimental detection of logarithmic dependenc...
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| Zitieren: | Special features of ultrarelativistic electron radiation in a thin layer of matter / A.S. Fomin, S.P. Fomin, N.F. Shul’ga // Вопросы атомной науки и техники. — 2011. — № 5. — С. 75-81. — Бібліогр.: 27 назв. — англ. |
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| author | Fomin, A.S. Fomin, S.P. Shul’ga, N.F. |
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| citation_txt | Special features of ultrarelativistic electron radiation in a thin layer of matter / A.S. Fomin, S.P. Fomin, N.F. Shul’ga // Вопросы атомной науки и техники. — 2011. — № 5. — С. 75-81. — Бібліогр.: 27 назв. — англ. |
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| description | The condition and specific features of non-dipole regime of radiation is discussed in connection with the results of the recent CERN experiment NA63 on measurement of the radiation power spectrum of 149 GeV electrons in thin tantalum targets. The first experimental detection of logarithmic dependence of radiation yield from the target thickness is the conclusive evidence of the e®ect of radiation suppression in a thin layer of matter, which was predicted many years ago, and which is the direct manifestation of the radiation of a relativistic electron with non-equilibrium own Coulomb field. The special features of the angular distribution of the radiation and its polarization in a thin target at non-dipole regime are proposed for a new experimental study.
Умови реалізації та особливості недипольного режиму випромінювання обговорюються в контексті результатів недавніх експериментів CERN NA 63 по вимірам спектрів випромінювання електронів з енергією 149 ГеВ у тонких мішенях танталу. Перше спостереження логарифмічної залежності виходу випромінення від товщини мішені, зроблене в цьому експерименті, є переконливим доказом існування ефекту пригнічення випромінювання в тонкому шарі речовини, який був теоретично передбачений багато років тому, і який є прямим проявом випромінювання релятивістських електронів з нерівновагим власним кулонівським полем. Пропонується проведення нових експериментальних досліджень, передбачуваних теорією особливостей кутового розподілу випромінювання і його поляризації в тонкій мішені в умовах недипольного режиму випромінювання.
Условия реализации и особенности недипольного режима излучения обсуждаются в контексте результатов недавних экспериментов CERN NA 63 по измерению спектров излучения электронов с энергией 149 ГэВ в тонких мишенях тантала. Первое наблюдение логарифмической зависимости выхода излучения от толщины мишени, сделанное в этом эксперименте, является убедительным доказательством существования эффекта подавления излучения в тонком слое вещества, который был предсказан много лет назад, и который является прямым проявлением излучения релятивистских электронов с неравновесным собственным кулоновским полем. Предлагается проведение новых экспериментальных исследований, предсказываемых теорией особенностей углового распределения излучения и его поляризации в тонкой мишени в условиях недипольного режима излучения.
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SPECIAL FEATURES OF ULTRARELATIVISTIC ELECTRON
RADIATION IN A THIN LAYER OF MATTER
A.S. Fomin∗, S.P. Fomin, N.F. Shul’ga
National Science Center ”Kharkov Institute of Physics and Technology”, 61108, Kharkov, Ukraine
(Received August 11, 2011)
The condition and specific features of non-dipole regime of radiation is discussed in connection with the results
of the recent CERN experiment NA63 on measurement of the radiation power spectrum of 149 GeV electrons in
thin tantalum targets. The first experimental detection of logarithmic dependence of radiation yield from the target
thickness is the conclusive evidence of the effect of radiation suppression in a thin layer of matter, which was predicted
many years ago, and which is the direct manifestation of the radiation of a relativistic electron with non-equilibrium
own Coulomb field. The special features of the angular distribution of the radiation and its polarization in a thin
target at non-dipole regime are proposed for a new experimental study.
PACS: 41.60.-m ; 41.75.Ht
1. INTRODUCTION
During last two years there were published the results
of recent experimental investigations on the special
features of a relativistic electron bremsstrahlung in a
thin target [1, 2]. These measurements were done
by international collaboration NA63 in CERN us-
ing SPS secondary electron beam with energy around
200 GeV . One of the main motives to carry out this
experiment was to make clear the unexpected result
of the SLAC experiment E-146 [3-5] that showed a
strange behavior of the radiation spectrum of 25 GeV
electrons in relatively small-thickness target, espe-
cially for the gold target with a thickness of 0.7%
of the radiation length [3, 4].
The SLAC experiment E-146 was generally de-
voted to the verification of the Migdal quantitative
theory of the Landau-Pomeranchuk-Migdal (LPM)
effect [6, 7], which describes the suppression of radia-
tion of relativistic electrons in an amorphous matter
due to the multiple scattering on atoms in compari-
son with the predictions of the Bethe-Heitler theory
[8]. The analysis of the data obtained in SLAC ex-
periment E-146 showed a good agreement between
the calculations using the Migdal formula (LPM ef-
fect) and the experimental data for relatively thick
targets and not very low photon energies. However,
for the case of the gold target with a thickness of
0.7% of radiation length there was a significant dis-
agreement between theory and experiment [4]. Such
”unexpected” behavior of the radiation spectrum at
low frequencies was named in [4] as ”edge effect” and
firstly they tried to exclude it by subtraction proce-
dure, because ”no satisfactory theoretical treatment
of this phenomenon” was found for that moment. Ac-
tually, they found out the Ternovskii article [9], in
which the Migdal theory of the LPM effect that de-
veloped for boundless amorphous medium was im-
proved for the finite target thickness case. However,
when they tried to use the Ternovskii formula to de-
scribe the ”edge effect”, they obtained the excess of
the Bethe-Heitler result [8] instead of the expected
suppression, and they wrote in [3] that this formula
gives ”unphysical result”.
The discrepancy observed in SLAC experiment
stimulated a new wave of theoretical investigations
of the multiple scattering effect on radiation (see [10-
15]). In [10] it was shown that the deviation from pre-
dictions of the Migdal theory observed in [3-5] takes
place, when the target thickness t is small in compar-
ison with the coherence length (or formation zone) of
radiation process lc = 2ε′ε/m2ω [16] (here m and ε
are the mass and initial energy of an electron, ω is
the emitted photon energy, ε′ = ε − ω, we use the
system of units: h = c = 1). Exactly this case t ¿ lc
was theoretically considered earlier in [17, 18], where
the specific effect of the suppression of radiation in
a thin layer of matter was described and discussed
in details including its essential distinction from the
LPM and BH regimes of radiation. As was shown
in [10], the ”unphysical result” obtained by the Ter-
novskii formula in [3] connected with the usage of the
asymptotic formula for a mean-square angle of mul-
tiple scattering, which is not applicable for the SLAC
experiment E-146 conditions.
The quantitative theory of the radiation suppres-
sion effect in a thin layer of matter was developed
later in [10-15] using different approaches. The re-
sults obtained in these works are in a good agreement
with the SLAC experimental data for the thin golden
target (see, for example, reviews [4, 19]). However,
∗Corresponding author E-mail address: ofomin@kipt.kharkov.ua
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2011, N5.
Series: Nuclear Physics Investigations (56), p.75-81.
75
it was the only one explicit manifestation of this ef-
fect during the SLAC experiment E-146 and it took
place in a relatively narrow photon energy region for
25 GeV electrons. That is why it was necessary to
carry out a special experimental investigation of this
effect at higher electron energy that gives a wider
photon energy region for observation of this effect
and, that is even more important, to study the thick-
ness dependence of radiation intensity in a thin tar-
get case, which is fundamentally differed from the BH
and LPM regime of radiation (see [17-19]).
A new experimental study of the LPM and analo-
gous effects at essentially higher electron energies (up
to ε = 287 GeV ) was carried out recently at CERN
by the NA63 Collaboration (see [20, 21] and also [1,
2,]). The results of measurements [20] for Ir, Ta and
Cu targets with thicknesses about 4 % of the radia-
tion length showed good agreement with the Migdal
theory of the LPM effect. The effect of suppression
of radiation in a thin target, named in [20] as the
Ternovskii-Shul’ga-Fomin (TSF) effect, was also con-
sidered in [20, 21], however, the photon energy region,
in which the TSF effect could be observed for chosen
target thicknesses, were below the energy threshold
of measured photons ωmin = 2 GeV for both these
experiments. The condition for the successful obser-
vation of the TSF effect in radiation spectrum was
realized later in CERN for 206 and 234 GeV electrons
radiation in 5...10 µm thin Ta targets [1].
Finally, probably the most complicated measure-
ments for realization, but the most important for
demonstration of the TSF effect essence, namely the
logarithmic thickness dependence of radiation inten-
sity in a thin target, were successfully carried out
recently by the CERN NA63 Collaboration [2]. This
is the first direct demonstration of the suppression of
radiation effect for a relativistic electron with non-
equilibrium own Coulomb field [18, 22]. This effect
should have its analog also in QCD at quark-gluon
interaction.
In this paper we present the theoretical analysis
and treatment of the recent CERN experimental re-
sults [1, 2]. We also propose to carry out a new ex-
periment to study the special features of the angular
distribution of radiation at the TSF effect conditions,
which were theoretically described in [23]. These fea-
tures can give a new opportunity for obtaining a high
degree of linear polarization of gamma-quanta that
was proposed in [24].
2. GENERAL CONDITIONS AND
FEATURES OF LPM AND TSF EFFECTS
According to the standard Bethe-Hietler theory of
bresstrahlung in amorphous matter the radiation
power spectrum dE/dω defined by scattering of rel-
ativistic electron on target atoms is proportional to
the target thickness t [8]:
dEBH
dω
=
2t
3X0
[(
1 +
ε′2
ε2
)
+
ω2
2ε2
]
, (1)
where X0 is the radiation length of target material.
Landau and Pomeranchuk showed [6] that if the
root-mean-square angle of electron multiple scatter-
ing θms at the distance of the coherence length lc ex-
ceeds the characteristic angle of relativistic particle
radiation θ ∼ γ−1, where γ = ε/m is the Lorentz fac-
tor of an electron, then the radiation power spectrum
will be suppressed in comparison with the Bethe-
Hietler result given by formula (1).
The root-mean-square angle of electron multiple
scattering on atoms in an amorphous medium at the
depth t is inversely proportional to the electron en-
ergy ε [8, 19]
θms(t) = (εs/ε)
√
t/X0 [1 + 0.038ln(t/X0)] ,
ε2
s = 4π ·m2/e2 , (2)
so, the target thickness lγ , at which θms(lγ) = γ−1
does not depend on the electron energy ε and is de-
termined by the target material only lγ ≈ 0.15% X0,
thus, the condition of the suppression of radiation
due to the multiple scattering effect θms(lc) > γ−1
(the so-called non-dipole regime of radiation) can be
written in the following form:
lc > lγ . (3)
If t < lγ , i.e. the target thickness t is less than
0.15% X0, the spectral density of radiation for all pos-
sible emitted photon energies is defined by the Bethe-
Heitler formula (1).
If t > lγ , there are three possible regimes of radi-
ation in this case depending on the energy region of
the emitted photon.
For the relatively hard part of emitted spectrum,
when lc < lγ , we have a dipole regime of radiation
describing by the Bethe-Hietler formula (1) too.
For the non-dipole radiation, lc > lγ , there are
two regions, defined by the ratio between the coher-
ence length lc and the target thickness t, with quite
a different behavior of the radiation spectrum. If the
target is thick enough, t À lc > lγ , the Migdal theory
[7] of the LPM effect, which describes the suppres-
sion of radiation in a boundless amorphous medium,
is applicable. For relatively thin target, lc À t > lγ
(intermediate case), the TSF mechanism of radiation
[9, 17] is realized.
Condition (3) determines the photon energy re-
gion, where the LPM effect is essential:
ω < ωLPM =
ε
1 + εLPM/ε
, (4)
εLPM =
e2m2
4π
X0 ≈ 7.7 TeV ·X0 (cm) .
It means that for ultra high electron energy (ε À
εLPM ) the whole radiation spectrum is suppressed
due to the LPM effect: ωLPM ≈ ε.
If ε ¿ εLPM , then ωLPM ≈ ε2/εLPM ≈ 1600 γ2/X0.
The Migdal function ΦM [7] describes the devia-
tion of the radiation spectrum for ω < ωLPM from
76
the Beth-Hietler formula (1) in a relatively soft part
of the spectrum (ω ¿ ε):
dELPM
dω
≈ dEBH
dω
ΦM (s) , (5)
ΦM (s) = 24s2
(∫ ∞
0
dx ctg(x) e−2sx − π
4
)
,
s =
1
2
√
ω
2ωLPM
.
The upper limit for the emitted photon energy
for the TSF regime of radiation TSF follows from the
TSF effect condition
lc À t > lγ . (6)
It is defined by the equality t = lc and can be written
in the following form:
ωTSF =
ε
1 + εTSF /ε
, (7)
εTSF =
m2t
2
≈ 6.6 PeV · t(cm) .
If ε À εTSF , one can use simpler expression for
the TSF effect threshold ωTSF ≈ 2γ2/t.
The quantitative theory of the multiple scattering
effect on a radiation of the relativistic electron in a
thin layer of matter (the TSF effect) was developed
in [10] using classical formulas for spectral density of
radiation and the results of the Bethe-Moliere theory
of multiple scattering [25]. This approach is valid if
ω ¿ ε. Namely such a condition was realized for
both experimental investigations at SLAC E-146 [3,
4] and at CERN NA63 [1, 2].
The radiation power spectrum in this case (lc À
t) is determined by formula [11]
dETSF
dω
=
2e2
π
∫
dθsfBM (θs)
[
2ξ2 + 1
ξ
√
ξ2 + 1
ln (ξ+
+
√
ξ2 + 1
)
− 1
]
, ξ = γθs/2 , (8)
in which the averaging over the electron multi-
ple scattering in a target is carried out with the
Bethe-Moliere distribution function fBM [25] (for de-
tails see [10, 19]). At t ¿ lγ (that means ξ ¿ 1)
formula (8) gives the Bethe-Hietler result with the
linear dependence from the target thickness. In the
opposite case, i.e. at t À lγ , formula (8) gives only
a logarithmic increasing of radiation power spectral
density with increasing the target thickness.
Such a strange behavior of the radiation power
(the scattering angle still increases linearly with
thickness, but radiation does not) can be explained
by the relativistic delay effect during regeneration of
the own Coulomb field of the relativistic electron after
its scattering on a large angle θs > γ−1, and it can be
treated as a radiation of the ”half-bare” electron, i.e.
the electron with non-equilibrium own Coulomb field
(see [18, 19, 22] for detailed discussion). This log-
arithmic behavior will be changed to the linear one
again when the target thickness reaches the value of
coherence length for the given photon energy ω.
The quantum treatment of the TSF effects was
done in [11-15] using different approaches and it
became important for ultrahigh electron energy
ε À εTSF , when ωTSF ≈ ε and the whole radiation
spectrum is suppressed due to the TSF effect.
There are two additional factors that have an
essential influence on the radiation process in mat-
ter, namely, the dielectric suppression (or the Ter-
Mikaelyan effect [16]) and the transition radiation
from the target bounds [5, 16]. Both these effects
could be neglected, if we consider photons energies
higher than ω0 = γωp , where ωp is the plasma fre-
quency [16]. For tantalum target and the electron
beam energy ε = 150 GeV this threshold is about
ω0 ≈ 25 MeV .
The qualitative difference between the different
regimes of radiation in amorphous matter, namely
the BH, LPM and TSF regimes and their conse-
quent changing clear demonstrates the thickness de-
pendence of the radiation power spectrum dE/dω.
The results of theoretical calculations of such depen-
dence are presented in Fig.1.
Fig.1. The radiation power spectrum of 150 GeV electrons in tantalum target via
target thickness t (%X0). A detailed description of the curves is given in the text
77
For t < lγ , i.e. when the target thickness t is
so small that the multiple scattering of relativistic
electrons in target is not enough to fulfill the con-
dition (3), the radiation process has a dipole char-
acter and the radiation power spectrum is described
by the Bethe-Hietler formula (1). The soft part of
the Bethe-Hietler spectrum (ω ¿ ε) does not de-
pend on ω and is described by a very simple formula
dEBH/dω = 4t/3X0. The corresponding curve is pre-
sented in Fig.1 by the dashed straight line ”BH”.
With increasing the target thickness the condition
t = lγ could be fulfilled, and at this point the di-
pole regime of radiation is changed to the non-dipole
one that leads to suppression of radiation comparing
with the Bethe-Hietler formula predictions. For rel-
atively soft photons, for which lc À t, the radiation
power for this part of radiation spectrum is deter-
mined by formula (8) that means the TSF regime
of radiation with a logarithmic dependence on the
target thickness t (solid line ”TSF” in Fig.1). As
follows from eq. (8) dETSF /dω does not depend on
the emitted photon energy ω , however, the validity
condition of the TSF regime (6) does. It means that
for different ωn the transition from the TSF to the
LPM regime of radiation takes place at different val-
ues of target thickness tn = lc(wn). In Fig.1 there
are three such points marked by arrows for different
photon energies ωn , namely ω1 = 150, ω2 = 350 and
ω3 = 800 MeV . There are also three different dot-
dashed lines ”LPM”, which are calculated using the
Migdal formula (5) for these values of photon energy
respectively. Thus, changing the target thickness one
can consequently observe three different mechanisms
of radiation of relativistic electron in the amorphous
target such as the BH, TSF and LPM.
The first experimental investigation of the thick-
ness dependence transformation from the linear
regime (BH) via the logarithmic one (TSF) to the
linear (LPM) one again was recently done in CERN
by the NA63 Collaboration [2]. In spite of all diffi-
culties connected with a very complicate experimen-
tal installation and by operating with a set of very
thin targets of several micrometers thickness, this ex-
periment gave a conclusive proof of the suppression
effect of relativistic electron radiation in a thin layer
of matter predicted many years ago [9, 17] and perse
it gave the unique demonstration of the space-time
evolution of the radiation process in matter as an
example of relativistic electron with non-equilibrium
own Coulomb field [18, 19, 22].
Fig.2. The radiation power per unit length for 149 GeV electron radiation in tantalum
target via target thickness t (%X0). A detailed description of the curves is given in text
The comparison of experimental data with the re-
sults of calculations using different approaches repre-
sented in [1, 2] shows a not only qualitative, but also
quantitative good agreement. In this short paper we
present the comparison of the results of our calcula-
tion with the experimental data [2] only for two values
of the emitted photon energy ω = 347 and 795 MeV
(see Fig.2). Following [2] we present here the radi-
ation power spectrum per unit length, i.e. dE/dω
multiplied by X0/t. In these units the linear depen-
dence of the radiation power spectrum for the BH
(dot-dashed line) and LPM (dashed line) regimes of
radiation are the constants (see Fig.2). The curves
TSF shows the logarithmic behavior of the radiation
power spectrum in the intermediate region lc > t > lγ
for given ω.
For numerical calculations we used the original
Fortran code based on the same formulas as the calcu-
lations of the SF curves presented in figures in [1, 2].
Following [2] we took into account the multiphoton
effect by corresponding normalization on the BH ra-
diation spectrum. The results of our calculations give
a little excess (about 10%) over the results presented
in [1, 2] by SF curves in all figures, thereby they show
good agreement with experimental data (see, for ex-
ample, Fig.2). The essential discrepancy observed
around the point t = lc is easily explainable by the
fact that the Migdal theory of the LPM effect is ap-
plicable at t À lc whereas the eq. (8) for the TSF
regime of radiation is derived for t À lc . In the in-
termediate region (2lc > t > lc/2) we have a smooth
transition between these two regimes.
3. ANGULAR DISTRIBUTION AND
POLARIZATION OF RADIATION IN THE
NON-DIPOLE REGIME IN CRYSTAL
As it was shown in [23], the non-dipole regime of ra-
diation changes essentially not only the spectrum of
78
emitted gamma quanta, but also their angular distri-
bution. In [24] it was proposed to use special features
of angular characteristics of non-dipole coherent ra-
diation in a thin crystal for production of intensive
photon beams with high degree of linear polarization.
This idea is based on the fact that the non-dipole
regime of radiation, when the scattering angle be-
comes larger than the characteristic angle of radia-
tion of a relativistic electron γ−1, gives a possibility
to avoid a mixture of the radiation emitted under the
different (greater than γ−1) angles. Using the pho-
ton collimators with angular width about γ−1 one
can organize the space-angular separation of photons
emitted by electrons that were scattered in essentially
different directions, for example, perpendicular. To
realize the non-dipole regime of radiation a high en-
ergy of electron beam is necessary. However, it means
that very narrow photon collimators should be used
for this purpose: for the electron energy ε = 150 GeV
the angle width of the collimator should be about
3 µrad. So, it is necessary to find the compromise
condition for realization of this idea.
Fig.3. The angular distributions (in units γ−1) of the radiation power spectrum emitted by the
3.5 GeV electron beam incident on the tungsten monocrystal of 10 µm thickness at the angle
ψL to the axis < 111 > (left) and the degree of linear polarization of this radiation (right)
To decrease the minimal electron energy for the
non-dipole regime radiation is possible by using the
coherent effect at relativistic electron scattering on
atomic chains along the crystallographic axis (the so-
called ”doughnut scattering effect”, see i.e. [19]). The
mean-square angle of multiple scattering in this case
can exceed essentially the analogous parameter for
amorphous matter [26]. This effect as strong, as high
nuclear charge of the crystal material is, so, the best
candidate for the crystal converter would be a tung-
sten monocrystal.
On the basis of the theoretical approach explained
in details in [24] we have carried out the calculations
of the angular distributions and polarization of ra-
diation by 3.5 GeV electrons incident on a tungsten
crystal at the angle ψ = ψL to the axis < 111 >
(where ψL is the Lindhard angle [27]). In this case
θms ≈ ψL = 0.6 µrad and the non-dipole parameter
is γθms ≈ 4. The results of these calculations are
presented in Fig.3.
The left part of Fig.3 presents the results of the
computer simulation (using binary collision model
[24]) for 3.5 GeV electron scattering by the 10 µm
tungsten crystal when the electron beam falls at the
angle ψ = ψL to the crystal axis < 111 >. On
the middle part of Fig.3 the angular distribution
of corresponding spectral-angular radiation density
d2E/dωdo of emitted photons is presented. The right
part of Fig.3 presents the angular distribution of the
linear polarization degree of emitted photons from
the 100% vertically polarized photons (P = −1) to
the 100% horizontal polarization (P = 1). All angles
in Fig.3 are measured in units γ−1.
The integral (over all angles) degree of linear
polarization of radiation is close to zero. However,
using the slit-type horizontal (or vertical) photon
collimator with the angular width ∆θγ = γ−1 and
putting it as shown in Fig.3 by dashed lines it is
possible to obtain a linearly polarized (along the col-
limator plane) photon beam with polarization degree
of about 60%. Note, that the radiation intensity in
the case of axially oriented crystal is much higher
than in the planar orientation case, which is applied
normally for production of polarized photon beams.
4. CONCLUSIONS
The comparison of the results of recent CERN ex-
periment NA63 on measurement of radiation power
spectrum of 149 GeV electrons in a series of thin tan-
79
talum targets [2] shows a good agreement with the
corresponding calculations based on the quantita-
tive theory of relativistic electron radiation in a thin
layer of matter developed earlier in [10, 11]. The ex-
perimental observation of logarithmic dependence of
radiation yield from the target thickness [2] is the first
direct demonstration of the suppression of radiation
effect for a relativistic electron with non-equilibrium
own Coulomb field (TSF effect), which was predicted
and theoretically studied in [9, 17, 18]. Note, that
this effect should have its analog also in QCD at
quark-gluon interaction. The special features of an-
gular distribution of radiation and its polarization
in a thin target at non-dipole regime of radiation
are proposed for a new experimental study. These
features can give a new opportunity for obtaining a
high degree of linear polarization of gamma-quanta.
ACKNOWLEDGMENTS
We are very grateful to all participants of CERN
NA63 Collaboration for a brilliant performance of
very complicated measurements of radiation in a set
of ultrathin targets. It allowed the first observation
of the logarithmic thickness dependence of the radi-
ation power of a relativistic electron at a non-dipole
regime that was predicted many years ago. Special
thanks to Ulrik Uggerhoj for fruitful discussions on
the subject of this investigation.
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ОСОБЕННОСТИ ИЗЛУЧЕНИЯ УЛЬТРАРЕЛЯТИВИСТСКОГО ЭЛЕКТРОНА В
ТОНКОМ СЛОЕ ВЕЩЕСТВА
А.С. Фомин, С.П. Фомин, Н.Ф. Шульга
Условия реализации и особенности недипольного режима излучения обсуждаются в контексте резуль-
татов недавних экспериментов CERN NA63 по измерению спектров излучения электронов с энергией
149ГэВ в тонких мишенях тантала. Первое наблюдение логарифмической зависимости выхода излу-
чения от толщины мишени, сделанное в этом эксперименте, является убедительным доказательством
существования эффекта подавления излучения в тонком слое вещества, который был предсказан много
лет назад, и который является прямым проявлением излучения релятивистских электронов с неравно-
весным собственным кулоновским полем. Предлагается проведение новых экспериментальных исследо-
ваний, предсказываемых теорией особенностей углового распределения излучения и его поляризации
в тонкой мишени в условиях недипольного режима излучения.
ОСОБЛИВОСТI ВИПРОМIНЮВАННЯ УЛЬТРАРЕЛЯТИВIСТСЬКОГО
ЕЛЕКТРОНА В ТОНКОМУ ШАРI РЕЧОВИНИ
О.С. Фомiн, С.П. Фомiн, М.Ф. Шульга
Умови реалiзацiї та особливостi недипольного режиму випромiнювання обговорюються в контекстi
результатiв недавнiх експериментiв CERN NA63 по вимiрам спектрiв випромiнювання електронiв з
енергiєю 149ГеВ у тонких мiшенях танталу. Перше спостереження логарифмiчної залежностi виходу
випромiнення вiд товщини мiшенi, зроблене в цьому експериментi, є переконливим доказом iснування
ефекту пригнiчення випромiнювання в тонкому шарi речовини, який був теоретично передбачений
багато рокiв тому, i який є прямим проявом випромiнювання релятивiстських електронiв з нерiвно-
вагим власним кулонiвським полем. Пропонується проведення нових експериментальних дослiджень,
передбачуваних теорiєю особливостей кутового розподiлу випромiнювання i його поляризацiї в тонкiй
мiшенi в умовах недипольного режиму випромiнювання.
81
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| id | nasplib_isofts_kiev_ua-123456789-111469 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-28T07:27:21Z |
| publishDate | 2011 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Fomin, A.S. Fomin, S.P. Shul’ga, N.F. 2017-01-10T11:52:07Z 2017-01-10T11:52:07Z 2011 Special features of ultrarelativistic electron radiation in a thin layer of matter / A.S. Fomin, S.P. Fomin, N.F. Shul’ga // Вопросы атомной науки и техники. — 2011. — № 5. — С. 75-81. — Бібліогр.: 27 назв. — англ. 1562-6016 PACS: 41.60.-m ; 41.75.Ht https://nasplib.isofts.kiev.ua/handle/123456789/111469 The condition and specific features of non-dipole regime of radiation is discussed in connection with the results of the recent CERN experiment NA63 on measurement of the radiation power spectrum of 149 GeV electrons in thin tantalum targets. The first experimental detection of logarithmic dependence of radiation yield from the target thickness is the conclusive evidence of the e®ect of radiation suppression in a thin layer of matter, which was predicted many years ago, and which is the direct manifestation of the radiation of a relativistic electron with non-equilibrium own Coulomb field. The special features of the angular distribution of the radiation and its polarization in a thin target at non-dipole regime are proposed for a new experimental study. Умови реалізації та особливості недипольного режиму випромінювання обговорюються в контексті результатів недавніх експериментів CERN NA 63 по вимірам спектрів випромінювання електронів з енергією 149 ГеВ у тонких мішенях танталу. Перше спостереження логарифмічної залежності виходу випромінення від товщини мішені, зроблене в цьому експерименті, є переконливим доказом існування ефекту пригнічення випромінювання в тонкому шарі речовини, який був теоретично передбачений багато років тому, і який є прямим проявом випромінювання релятивістських електронів з нерівновагим власним кулонівським полем. Пропонується проведення нових експериментальних досліджень, передбачуваних теорією особливостей кутового розподілу випромінювання і його поляризації в тонкій мішені в умовах недипольного режиму випромінювання. Условия реализации и особенности недипольного режима излучения обсуждаются в контексте результатов недавних экспериментов CERN NA 63 по измерению спектров излучения электронов с энергией 149 ГэВ в тонких мишенях тантала. Первое наблюдение логарифмической зависимости выхода излучения от толщины мишени, сделанное в этом эксперименте, является убедительным доказательством существования эффекта подавления излучения в тонком слое вещества, который был предсказан много лет назад, и который является прямым проявлением излучения релятивистских электронов с неравновесным собственным кулоновским полем. Предлагается проведение новых экспериментальных исследований, предсказываемых теорией особенностей углового распределения излучения и его поляризации в тонкой мишени в условиях недипольного режима излучения. We are very grateful to all participants of CERN NA63 Collaboration for a brilliant performance of very complicated measurements of radiation in a set of ultrathin targets. It allowed the first observation of the logarithmic thickness dependence of the radiation power of a relativistic electron at a non-dipole regime that was predicted many years ago. Special thanks to Ulrik Uggerhoj for fruitful discussions on the subject of this investigation. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Электродинамика Special features of ultrarelativistic electron radiation in a thin layer of matter Особливостi випромiнювання ультрарелятивiстського електрона в тонкому шарi речовини Особенности излучения ультрарелятивистского электрона в тонком слое вещества Article published earlier |
| spellingShingle | Special features of ultrarelativistic electron radiation in a thin layer of matter Fomin, A.S. Fomin, S.P. Shul’ga, N.F. Электродинамика |
| title | Special features of ultrarelativistic electron radiation in a thin layer of matter |
| title_alt | Особливостi випромiнювання ультрарелятивiстського електрона в тонкому шарi речовини Особенности излучения ультрарелятивистского электрона в тонком слое вещества |
| title_full | Special features of ultrarelativistic electron radiation in a thin layer of matter |
| title_fullStr | Special features of ultrarelativistic electron radiation in a thin layer of matter |
| title_full_unstemmed | Special features of ultrarelativistic electron radiation in a thin layer of matter |
| title_short | Special features of ultrarelativistic electron radiation in a thin layer of matter |
| title_sort | special features of ultrarelativistic electron radiation in a thin layer of matter |
| topic | Электродинамика |
| topic_facet | Электродинамика |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/111469 |
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