-
S Araki,
Y Higashi,
Y Honda,
Y Kurihara,
M. Kuriki,
T. Okugi,
T Omori,
T Taniguchi,
N Terunuma,
J. Urakawa, [......],
N. Sasao,
H Yokoyama,
M Fukuda,
K Hirano,
M Takano,
T Takahashi,
H Sato,
A. Tsunemi,
J Gao,
V. Soskov
[show abstract]
[hide abstract]
ABSTRACT: We describe a scheme for producing polarised positrons at the ILC from polarised X-rays created by Compton scattering of a few-GeV electron beam off a CO2 or YAG laser. This scheme is very energy effective using high finesse laser cavities in conjunction with an electron storage ring.
10/2005;
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X. Artru,
V. Baier,
K. Beloborodov,
A. Bogdanov,
A Bukin,
S Burdin,
R. Chehab,
M Chevallier,
R. Cizeron,
D. Dauvergne, [......],
V. Kulibaba,
P. Lautesse,
J. Major,
J C Poizat,
A. Potylitsin,
J. Remillieux,
S. Serednyakov,
V Shary,
V. Strakhovenko,
C. Sylvia
[show abstract]
[hide abstract]
ABSTRACT: New kind of positron sources for future linear colliders, where the converter is a tungsten crystal oriented on the <111> axis, has been studied at CERN in the WA103 experiment. In such sources the photons which create the $e^+ e^-$ pairs result from channeling radiation and coherent bremsstrahlung. In this experiment electron beams of 6 and 10 GeV were sent on different kinds of targets: a 4 mm thick crystal, a 8 mm thick crystal and a compound taraget (4 mm crystal + 4 mm amorphous disk). An amorphous tungsten target 20 mm thick was also used for comparison with the 8 mm crystal. Tracks of outgoing charged particles were detected and analyzed by a drift chamber in a magnetic field. The energy and angle spectra of the positrons were obtained for energies up to 150 MeV and angles up to 30 degrees. The measured positron distribution in momentum space (longitudinal versus transverse) is also presented, giving a full momentum space description of the source. Results on outgoing photons are also presented. A significant enhancement of both photon and positron production is clearly observed. At 10 GeV incident energy, the positron enhancement factor is 4 for the 4 mm crystal, about 2 for the 8 mm crystal. Besides, the simulation code for the crystal processes is validated by a quite good agreement between the simulated and experimental spectra, both for positrons and photons.
07/2005;
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[show abstract]
[hide abstract]
ABSTRACT: The characteristics of the electron-photon showers initiated by 2 to 10 GeV electrons aligned along the <111>-axis of tungsten crystals are compared with those for the amorphous tungsten . In this energy range, as known, the positron yield at the optimal target thicknesses is larger in a crystal case only by several percent. However, the amount of the energy deposition in a crystal turns out to be considerably (by 20 - 50 %) lower than in an amorphous target providing the same positron yield, while the peak energy-deposition density is approximately of the same magnitude in the both cases. Comment: 9 pages, 5 figures
07/2003;
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R. Chehab,
R. Cizeron,
C. Sylvia,
V. Baier,
K. Beloborodov,
A Bukin,
S Burdin,
T. Dimova,
A. Drozdetsky,
V Druzhinin, [......],
A. Jejcic,
P. Keppler,
J. Major,
L Gatignon,
G. Bochek,
V. Kulibaba,
N. Maslov,
A. Bogdanov,
A. Potylitsin,
I. Vnukov
[show abstract]
[hide abstract]
ABSTRACT: Numerical simulations and `proof of principle' experiments showed clearly the interest of using crystals as photon generators dedicated to intense positron sources for linear colliders. An experimental investigation, using a 10 GeV secondary electron beam, of the SPS-CERN, impinging on an axially oriented thick tungsten crystal, has been prepared and operated between May and August 2000. After a short recall on the main features of positron sources using channeling in oriented crystals, the experimental set-up is described. A particular emphasis is put on the positron detector made of a drift chamber, partially immersed in a magnetic field. The enhancement in photon and positron production in the aligned crystal have been observed in the energy range 5 to 40 GeV, for the incident electrons, in crystals of 4 and 8 mm as in an hybrid target. The first results concerning this experiment are presented hereafter.
09/2000;
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[show abstract]
[hide abstract]
ABSTRACT: The interest in using optical transition radiation (OTR) in high energy (multiGeV) beam diagnostics has motivated theoretical and experimental investigations on the limitations brought by diffraction on the attainable resolution. This paper presents calculations of the diffraction effects in an optical set-up using OTR. The OTR diffraction pattern in a telescopic system is calculated taking into account the radial polarization of OTR. The obtained diffraction pattern is compared to the patterns obtained by other authors and the effects of different parameters on the shape and on the size of the OTR diffraction pattern are studied. The major role played by the radial polarization on the shape of the diffraction pattern is outlined. An alternative method to calculate the OTR diffraction pattern is also sketched
04/1999;
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[show abstract]
[hide abstract]
ABSTRACT: Optical Transition Radiation (OTR) provides an attractive method for diagnostics on electron/positron beams of small dimensions at high energies (GeV). However, some limits on the geometrical resolution at very high energies have been often discussed in the literature and a minimum value given by '' has been invoked. In order to bring an experimental contribution to the problem, systematic measurements of electron beam profiles, in the energy range of 1—2 GeV and at optical wavelength between 400 and 700 nm, have been carried out at the Orsay 2 GeV Linear Accelerator. OTR emitted from an aluminium foil at a 30° incidence angle was collected by a two-lens telescope and recorded by an intensified CCD camera. The OTR beam profiles were compared to the profiles obtained by a SEM Grid having a resolution better than 0.5 mm. After a theoretical introduction presenting the different resolution limits, which can be invoked with diffraction phenomenon, and a presentation of our calibration procedure, the experimental results are presented and compared to these limits. They show that the resolution in OTR measurements is definitely better than the already invoked -limit. For a small size electron beam an r.m.s. beam width about 170 m has been determined. This value can be compared to "2.5 mm (E"2 GeV and "650 nm). Our theoretical analysis also provides a more precise evaluation of the resolution power of OTR, which depends on the sensitivity of the detector; this could be of interest for much higher energies. 1998 Elsevier Science B.V. All rights reserved.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/1998; 410:148-158. · 1.21 Impact Factor
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Radiation Effects and Defects in Solids 07/1994; 130-131(1):415-432. · 0.40 Impact Factor
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R. Chehab,
T. Baier,
P. Jean, X. Artru,
M. Chevallier,
R. Kirsch,
J.C. Poizat,
J. Remillieux,
A. Jejcic,
J. Maillard,
J. Silva,
E. Wourany,
G. Renou,
J.P. Didelez,
A. Elayi,
L. Rosier,
V.N. Baier,
V.M. Katkov,
V.M. Strakhovenko,
K. Maier
[show abstract]
[hide abstract]
ABSTRACT: Starting from extensive simulations of photon emission by
channeled electrons in tungsten crystals, a test experiment has been
proposed. It concerns a 2 GeV electron beam impinging on a 1 mm tungsten
crystal oriented along its 〈111〉 axis. Radiation measurements
are ensured by a preshower detector followed by a lead-plexiglas
calorimeter. Channeling data are compared to those obtained for random
incidence. They can be associated with simulations using shower codes
(GEANT) for estimating performances of positron sources based on this
principle
Particle Accelerator Conference, 1993., Proceedings of the 1993; 06/1993
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[show abstract]
[hide abstract]
ABSTRACT: Simulations of a nonconventional positron source, using a 1.5-20-GeV electron beam impinging on an assemblage of a tungsten crystal oriented along its <111> axis and an amorphous target of the same material, are presented. An overall simulation taking into account photon creation in the optimum length of the crystal, positron generation in the target, and positron capture and transport allows optimization of the source. Positron yield has been calculated for different operating conditions. This crystalline positron source features a higher level of photon radiation compared to classical bremsstrahlung; a positron production enhancement of the same order as the radiation increase; and the possibility of using thin amorphous targets behind the crystal, which allows weak positron transverse momentum and lowers the amount of deposited energy in the target.< >
Particle Accelerator Conference, 1991. Accelerator Science and Technology., Conference Record of the 1991 IEEE; 06/1991
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[show abstract]
[hide abstract]
ABSTRACT: Radiation by channeled electrons in germanium and silicon crystals
along the <110> axis is studied as a very promising photon source
of small angular divergence for positron generation in amorphous
targets. Radiation rates for different crystal lengths-from some tenths
of a millimeter to 10 mm-and two electron incident energies, 5 and 20
GeV, are considered, and a comparison between the two crystals is
presented. The thermal behavior of the crystal under incidence of
bunches of 10<sup>10</sup> electrons is also examined. The corresponding
positron yields for amorphous tungsten converters of 0.5 and 1 X<sub>0
</sub> thickness are calculated for a germanium photon generator.
Assuming a large acceptance optical matching system as the adiabatic
device of the SLC (Stanford Linear Collider), accepted positrons are
evaluated and positron yields larger than 1 e<sup>+</sup>/e<sup>-</sup>
are obtained
Particle Accelerator Conference, 1989. Accelerator Science and Technology., Proceedings of the 1989 IEEE; 04/1989
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X. Artru
[show abstract]
[hide abstract]
ABSTRACT: The asymptotic behaviour of hadron form factors and the threshold behaviours of structure functions are investigated in a
model based on i) unitarity with
q[`(q)]q\bar q
intermediate states in thet =q
2 channel, and dispersion relations; ii) asymptotic behaviour of the quark-hadron amplitude governed by the spins of the exchanged
(spectators) partons; iii) Bloom-Gilman duality. Our model emphasizes the infra-red region of the impulse diagram and is supposed
to work in an intermediateq
2 region in which scaling violation and gluon jets are not too important. We find, fort → ∞,
[`(f)]l hadron (t) ~ [`(f)]l quark (t)Õi tSi - 1 Õj taj (0)\bar f_\lambda ^{hadron} (t) \sim \bar f_\lambda ^{quark} (t)\prod\limits_i {t^{S_i - 1} } \prod\limits_j {t^{\alpha _j (0)} }
, where
[`(f)]l\bar f_\lambda
is the form factor for the current helicity ι, summed over the hadronic helicities,8
i the spin of thei-th elementary spectator and α3 the Regge trajectory of thej-th composite spectator. The threshold behaviours of the structure functions are given by the Drell-Yan-West relation. For
mesons we predict
$\bar f_0 \sim t^{ - 1} , \bar f_{ \pm 1} \sim t^{ - \raise.5ex\hbox{$\bar f_0 \sim t^{ - 1} , \bar f_{ \pm 1} \sim t^{ - \raise.5ex\hbox{
(in contradiction with helicity selection rules),νW
2 (ω = 1) ≠ 0. For baryons, the dipole fit suggests the existence of a spin-zero neutral parton in addition to the quarks.
The deuteron data are compatible with our predictions,
Fd ~ FN t - 1.3F^d \sim F^\mathcal{N} t^{ - 1.3}
,vW
2
d
∼(ω − 1)−5.6.
Si studia il comportamento asintotico dei fattori di forma adronici e i comportamenti di soglia delle funzioni di struttura
in un modello che si basa i) sull’ unitarietà con stati intermedi q-q nel canalet = q2 e sulle relazioni di dispersione, ii) sul comportamento asintotico dell’ ampiezza quark-hadroni governata dagli spin dei
partoni spettatori scambiati, iii) sulla dualità di Bloom-Gilman. Questo modello mette in evidenza la regione infrarossa del
diagramma degli impulsi e si suppone sia valido in una regione intermedia di q2 in cui la riduzione di scala e i getti di gluoni non sono troppo importanti. Si trova, pert → ∞,
q[`(q)]q\bar q
, dove
_j t^ _j (0) \bar f_\lambda ^{hadron} (t) \sim \bar f_\lambda ^{quark} (t)\prod\limits_i {t^{S_i - 1} } \prod\limits_j {t^{\alpha _j (0)} }
, dove
[`(f)]l\bar f_\lambda
è il fattore di forma dell’elicità di corrente λ, sommato rispetto alle elicità adroniche, Si è lo spin dell’ i-esimo spettatore elementare e αi la traiettoria di Regge del j-esimo spettatore composto. I comportamenti di soglia delle funzioni di struttura sono dati
dalla relazione di Drell-Yan-West. Per i mesoni si prevede
$\bar f_0 \sim t^{ - 1} , \bar f_{ \pm 1} \sim t^{ - \raise.5ex\hbox{$\bar f_0 \sim t^{ - 1} , \bar f_{ \pm 1} \sim t^{ - \raise.5ex\hbox{
(in contrasto con le regole di selezione dell’ elioità),νW
2(ω = 1)≠ 0. Per i barioni, l’approssimazione dipolare suggerisce di un partone neutro con spin zero oltre ai quark. I dati del
deuterone sono compatibili con le nostre previsioni,
Fd ~ FN t - 1.3F^d \sim F^\mathcal{N} t^{ - 1.3}
,vW
2
d
∼ (ω − 1)−5.6.
Исследуются асимптотическое поведение адронных форм-факторов и пороговые поведения структурных функций. Исследование проводится
в рамках модели, основанной на 1) унитарности с (
q[`(q)]q\bar q
) промежуточными состояниями в t=q2 канале и дисперсионных соотношениях; 2) асимптотическом поведении кварк-адрон ной амплитуды, определяемой спинами обменных
партонов; 3) дуальности БлумаДжилмана. В нашей модели придается особое значение инфракрасной области импульсной диаграммы
и предполагается, что эта модель работает в промежуточной q2 области, где нарушение скейлинга и глуонные струи не являются слишком важными. Для t → ∞ мы находим
_j t^ _j (0) ,\bar f_\lambda ^{hadron} (t) \sim \bar f_\lambda ^{quark} (t)\prod\limits_i {t^{S_i - 1} } \prod\limits_j {t^{\alpha _j (0)} } ,
где
[`(f)]l\bar f_\lambda
есть форм-фактор для спиральности тока λ, суммирование проводится по адронным спиральностям, Si, есть спин i-ого элементарного партона и αj Реджетраектория j-oro составного партона. Пороговые поведения структурных функций определяются соотношением Дрелла-Яна-Веста.
Для мезонов мы предсказываем
$\bar f_0 \sim t^{ - 1} , \bar f_{ \pm 1} \sim t^{ - \raise.5ex\hbox{$\bar f_0 \sim t^{ - 1} , \bar f_{ \pm 1} \sim t^{ - \raise.5ex\hbox{
(в противоположность правилам отбора спиральности),vW
2 (ω = 1) ≠ 0. Для барионов подгонка диполя предполагает существование нейтрального партона с нулевым спином в дополнение к
кваркам. Дейтронные данные сопоставимы с нашими предсказаниями,
Fd ~ FN t - 1.3F^d \sim F^\mathcal{N} t^{ - 1.3}
,vW
2
d
(ω − 1)−5.6.
Il Nuovo Cimento A 09/1982; 71(3):341-369.
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[show abstract]
[hide abstract]
ABSTRACT: The exploitation of the enhancement of positron sources by channeling effects, in particular for Linear Colliders (LC), relies on the long term resistance of the crystal to radiation damage. Such dama ge has been tested on a 0.3 mm thick tungsten monocrystal exposed during 6 months to the 30 Gev incident electron beam of the SLAC Linear Collider (SLC). The crystal was placed in the converter region , orientated in a random direction and received an integrated flux of e- (fluence) of 2 x 10^18 e-/mm^2. The crystal was analyzed before and after irradiation by X and Gamma diffractometry. No damage was observed, the mosaic spread remained unchanged during irradiation (0.4 mrad FWHM). Implications for use of orientated crystal as converter for positron sources of future LCs are discussed.
-
R. Chehab,
R. Cizeron,
C. Sylvia,
V. Baier,
K. I. Beloborodov,
A Bukin,
S. V. Burdin,
T. V. Dimova,
A. A. Drozdetsky,
V. P. Druzhinin, [......],
A. Jejcic,
P. Keppler,
J V Major,
L Gatignon,
G L Bochek,
V. Kulibaba,
N I Maslov,
A. Bogdanov,
A P Potylitsin,
I E Vnukov
[show abstract]
[hide abstract]
ABSTRACT: Numerical simulations and `proof of principle' experiments showed clearly the interest of using crystals as photon generators dedicated to intense positron sources for linear colliders. An experimental investigation, using a 10 GeV secondary electron beam, of the SPS-CERN, impinging on an axially oriented thick tungsten crystal, has been prepared and operated between May and August 2000. After a short recall on the main features of positron sources using channeling in oriented crystals, the experimental set-up is described. A particular emphasis is put on the positron detector made of a drift chamber, partially immersed in a magnetic field. The enhancement in photon and positron production in the aligned crystal have been observed in the energy range 5 to 40 GeV, for the incident electrons, in crystals of 4 and 8 mm as in an hybrid target. The first results concerning this experiment are presented hereafter.
-
Frank Zimmermann,
S Araki, X. Artru,
H Braun,
E. Bulyak,
R. Chehab,
M Chevallier,
M Fukuda,
J Gao,
P. Gladkikh, [......],
V M Strakhovenko,
M Takano,
T Takahashi,
T Taniguchi,
N Terunuma,
A. Tsunemi,
J. Urakawa,
A. Variola,
M Washio,
F Zomer
[show abstract]
[hide abstract]
ABSTRACT: We describe a possible layout and parameters of a polarized positron source for CLIC, where the positrons are produced from polarized gamma rays created by Compton scattering of a 1.3-GeV electron beam off a YAG laser. This scheme is very energy effective using high finesse laser cavities in conjunction with an electron storage ring. We point out the differences with respect to a similar system proposed for the ILC.
-
International Workshop on Linear Colliders 2010 (IWLC2010).
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[show abstract]
[hide abstract]
ABSTRACT: A two-step positron facility using a multi-GeV electron beam is under study for electron–positron colliders as ILC or the SuperB factory. In the first step, the electron beam impinges on an oriented tungsten crystal. Channelling radiation provides a large number of γ-rays and consequently creates a large number of pairs in an amorphous target placed after the crystal. Such a method has been successfully tested at CERN and KEK and is now operating at KEK. As a second step and as an upgrade of the system, the electron beam, instead of being sent to the crystal, collides with a circularly polarized laser beam, creating circularly polarized Compton backscattered γ-rays, which impinge on a thin amorphous target where they generate longitudinally polarized positrons. Simulation results are provided for the two steps and the choice of the parameters is discussed for ILC and for the SuperB factory. Particularly, the choice of an ERL instead of a classical linac is recommended for the ILC.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms.
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X. Artru,
V. Baier,
K. Beloborodov,
G. Bochek,
A. Bogdanov,
A. Bozhenok,
A. Bukin,
S. Burdin,
R. Chehab,
M. Chevallier, [......],
J. Major,
N. Maslov,
J.-C. Poizat,
A. Potylitsin,
J. Remillieux,
S. Serednyakov,
V. Shary,
V. Strakhovenko,
C. Sylvia,
I. Vnukov
[show abstract]
[hide abstract]
ABSTRACT: Axially oriented crystals, penetrated by high-energy electrons, are powerful photon sources and, hence, intense positron sources. Such kinds of positron sources have been studied experimentally at CERN, with the tertiary electron beam of the SPS having an energy of 6 and 10 GeV. Four and eight millimeters thick tungsten crystals and a compound target made of a 4 mm crystal followed by a 4 mm amorphous disk were used with an orientation along the 〈111〉 axis. The positrons were detected by a drift chamber, partially immersed in a magnetic field. The reconstructed trajectories allowed the determination of their energy and angular spectra. Significant enhancements were observed for the crystal source when compared to the amorphous one. The gain was about 3 for the 4 mm target and about 2 for the 8 mm and the compound targets. These preliminary results are described after short presentations of the experimental set-up and of the method of track reconstruction.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms.
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V.N. Baier,
A.D. Bukin,
T.V. Dimova,
V.P. Druzhinin,
M.S. Dubrovin,
V.B. Golubev,
S.I. Serednyakov,
V.V. Shary,
V.M. Strakhovenko, X. Artru,
M. Chevallier,
R. Kirsch,
J-C. Poizat,
J. Remillieux,
R. Chehab,
A. Jejcic,
J. Silva,
J. Major,
A.P. Potylitsin,
I.E. Vnukov
[show abstract]
[hide abstract]
ABSTRACT: A new experiment is suggested in order to investigate the positron yield at the exit of crystal tungsten targets of different thicknesses submitted to 10 GeV electron beam at one of the SPS CERN transfer lines. The Set-up consists of the beam control counters, targets mounted on the goniometer, positron detector and photon detector. The positron detector is based mainly on a drift chamber inserted between the poles of the magnet. It allows to reconstruct the track of the charged particles, to define the vertex coordinates and initial angle of the particles at the exit of the target, to measure the total and transverse momenta. A Monte Carlo simulation corresponding to the theoretical description of chanelling radiation and also numerical calculation were provided for the estimations of the expected distributions and detector response. The optimization of the Set-up is considered, as well as the status of the project in general.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms.
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R Chehab,
R Cizeron,
C Sylvia,
V Baier,
K Beloborodov,
A Bukin,
S Burdin,
T Dimova,
A Drozdetsky,
V Druzhinin, [......],
A Jejcic,
P Keppler,
J Major,
L Gatignon,
G Bochek,
V Kulibaba,
N Maslov,
A Bogdanov,
A Potylitsin,
I Vnukov
[show abstract]
[hide abstract]
ABSTRACT: Tungsten crystals oriented on their 〈111〉 axis, were submitted to 6 and 10 GeV electron beams on the SPS-CERN transfer lines. The crystals, 4 and 8 mm thick, used alone or associated to 4 mm thick amorphous disk, were studied as positron sources. The emerging positrons were detected by a Drift Chamber partially immersed in a magnetic field, where their trajectories were reconstructed providing the energy spectrum and the angular distribution. Significant enhancements were observed for the crystal source when compared to the amorphous one of the same thickness. The gain was larger than 3 and 2 for the 4 mm and 8 mm targets, respectively. The presented results look very promising for e+e− linear colliders.
Physics Letters B.
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[show abstract]
[hide abstract]
ABSTRACT: The spatial resolution power of Optical Transition Radiation (OTR), applied to beam profile measurements at high Lorentz factor γ, is studied taking into account diffraction and self-diffraction effects. Microscopic and macroscopic points of view about the different geometrical natures of the forward and backward OTR sources are presented. Properties of the impact parameter profile I(b) of the OTR emitted by one electron are described. Curves for the modulation transfer function and for the OTR profile of a laminar beam are given. Two methods of improving the resolution are investigated : (a) putting a mask to eliminate small-angle photons, (b) using a polarizer.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 145:160-168. · 1.21 Impact Factor
