The process of radiation from high-energy electron and electron-positron pair production by a photon in oriented single crystal is considered using the method which permits inseparable consideration of both coherent and incoherent mechanisms of photon emission from an electron and of pair creation by a photon and includes the action of field of axis (or plane) as well as the multiple scattering of radiating electron or particles of the created pair (the Landau-Pomeranchuk- Migdal (LPM) effect). The total intensity of radiation and total probability pair creation are calculated. The theory, where the energy loss of projectile has to be taken into account, and found probabilities of pair creation agree quite satisfactory with available CERN data. From obtained results it follows that multiple scattering appears only for relatively low energy of radiating electron or a photon, while at higher energies the field action excludes the LPM effect.

Digital subtraction angiography (DSA), also known as Dichromography, using synchrotron radiation beams has been developed at Stanford University (R. Hofstadter) and was subsequently taken over at the Brookhaven Synchrotron and later at Hamburg (HASYLAB) [see, e.g., W.R. Dix, Physik in unserer Zeit. 30 (1999) 160]. The imaging of coronary arteries is carried out with an iodine-based contrast agent which need not be injected into the heart. The radiation must be monochromatized and is applied above and below the K-edge of iodine (33.16 keV), with a subsequent digital subtraction of the two images. Monochromatization of the synchrotron radiation causes a loss of intensity of 10^-3. We propose instead the use of coherent bremsstrahlung [see, e.g., A.W. Saenz and H. Uberall, Phys. Rev. B25 (1982) 448] which is inherently monochromatic, furnishing a flux of 10¹² photon/sec. This requires a 10-20 MeV electron linac which can be obtained by many larger hospitals, eliminating the scheduling problems present at synchrotrons. The large, broad incoherent bremsstrahlung background underlying the monochromatic spike would lead to inadmissible overexposure of the patient. This problem can be solved with the use of Kumakhov's capillary optics [see e.g., S.B.Dabagov, Physics-Uspekhi 46 (2003) 1053]: the low-energy spiked radiation can be deflected towards the patient, while the higher energy incoherent background continues forward, avoiding the patient who is placed several meters from the source.

Several experiments on investigation of electrons coherent scattering and radiation processes in crystals on SPARC accelerator are proposed. The propositions are based on the theoretical analysis and simulations of these processes in oriented crystals.

The promising scheme to design the intense positron source is based on using of oriented crystal to generate an intense photon beam and amorphous converter for shower producing. Properties of a diamond crystal such as a high thermal conductivity ( 660 W/m.K versus 170 W/m.K for tungsten), high Debye temperature (1860K versus 379K tungsten) and the shortest lattice constant allow us to consider a thick diamond crystal (> 10mm) as a best candidate for a photon source. For axial orientation of such thick crystal only initial part of a crystal forms channeling radiation (around 0.5 mm for 10 GeV electrons); electrons emit coherent bremsstrahlung (CBS) in the remained part of a crystal. The model for estimation of radiation losses, mean photon energy and photon multiplicity in coherent bremsstrahlung processes is described in the report. The comparison of existing experimental results with developed approach has been performed. Our estimations show that for electron with energy 4.5 GeV passing through 10mm diamond target along < 111 > axis, the photon multiplicity may achieve 10 photons per each electron. The efficiency of positron production by a photon beam from a thick diamond target was estimated and possibility to achieve the efficiency about one accelerated positron per each initial electron with energy ~ 10 GeV was shown.

Linearly polarized photons are needed in modern nuclear and particle physics experiments in order to achieve decisive progress as cross section measurements alone can not unravel the details of small amplitudes in the presence of larger ones. The most common productions method is the coherent bremsstrahlung process which is well understood theoretically. However, in practice there are additional effects due to beam divergence and the radiator thickness as well as due to collimation which are more difficult to assess. These influence the shape and the degree of polarization of the photons. The method of shape analysis which is widely used to determine the degree of linear polarization is scrutinized with respect to the above effects and traditional methods of their simulation. Results from recent Monte Carlo simulations and from some test experiments are presented together with a new normalization procedure.

The results of theoretical investigation of multiple scattering effect on spectral, angular and polarization characteristics of radiation by a relativistic electron passing through a thin amorphous target (with respect to a coherence length) are presented. It is shown that due to this effect the radiation spectrum may essentially differ from the both predictions of the Bethe-Heitler theory of bremsstrahlung and results of the Migdal theory of the Landau-Pomeranchuk-Migdal effect (LPM). It is also shown that non-dipole regime of radiation in the case of intensive multiple scattering leads to significant changes of angular distribution of emitted gamma-quanta and, as a result, to a new possibility for getting highly linear polarized gamma-quanta. The conditions for experimental observation of these effects are discussed.

Collective effects in the polarization bremsstrahlung from relativistic electrons moving through media ordered in part are considered theoretically and experimentally. The connection of emission spectral-angular characteristics with atomic structures of such targets as polycrystals with accidentally oriented microcrystals and textured polycrystals are elucidated in the work. Results of experimental search of polarization bremsstrahlung from 7MeV electrons crossing polycrystalline targets of Al, Cu and Ni are discussed. Comparison of measured data with theoretical predictions has shown a good agreement for positions and intensities of observed coherent peaks.

Theory of one-dimensional relativistic oscillator in dispersive medium is developed. It is shown that besides the threshold there is another special value for the oscillator energy (equals to the double of threshold). When the oscillator energy gets over this value, the spectrum of the radiated photons number modifies. Within this theory the problem of radiation by planar channeled positrons, taking into account the medium polarization, is considered. Radiation theory for planar channeled positrons at arbitrary incidence angle and transverse coordinate is constructed. The spectral distributions of radiation and energy of radiation are derived. It is shown that both the oscillation amplitude and the radiation frequency range depend on the initial positron incidence angle and transverse coordinate. Averaging of spectral distributions over initial transverse coordinates is performed; the formulas for distributions of the number of photons and energy of radiation for a channeling positron bunch are obtained. It is shown that there is an optimal positron incidence angle √2 times smaller than the Lindhard angle. The form of the spectral distribution of the radiated photons number depends on the medium polarization, which, in turn, stipulates two special values of the bunch energy: the threshold and the critical one. If the bunch energy is between this two values, the spectrum of radiated photons has one minimum, otherwise - two minimums. Theory is compared with experimental results. For the coincidence of the theory with experiment it is necessary to take into account strong polarization of the atomic electron clouds, through which positrons makes the main contribution in the radiation pass.

The bremsstrahlung spectrum of the nanosecond electron accelerator on the basis of the vacuum diode supplied by the high-voltage nanosecond generator SINUS - 150 with the coaxial forming line combined with the transformer has been monochromatized by the tungsten crystal under the Bragg - geometry (θ_B = 45⁰). The dose field map has been taken by the dosimeter on the basis of the diamond detector in the median acceleration plane. The bremsstrahlung radiation beam divergence has left 62°. It has been shown that the maximum dose is 16 cGrey/s at the distance of 10 cm from the collector, then it falls down proportionally to the square of distance to the level less than 0.1 cGrey/s at the distance of 1 m. The X-Ray spectrum has been measured by the silicon semi-conductor X-ray spectrometer with energy resolution 280 eV for 5.9 keV. It has been shown that the two maximum at the spectrum corresponds the second and third orders of diffraction on (111) planes of a tungsten crystal.

The Dirac equation was solved for electrons under planar channeling in a crystal. The potential of crystal plane was approximated by parabolic potential. The spectrum of bound energy states was evaluated, and the problem of the energy spectrum change when the electron spin is taken into account, was considered. Also comparison of the results obtained by solving both Dirac and Klein-Gordon equations with the same potential was done. This analysis points that interaction of electron spin and electrical field of a crystal results in splitting every energy level into two levels. These levels differ by spin polarization along or opposite longitudinal momentum.

The processes of scattering and radiation when relativistic electron falls towards to a long bunch of relativistic particles under a small angle to its axis are considered. The analogy between these processes and the processes of scattering and radiation by relativistic electron in the field of an atomic string in a crystal falling under small angle to the crystal axis is considered. Similar features and distinctions of these processes are pointed out.

Peculiarities in the manifestation of a density effect in polarization bremsstrahlung from relativistic electrons moving through a solid target are studied. It is shown that the influence of above mentioned effect on emission characteristics increases substantially if the targets possess an ordinary for solids polycrystalline structure. The strong enhancement of coherent peak in polarization bremsstrahlung spectrum is predicted for the photon flux emitted to backward direction relative to emitting electron velocity.

History of bent crystal applications for steering high energy particles is outlined, from the prediction of the phenomenon to the first bending experiments and crystal beam extraction demonstrations. Monte Carlo calculations of crystal halo scrapers in colliders were performed and parameters of such scrapers were optimized.

TeV-range bent crystal channeling has interesting advantages for several applications at high energy accelerators. Observations of enhanced deflection over the whole arc of a bent crystal at RHIC and recently at the Tevatron may be due to a process called "volume reflection." More investigations of volume reflection and of the complimentary process, volume capture, are needed. So-called quasimosaic bending processes also deserve additional study. Negative particle channeling may be relevant to channeling collimation for electron machines. Electron and positron channeling and channeling radiation are interwoven so that the impact of channeling radiation on applications needs to be better understood. Beams in the 0.1 to 1 GeV range may be useful for some of these investigations. Finally there has been little or no study of positive and negative muon channeling. The current understanding of these topics and the desirability of further work is reviewed.

We demonstrate that channeling in a crystal can serve as a primary scraper for the collimation system of the Large Hadron Collider. It has been proven both experimentally and in Monte Carlo simulations that crystal as a scraper meets all technical requirements imposed on the LHC collimation system. Crystal scraper works in efficient, predictable, reliable manner with beams of very high intensity over years. If used as a primary element in the LHC collimation system, crystal makes the machine cleaner by a factor of 10 due to channeling with efficiency of about 90% - the figure already demonstrated experimentally at 70 GeV and in simulations for the LHC and Tevatron.

This paper presents an assessment of the deflection efficiency in a bent crystal for different charge states. For a possible application of the phenomenon of relativistic heavy ion deflection in bent crystals, it is desirable to know if particles with similar momentum per charge can be deflected with similar efficiencies. In contrast to deflection in a magnetic dipole, the deflection angle does not depend on the momentum per charge, but the deflection efficiency does. In this respect, a bent crystal is a non-dispersive extraction/deflection device.

The activity of IHEP (Protvino) is made on some directions within the framework of the INTAS program. Experiments to study the volume reflection effect and the capability of its use in the beam scraper and extraction systems are planned. Both analytical estimation and computer simulation of these processes at the Y-70 with silicon, tungsten and carbon crystals are performed. Possibility of volume reflection in crystals for ultra-high protons at accelerators like SPS and LHC is studied.

Bent crystal channeling has promising advantages for accelerator beam collimation at high energy hadron facilities such as the LHC. This significance has been amplified by several surprising developments including multi-pass channeling and the observation of enhanced deflections over the entire arc of a bent crystal. The second effect has been observed both at RHIC and recently at the Tevatron. Results are reported showing channeling collimation of the circulating proton beam halo at the Tevatron. Parenthetically, this study is the highest energy proton channeling experiment ever carried out. The study is continuing.

An experiment on deflection of a proton beam using a Silicon crystal was performed for the first time in Japan at the 12-GeV Proton Synchrotron of KEK. The (111) plane of the crystal was used to deflect a 12 GeV proton beam at an angle of 32.6 mrad. The beam extraction efficiency of the crystal was reached 13%. The divergence of the proton beam can be identified by comparison of the experimental data with simulated results.

The possibilities to deflect high-energy protons by bent atomic axes with the purpose of its further use for halo cleaning at the LHC are investigated. Our simulations show that more than 80% of the LHC protons initially moving at small angles with respect to bent crystal axes can be deflected at the angles of about one hundred microradians to the initial beam direction due to the volume capture into the planar channeling regime. The deflection efficiency exceeding 95% is reached at crystal bending angles of about 10 microradians.

For the new generation of high intensity hadronic machines as, for instance, LHC, halo collimation is a necessary issue for the accelerator to operate at the highest possible luminosity and to prevent the damage of superconductor magnets. We propose an experiment aimed to systematic study of the channeling phenomenology and of the newly observed "volume reflection" effect. This experiment will be performed for an external SPS beamline and will make use of a primary proton beam with 400 GeV/c momentum and very small (∼ 3 &mgr;rad) divergence. The advantage of a proposed experiment is precise tracking of particles that interacted with a crystal, so that to determine the single-pass effciency for all the processes involved. For this purpose, a telescope equipped with high-resolution silicon microstrip detectors will be used. New generation silicon crystals and an extra-precise goniometer are mandatory issues. Main goal of the experiment is to get the precise information on channeling of relativistic particles and, ultimately, on the feasibility of such technique for halo collimation at LHC. In this contribution we review the status of the setting-up of experimental apparatus and its future development in sight of the planned run in September 2006.

Presently MeV energy micro-beams are employed to study the cell response to radiation-induced damage. In fact, one of the frontiers is the study of radiobiological effects of particle radiation on human tissues. At relatively low energy (of the order of MeV), micro-beam facilities have been constructed to irradiate living cells with the aim to understand the architecture of biological tissues on radiation response and its behaviour at low dose. Interaction of radiation at high energy (GeV or higher) and its effects have indeed been considered for interplanetary space missions where a human equipage is being submitted to prolonged interaction with direct cosmic radiation. Thus, some particle accelerator laboratories study methods for implementation of micro-beam facilities to address the interaction of high-energy protons and ions with cells. A channeling-based scheme for generation of micro-beams has been proposed in the past; two designs for micro-collimator devices have been considered in this study and preliminary samples have been accordingly produced.

During the last years, because of the low cost, high crystalline perfection and sound knowledge on the handling, the use of bent silicon crystals for applications in accelerators has been intensively investigated. In particular, great attention has been paid towards improving extraction efficiency by the methods used to realize the crystals. For example, 70 GeV protons were extracted from the beam accelerator in Protvino with silicon crystal, obtaining a channeling efficiency close to 85%. The key reason for this successful operation was the use of very short bent crystals. Realization of the short bent crystal devices, as a crystalline undulator, can be difficult by traditional mechanical techniques; a possible alternative method could be the deposition of a high residual stress film onto a Si wafer. We have studied and tested two alternative methods to achieve a uniform curvature of silicon wafers: deposition of both silicon nitride films and thick aluminium films.

Dynamics of the trajectory change has been simulated in order to study the energy losses of channeled ions as well as the angular and energy distributions of ions transmitted through a thin crystal as the functions of single crystal composition, of impact parameters with respect to the channel center and of initial energy. It has been established that the inelastic interactions define the main energy loss for a paraxial part of channeled beam. The elastic energy losses for channeled ions are larger in a Cu₃Au (100) crystal than in a Cu (100). Because of the fact that Au atoms are heavier than Cu atoms, in a case of Cu₃Au (100) the ion dechanneling rate is greater and the channeling range is smaller in comparison with the similar characteristics for Cu (100).

We report the results of theoretical and numerical analysis of the crystalline undulators planned to be used in the experiments which are the part of the ongoing PECU project. The goal of such an analysis was to define the parameters (different from those pre-set by the experimental setup) of the undulators which ensure the highest yield of photons of specified energies. The calculations were performed for 0.6 and 10 GeV positrons channeling through periodically bent Si and Si_1-xGe_x crystals.

When a transverse periodic perturbation of amplitude much larger than the interplanar spacing is propagating through a single crystal, the crystal is bent periodically which results in the emission of undulator radiation in addition to channeling radiation from the channeled particles. When the amplitude is small compared to the interplanar spacing, undulator radiation contribution is negligible in the spectrum. In this work, we are considering the propagation of a low amplitude periodic perturbation. The angular and spectral distribution of emitted radiation is calculated and the corresponding intensity is estimated.

The motion of relativistic particles in crystals is complicated. At certain crystal orientations with respect to an electron beam, the motion of particles may become either regular (periodic) or chaotic. A regular type of electron motion results in interfering the emitted radiation due to periodical collisions of electrons with the atomic strings. In this case, sharp maxima appear in photon radiation spectra. Existence of periodical electron motion may result in high polarization of the radiation. For particles with an irregular type of the motion, periodicity of the atomic strings does not have any essential influence to radiation characteristics, and, hence, dynamic chaos phenomenon will take place. Subsequently, interference of radiation, due to electron scattering by single strings, disappears, and the radiation spectra have no sharp maxima; however, intensity of such radiation is significantly higher than radiation intensity in amorphous matter. The radiation spectra and polarization are very sensitive to the type of particle motion in a crystal, and depend on initial energy of particles. At electron energies of about a few hundred MeV the coherent effects of radiation in crystals are not sufficiently investigated. In this report the expected radiation characteristics (spectra and polarization) are presented for these electron energies, and possibilities of its experimental investigation at the SPARC facility (Frascati) are considered. Possibilities for experimental studying the dynamic chaos phenomena at electron motion in a crystal are discussed.

Planar channeling radiation from 32 MeV electrons channeled in quartz has for the first time been measured at the radiation source ELBE. The theory of channeling radiation was applied for the assignment of the observed spectra to the crystal planes. Calculations of the continuum potentials, transverse electron states, transition energies, and radiation intensities have been performed for selected planes of quartz. Specific properties of the hexagonal binary quartz crystal influencing the generation of channeling radiation are discussed.

Computer experiments to study spatial and angular distributions of relativistic electrons and positrons in a tungsten crystal are performed using the binary collision model. The results of computer experiments for <100> and <110> directions in a tungsten crystal showed that the mean square angle of multiple scattering depends on the particle charge sign and exceeds considerably the one in an amorphous target of the same thickness, in accordance with earlier theoretical predictions based on the model of multiple scattering by continuous potentials of the crystal axes.

The "CUP" project studies the positron channeling for the development of Crystal Undulator for Positrons and represents the first step of an ambitious project that investigates the possibility to create new, powerful sources of high-frequency monochromatic electromagnetic radiation: crystalline undulator and γ-laser, based on crystalline undulator. The physical phenomena to investigate are essentially two: the spontaneous undulator radiation by channeling of relativistic positrons and the stimulated emission in periodically bent crystals (the lasing effect). The important and novel idea consists in realizing a microundulator, that is a suitable periodically bent crystal, that allows to achieve much higher energy range for the emitted photons respect to the conventional free electron laser (FEL). A crystalline undulator can be realized either dynamically, using high amplitude transverse acoustic wave, or statically using graded composition of strained layers. Both methods are easily applicable by means of modern technology. The theoretical results establish the feasibility of a crystalline undulator, but in order to make the project to advance it is mandatory to carry out experiments to test the idea and to characterize the emitted radiation as a function of several parameters. In this context the Daφne Beam Test Facility, located at the Laboratori Nazionali di Frascati (BTF LNF), in Italy, has been proposed as an important starting point, where the CUP project can test the initial experimental set-up and collect the first results to analyze well-accepted channeling radiation theoretical predictions.

We present the theoretical model and results of computer simulations of electromagnetic dissociation (EMD) of relativistic deuterons under channeling conditions in a crystal. The computer code is based on the binary collision model and involves the impact-parameter dependent probability of deuteron EMD in collision with a separate crystal atom. The numerical results are presented for EMD of (100-5000) MeV/nucleon deuterons channeled in a tungsten crystal. Possible applications and future developments are discussed.

By the methods of channeling and mathematical simulation the distribution profiles of damage produced in Ni under irradiation by ions of He⁺, Ar⁺, Kr⁺, , Xe⁺ with energy 0.2-1 MeV in the range of doses 10¹⁵ ÷ 10¹⁷ cm^-2 are investigated. Location of the implanted atoms of Xe in a Ni monocrystal lattice is determined; their interaction with radiation defects, kinetics of impurity complexes formation and their configuration are defined.

Progress in Light Sources (LS) based on the emission of electromagnetic radiation by the electron and ion beams in periodic electromagnetic fields of undulators becomes to be highly promising. Trends in the development of such sources and problems of high current, low emittance electron and ion beam production for spontaneous incoherent sources and short period trains of the bunches for coherent and stimulated sources will be discussed.

A charged particle passing through an optical fiber induces emission of light guided by the fiber. The formula giving the spontaneous emission amplitude are given in the general case when the particle trajectory is not parallel to the fiber axis. At small angle, the photon yield grows like the inverse power of the angle and in the parallel limiting case the fiber Cherenkov effect studied by Bogdankevich and Bolotovskii is recovered. Possible application to beam diagnostics are discussed, as well as resonance effects when the particle trajectory or the fiber is bent periodically.

Features of forward diffracted Parametric X-Radiation (PXR) were investigated at experiments with the 855 MeV electron beam of the Mainz Microtron MAMI employing a 410 &mgr;m thick tungsten single crystal. Virtual photons from the electron field are diffracted by the (101)[bar above final 1] plane at a Bragg angle of 3.977°. Forward emitted radiation was analyzed at an energy of 40 keV with the (111) lattice planes of a flat silicon single crystal in Bragg geometry. Clear peak structures were observed in an angular scan of the tungsten single crystal. The results were analyzed with a model which describes forward diffracted PXR under real experimental conditions. The experiments show that forward diffracted PXR may be employed to diagnose bending radii of lattice planes in large area single crystals.

The characterization of the transverse phase space of electron beams with high charge density and high energy is a fundamental requirement for particle accelerator facilities. The knowledge of characteristics of the accelerated beams is of great importance also for the successful development of the next generation light sources and linear colliders. In order to measure the properties of such beams, development of non-invasive and non-intercepting beam diagnostics techniques is necessary. A promising canditate is Optical Diffraction Radiation (ODR), as testified by the interest of many laboratories all around the world. At this purpose, an experiment using ODR to measure the electron beam transverse parameters has been set up at FLASH (former VUV-FEL) at DESY (Hamburg). Radiation emitted by 620 MeV electron beam passing through a 1 mm slit on a screen made of aluminum deposited on a silicon substrate is detected by a low noise, high sensitivity CCD camera.

The monochromatic X-ray source based on parametric X-ray radiation (PXR) was developed by using Si(111) perfect crystals and the electron beam from the 125-MeV linac at Nihon University. Since the X-ray beam from the PXR system has a large exposure area with uniform flux density, the PXR-based source is suited for X-ray radiography. In addition to ordinary radiography, X-ray absorption spectroscopy and phase-contrast imaging have been developed as advanced applications of PXR. The absorption spectra of several samples were obtained using the energy dispersion of PXR, and the X-ray absorption fine structures (XAFS) were actually found in the spectra. With respect to phase-contrast imaging, refraction-contrast images have been obtained by using the X-ray diffraction in the (+, −, +) arrangement of perfect crystals. The high-contrast and the phase-reversal of the images taken in the experiment suggest that LEBRA-PXR has a high spatial coherence sufficient for phase-contrast imaging.

Parametric X-ray radiation (PXR) and coherent bremsstrahlung (CB) from non-relativistic (or slow relativistic) electrons in crystals are analyzed theoretically in details. The influence of electron multiple scattering and incoherent bremsstrahlung background are taken into account when simulating of the PXR and CBS spectra. It is shown for the first time that the optimal geometry can allow one to suppress the influence of the electron multiple scattering if the following condition is fulfilled (see equation in manuscript) where ψ is the inclination angle of electron velocity vector relative to the reciprocal lattice vector corresponding to the radiation peak under consideration; βu = u/c; u is the value of electron velocity; &thgr; is the angle between electron velocity and wave vector of a photon. Optimal geometry gives possibility to use the thicker crystals and to increase the PXR intensity. For simulation of the PXR and CB spectra and calculation of their characteristics a software package "PXR analysis" is developed.

In the present work an essential difference is revealed between the undulator and transition radiation processes. In the first case emission of a photon occurs at a certain angle, while in the second case radiation takes place with equal probability in both dense and dilute parts of the medium and at various angles. These angles are different for different harmonics and their angular widths, which determine the frequency spectrum of radiation, do not depend on the harmonic number. The higher harmonic the wider the frequency ranges of emission. The weighting function of overlap of the harmonic spectra has a sharp peak in the soft range of frequencies. The peak increases and its width quadratic decreases depending on the electron energy. Therefore, the number of emitted soft photons does not depend on the energy and quadratic depends on the number of harmonics. A new physical phenomenon has been revealed: coherent emission of harmonics in the soft frequency range. Thus, it is possible to obtain intense beams of soft photons using high-current electron bunches.

The angular-spectral distributions as well as the dependence of the total number of photons of X-ray Cherenkov radiation upon the number, thickness of the layers and on particle energy have been calculated using the theoretical formulae taking into account the reflection from the interfaces between the two media of the Si/Mo multilayers. The possibilities of the experimental investigation have been discussed.

Features of a PXR source at a 100 MeV linac in θ-2θ target-to-detector arrangement were numerically simulated on the base of general expressions taking into account diffracted x-ray transition radiation (DTR) and interference between PXR and DTR. We have calculated x-ray intensities and polarization in symmetric Laue geometry for Bragg angles from 2 through 45 degrees. Thickness of Si target of 0.01 and 0.001 cm, detector aperture of 0.01 rad and x-ray energy resolution of 0.05 were accepted. Wide range x-ray energy tuning with minor intensity variation may be obtained using crystal target of optimal thickness that is close to the Bremsstrahlung coherence length. Calculations of the asymmetric case have shown considerable x-ray intensity increase due to the choice of optimal absorption of the emitted x-ray quanta. Dynamical effects expressed in appearance of the peculiarities in the PXR spectral-angular and angular distributions were also observed both for symmetric and asymmetric generation geometries. It could be important for a PXR source use, especially for experiments with high resolution x-ray diffractometry.

Measurements of angular distribution of coherent transition radiation (CTR) from electron bunches with energy 6.1 MeV and length σ_z =1.3mm were carried out using the detector based on broadband antenna and high-frequency diode with resulting sensitivity 0.3V/mW at a room temperature. Parabolic mirror use for CTR focusing rejects a pre-wave zone effect. The absolute value of the CTR power agrees with theoretical prediction within experimental accuracy level.

Strong monochromatization of the parametric x-ray emission spectrum is predicted for electrons moving at small angles to the reflecting crystallographic plane of target crystals. The effect can only be realized far from the Bragg-resonance condition and is caused by a long "tail" in the angular parametric-x-ray distribution. In addition, there can be a substantial enhancement of the parametric x-ray yield from grazing-incidence electrons when there is strong asymmetric diffraction (the reflecting crystallographic plane is not parallel to the surface of the crystal). It is shown that this allows one to suppress the influence of photoabsorption on parametric x-ray emission.

The analytical expressions for the difference between the classical frequency of the parametric X-ray radiation (PXR) and the Bragg frequency in the PXR reflection are derived. The difference increases proportionally to the square of the angular distance to the PXR reflection center and also the Bragg frequency always exceeds the PXR one from the same system of crystallographic planes. A possibility of the existence of PXR diffraction from electrons of moderate energy to forward direction due to PXR peak broadening in a thin crystal and also in polycrystal or mosaic crystal is described. The experiment at accelerator for observation of PXR diffracted to forward direction in textured polycrystal or mosaic crystal is proposed. Application of PXR spectral peak broadening for measurement of thin crystal thickness, crystalline grains or domains size is proposed.

After considering the necessary targets-radiators of pure highly oriented nanotubes it is discussed the possibility of the experimental investigation of some processes accompanying the passage of particles through nanotubes. Arrangements designed for the measurement of the yield of quasimonochromatic X-ray photon beams due to the processes of coherent bremsstrahlung, channeling, parametric X-ray and nanotube undulator radiations as well as for the study of secondary electron production are considered. The proposed experiments are based on the recent theoretical and numerical results of the collaboration Lyon-Yerevan-Moscow-Kharkov and of other groups as well as experimental results obtained with the help of nanotubes.

A new experimental channel for X-radiation beam on modern proton accelerators is suggested on the base of parametric radiation (PXR) of particles in crystals. As a source of radiation one used a specially bent crystal deflector placed inside the accelerator vacuum chamber and oriented respect to the circulating beam.

The types of x-ray radiation, choherent polarization bremsstrahlung (PB) and traditional coherent bremsstrahlung (BR) generated in a process of fast multi-charge cluster interaction with a medium cluster, are considered. As indicated, new coherent PB and BR effects connected with the both mutual screening in clusters, which consist of positive and negative charged particles, and transformations of x-ray spectra may be used in nano-object diagnostics.

Coherent emission at zero angle by a relativistic electron beam interacting with two laser lines in the helical undulator is studied. The laser waves generate axially directed periodical ponderomotive force, which bunches the electron beam. Thereby, electrons produce powerful quasi monochromatic and narrow directed high brilliance photon beam in the sub millimeter region. Analytic calculation of the gain in coherent radiation from modulation beam is presented.

The SPARX project consists in an X-ray-FEL facility jointly supported by MIUR (Research Department of Italian Government), Regione Lazio, CNR, ENEA, INFN and Rome University Tor Vergata. It is the natural extension of the ongoing activities of the SPARC collaboration. The aim is the generation of electron beams characterized by ultra-high peak brightness at the energy of 1 and 2 GeV, for the first and the second phase respectively. The beam is expected to drive a single pass FEL experiment in the range of 13.5-6 nm and 6-1.5 nm, at 1 GeV and 2 GeV respectively, both in SASE and SEEDED FEL configurations. A hybrid scheme of RF and magnetic compression will be adopted, based on the expertise achieved at the SPARC high brightness photoinjector presently under commissioning at Frascati INFNLNF Laboratories. The use of superconducting and exotic undulator sections will be also exploited. In this paper we report the progress of the collaboration together with start to end simulation results based on a combined scheme of RF compression techniques.

This communication describes the research work plan that is under implementation at the SPARC FEL facility in the framework of the DS4 EUROFEL programme. The main goal of the collaboration is to study and test the amplification and the FEL harmonic generation process of an input seed signal obtained as higher order harmonics generated both in crystals (400 nm and 266 nm) and in gases (266 nm, 160 nm, 114 nm). The SPARC FEL can be con-figured to test several cascaded FEL layouts that will be briefly analysed.

The INFN Strategic Project PLASMONX (PLASma acceleration and MONochromatic X-ray production) deals with the creation of a High Intensity Laser Laboratory at LNF (HILL@LNF) beside the SPARC bunker, with which it will communicate via a channel for the propagation of laser beams. In this laboratory FLAME ( Frascati Laser for Acceleration and Multidisciplinary Experiments), a 200TW, 30fs, 10Hz Ti:Sapphire Laser, will be set up. The main goals of this project are: 1) demonstration of high-gradient acceleration of relativistic electrons injected into electron plasma waves excited by ultra-short, super-intense laser pulses; 2) development of a monochromatic and tuneable X-ray source in the 20-1000 keV range, based on Thomson Scattering of laser pulses by the 20-200 MeV electrons of the LINAC of the SPARC project. One of the aims of the project consists in the realization of a pulsed source of ionizing radiation for R&D activity in different fields.

We present a study based on a parametric optimization of a Thomson Source operated in FEL mode. This deals with the proposed scheme to use a high intensity laser pulse colliding with a high brightness electron beam of low to medium energy (around 10 MeV). Electrons undulating in the incoming laser field may emit radiation in a FEL coherent mode as far as some conditions are satisfied. A set of simple analytical formulas taking into account 3D effects is derived, in order to express these conditions in terms of three free parameters, namely the wavelength of the colliding laser pulse, the FEL ρ parameter, and the peak current carried by the electron beam. A few examples of possible operating points are compared with results of 3D numerical simulations, showing the FEL coherent emission of X-rays by high brightness electron beams colliding with high intensity laser beams carrying pulse energies of about 10 J.

In this paper we describe recent studies on X-ray emission from ultra-fast laser interactions with solids. We describe the dedicated equipment including a powerful femtosecond, Titanium-Sapphire laser system and custom developed diagnostics for the characterization of both the laser performance and the X-ray emission. We show the experimental results obtained from irradiation of Aluminium and Titanium targets including X-ray yield and spectra obtained using single-photon counting and spectroscopy. We discuss correlation of X-ray emission with the measured properties of hot electrons emerging from the target rear side. In particular, forward accelerated fast electrons propagating through a Ti foil are found to be emitted in a cone perpendicular to the target. A comparison of the experimental findings with the results of a PIC simulation is also reported, aimed at identifying the physical processes responsible for the production of this forward propagating population of fast electrons. Finally, we show results of simple optical spectroscopy measurements of scattered light and we discuss the use of these results in view of optimization and control of this kind of X-ray sources.

In the SPARC photoinjector, the amplified Ti:Sa laser system is conceived to produce an UV flat top pulse profile required to reduce the beam emittance by minimizing the non-linear space charge effects in the photoelectrons pulse. Beam dynamic simulations indicate that the optimal pulse distribution must be flat top in space and time with 10 ps FWHM duration, 1 ps of rise and fall time and a limited ripple on the plateau. In a previous work it was demonstrated the possibility to use a programmable dispersive acousto-optics (AO) filter to achieve pulse profile close to the optimal one. In this paper we report the characterization of the effects of harmonics conversion on the pulse temporal profile. A technique to overcome the harmonics conversion distortions on the laser pulses at the fundamental wavelength in order to obtain the target pulse profile is explained too. Measurements and simulations in the temporal and spectral domain at the fundamental laser wavelength and at the second and third harmonics are presented in order to validate our work. It is also described a time diagnostic device for the UV pulses.

Guiding focused pulses along path lengths much larger than the depth of focus is one of the major tasks for the progress of laser acceleration of electrons in plasmas. We will present the results of the production of hollow plasmas to be used as guiding medium, obtained inducing optical breakdown in Helium subsonic gas-jet with nanosecond laser pulses similar to the Amplified Spontaneous Emission (ASE) pedestal of a powerful ultrashort laser pulse. These plasmas have been then carefully characterized by the deconvolution, with original algorithms, of high quality interferograms obtained with high resolution interferometry and the relevant channel parameters were measured, including length, width, electron density at the channel axis and at its boundary. The electron density profiles we obtained match the requirements for an efficient guiding in laser wakefield acceleration (LWFA) experiments. The acceleration length can be further increased by using longer gas-jets and larger f/N numbers. New studies are planned with supersonic gas-jets, providing more homogeneous density profiles and steeper boundaries.

The maintenance of the growth of the multibillion-dollar semiconductor industry requires the development of techniques for the fabrication and characterisation of nanoscale devices. Consequently, there is great interest in photolithography techniques such as extreme UV and x-ray. Both of these techniques are extremely expensive and technologically very demanding. In this paper we describe research on the feasibility of exploiting x-ray propagation within carbon nanotubes (CNT's) for the fabrication and characterisation of nanoscale devices. This work discusses the parameters determining the design space available. To demonstrate experimentally the feasibility of x-ray propagation, arrays of carbon nanotubes have been grown on silicon membranes. The latter are required to provide structural support for the CNT's while minimising energy loss. To form a waveguide metal is deposited between the nanotubes to block x-ray transmission in this region at the same time as cladding the CNT's. The major challenge has been to fill the spaces between the CNT's with material of sufficient thickness to block x-ray transmission while maintaining the structural integrity of the CNT's. Various techniques have been employed to fill the gaps between the nanotubes including electroplating, sputtering and evaporation. This work highlights challenges encountered in optimising the process.

The field emission properties of single-walled carbon nanotubes deposited by chemical vapour deposition on plane substrates and on wires have been investigated. The good emitting performances of the nanotubes are promising for the assembling of robust and efficient cold cathodes, and in particular for the use as an electron source for X-ray production. Tiny electron sources have been fabricated by coating metal wires (W, 300 &mgr;m diameter) with nanotubes. To assess the efficiency of such nanotube-based cathodes for generating X radiation, a prototype X-ray tube has been fabricated. Preliminary measurements of X-ray emission obtained with such a device are presented.

Compound refractive X-ray lens, consisting of a lot number of placed in-line concave microlenses, is a unique device to control X-ray beams. It works like ordinary refractive lens for visual light and, in contrast to other X-ray optical devices, is useful for forming image of X-ray source. The size of the source image S1 depends on the distance a between the source and the lens and may be calculated as S1=S M, where S is source size, M- magnification. The magnification M depends on a and b as M=b/a, where b is distance from the lens to the source image. This distance b satisfies to a well-known lens formula 1/a+1/b=1/f, where f is lens focal length. This lens property may be used for forming small-sized X-ray spots at a large enough distances from the lens. Such beams are of great interest for experiments on SAXS and X-ray diffraction. Here we report results of our first experiments in Istituto per lo Studio dei Materiali Nanostrutturati and Laboratori Nazionali di Frascati on using compound refractive X-ray lenses for forming X-ray beams.

Polycapillary optics are highly efficient devices for focusing high-energy photons and thermal neutrons. Here we will present our studies by modeling and simulating X-ray propagation through cylindrical polycapillary optics using PolyCAD, a ray-tracing original package developed by our group. PolyCAD is a CAD program designed for X-ray photon tracing in polycapillary optics. PolyCAD allows simulating any type of X-ray source like an X-ray tube of finite beam dimensions or an astrophysical object in combination with different kinds of polycapillary optics. Experimental data have been compared with theoretical predictions, in particular the focusing properties of a cylindrical lens have been visualized by collecting 3D images, and reconstructed using PolyCAD simulations. The acquired images put into evidence how the focal spot profiles, including intensity and widths, at different projection distances, agree with calculations. In the second part of this work, we present some characterization methodologies used for studying several kind of polycapillary optics. The procedure is divided principally in two kind of measurements: "angular measurements" for studying lens's transmission coefficient and focusing properties, and "CCD images" for characterizing lens's focal spot.

The article summarizes the experimental results on the search for total external reflection effect for hard γ-radiation (E = 0-11.8 MeV). The experimental setup is described. The angular distributions of the beam formed by slit collimator (slit width - 50 &mgr;) and scattered from the surface of a reflector (angle of inclination - 83 &mgr;rad) are presented. The results indicate the possibility to efficiently control the beams of high-energy γ-quanta.

For the secondary electron emission studies a series of poly- and nano-crystalline diamond films with different characteristics (crystallinity, morphology and dopants) were produced using an innovative CVD apparatus that allows the doping of diamond layers. Moreover additional hydrogenation processes were carried out after the first emission experiments in order to obtain H termination at three diamond surface and enhance the electron yield. At 1 KeV a gain of 5.5 has been obtained for Ti-doped diamond layers and for diamond layers containing C-sp² clusters.

This PDF file contains the front matter associated with SPIE Proceedings Volume 6634, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.