Parametric X-ray Radiation Research Articles

Interference effects in radiation by the relativistic electron in the structure of “amorphous matter layers–single crystal”

In the present work a theory of coherent radiation of a relativistic electron moving at a constant speed in a combined target, consisting of several amorphous matter layers and a monocrystalline layer is built. The expressions describing the amplitudes of diffracted transition radiation (DTR) and parametric X-ray radiation (PXR) are derived within the framework of two-wave approach of the dynamic diffraction theory. The cases of one and two amorphous matter layers in the structure were considered. Also the extreme case, when vacuum is considered as the second amorphous layer in the structure, is investigated. The expressions obtained describe a spectral-angular distribution of DTR, PXR and their interference in such a structure. The X-ray wave generation and propagation processes in crystalline layer are considered in Laue scattering geometry for the general case of asymmetric reflection.

Element-sensitive computed tomography by fine tuning of PXR-based X-ray source

Element-sensitive computed tomography (CT) experiments were carried out based on the absorption edge of a specific element using a finely tunable X-ray beam generated by parametric X-ray radiation (PXR). Tomographic images of specimens containing strontium were measured at energies both lower and higher than that of the Sr absorption edge. The difference between the images of the two energies successfully reveals the three-dimensional distributions of Sr. The results demonstrate that this method is effective for elemental analysis of considerably thick samples and could complement X-ray fluorescence analysis.

Coherent X-Rays Generated by Relativistic Electrons in a Tungsten Monocrystal

In an experiment conducted at the Tomsk synchrotron "Sirius", the photon yield of parametric X-ray radiation generated by 500 MeV electrons in a tungsten monocrystal in Bragg geometry has been studied. The (111) tungsten monocrystal, having a thickness of 1.7 mm and a surface mosaicity of not more than 80², was oriented at the Bragg angle θB= 45°to the direction of the electron beam. The photons were detected at the angle 2θB= 90° relative to the electron beam. A comparison of PXR angular distributions with calculations has been carried out with taking into account the actual conditions of the experiment.

The Effects of Dynamic Diffraction in Parametric X-Ray Radiation of Relativistic Electrons in a Periodically Layered Medium

Possible manifestation of the effects of dynamic diffraction in parametric X-ray radiation of a relativistic electron transversing a periodically layered medium is investigated in the Laue diffraction geometry. Such dynamic effects as Bormann’s effect and broadening of the PXR spectrum are predicted.

X-ray imaging based on small-angle X-ray scattering using spatial coherence of parametric X-ray radiation

X-ray imaging based on small-angle X-ray scattering (SAXS) was carried out using the parametric X-ray radiation (PXR) source at the Laboratory for Electron Beam Research and Application (LEBRA) of Nihon University. The experimental setup employed in this novel imaging approach is the same as that employed in diffraction-enhanced imaging (DEI), a kind of X-ray phase-contrast imaging method. In SAXS-based imaging, the image contrast is correlated with the broadening of the rocking curve peak due to the scattering from micron- or sub-micron-sized grains in the sample material. An experiment using the 25.5-keV PXR beam demonstrated that SAXS-based imaging with PXR provides a substantially strong contrast for granular materials despite the extremely low density of the material.

Spectral distribution in the reflection of parametric X-rays

The parametric X-ray radiation (PXR) spectra are measured on condition when the angular size of PXR cone is smaller than the angular resolution of the experiment. The PXR is generated under interaction of 50GeV proton beam with silicon crystal in Bragg geometry. The comparison of experimental data with results of developed theoretical model is presented and discussed.

X-ray transition radiation of electrons with energy of 300 to 900 MeV in periodic multifoil radiators

Results of experiments conducted at the Tomsk synchrotron to study resonant X-ray transition radiation generated by relativistic electrons in periodic multifoil radiators are reviewed. Both the internal synchrotron beam and the external secondary electron beam from the pair magnetic γ-spectrometer with energies ranging from 300 to 900 MeV were used in the experiments. The radiators consisted of many thin amorphous foils of various materials. The generation of X-ray radiation in a compound radiator consisting of a multifoil radiator and a crystal is also studied. In this case, the resonant X-ray transition radiation generated in the multifoil radiator is diffracted in the crystal and emitted at Bragg angles, together with the parametric X-ray radiation generated in the crystal. Spectral and angular properties of the resonant X-ray transition radiation and diffracted resonant X-ray transition radiation are investigated. The ratio between the contributions from the diffracted resonant X-ray transition radiation and other types of radiation to the total coherent X-ray radiation flux generated by electrons in periodic structures and crystals is estimated.

X-ray imaging using a tunable coherent X-ray source based on parametric X-ray radiation

A novel X-ray source based on parametric X-ray radiation (PXR) has been employed for X-ray imaging at the Laboratory for Electron Beam Research and Application (LEBRA), Nihon University. Notable features of PXR are tunable energy, monochromaticity with spatial chirp, narrow local bandwidth and spatial coherence. Since the X-ray beam from the PXR system has a large irradiation area with uniform flux density, the PXR-based source is suited for X-ray imaging, especially for application to phase-contrast imaging. Despite the cone-like X-ray beam, diffraction-enhanced imaging (DEI) can be employed as a phase contrast imaging technique. DEI experiments were performed using 14- to 34-keV X-rays and the phase-gradient images were obtained. The results demonstrated the capability of PXR as an X-ray source for phase-contrast imaging with a large irradiation field attributed to the cone-beam effect. Given the significant properties of the LEBRA-PXR source, the result suggests the possible construction of a compact linac-driven PXR-Imaging instrument and its application to medical diagnoses.

New method for measuring beam profiles using a parametric X-ray pinhole camera

We propose a new method for measuring electron beam profiles using parametric X-ray radiation. In this method, a pinhole is placed between the source of parametric X-ray radiation and a two-dimensional X-ray detector, and the beam profile can be reconstructed on the detector, i.e., based on the principle of a pinhole camera. The profiles are in good agreement with the results obtained using a standard method with optical transition radiation. This method may prove useful to measure profiles of electron beams with short bunch lengths in recent advanced linear accelerators. • We propose a new method for measuring beam profiles using parametric X-ray radiation. • The proposed method is based on the principle of a pinhole camera. • We have succeeded in performing a proof-of-principle experiment. • The proposed method may be useful for beam monitors in recent advanced accelerators.

Increase of parametric X-ray intensity due to the Borrmann effect

Parametric X-ray radiation (PXR) from relativistic electrons in a crystal with a thickness larger than the X-ray absorption length is considered. The characteristics of this radiation are analysed in detail taking into account the dynamical diffraction theory. It is shown that the PXR intensity increases and its dependence on the electron energy changes when the X-ray quanta are emitted under conditions of anomalous absorption (the Borrmann effect). The details of the PXR angular distribution and its comparison with the experimental data are also discussed.

Parametric X-ray radiation as a conversion of virtual to real quanta

The emission of parametric X-ray radiation (PXR) by a relativistic charged particle moving in a crystal rectilinearly is considered in terms of a conversion of virtual quanta accompanying the particle to real quanta. Some recent experimental data on the PXR properties are analyzed and the asymmetry of PXR reflection is considered. Simple analytical expressions for conversion factors are obtained from experimentally confirmed data. The properties of the conversion factors for the parametric X-ray radiation are discussed.

Channeling and parametric X-ray studies at the SAGA Light Source

We present experimental results on channeling and parametric X-ray radiation obtained using a 255-MeV electron beam from an injector linac at the SAGA Light Source. Using a screen monitor, we observed both channeling phenomena and doughnut scattering by measuring the profile of an electron beam transmitted through a 20-μm-thick Si crystal. We also measured the angular distribution of parametric X-ray radiation using an imaging plate as a two-dimensional X-ray detector. The obtained results are in good agreement with theory. The final goal of these studies is the first observation of diffracted channeling radiation, and our strategy for achieving this is discussed.

Comparison of the results of kinematic and dynamic approximations for parametric X‐ray radiation in the Bragg direction

AbstractA theoretical study on the kinematic and dynamic approximations of parametric X‐ray radiation (PXR) is presented. The results obtained are examined and compared. The ratio of the absolute maxima of kinematic and dynamic PXR can be obtained. The results are closer at lower energies and their correlation depends on the angle of incidence. These theoretical results indicate that in some energy regions and angle of incidence it may be necessary to apply the dynamic approximation of PXR for greater accuracy.

Computed tomography for light materials using a monochromatic X-ray beam produced by parametric X-ray radiation

Computed tomography (CT) for light materials such as soft biological tissues was performed using a monochromatic X-ray beam provided by a parametric X-ray radiation (PXR) source at the Laboratory for Electron Beam Research and Application (LEBRA) of Nihon University. Using a high-efficiency flat panel detector (FPD), each projection image for CT was taken with exposure times of 5 or 10s, and 60–360 projection images in each run were obtained with total measurement time of 5min to 1h. CT images were obtained from the projection images using the conventional calculation method. The typical tomograms obtained had sharp outlines, which are likely attributable to the propagation-based phase contrast.

Time dependence of the intensity of parametric X-ray radiation produced by relativistic particles passing through crystals

The time evolution of parametric X-ray radiation (PXR) produced by a relativistic charged particle passing through a crystal is studied. It is shown that the duration of PXR pulses can be much longer than the particle flight time through the crystal. This enables a thorough experimental investigation of the time structure of parametric X-ray pulses generated by electron bunches available with modern accelerators. The complicated time structure of parametric radiation can also be observed in artificial (electromagnetic, photonic) crystals in optical, terahertz, and microwave ranges of wavelengths.

Parametric X-ray radiation as a beam size monitor

We propose two new approaches, referred to as the local and remote methods, for measuring electron beam sizes using parametric X-ray radiation. Using the local method, we have carried out a proof-of-principle experiment, and good agreement was obtained with the results of a standard method using a fluorescent screen. For the remote method, we have proposed a scheme to measure beam sizes using a Fresnel zone plate as an X-ray lens. These methods may prove useful for measuring the sizes of electron beams with small emittances or short bunch lengths in recent advanced accelerators.

Quantum effects for parametric X-ray radiation during channeling: Theory and first experimental observation

The theory of X-ray radiation from relativistic channeled electrons at the Bragg angles—parametric X-ray radiation (PXR) during channeling (PXRC)—is developed while accounting for two quantum effects: the initial population of bound states of transverse motion and the transverse “form-factor” of channeled electrons. An experiment was conducted using a 255 MeV electron beam from a linac at the SAGA Light Source. We have identified a difference in the angular distributions of PXR and PXRC and obtained a fairly good agreement between the theoretical and experimental results.

Parametric X‐ray radiation as a novel source for X‐ray imaging

A novel X‐ray source based on parametric X‐ray radiation (PXR) has been put into practical use at the Laboratory for Electron Beam Research and Application (LEBRA), Nihon University, Japan. The PXR beam has been generated from a Si single crystal irradiated by a 100‐MeV electron beam from a linac at the LEBRA. In this study, phase‐contrast imaging experiments using a diffraction‐enhanced imaging (DEI) method have been carried out by using the parametric X‐rays at an energy of 17.5 keV. The successful images obtained by the DEI method have shown detailed inner structures of soft biological tissues more clearly as compared with those by conventional absorption radiography. Given the significant properties of the LEBRA PXR source, i.e., compact system, large X‐ray beam irradiation field of approximately 80 mm in diameter and quasi‐monochromaticity, the result suggests a possible construction of a compact linac‐driven PXR‐DEI device and application to medical diagnoses. Copyright © 2012 John Wiley & Sons, Ltd.

A possibility of transverse beam size diagnostics using parametric X-ray radiation

A method of transverse beam size diagnostics with μm space resolution by parametric X-ray radiation is proposed.

Diffracted transition radiation of relativistic electrons in an artificial periodic structure

A theory concerning the coherent X-ray radiation of relativistic electrons crossing an artificial periodic medium in Laue scattering geometry has been constructed. Expressions describing the spectralangular characteristics of radiation in the Bragg scattering direction have been obtained and studied. Radiation is considered in analogy with that in the crystal medium as a result of the coherent summation of the contributions of two radiation mechanisms, in particular, parametric X-ray radiation (PXR) and diffracted transition radiation (DTR). It is shown that the DTR yield from a layered target can exceed the particle radiation yield in a single-crystal radiator by one order or more under similar conditions.