High-intensity X-ray Sources Research Articles

Extended X-ray Absorption Fine Structure (EXAFS) Measurements on Alkali Metal Superatoms of Ta-Atom-Encapsulated Si16 Cage.

The silicon cage nanoclusters encapsulating a tantalum atom, termed Ta@Si16, exhibit characteristics of alkali metal "superatoms (SAs)". Despite this conceptual framework, the precise structures of Ta@Si16 and Ta@Si16+ remain unclear in quantum calculations due to three energetically close structural isomers: C3v, Td, and D4d structures. To identify the geometrical structure of Ta@Si16 SAs, structural analysis was conducted using extended X-ray absorption fine structure (EXAFS) with a high-intensity monochromatic X-ray source, keeping anaerobic conditions. Focusing on "superordered" films, which constitute amorphous thin films composed solely of Ta@Si16 SAs, this analysis preserved locally ordered structures. Spectral comparisons between experimental and simulated Ta L3-edge EXAFS unveil that Ta@Si16 SAs on a substrate adopt a C3v-derived structure, while Si K-edge EXAFS introduces spectral ambiguity in structural identifications, attributed to both intracluster and intercluster scatterings. These findings underscore the significance of locally ordered structure analyses in understanding and characterizing novel nanoscale materials.

Dynamic flyer in barrel imaging via high intensity short-pulse laser.

The thin flyer is a small-scale flying object, which is well known as the core functional element of the initiator. Understanding how flyers perform has been a long-standing issue in detonator science. However, it remains a significant challenge to explore how the flyer is formed and functions in the barrel of the initiator via tabletop devices. In this study, we present dynamic and unprecedented images of flyer in barrel via high intensity short-pulse laser. Advanced radiography, coupled with a high-intensity picosecond laser X-ray source, has enabled the provision of state-of-the-art radiographs in a single-shot experiment for observing micron-scale flyer formation in a hollow cylinder in nanoseconds. The flyer was clearly visible in the barrel and was accelerated and restricted differently from that without the barrel. This first implementation of a tabletop X-ray source provided a new approach for capturing dynamic photographs of small-scale flying objects, which were previously reported to be accessible only via an X-ray phase-contrast imaging system at the advanced photon source. These efforts have led to a significant improvement of radiographic capability and a greater understanding of the mechanisms of "burst" of exploding foil initiators for this application.

High granularity resistive Micromegas for high particle rates environment

The new era of particle physics experiments is moving towards new upgrades of present accelerators (Large Hadron Collider at CERN) and the design of high energy (tens/hundreds TeV scale) and very high intensity new particle accelerators (FCC-ee/hh, EIC, Muon Collider). Cost effective, high efficiency particle detection in a high background and high radiation environment is fundamental to accomplish their physics program. We present a new high granularity resistive Micromegas detector capable to ensure full efficient and stable operation and a good tracking capabilities up to particle fluxes of 10 MHz/cm2. A summary of the detector performances, measured by mean of high intensity X-ray, muon and pion sources, is reported, together with most recent results from test beam activities.

X-ray third-order nonlinear asymmetric diffraction in the transmission geometry

For high intensity x-ray sources, the investigations of the nonlinear x-ray effects become essential. The x-ray third-order nonlinear asymmetric transmission case dynamical diffraction is investigated theoretically in perfect crystals. The three essential input parameters are taken into account: the deviation from the Bragg exact orientation, the asymmetry angle of reflecting atomic planes and the intensity of incident wave. The third-order nonlinear equations for the asymmetrical dynamical diffraction and two integrals of motion are presented. The exact solutions for the wave amplitudes, presented via Jacobi elliptic functions, have been found. The solutions are periodic functions of the depth. It is shown that the behavior of the waves inside the crystal is determined by the sign of a combined parameter, which includes the three input parameters, mentioned above. The regions, where this parameter is positive, negative or zero, are found. For positive values, the energy is concentrated both in the transmitted and diffracted waves while for the negative values, the energy is concentrated mainly in the transmitted beam. It is found that when this combined parameter is zero, the amplitudes are elementary periodic or non-periodic functions. For the periodic solutions, the nonlinear Pendellösung effect takes place, i.e. the transmitted and diffracted waves periodically exchange with their energies. For the period, called an extinction length, an exact expression is found. It is shown that for large values of the asymmetry factor, the observation of the nonlinear diffraction effects can be realized for sufficiently low intensities of the incident wave. The obtained results can be used for experimental investigation of the nonlinear Bragg diffraction and for preparation of high intensity x-ray beams with given parameters. The expression for the nonlinear extinction length allows to estimate the third-order nonlinear susceptibilities of crystals by measuring the extinction length in experiments.

Production of warm dense water in the laboratory using intense ion beams at FAIR: Application to planetary physics

This paper presents two-dimensional hydrodynamic simulations of implosion of a water sample, which is enclosed in a cylindrical shell of tungsten that is driven by an intense uranium beam. The considered beam parameters match the characteristics of the beam which will be delivered by the heavy ion synchrotron, SIS100, at the Facility for Antiprotons and Ion Research (FAIR). An experimental scheme based on this concept, which is named LAPLAS, is an important part of the high energy density physics research program at FAIR. The simulations show that the LAPLAS implosion leads to a low-entropy compression of water, which generates core conditions of water-rich planets. The importance of this work is underscored by the fact that more than 30% of the discovered extrasolar planets are Neptune-like water-rich planets. To be able to construct a reliable physical model of the formation and evolution of these planets, it is important to have correct understanding of the equation of state of the exotic states of water that exist in the planetary interior. It is thus expected that the knowledge obtained from the LAPLAS experiments will be a very valuable contribution to the field of planetary physics. We show that x-ray radiographic imaging using a high-intensity laser-driven hard x-ray source would be a suitable diagnostic capable of delivering high-resolution images of the hydrodynamic evolution.

X-ray photons produced from a plasma-cathode electron beam for radiation biology applications

A compact low-energy and high-intensity x-ray source for radiation biology applications is presented. A laser-induced plasma moves inside a 30 kV diode and produces a beam of 1014 electrons at the anode location. An aluminum foil converts a part of the energy of these electrons into x-ray photons, which are characterized using filtered imaging plates. The dose that would be deposited by these x-ray photons in C. elegans larvae is calculated from Geant4 simulations. It can be set to a value ranging between 10 μGy and 10 mGy per laser shot by simply changing the aluminum foil thickness and the diode voltage. Therefore, this versatile and compact x-ray source opens a new path to explore the radiation effects induced by dose rates varying over several orders of magnitude.

Attosecond betatron radiation pulse train

High-intensity X-ray sources are essential diagnostic tools for science, technology and medicine. Such X-ray sources can be produced in laser-plasma accelerators, where electrons emit short-wavelength radiation due to their betatron oscillations in the plasma wake of a laser pulse. Contemporary available betatron radiation X-ray sources can deliver a collimated X-ray pulse of duration on the order of several femtoseconds from a source size of the order of several micrometres. In this paper we demonstrate, through particle-in-cell simulations, that the temporal resolution of such a source can be enhanced by an order of magnitude by a spatial modulation of the emitting relativistic electron bunch. The modulation is achieved by the interaction of the that electron bunch with a co-propagating laser beam which results in the generation of a train of equidistant sub-femtosecond X-ray pulses. The distance between the single pulses of a train is tuned by the wavelength of the modulation laser pulse. The modelled experimental setup is achievable with current technologies. Potential applications include stroboscopic sampling of ultrafast fundamental processes.

Radiation emission in laser-wakefields driven by structured laser pulses with orbital angular momentum

High-intensity X-ray sources are invaluable tools, enabling experiments at the forefront of our understanding of materials science, chemistry, biology, and physics. Laser-plasma electron accelerators are sources of high-intensity X-rays, as electrons accelerated in wakefields emit short-wavelength radiation due to betatron oscillations. While applications such as phasecontrast imaging with these betatron sources have already been demonstrated, others would require higher photon number and would benefit from increased tunability. In this paper we demonstrate, through detailed 3D simulations, a novel configuration for a laser-wakefield betatron source that increases the energy of the X-ray emission and also provides increased flexibility in the tuning of the X-ray photon energy. This is made by combining two Laguerre-Gaussian pulses with non-zero net orbital angular momentum, leading to a rotation of the intensity pattern, and hence, of the driven wakefields. The helical motion driven by the laser rotation is found to dominate the radiation emission, rather than the betatron oscillations. Moreover, the radius of this helical motion can be controlled through the laser spot size and orbital angular momentum indexes, meaning that the radiation can be tuned fully independently of the plasma parameters.

First results on the use of a EDXRF scanner for 3D imaging of paintings

A 3D map of chemical elements distribution from energy-dispersive X-ray fluorescence (EDXRF) analysis would be a perfect conclusion<br />in a detailed study of any type of artifact. This map can be easily achieved by using synchrotron light as source of radiation, and micro-<br />optics both at the source and at the detector. In such a manner a micro-voxel is irradiated and detected, which can be at any depth with<br />respect to the surface of the artifact. This method is effective but needs a high-intensity X-ray source; therefore, its use in archaeometry<br />is limited. An alternative method is proposed in the present paper, which uses a portable EDXRF-device to measure the altered Ka/Kb<br />or La/Lb-ratios, which allow to locate the chemical elements. Several examples are described.

Experimental study on fluence rate response of LaBr3 to pulsed X-rays

The linear response is the key property employed by a radiation detector to determine the accurate intensity of a pulse radiation field. In this study, we investigated the high fluence rate response behavior of a LaBr3 scintillator. We used a high-intensity pulsed X-ray source called “QiangGuang-I” which could produce an X-ray pulse with a total dose of 100 Gy, full width at half maximum of 20 ± 5 ns, and an average energy of 1 MeV, to test the linear response of the LaBr3 scintillator. The Lissajous figure method was used in this experiment. The results showed that the fluence rate linear response limit was more than 1.8 × 1020 MeV/(cm2·s).

Development of high intensity X-ray sources at the National Ignition Facility

Laser heated plasmas have provided recently some of the most powerful and energetic nanosecond length laboratory sources of x-ray photons (Ephoton = 1–30 keV). The highest x-ray to laser conversion is currently accessible by using underdense (ne ∼ 0.25 nc) plasmas since optimal laser coupling is obtained in millimeter scale targets. The targets can have conversion efficiencies of up to 10%. Several types of targets can be used to produce underdense plasmas: metal lined cylindrical cavities, gas pipes, and most recently nano-wire foams. Both the experimental and simulation details of these high intensity x-ray sources are discussed.

High-intensity attosecond X-ray source generation by using low-intensity spatial inhomogeneous mid-infrared pulse combined with an ultraviolet pulse

We theoretically investigate the high-order harmonic spectra and the attosecond pulse generation from He[Formula: see text] ion driven by the spatial inhomogeneous combined field, consisting of a two-color low-intensity mid-infrared pulse ([Formula: see text] W/cm2) and an ultraviolet (UV) pulse ([Formula: see text] W/cm2). The numerical results show that due to the spatial inhomogeneous effect, the harmonic cutoffs are remarkably extended, and a 986 eV super-continuum can be obtained. Further with the proper introduction of an UV pulse (from 60 nm to 20 nm) to the two-color field, the harmonic yields are enhanced, especially for adding the 30 nm pulse case, a 1113 eV super-continuum (corresponding to a 34.1 dB enhanced field) with less harmonic modulation and six orders of magnitude enhancement can be obtained. Similar calculations have been performed for He atom and an 896 eV super-continuum with four orders of magnitude enhancement can be produced. Time–frequency harmonic distribution and time-dependent electron populations show that the single short quantum path contribution is responsible for the less harmonic modulation and the laser-induced electron excitation is responsible for the harmonic enhancement. Finally, by properly superposing the harmonics, a series of sub-50-as pulses including the whole X-ray region with 3–6 orders of magnitude enhancement can be obtained.

Experimental study on high dose rate response of cadmium zinc telluride detectors to pulsed X-ray

The linear response is the key property for a radiation detector to obtain accurate intensity of the radiation field. In this experiment, a high-intensity pulsed X-ray source, named “QiangGuang-I” is utilized to test the linear response of cadmium zinc telluride (CZT) detector. The total dose per pulse 20 cm from the pulse source is 200–3000 Gy. The full width at half maximum of each pulse is 20–30 ns, and the average energy of X-ray is approximately 1 MeV. Two detectors are placed in different intensities, and their responding curves are used to draw the Lissajous figure, analyzing the maximum energy dose rate of the CZT detector. The total dose of the pulsed X-ray into the experimental detectors is simultaneously measured by thermoluminescent dosimeter (TLD) chips. The result shows that the output of CZT detectors remains linear when the energy fluence rate is lower than 1017 MeV/(cm2·s).

Application of suppression of the borrmann effect in vibrating crystals for spatial separation of pulsed X-ray beams

The effect of suppression of the anomalous transmission of X rays due to the destruction of the system of weakly and strongly absorbing Bloch waves under ultrasound has been proposed to separate the radiation of high-intensity pulsed X-ray sources. The switching speed from the anomalous transmission mode to the zero transmission state is actually determined by only the X-ray frequency, which suggests that the switching time is several tens of nanoseconds.

On the scaling of multicrystal data sets collected at high-intensity X-ray and electron sources.

The need for data-scaling has become increasingly evident as time-resolved pump-probe photocrystallography is rapidly developing at high intensity X-ray sources. Several aspects of the scaling of data sets collected at synchrotrons, XFELs (X-ray Free Electron Lasers) and high-intensity pulsed electron sources are discussed. They include laser-ON/laser-OFF data scaling, inter- and intra-data set scaling.

Stable and high current density electron emission using coniferous carbon nano-structured emitter

The electron emission properties of a coniferous carbon nano-structure (CCNS) based field emission electron gun have been measured. The CCNS was grown on a stainless steel substrate using chemical vapor deposition (CVD) and biased to about 50kV. Stable, high-current-density electron emission (102mA/cm2) was measured continuously for more than 1300h. This result compares favorably to printed and directly grown carbon nanotube (CNT) based emitters. A wide range of potential applications are foreseen for CCNS based electron emitters, such as high intensity X-ray sources.

First steps towards time-resolved 'in-house' X-ray diffraction experiments

High-intensity X-ray sources, such as synchrotrons or X-ray free electron lasers, providing up to 100 ps time-resolution allow for studying very short-lived excited electronic states in molecular crystals. Some recent examples constitute investigations of Rh...Rh bond shortening,[1] or metal-to-ligand charge transfer processes in CuI complexes.[2] Nevertheless, in cases in which the lifetime of excited state species exceeds 10 μs it is now possible, due to the dramatic increase in the brightness of X-ray sources and the sensitivity of detectors, to use laboratory equipment to explore structural changes upon excitation. Consequently, in this contribution we present detailed technical description of the 'in-house' X-ray diffraction setup allowing for the laser-pump X-ray-probe experiments within the time-resolution at the order of 10 μs or larger. The experimental setup consists of a modified Bruker Mo-rotating-anode diffractometer, coupled with the high-frequency Nd:YAG laser (λ = 355 nm). The required synchronization of the laser pulses and the X-ray beam is realized via the optical chopper mounted across the beam-path. Chopper and laser capabilities enable high-repetition-rate experiments reaching up to 100 kHz. In addition, the laser shutter is being directly controlled though the original diffractometer software, allowing for collection of the data in a similar manner as done at the synchrotron (alternating light-ON & light-OFF frames). The laser beam itself is split into two allowing for improved uniform light delivery onto the crystal specimen. The designed setup was tested on the chosen set of crystals exhibiting rather long-lived excited state, such as, the Cu2Br2L2 (L = C5H4N-NMe2) complex, for which the determined lifetime is about 100 μs at 90 K. The results shall be presented. Research is funded by the National Science Foundation (CHE1213223). KNJ is supported by the Polish Ministry of Science and Higher Education through the "Mobility Plus" program.

Prospects of biomolecule sequencing with the techniques of translocation through nanopores: A review

The interest in the functional properties of biomolecules in native solutions (in particular, their interaction with membranes) constantly increases with accumulation of data on the macromolecular structure, obtained by X-ray diffraction (with synchrotron radiation sources), nuclear magnetic resonance, and mass spectrometry; this interest is closely related to the development of new technologies of sequencing (i.e., determining the sequence of nucleotides in DNA biomolecule). One of the most promising “physical” approaches to sequencing is the application of methods based on the use of nanochannels or nanopores, through which biomolecules pass in ionic solutions under an electric field applied. A nanopore provides spatial localization of molecules and makes it possible to detect a signal (electric, fluorescent, etc.) from an individual nucleotide. In view of the development of new high-intensity pulsed X-ray sources, the popularity of fluorescence analysis constantly increases. The existing methods for simulating the motion of biomolecules and interpreting their structure, sequencing techniques, and the prospects of further development of investigations in this field are discussed.

High-Gain Thompson-Scattering X-Ray Free-Electron Laser by Time-Synchronic Laterally Tilted Optical Wave

A novel approach to generating coherent x rays with 10(9)-10(10) photons and femtoseconds duration per laser pulse is proposed. This high intensity x-ray source is realized first by the pulse front tilt of a lateral fed laser to extend the electron-laser synchronic interaction time by several orders, which accomplishes the high-gain free-electron-laser-type exponential growth process and coherent emission with highly microbunched electron beam. Second, two methods are presented to enhance the effective optical undulator strength parameter. One is to invoke lenses to focus two counterpropagating lasers that are at normal incidence to the electron beam as a transverse standing wave; the other is to invent a periodic microstructure that can significantly enhance the center electromagnetic field realized by a resonant standing wave and the quadrupole waveguides. The energy coupling efficiency between the electron beam and laser is therefore greatly improved to generate the high brightness x rays, which is demonstrated by analytical and simulation results.

In situ X-ray diffraction of surface oxide on type 430 stainless steel in breakaway condition using synchrotron radiation

Changes in the crystal structure of type 430 stainless steel and the oxides on its surface were studied in situ at 1373K using a high-intensity synchrotron X-ray source provided by SPring-8 in Japan. The surface of the steel was initially covered with Cr2O3, which was then converted to FeCr2O4, and finally Fe3O4 and Fe2O3 formed on it. These results indicated that the reason for the breakaway oxidation in type 430 stainless steel is Cr depletion beneath Cr2O3 layer and the subsequent ionisation of Fe, not the simple mechanical failure of Cr2O3.