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International audience; The range of photon energies used for type testing of radiation protection dosimeter extends from a few keV to 10 MeV. Most National Metrological Institutes have X-ray generators for energies up to about 300 keV and then rely on isotopic sources of 137Cs and 60Co to reach 1.33 MeV. The high energy range up to 10 MeV requires dedicated facilities such as particle accelerators or nuclear reactors. The CEA LIST LNE LNHB, has proposed to mutualize the use of a medical LINAC dedicated to national references for radiotherapy by adding a target/filter/attenuator system on the radiotherapy electron beam to obtain a radiation protection beam of photons of average energy between 6 and 7 MeV. The proposed poster describes the design of the target/filter/attenuator assembly and the steps to achieve a primary reference in terms of air kerma by means of ionization chambers specially adapted to these energies and then the conversion of this reference in terms of ambient dose equivalent H*(10).

We propose a new design for the master oscillator of a medical Thomson laser-electron generator. By means of numerical simulations, we show that negative optoelectronic feedback together with highfrequency modulation (5 GHz used in accelerators) allows one to single out one pulse not longer than 15 ps in the axial interval, as well as to synchronize the pulse with the accelerator system.

Background: In the calibration and testing laboratory of Korea Atomic Energy Research Institute, the old X-ray generator used for the production of reference X-ray fields was replaced with a new one. For this newly installed X-ray irradiation system, beam alignment as well as the verification of beam qualities was conducted. Materials and Methods: The existing X-ray generator, Phillips MG325, was replaced with YXLON Y.TU 320-D03 in order to generate reference X-ray fields. Theoretical calculations and Monte Carlo simulations were used to determine initial filter thickness. Beam alignment was performed in three steps to deliver a homogeneous radiation dosage to the target at different distances. Finally, the half-value layers were measured for different X-ray fields to verify beam qualities by using an ion chamber. Results and Discussion: Beam alignment was performed in three steps, and collimators and other components were arranged to maintain the uniformity of the mean air kerma rate within ±2.5% at the effective beam diameter of 28 cm. The beam quality was verified by using halfvalue layer measurement methods specified by American National Standard Institute (ANSI) N13.11-2009 and International Organization for Standardization (ISO)-4037. For each of the nine beams than can be generated by the new X-ray irradiation system, air kerma rates for Xray fields of different beam qualifies were measured. The results showed that each air kerma rate and homogeneity coefficient of the first and second half-value layers were within ±5% of the recommended values in the standard documents. Conclusion: The results showed that the new X-ray irradiation system provides beam qualities that are as high as moderate beam qualities offered by National Institute of Standards and Technology in ANSI N13.11-2009 and those for narrow-spectrum series of ISO-4037.

We present the measurements of the spot size of a powerful X-ray generator at an ISAS 30m X-ray beamline facility. The generator was manufactured by Rigaku corporation. A parallel light is ideal to measure the point spread function of an X-ray telescope. However, we cannot make purely parallel light because we have to use an X-ray source with a finite size at a finite distance in a ground facility. When we evaluate a performance of X-ray telescope on the ground, an apparent size of an X-ray source often limits measurements of its point-spread function (PSF). The smaller X-ray source at the larger distance is needed to measure the PSF core of X-ray telescope. A high power X-ray source is also need to illuminate a telescope with a raster scan method that allows us precise measurements of a PSF tail. Therefore a powerful X-ray generator with a small spot size is strongly favoured in terms of the measurements of X-ray telescopes. We then introduced a powerful 18 kW rotating anode generator with a fine point focus at ISAS in 2016. The minimum and maximum voltage is 5 and 60 keV, respectively. A small spot size is technically more difficult on a lower voltage. In order to measure the spot size of the generator, we place a pinhole with a 0.1 mm diameter at 12.7 m away from the generator. The flipped image was taken at a CCD imager place at 33.5 m away from the generator. We made measurements of the Cu-K line at 8 keV with two options. One is a high-power mode (normal filament option) with a wider spot size whereas the other is a low-power mode with a finer size (fine filament option). As a result, we found that a spot size of the normal and fine filament options are 2.8 mm and 0.80 mm (FWZI), respectively. We supplied a bias voltage of 800 V for the fine filament option. The spot size of 0.8 mm is equivalent to the angular extent of as good as 6 arcsecs in the ISAS X-ray beamline facility.

The performance of a field-enhanced emitter (FEE) array in an enclosed and ex-situ operated device has long been known to deviate from the ideal characteristics observed in laboratory settings. Here we report on the performance and failure mechanisms measured in FEE arrays operating in high-voltage sealed x-ray generators. The emitters are fabricated from etched silicon forming pyramids which are coated with metal. Unlike many previously reported arrays, here the pitch is large (1cm) and affords easy measurement and diagnosis of individual emitters. We report on emitter performance and likely causes of deviations from ideal, including the impact of anode treatment, emitter geometry and catastrophic failure mechanisms.

A novel type of pulsed X-ray generator especially suitable for rare event searches, as dark matter and neutrino experiments, has been developed. Being compact and built with selected radio-pure materials, it is appropriate for low-background experiments. UV light generated by a pulsed lamp produces photoelectrons on a metallic cathode, which are subsequently accelerated to produce X-rays. The X-rays are emitted in bunches with a time resolution better than 1 ns and the system provides a fast trigger for event tagging. We present the idea of the new X-ray generator as well as experimental results showing the proof of concept of the device. Data are in good agreement with simulation results and future optimisations of the system are also discussed., Comment: 16 pages. Preprint to be soon submitted to a Journal

Purpose To investigate the feasibility of using kV flat panel detector on linac for consistency evaluations of kV x-ray generator performance. Methods An in-house designed aluminum (Al) array phantom with six 9 × 9 cm2 square regions having various thickness was proposed and used in this study. Through XML script-driven image acquisition, kV images with various acquisition settings were obtained using the kV flat panel detector. Utilizing pre-established baseline curves, the consistency of x-ray tube output characteristics, including tube voltage accuracy, exposure accuracy and exposure linearity was assessed through image quality assessment metrics including ROI mean intensity, ROI standard deviation (SD), and noise power spectrums (NPS). The robustness of this method was tested on two linacs for a 3-month period. Results With the proposed method, tube voltage accuracy can be verified through conscience check with a 2% tolerance and 2 kVp intervals for forty different kVp settings. The exposure accuracy can be tested with a 4% consistency tolerance for three mAs settings over forty kVp settings. The exposure linearity tested with 3 mAs settings achieved a coefficient of variation (CV) of 0.1. Conclusion We proposed a novel approach that uses the kV flat panel detector available on linac for x-ray generator test. This approach eliminates the inefficiencies and variability associated with using third-party QA detectors while enabling an automated process.

The properties of X-ray emission from a pyroelectric accelerator based on ferroelectric ceramics have been experimentally studied, including the maximum energy of X-ray photons and their maximum yield generated by accelerated electrons at various pressures of residual gas in the generator chamber. The maximum X-ray yield and maximum energy of X-ray photons and accelerated electrons have been observed at a residual-gas pressure of around several millitorr.

In regenerative medicine, evaluation of bone mineral density using a microfocus X-ray generator could eventually be used to determine the degree of bone tissue regeneration. To evaluate bone mineral density against regenerated bone material, two low-energy X-rays are necessary. Herein, the acquisition of quasi-monochromatic, dual-energy soft X-ray and the subsequent medical application were examined using the K-absorption edges of two types of metal filters (i.e., zirconium and tin) in a microfocus X-ray generator. Investigation of the optimal tube voltage and filter thickness to form a quasi-monochromatic energy spectrum with a single filter revealed that a filter thickness of 0.3 mm results in an optimal monochromatization state. When a dual filter was used, the required filter thickness was 0.3 mm for tin and 0.2 mm for zirconium at a tube voltage of 35 kV. For the medical application, we measured quasi-monochromatic, dual-energy X-rays to evaluate the measurement accuracy of bone mineral density. Using aluminum as a simulated bone sample, a relative error of &le, 5% was consistent within the aluminum thickness range of 1&ndash, 3 mm. These data suggest that a bone mineral density indicator of recycled bone material can be easily obtained with the quasi-monochromatic X-ray technique using a microfocus X-ray generator.

Over the 100 years of their use, X-ray generators have proven to be indispensable in a wide array of applications. However, the methods for generating X-rays have not developed significantly, and the inherent size and power draw of existing X-ray generators limit the manufacture of more portable X-ray systems. The first demonstration of applying the pyroelectric effect for X-ray generation in 1992 made it a promising candidate for in-field and on-line analyses. This method of thermally cycling a pyroelectric material in a high vacuum exhibits advantages of being lightweight, compact and battery operated. In this thesis, an X-ray generator that utilises the pyroelectric effect was developed and optimised to maximise its performance, in terms of X-ray flux and end-point energy. The generation of X-rays relied on the emission of electrons which was dependent on the electric field created between the pyroelectric crystal and the target placed at a gap distance. Evaluation of the material figures-of-merit and utilisation of electrostatics simulations to estimate the electric field in the gap determined a theoretical optimal combination of material properties, crystal thickness and gap distance. An experimental system was built to simultaneously control the temperature of the pyroelectric crystal in a high vacuum chamber and collect time and energy-resolved X-ray emissions. The effects of various parametric combinations were then investigated and found to deviate from the theoretical findings. Thus, the most optimal combination of parameters was using the pyroelectric crystal, lithium tantalate, at a gap distance of 5 mm and pressure of 0.33 Pa. This produced an X-ray flux of 1.22e5 cm2/s and end-point energy of 40 keV. The enhancement of the electric field at the crystal edges was exploited in an attempt to improve the X-ray generator’s performance by dicing the crystal to introduce more edges per unit area. Using lithium tantalate, a range of dicing combinations were assessed and found to underperform compared to its uniform counterpart. Finally, the X-ray generator was operated over 200 cumulative hours and its output monitored. The X-ray flux and end-point energy fluctuated over this time and was found to correlate with the gradual surface degradation observed on the pyroelectric crystal.

The paper presents a general theoretical framework and related Monte Carlo simulation of novel type of the X-ray sources based on relativistic Thomson scattering of powerful laser radiation. Special attention is paid to the linac X-ray generators by way of two examples: conceptual design for production of 12.4 keV photons and presently operating X-ray source of 29.4 keV photons. Our analysis shows that state-of-the-art laser and accelerator technologies enable to build up a compact linac-based Thomson source for the same X-ray imaging and diffraction experiments as in using of a large-scale X-ray radiation facility like a synchrotron or Thomson generator based on electron storage ring.

The development of microcollimators for photon energy in the range of 30-200 keV was carried out. A quasi-spherical or quasi-plane X-ray wave can be formed when the propagation vector of the collimator is locally parallel to the wave front, either near the X-ray focus or away from it. The method was tested to collimate the widespread beam from an X-ray generator. In the experiment, a flat nickel raster 1200 μm thick with tubes of 80 μm in diameter manufactured using LIGA technique, was used. For a flash X-ray device with an explosive electron emission and an anode voltage of 150 kV, a quasi-collimated X-ray beam with an angular divergence of up to 2.8 degrees (FWHM) was formed.

X-ray fluorescence spectroscopy (XRF) is a method for elemental analyses of materials. In comparison to other analysing methods such as energy dispersive X-Ray spectroscopy (EDS) within a scanning electron microscope (SEM) or optical emission spectroscopy (OES) there are several advantages. This paper contains experimental investigations to improve the emission behaviour of a pyroelectric X-ray source regarding X-ray energy and output intensity. Pyroelectric lithiumtantalate (LiTaO3) was used to emit and accelerate electrons and to generate primary X-rays subsequently. Geometrical conditions were altered and the design of the X-ray source was optimized. All steps of optimization have been performed with respect to an application in a spectroscopic device in combination with an optical microscope (OM). Based on this purpose, the miniaturization of all applied components is of major importance. Different pure metals, alloys, and a coated specimen were analysed to demonstrate potential applications and current limitations of the designed system. Materials with a wide range of necessary excitation energy for chemical analyses of 1.5 to 10 keV for the Kα and Lα X-ray fluorescent lines were used to demonstrate the technical relevance of this type of application. As a result, a prototype of a spectrometer that combines XRF and OM was designed and tested.

The approach of the scheme is to pile-up X-ray photons on the scintillator to generate a high energy peak in the spectrum. The system includes a miniature X-ray generator, a brass disk with a thin slit rotated by a motor and placed in front of the X-ray window, and a collimator placed in front of the scintillation detector to reduce the time of alignment between the scintillation detector and the X-ray generator. The rotating brass disk placed between the X-ray source and the collimator is deployed as a high-frequency obturator. If, during a time duration lower than the integration time of the scintillation detector, a large number of photons interact with the scintillator, the energy is added and the spectrometer records this energy as the contribution of a high energy single photon. Experimental results underlines a tangible proof of concept for a selfcalibration device, which will be valuable for the correction of the temperature drift in the scintillator-photomultiplier pair.

The possibility of using PZT-19 ceramic in a pyroelectric x-ray generator is investigated experimentally. Measurements of the x-ray spectra showed the possibility of obtaining on a ceramic surface in vacuum potentials up to 7 kV, which is very low compared with typical similar values for pyroelectric crystals of lithium niobate and tantalate. This feature is due to the significant permittivity of the ceramic. It is shown that the main criterion for picking a ceramic for a pyroelectric x-ray generation could be the maximum value of the ratio of the pyroelectric constant to the permittivity.

A diagnostic fluoroscopy X-ray system uses a 32kW or greater X-ray generator for obtaining real-time moving images and high-resolution images. Fluoroscopy X-ray systems have to use a high-capacity AC power source to perform long-time low-power fluoroscopy and short-time high-power spot exposure. In this paper, we propose a hybrid type X-ray generator for fluoroscopy X-ray system which can perform fluoroscopy and spot exposure with a low-capacity AC power source and an energy storage device. The characteristics of energy storage devices are compared and each energy storage device is modelled to equivalent circuit. And the characteristics of available energy are analyzed as a function of output voltage and power. A 32kW class hybrid X-ray generator with EDLC as an energy storage device for fluoroscopy X-ray system was constructed, and its validity was verified by means of simulations and experiments.

The work is dedicated to one of the systems of the NESTOR X-ray generator. The injection system is at the highest stage of readiness after the magnetic system. Structurally, the injection system can be represented as an injector (linear accelerator), channel of parallel transportation (transport channel), channel of the beam entry into the vacuum chamber, and pulsed inflector. All equipment has been tested, and the beam passed through all the components in the volume of the storage ring.

The work considers the control system of magnetic components of the NESTOR Compton back-scattering X-ray generator. The control system allows integration of the control and visualization modules of other subsystems of the generator. The described system was experimentally tested, and during the test a beam was inputted into the physical volume of the NESTOR storage element.

Micro x-ray fluorescence spectroscopy (μXRF) is a technique for local chemical analyses of materials. There are several advantages in comparison to other similar methods like energy dispersive x-ray spectroscopy in a scanning electron microscope (SEM). The main advantage is the possible abdication of an evacuated sample chamber, which offers the possibility to analyze wet and oil contaminated specimens as well as specimens with intrinsic pores in addition to conventional samples used in SEM analyses. The subject of this report is the investigation of the pyroelectric effect with regard to its application for the generation of focused x-rays and first steps to a successive usage of the generated radiation for μXRF applications. In order to answer questions concerning the energy and intensity of primary radiation and geometric parameters for a successful focusing, this paper describes several experiments and results against the background of the described aims. Different setups and measurements have been used, optimizing the experimental setups to find the basic parameters to potentially generate focal spots of the primary x-rays. Emission behavior of electrons has been visualized and characterized by using a phosphor screen positioned in front of a pyroelectric crystal. Radiation has been measured and characterized by using an energy dispersive silicon drift x-ray detector. All x-ray experiments were executed in a vacuum test rig. This allowed the optimization of the working pressure of the residual gas surrounding the crystal in an evacuated atmosphere (rarefied air). It has been shown that emitted x-ray energies are strongly influenced by the vacuum pressure. Lithiumniobate and lithiumtantalate of different geometries were used as the pyroelectric material. Different target materials and target angles have been compared to optimize the combination of the constructed x-rays source with an aperture as well as with an x-ray optic to focus the primary x-rays. A glass fiber capillary lens was used as the focusing optic. A first step to a μXRF application is shown.Micro x-ray fluorescence spectroscopy (μXRF) is a technique for local chemical analyses of materials. There are several advantages in comparison to other similar methods like energy dispersive x-ray spectroscopy in a scanning electron microscope (SEM). The main advantage is the possible abdication of an evacuated sample chamber, which offers the possibility to analyze wet and oil contaminated specimens as well as specimens with intrinsic pores in addition to conventional samples used in SEM analyses. The subject of this report is the investigation of the pyroelectric effect with regard to its application for the generation of focused x-rays and first steps to a successive usage of the generated radiation for μXRF applications. In order to answer questions concerning the energy and intensity of primary radiation and geometric parameters for a successful focusing, this paper describes several experiments and results against the background of the described aims. Different setups and measurements have been us...

The production of pyroelectric type X-ray generators has a long term background. In case of using X-ray generators containing two pyroelectric crystals, some parameters have not been practically measured yet. This article aims to calculate such parameters by means of Geant4 Mont Carlo codes. The obtained edge energy of initial electrons was 3 keV at a constant pressure of 1mTorr and electric field of 250 kV/cm. The amplification coefficient production of electrons was increased reaching to a constant value of 2.7. The observed mean energy of produced gas ions was approximately 39 eV, equivalent to 5.7% of the emitted electrons. The efficiency of the generated X-ray was about 63% and did not show a considerable change as the energy of initial electrons increased.