Beam characteristics of a terahertz/subterahertz radiation obtained by collimation of coherent diffraction radiation (DR) emitted by ultrarelativistic electrons are considered. To achieve the maximum intensity on the beam axis of such radiation, it is proposed to use a semi-parabolic target with a focal length equal to the distance between the target and the collimator aperture. It is shown that for the proposed geometry, the DR distribution on the aperture plane has a maximum along the beam axis, in contrast to the previously used coherent transition radiation mechanism, which is characterized by a “funnel-shaped” structure with a minimum along the beam axis.

The results of experimental observation of coherent Cherenkov radiation from picosecond electron bunches traveling along the axis of a dielectric loaded cylindrical waveguide are presented. Experiments have been performed at the AREAL linear accelerator at the CANDLE Synchrotron Research Institute. The angular distribution of radiation from 3.7 MeV electron bunches passing through cylindrical quartz sample is investigated. In the second part of the paper we argue that, by tuning the ratio of the distance between the bunches crossing the plate inside the waveguide and the radius of the waveguide, one can further increase the intensity of quasi-coherent Cherenkov radiation on several neighboring modes.

The generation of electrons and X-rays using a pyroelectric accelerator is highly appealing from a practical point of view due to the potential for compact and energy-efficient devices. This study focuses on investigating the influence of accelerator geometry, particularly the position and area of the target. We have determined that a smaller target area enhances X-ray intensity and monoenergetic electron flux, while the balance between positive and negative polarity exhibits weak dependence on geometry. Altering the position of the target-collimator enables regulation of the energy of the collimated electron flow. The focal spot of the electron flow in a pyroelectric accelerator exhibits a complex longitudinal structure, as demonstrated by both experimentation and computer modelling. Furthermore, increasing the distance between the crystal and the target enhances the stability of the pyroelectric accelerator. Consequently, the combined effect of target area and its position relative to the crystal significantly influences the observed particle flux, and we propose approaches for their regulation in practical devices.

In this paper, we focus on simulating a pyroelectric accelerator using COMSOL Multiphysics. We utilize the static surface charge distribution obtained from an experiment conducted on a LiTaO3 3 single crystal surface. We analyze the characteristics of the electron flow generated by the accelerator and determine the emittance and Twiss parameters. Our findings reveal that the normalized RMS emittance remains relatively constant in the space behind the target.

This article presents an investigation into the interaction between ultrashort electron beams and DNA molecules. With the advent of advanced electron beam technology, the potential applications in various fields, including medicine and genetic engineering, have garnered significant attention. However, the intricate mechanisms underlying the interaction between ultrashort electron beams and DNA molecules remain largely unexplored. This study aims to bridge this gap in knowledge by obtaining experimental data. We used Cu containing water-soluble cationic 4-N meso-tetra-oxyethyl-pyridyl porphyrin. The electron beam irradiated the samples with different relative concentrations of porphyrin per base pair. It was shown that the presence of porphyrin enhances DNA stability, making it more resistant to radiation-induced damage, with the effect varying based on porphyrin concentration and irradiation dose.

Results of experimental and theoretical investigation of coherent transition radiation from a finite-size target in the prewave zone are presented. The measurements were conducted in sub-terahertz frequency range on the 100-MeV electron beam extracted from LINAC-200 (JINR). A formula for the spectral-angular density of coherent transition radiation is obtained. Results of the simulation of experimental conditions and experimental data are jointly analyzed. Estimation of the bunch length based on experimental data and obtained theoretical model deviates from the expected value.

Conventional X-ray sources are far too bulky and require a high-power DC voltage. The pyroelectric X-ray generator technology has enabled us to develop portable, low-power X-ray sources for use in materials analysis, imaging, and other applications. Changing the temperature of single crystal lithium tantalate (LiTaO3) at moderate vacuum conditions gives an attractive possibility to generate and accelerate electron up to 100 keV. The electrons are ejected either from the crystal or from the target (depending on polarity). The electrons then generate X-rays via bremsstrahlung and characteristic X-ray emission processes. The aim of this experimental investigation is to explore the interesting feature of the pyroelectric accelerator that generates a monoenergetic electron flux with a stable value of peak energy for a long time. Here we present studies of features of electron flux in pyroelectric accelerator depending on the pressure of residual gas and the distance between the crystal and the target-collimator. We examine the correlation between monoenergetic electron production and avalanche discharge. We also studied outgassing from some accelerator components. The pyroelectric X-ray generator technology is currently being developed is a reliable, compact, stable, and reproducible X-ray source with controllable parameters, which does not require a high-power DC voltage or the use of hazardous (radioactive) materials.

We exploit the coherent emission of Cherenkov diffraction radiation (ChDR) by a relativistic electron beam to sense its position even in the presence of other particle beams. ChDR is produced in alumina inserts embedded in the vacuum chamber walls and recorded in a narrow band centered at 30 GHz. This nontrivial solution has been implemented for plasma wakefield accelerators, where the electron beam to be sensed can copropagate with another high-energy proton beam that generates the plasma wakefield. In addition, at variance with most existing position detectors, this method is insensitive to spurious electric charges due to the presence of plasma. We present the overall design of the detector as well as experimental results obtained in the AWAKE facility at CERN.

By changing the temperature of Lithium Tantalate (LiTaO3) single crystal at moderate vacuum conditions leads to generation of strong electric field. The uncompensated polarization during the heating or cooling of the crystal causes the ejection of electrons from either the dielectric layer on the surface of the crystal or from a metal target depending on the polarity. The electrons are accelerated and gain energy of up to 100 keV. The energy of these electrons can be determined by measuring the end-point energy of the X-ray spectrum that resulted from the electron interactions with the target. The conception of a pyroelectric accelerator enabled us to develop compact (portable) electron source, which does not require an external high-voltage and the use of hazardous materials. The compact and portable nature of pyroelectric-driven particle sources holds significant promise for applications in materials science, particularly for materials analysis methodologies. The research demonstrates the feasibility of utilizing the X-ray signal generated by irradiation with electrons to identify elements in each sample. It is revealed that employing only the electron beam enables the successful acquisition of quantitative information regarding the sample structure through pyroelectric driven PD-PIXE analysis. These findings set the stage for the development of a compact and versatile apparatus for elemental analysis of materials based on a pyroelectric source.

A comparison of the induction current and the emission current during the pyroelectric effect in vacuum conditions with periodic variation in the temperature of a single crystal of lithium tantalate is presented. An increase in the variation frequency leads to suppression of the emission current, which does not allow one to observe the effect of the optimal frequency with the maximum amplitude, as for the induction current. The conformity of both current forms is shown, except for the region of 2 mHz or less, where an additional current wave is observed. It is established that this additional wave is initiated above a certain threshold of potential difference and leads to its stabilization.

Realization of a pyroelectric effect in vacuum provides the possibility to develop a compact and relatively inexpensive electron source. In this paper we observe and analyze the I-V curve of electron flow generated during the pyroelectric effect in a lithium tantalate single crystal. The region of the monoenergetic electron flow with a slow change in the peak energy is determined. This phenomenon is accompanied by a current avalanche process. The analysis of the electron spectra and the I-V curve shows that the observed avalanche process and the stabilization of the peak energy occurs due to a sharp increase of secondary electrons in the total electron flow.

A comparison of the induction current and the emission current during the pyroelectric effect under vacuum conditions with periodic variation in the temperature of a single crystal of lithium tantalate is presented. An increase in the variation frequency leads to suppression of the emission current, which prevents observing the effect of the optimal frequency with the maximum amplitude as in the case of the induction current. The conformity of both current forms is shown, except for the region of 2 mHz and less where an additional current wave is observed. It is established that this additional wave is initiated above a certain threshold of potential difference and leads to its stabilization. Keywords: pyroelectric effect, ferroelectric electron emission, pyroelectric accelerator, lithium tantalate.

We report on development of an array of spectral sensitive detectors cooled down to 70 K by the compact cryocooler. The spectral sensitive operation of the detectors, explored between 0.16 THz and 0.22 THz, is due to the resonant excitation of the plasma waves in the two-dimensional electron gas of GaAs/AlGaAs heterostructure. A typical responsivity of the detectors is 0.01 A/W at 70 K while it increases by two orders of magnitude when the detector array is cooled down to 0.5 K. The photo-response has surprisingly a narrow peak of spectral sensitivity, $$\sim$$ 2–5%, which are highly likely due to the dimensional resonances of the plasma waves. As a demonstration of the spectral sensitive operation we detect a spectral feature of LiNbO $$_{3}$$ crystal at 0.174 THz.

The first observation and investigation of a new mechanism of resonant Cherenkov diffraction radiation appearing when relativistic 6 MeV electrons move alongside a periodically shaped Teflon target have been presented and analysed. Numerical simulations performed using computer code KARAT are in good agreement with the experimental results. This new mechanism is a promising technique for generation and monochromatisation of THz and sub-THz radiation beams that could be integrated into any short bunch linear accelerator facility including 4th generation light sources providing new opportunities for user community.

This paper describes indicators that can be used to monitor the operating mode of a pyroelectric accelerator. It is shown that the ratio of the characteristic X-ray emission lines from the target and the vacuum chamber walls is very sensitive to the state of the accelerator. Also, the peak to total count rate ratio in the electron spectrum exhibits similar properties. These parameters change sharply ahead of the electric breakdown and are very sensitive to the residual gas pressure level. Monitoring these indicators during the accelerator operation provides a fine tool aiding the implementation of pyroelectric technology for stable and reliable charged particle generation and acceleration.

Lithium niobate (LiNbO3) single crystal is one of the pyroelectric materials, which can be applicable in energy storage and conversion devices. A theoretical and experimental study of the sinusoidal temperature variation of a single crystal of LiNbO3 with ultra-low frequency of 1–80 mHz is presented here. The previously unreported phenomenon of the optimal frequency range with the maximum amplitude of pyroelectric current oscillations is shown. It is noted that the observed effect is very sensitive to the thermal properties of the material. The impact of thermal properties of the crystal on the optimal frequency range is discussed. The accurate calculations of the pyroelectric coefficient using sinusoidal temperature variation are introduced. The observed phenomenon can be applied in pyroelectric energy converters and storage devices having a cycle time of 10–1000 s.

Optical Cherenkov radiation of moderately relativistic ions in a CVD-diamond plate with frequency dispersion is considered. It has been shown that Cherenkov radiation extracted from the inclined diamond plate to vacuum at a fixed observation angle becomes monochromatic. The wavelength of the spectral line depends on the energy of an ion and on the geometry of an experiment (observation angle and plate inclination angle). An experiment has been proposed to study the monochromatization of Cherenkov radiation on the beam of the JINR Nuclotron for the purpose of its subsequent use in the diagnostics of ion beams. The method can be applied to monitor the NICA ion beams energy.

We report on the study of shadowing of electromagnetic fields radiated in the Terahertz (THz) region from two consecutive sources of coherent diffraction and transition radiation. In these conditions, the formation length is predicted to be less than or similar to 100 m, and shadowing effects should result in an almost complete suppression of radiated fields within distances of the order of tens of centimeters. We experimentally measured that shadowing effects disappear for distances significantly shorter than those predicted. We propose a new model that explains our experimental observations by taking into account 3D diffraction effects. These findings will have a positive impact on the beneficial use of consecutive radiators both for the generation of intense electromagnetic radiation and for beam diagnostics using coherent polarization radiation from ultra-relativistic charged particles. (C) 2021 Elsevier B.V. All rights reserved.

In this paper, CST simulations of the coherent Cherenkov Diffraction Radiation with a range of parameters for different dielectric target materials and geometries are discussed and compared with the theoretical investigation of the Polarization Current Approach to design a prototype of a radiator for the bunch length/profile monitor for AWAKE Run 2. It was found that the result of PCA theory and CST simulation are consistent with each other regarding the shape of the emitted ChDR cone.

In recent years Cherenkov Diffraction Radiation (ChDR) has been reported as a phenomenon suitable for various types of particle accelerator diagnostics. As it would typically work best for highly relativistic beams, past studies and experiments have been mostly focusing on lepton machines. This contribution investigates the prospects on the utilization of ChDR as a diagnostic tool for the Large Hadron Collider (LHC). Based on theoretical considerations and simulation results we estimate the properties of the expected radiation, both in the incoherent and coherent domain, and we compare them with the requirements of the existing diagnostic systems. We also address the potential problem of the use of dielectric radiators in circular machines, where secondary electrons could potentially lead to the creation of electron clouds inside the beam pipe that may affect the radiator.