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.

Recently, it was established that the X-ray generation intensity increases in a certain range of temperature variation rates (6–8°C/min) of lithium tantalate single crystal (LiTaO3). In this work, the pyroelectric current generation is studied as a function of the temperature variation rate. Four stages of the pyroelectric current generation dynamics are determined. In the same rate range (6–8°C/min), an anomalously long stage of current saturation is observed, which is most likely the cause of the observed effect of an increase in the X-ray intensity. The observed anomaly is described, as well as systematic features in the pyroelectric current dynamics with varying the pyroelectric material temperature with a constant rate.

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.

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.

This paper presents the results of the study of the dependence of the endpoint energy of X-ray radiation on the preliminary change in the temperature of the lithium tantalate (LiTaO3) single crystal, which is a source of a strong electric field of the pyroelectric effect under vacuum conditions. Measurements were performed in a pulsed mode of X-ray generation, consisting in a preliminary change in the pyroelectric sample temperature in high vacuum and the use of an additional electron source for complete pyroelectric discharge. The obtained dependence suggests that the maximum capacity of X-ray generation by a pyroelectric source manifests itself when using the pulsed mode.

The results of experimental studies on the generation of x-rays when operating a piezoelectric kitchen lighter in a vacuum are presented. For the first time, a new method for increasing the intensity of x-ray radiation in the piezoelectric effect in a high vacuum through the use of an additional electron emitter is proposed and demonstrated. The maximum energy of x-ray bremsstrahlung reaches 14 keV. This means that electrons are accelerated in vacuum in the field of a piezoelectric ceramic to energy of at least 14 keV.

The possibility of neutron generation by irradiating deuterated crystalline structures with an electron beam with an energy of 20–40 keV was studied. As targets, the deuterated crystalline structures of palladium and textured CVD diamond were used. Measurements of neutron emission are presented, which were carried out by three independent methods—scintillation detectors, counters based on He-3, and track detectors CR-39.The average neutron flux during irradiation was estimated as 1–10 s $${}^{-1}$$ in 4 $$\pi$$ sr.

The paper focuses on the surfaces electrization of Z-cut single-crystal lithium niobate during the pyroelectric effect. It is shown that the properties of the electric current passing through the surfaces of single-crystal lithium niobate depend on the ground circuit, the rate of temperature change, and orientation of polar axes. Experiments show that grounding of lithium niobate surfaces has an effect on the X-ray radiation during the pyroelectric effect.

In the coming years, the compact monoenergetic neutron generators (CNG) producing up to 104 n/s may become an alternative to the standard neutron sources based on radioactive isotopes for the calibrations of neutrino and dark matter detectors. Such neutron generators have a typical size of about several centimetres, they may be manufactured using low-background materials and may require only low voltage power supply for operation. We discuss the advantages and disadvantages of two main types of the compact neutron generators, namely a pyroelectric neutron source and a high voltage neutron generator. Also the results of the technical analysis of the possibilities to apply such sources for the calibration of low-background experiments are given, the variant of the internal device design is shown and the full-size compact neutron generator prototype are presented.

The pyroelectric neutron generator is a compact source of fast neutrons with an energy of 2.45 MeV and a yield up to ∼104 neutrons/s. The device is designed for calibration of low-background neutrino and dark matter detectors and may also serve as an alternative to traditional radioactive sources of fast neutrons in physical research and practical work. Numerical simulation of the angular distribution of neutrons emitted by the pyroelectric generator with the D(d, n)3He reaction proceeding within it was performed in order to calculate the neutron yield in the full solid angle and in a given direction correctly. The angular distribution was found to be anisotropic: the neutron yield increased in the direction of motion of incident deuterium ions. This anisotropy was as large as ∼25% at a maximum energy of 28 keV of incident particles. The anisotropy increased nonlinearly with the ion energy: it reached ∼70% at 50 keV and a monoenergetic flux, but was virtually zero below 10 keV. The obtained angular distribution is similar to that of neutrons in the case of a 15-keV monoenergetic flux of deuterium ions.

1 Belgorod National Research University, 85, Pobedy Str., 308015 Belgorod, Russia 2 V.N. Karazin Kharkiv National University, 4, Svobody Sq., 61000 Kharkiv, Ukraine 3 Institute of Solid State Physics Russian Academy of Sciences Moscow District, 2, Academician Ossipyan Str., 142432 Chernogolovka, Russia 4 Belgorod State Technological University named after V.G. Shoukhov, 46, Kostyukov Str., 308012 Belgorod, Russia

In this work we present the results of the experimental studies of the dependence of the X-ray radiation on the temperature change speed of the lithium tantalate monocrystal in the pyroelectric source of the X-ray radiation. We have found an optimized linear temperature speed change pattern for the pyroelectric crystal designed for generation of the X-ray radiation with enhanced capabilities. The studies that were made open an opportunity to determine the most convenient conditions for generation of X-ray radiation with pyroelectric effect and for development of high-capacity pyroelectric X-ray radiation sources.

In this letter, we report the observation of fast neutrons generated when a positive acceleration potential is applied to an array of orientated carbon nanotubes, which are used as an ion source. The neutrons with energy of 2.45 MeV are generated as a result of D-D fusion reaction. The dependencies of the neutron yield on the value of the applied potential and residual pressure of deuterium are measured. The proposed approach is planned to be used for the development of compact neutron generators.

In the presented work, we investigated several digital methods of a discrimination signals from fast neutrons and gamma quanta The experimental setup consists of a Pu-Be neutron source, a scintillation detector with an organic para-terphenyl monocrystal, and a digitizer (CAEN DT5730, 500 MS/s). Mixed waveform sequences were stored and then separated by pulse shape. Four methods were used for signals separation. Comparison of the traditional and the new methods of Figure of Merit (FOM) calculation is given. FOM = 1.5 was obtained in our setup for the minimum threshold value. A scintillation detector with a para-terphenyl crystal was used to measure neutron yield in the neutron generator with carbon nanotubes.

The compact 2.45 MeV fast neutron generator with a reduced supply voltage for calibration of low-background neutrino and dark matter detectors was tested. The generator is based on an array of carbon nanotubes. Neutron generation is carried out by applying a high voltage in the range of +10 to +25 kV to a nanotube array, which cause an ionization of deuterium molecules with the following acceleration of ions in the direction of the grounded target covered by a deuterated polyethylene film. The d(d,n)He-3 nuclear reaction happens as the result of ions collisions with the target. The dependences of the neutron yield as functions of the applied voltage were obtained for two different types of carbon nanotubes array. It is shown that the type of nanotubes array does not influence significantly on the neutron yield.

Results of experimental investigation for application carbon nanotubes (CNT) array in a pyroelectric X-ray source are presented. It is shown that CNT allows increasing X-ray yield and energy, but the orientation of CNT array should be taken into account since the accidentally oriented CNT array is more efficient. Also, an optimal residual gas pressure condition for the pyroelectric X-ray source with CNT arrays has been found. It has been determined that the maximum of X-ray yield observed at 0.1 mTorr. Effects that lead to an increasing of the X-ray yield and perspectives of the pyroelectric source with CNT arrays are discussed.