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Synchronous spatiotemporal measurements of hard X rays emitted during the development of a high-voltage discharge at voltages of ~1 MV in half-meter open air gaps have been carried out for the first time. Using an array of scintillation detectors with lead diaphragms and the nanosecond photography of the discharge in the intrinsic luminescence, it has been shown that X rays are emitted in the discharge development stage when numerous brightly luminescent plasma channels are formed in the entire discharge gap and the discharge current with an amplitude of hundreds of amperes flows. It has been found that the emission of X rays (photons with energies above 5 keV) can start almost synchronously in the entire discharge gap, including the cathode and anode regions, near-cathode and near-anode regions, and the middle of the discharge gap. The statistical distributions of the total power and the number of the observed X-ray flashes along the discharge gap have been obtained. [ABSTRACT FROM AUTHOR]

We consider the formation of an electric spark from a point anode in atmospheric air when the primary spark channel from a very early stage of its evolution immediately begins to develop in the form of a cluster of highly ionized plasma microchannels. Using laser probing at a wavelength of 1064 nm, spark microchannels are resolved in the near-anode region of the discharge, and the data on the magnitude and distribution of the plasma electron density of single microchannels are obtained. It is shown that during the first nanoseconds after the discharge gap breakdown, the electron density in individual microchannels is distributed nonuniformly and ranges from 1018 to 5 × 1019 cm–3, with characteristic microchannel diameters being of 20–50 μm. [ABSTRACT FROM AUTHOR]

Spectral characteristics of ultrahigh-frequency radiation generated by a pulsed electric spark in a millimeter air gap are studied, together with its temporal correlation with the behavior of the discharge current and voltage in a nanosecond time scale. Systematic features of the UHF emission and general picture of possible phenomena in the spark gap are discussed. [ABSTRACT FROM AUTHOR]

Spectroscopy methods were used for studying the dynamics of neutral plasma component in current sheets formed in two-dimensional (2D) and three-dimensional (3D) magnetic configurations during discharge in helium. It has been ascertained that when the current sheet is formed in the 2D magnetic field, flows of fast suprathermal helium atoms appear in it, which are directed along the current sheet width (the largest of the sheet transverse dimensions). It is shown that helium atoms can acquire the directed energy Wx due to the resonance charge exchange of accelerated ions in the current sheet plasma. The energy of directed motion of helium atoms can reach Wx ≈ (480 ± 120) eV, which is ~20 times higher than the temperature of helium atoms Ta ≈ (20 ± 2) eV at the same times. During the current sheet formation in the 3D magnetic configuration, fast helium atoms were not observed. [ABSTRACT FROM AUTHOR]

The yield of the nuclear reaction B + p → 3α near the resonant proton energy of 675 keV in the injector beam of the "Prometheus" proton accelerator is studied. The reaction products (alpha particles) are recorded using a CR-39 track detector. The alpha particle yield from the boron target is estimated as ~10–4 per proton. [ABSTRACT FROM AUTHOR]

At the HELIS ion accelerator, the dependence of the yield of DD nuclear-reaction products (neutrons and protons) on the angle of rotation of a Ti and CVD diamond (diamond obtained by chemical vapor deposition) target relative to the axis of the D+ ion beam at energies of E ≤ 35 keV is studied. Neutron detection is carried out by two independent methods: proportional counters filled with 3He and a scintillation detector with a stilbene crystal. Protons are detected using a diamond detector. The detectors are located on the side and behind the target. The CVD-diamond target has a polycrystalline structure and texture with the (100) grain orientation. The crystal structure of the titanium target is homogeneous and isotropic. The measurements show the dependence of the neutron flux recorded by the detectors located on the side and behind the target on the orientation of the target made of textured CVD diamond in the deuterium ion beam at energies of 25 and 30 keV. The proton yield from the CVD diamond target shows a dependence on the target-rotation angle at an energy of 25 keV. For the Ti target, no such effects are observed. The orientational dependence in the yield of neutrons and protons from textured diamond is explained by the effect of channeling deuterium ions in its structure. [ABSTRACT FROM AUTHOR]

Abstract—The results of measuring the plasma density in those areas of the current sheet where helium atoms are predominantly localized are presented. The measurements were carried out based on the analysis of the profiles of neutral helium spectral lines of 447 and 492 nm using a new method—determination of the half-width at the half-height of the red wing of the spectral line. This method has a number of advantages over classical methods in conditions of a large dynamic range of changes in plasma density and interferences from spectral lines of impurities. The application of this method made it possible for the first time to determine the concentration of electrons in various regions of the current sheet, as well as at different configurations of the magnetic field and the values of the initial pressure of helium at which the current sheet is formed. The results obtained are in qualitative agreement with the electron concentration measurements based on the analysis of the profiles of the spectral lines of the helium ion, but differ somewhat from them quantitatively, due to the localization of the helium ions and atoms in different regions of the current sheet. [ABSTRACT FROM AUTHOR]

The distributions of time and energy parameters of X-ray radiation of the nanosecond megavolt atmospheric discharge of "reverse-conical cathode with a tip–grid anode" configuration have been measured for the first time on the coordinate along the discharge axis with a resolution of 12 cm. The discharge gap length is 60.5 cm and the maximum applied voltage is 1.2 MV with a front rise time of ~220 ns. The photon energy has been evaluated using lead filters of stepped attenuation with thicknesses up to 10 mm. About 1200 axial discharges have been examined. It has been found that radiation pulses are clustered in time and arise together with features of the time derivative of the applied voltage. The most intense and hard X-ray and gamma radiation is observed at the time when the applied voltage reaches its maximum value. The radiation energy from the anode region exceeds the radiation energy from the gas gap by a factor of 5–8. Radiation energy maxima are also observed near the cathode region. The maximum photon energy does not exceed ~400 keV. The amplitude spectra of ionizing radiation are studied. Relativistic electrons deceleration in the anode material can be the bremsstrahlung source for the observed radiation. [ABSTRACT FROM AUTHOR]

The distributions of time and energy parameters of X-ray radiation of the megavolt atmospheric discharge of the ERG system with a front of 220 ns and with "reverse-conical cathode with a tip – grid anode" configuration were studied along the coordinate along the discharge axis with a resolution of 12 cm. It was discovered for the first time, that the radiation with quantum energy of more than 100 keV is emitted mainly from the anode region earlier than from the cathode region: maximum of the radiation intensity from the anode region is observed ~140 ns earlier, than maximum of the radiation intensity from the cathode region. It is defined that X-ray pulses coincide with high-frequency oscillations of the discharge current and extrema of time dependence of derivative of the voltage applied across the discharge gap dU/dt. The radiation from the anode region and from the interelectrode gap could be related to relativistic electron bremsstrahlung. The cathode region radiation nature requires further comprehension. [ABSTRACT FROM AUTHOR]

The experimental data on the yield of d + d-reaction products for polycrystalline diamond target, obtained in the studies at the HELIS ion accelerator are presented. The equipment and neutron and charged particle detectors used in the study are described. The possibility of using the Unique Scientific Facility (USF) HELIS to verify operating characteristics of semiconductor detectors of alpha particles intended in studies of the boron–proton capture reaction at the Prometheus proton therapy complex is shown. [ABSTRACT FROM AUTHOR]

The technique for localizing a gigahertz radio emission source generated by a high-current atmospheric spark discharge using two ultra-wideband antennas is described. The spatial position in space of the sources of the first highest-frequency radio emission pulses in the discharge gap is determined. [ABSTRACT FROM AUTHOR]

Scintillation detectors for detecting X-ray, gamma, and neutron radiation with time resolutions of 3-4 ns and having high noise stability have been developed. The detector housings are shielded from the strong electromagnetic interference produced at the moment of discharge. The detector design features an original voltage divider. With these detectors, the parameters of the high-energy radiation from a megavolt atmospheric nanosecond discharge can be studied at the limit of sensitivity of this class of devices. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.3103/S1068335623020094 [ABSTRACT FROM AUTHOR]