Note: Measurement of extreme-short current pulse duration of runaway electron beam in atmospheric pressure air

This note reports the time-amplitude characteristic of the supershort avalanche electron beam with up to 20 ps time resolution. For the first time it is shown that the electron beam downstream of small-diameter diaphragms in atmospheric pressure air has a complex structure which depends on the interelectrode gap width and cathode design. With a spherical cathode and collimator the minimum duration at half maximum of the supershort avalanche electron beam current pulse was shown to be ～25 ps. The minimum duration at half maximum of one peak in the pulses with two peaks can reach ～25 ps too.     

Three-Component Portable Magnetometer Equipped with Ferromagnetic Transducers Built around Bistable Amorphous Microwire Cores

The paper is dedicated to designing small portable magnetometers with autonomous power supplies for measuring magnetic fields in the range of 0.2–200 A/m. Ferromagnetic transducers are built around bistable amorphous microscopic wires 10–20 mm in diameter from the alloy (Co₉₂Fe₈)₆₃Ni₁₀B₁₆Si₁₁ in glass insulation. The properties of these cores and characteristics of transducers built around these cores have been studied; regimes of magnetization and dimensions of the cores have been selected. The IGMP-3B three-component magnetometer incorporating a one-chip microcomputer for medical and biological research is described in detail.     

A coaxial chopping gap filled with air at atmospheric pressure with a pulse decay time ≤100 ps

The results of experimental studies of a coaxial chopping gap filled with air at atmospheric pressure are presented. At a pulse rise time of 100–300 ps and a voltage pulse amplitude of 30–145 kV, the obtained duration of the voltage-pulse decay time is ≤ 100 ps. The high stability of the gap operation is attained in the presence of the edge with a small radius of curvature on one of the electrodes. The fast voltage decay across the gap is determined by the preionization of the gap by runaway electrons.     

Calculation of absolute values of the spectral energy density of polychromatic radiation

A method for calculating absolute values of the spectral distribution of the radiant energy of a polychromatic source is described for the case in which the spectral distribution of the radiant energy is recorded in relative units, and the time dependence of a current pulse of a photodetector the spectral sensitivity of which is known in absolute units is measured. The expression for the time-averaged spectral density of the radiation power for the pulse-periodic operation of a radiant source is given.     

KrCl and XeCl exciplex glow discharge lamps with an output power of ∼1.5 kW

A high-power multisection cylindrical exciplex lamp pumped by a glow discharge is created. The energy, temporal, and spectral characteristics of the emission from KrCl* (λ～-222 nm) and XeCl* (λ～308 nm) molecules are studied. The average output UV radiation power is 1.6 kW (for 222 nm) and 1.1 kW (for 308 nm) at a power pumping efficiency of up to 14%.     

To the theory of grain-boundary diffusion in nanostructured materials

Using an asymptotic method of solving diffusion equations and a Laplace transform, the theory of grain-boundary diffusion is extended to the case of a coefficient of bulk diffusion strongly changing near the structural boundaries of grains under the conditions of annealing corresponding to regime C in usual polycrystals. An analysis of the layer activity measured in the diffusion experiment was performed and, on the example of copper, its radical difference from the case of equilibrium boundaries was shown. Results of numerical calculations and qualitative estimates are presented, which make it possible to establish the field of the applicability of the approach suggested.     

Effective regimes of runaway electron beam generation in helium,hydrogen, and nitrogen

Runaway electron beam parameters and current-voltage characteristics of discharge in helium, hydrogen, and nitrogen at pressures in the range of several Torr to several hundred Torr have been studied. It is found that the maximum amplitudes of supershort avalanche electron beams (SAEBs) with a pulse full width at half maximum (FWHM) of ∼100 ps are achieved in helium, hydrogen, and nitrogen at a pressure of ∼60, ∼30, and ∼10 Torr, respectively. It is shown that, as the gas pressure is increased in the indicated range, the breakdown voltage of the gas-filled gap decreases, which leads to a decrease in the SAEB current amplitude. At pressures of helium within 20–60 Torr, hydrogen within 10–30 Torr, and nitrogen within 3–10 Torr, the regime of the runaway electron beam generation changes and, by varying the pressure in the gas-filled diode in the indicated intervals, it is possible to smoothly control the current pulse duration (FWHM) from ∼100 to ∼500 ps, while the beam current amplitude increases by a factor of 1.5–3.