Improved passivation depth of porous fluorescent 6H-SiC with Si/C faces using atomic layer deposition

We investigated the effects of different growth facets of 6H-SiC and different voltage waveforms on the porous structure and luminescence properties. The structure formed on the surface after anodic etching significantly changed because of the difference in the growth plane, whereas dendritic and columnar pores were observed inside the Si- and C-face samples. These large porous structures were shown to promote the penetration depth of the atomic-layer-deposited Al2O3 films, and a recorded passivation depth of 30-µm layer was confirmed in C-face porous SiC. From the results using fluorescence microscope and PL spectra measurement, it was concluded that the pulsed-voltage etching was preferable for fabricating uniform porous structures compared with the constant-voltage etching. However, the enhancement of the luminescence intensity needs to be further improved to realize high luminescent efficiency in porous fluorescent SiC.

40 year anniversary of the RADAN systems – compact pulsed power sources for various investigations

This article includes a brief overview of the compact RADAN-series subgigawatt pulsed voltage sources and describes their capabilities in various electrophysical researches. We present the results obtained in the experiments at nano- and subnanosecond time scales on the formation of the voltage pulses with a special shape, electron beams emission in air gaps and by the cold cathodes in vacuum, as well as generation of electromagnetic radiation. Particular attention is paid to the promising application of the RADAN systems.

Influence of the switching frequency of the switch and the amplitude of the reference voltage of a pulsed voltage regulator of the lowering type on its stability

On the basis of classical stability criteria, using the expressions of the transfer function, according to the block diagram, the stability of the impulse controller with feedback is estimated. The influence of the switching frequency of the switch and the amplitude of the reference voltage on the stability of a pulsed voltage regulator of a lowering type with deterministic parameters of the system is analyzed. In accordance with the Nyquist criterion for the transfer function of an open-loop system, both stability and phase stability margins for a closed-loop system can be estimated. When simulating the operation of the device, the phase stability margin was obtained, according to the Nyquist criterion, which is с = Н = 7. An increase in the sawtooth voltage is not a desirable phenomenon, which, although it increases the margin of stability, however, reduces stability. Moreover, the dependence of the ripple, affecting the stability of operation, on the amplitude of the sawtooth voltage is not a predictable value and takes on a random value.

PEA Electromagnetic Distortion Reduction by Impedance Grounding and Pulsed Voltage Electrode Configurations

Space charges are one of the main challenges facing the constantly increasing use of extruded high voltage direct current (HVDC) cables. The Pulsed Electro-Acoustic (PEA) method is one of the most common procedures for space charge measurements of insulation. One issue with the PEA method is distortion due to the crosstalk between the applied voltage pulse and the acoustic sensor. This work analyzed two factors involved in the reduction in this distortion: the influence of the exposed semiconductor distance between the injection electrodes and PEA test cell, and the influence of adding a reactance at the grounding circuit of the PEA test cell. The interaction of these two factors with the distortion was analyzed through a series of experimental testing. Moreover, the performance regarding distortion after applying a developed coaxial injection was compared with the standard non-coaxial injection configuration. It was observed that these two factors had a direct impact on distortion and can be utilized for the reduction in distortion arising from the crosstalk of the applied pulsed voltage. The results can be utilized for the consideration of practical aspects during the construction of a PEA test setup for the measurement of full-size HVDC cables.

TRIGGERING PULSE GENERATORS DEVELOPED FOR THE HIGH-VOLTAGE DISCHARGERS OF MAGNETIC SYSTEMS AND FOR THE GENERATOR OF PULSE VOLTAGES USED BY THE RELATIVISTIC ELECTRON BEAM ACCELERATOR “TEMP-B”

The pulse generators were developed to trigger the high-voltage dischargers of magnetic systems and the dischargers of the generators of pulsed voltages used by the relativistic electron beam (REB) accelerator “TEMP-B”. The description of the triggering pulse generators designed by the NSC KIPT to actuate the dischargers of the pulsed voltage generators (PVG) and the dischargers of magnetic systems has been given. These are used by the commutation systems of capacitor banks with the stored energy margin in the range of 60 to 150 kJ. The generators provide the generation of voltage pulses with the amplitude of up to 20 kV.