Rise Time High Voltage Pulse Research Articles

Enhanced electrospinning: Multi-level fiber alignment by control of electrohydrodynamic jet motion for tissue engineering

This paper proposes a novel electrospinning method for controllable fiber alignment and deposition on a dielectric substrate by the electric field manipulation using nanosecond rise time high-voltage pulse generators. A peculiarity of the proposed technical solution is the ability to control polymer jet localization in the interelectrode space with the possibility of stabilization and retention of the jet at an arbitrary point. A preliminary numerical simulation shows electric field distribution in proposed geometry with a syringe and two cylindrical collectors. Samples of oriented materials based on a polyamide 6/66 copolymer with 2–4° degrees of disorientation were obtained. The study of thermal and mechanical behavior of oriented materials based on polyamide was carried out, and macromolecular orientation was established by X-ray diffraction in small and wide angles. The possibility to create material by stacking multiple layers with given fiber orientation at 65° and 90° and polymer spinning on various dielectric materials by means of the reverse polarity operating principle is demonstrated. The ability to control fiber alignment in electrospinning will expand the possibilities of high-performance production of polymeric nonwoven materials with a given architecture and unique physicochemical characteristics required for solving a whole range of medical and technological challenges of a different profile.

Investigation on a fast rise time high voltage pulse transformer.

A pulse transformer has advantages of compactness and long lifetime achievability, and is considered an important candidate for the development of high voltage pulse generators. In this paper, a fast rise time high voltage pulse transformer with a compact structure is studied numerically and experimentally. Specifically, the structure of the pulse transformer was designed with paralleled winding groups. The response and insulation characteristics of the pulse transformer are investigated numerically. After that, a fast rise time high voltage pulse transformer was built, and scaling experiments were performed to analyze the influence of the feed structure of the pulse transformer. Importantly, the pulse transformer was successfully used in a low impedance generator, and high voltage pulses with a peak voltage of about 260 kV, a pulse duration of 170 ns, and a rise time of 65 ns were achieved on a resistive load of 32 Ω. The ratio of the transformer is approximately 1:3. Experiments show reasonable agreement with the numerical analysis.

A Step Forward in Tissue Engineering Design: Control on Multi-Scale Fiber Alignment by Electrospinning

This paper proposes a novel electrospinning method for controllable fiber alignment and deposition on a dielectric substrate by the electric field manipulation using nanosecond rise time high-voltage pulse generators. A preliminary numerical simulation shows electric field distribution in proposed geometry with a syringe and two cylindrical collectors. Samples of oriented materials based on a polyamide 6/66 copolymer with a low degree of disorientation 2-4° were obtained. The study of thermal and mechanical behavior of oriented materials based on polyamide was carried out, and for the first time for electrospun fibers the microscale orientation effects of polymer crystallites were found by X-ray diffraction in small and wide angles. Orientation occurs in the developed materials both at macro and micro levels. The possibility to create material by stacking multiple layers with given fiber orientation at 65° and 90° and spinning on various dielectric materials due to the reverse polarity operating principle is demonstrated. The ability to control fiber alignment in electrospinning will expand the possibilities of high-performance polymer nonwoven materials production with a given architecture and unique physicochemical characteristics for solving a whole range of medical and technological challenges of a different profile.

Development of a novel voltage divider for measurement of sub-nanosecond rise time high voltage pulses.

This paper is about the development of a copper sulphate based aqueous-electrolytic voltage divider for the measurement of high voltage pulses, 100 kV, with pulse widths of 1-2 ns and rise time <1 ns. Novel features are incorporated in the design of the divider, to meet the performance requirements for the application. Analytical calculations to justify design are described. Structural simulation of the divider is carried out using field wave simulation software to verify the effectiveness. A calibration procedure has been developed to calibrate the divider. Results obtained during calibration are subjected to statistical analysis to determine the confidence of measurement. Details of design, analysis, and simulation are described in this paper.

Diode laser spectroscopic measurements of gas temperature in a pulsed dielectric barrier discharge using collisional broadening and shift of 1s3−2p2and 1s5−2p7argon transitions

The average gas temperature rise within an argon dielectric barrier discharge operating from 50 to 500 Torr excited by 5 kHz repetition rate fast rise time high voltage pulse has been measured. For these measurements within high pressure discharges, we have employed two novel gas temperature measurement techniques based upon tunable diode laser absorption spectroscopy that take advantage of the nonresonant collision line broadening and collisional frequency shifts from relatively strong argon 1s3-2p2 and 1s5-2p7 transitions from the metastable states. An in situ estimate of collisional broadening coefficients for both transitions have been obtained from 5 to 30 Torr data using an independent estimate of gas temperature from Doppler line width measurements. Our measurements show that the effect of the isolated line assumption inherent within the van der Waals collisional impact approximation limit begins to fail for the 1s3-2p2 and 1s5-2p7 spectral lines when collisional line broadening exceeds ∼23 GHz line separation at gas pressure >300 Torr with gas temperature near ambient. A comparison of gas temperature estimates from both line broadening and peak frequency shift shows that the frequency shift provides a more reliable measurement of gas temperature, indicating that the isolated line assumption holds for collisional peak frequency shifts, even for partially overlapping lines.

Numerical simulation of runaway electrons generation in sulfur hexafluoride

The results of the numerical simulation of the generation of runaway electrons in sulfur hexafluoride are presented. It is shown that the emission of the runaway electrons occurs from the cathode and its vicinity. The generation of these electrons is terminated because of the formation primarily by negative ions of a virtual cathode which causes the field emission to be screened. The simulations showed that the virtual cathode consists mainly of negative ions and cannot be an effective source of runaway electrons. In addition, the results of the simulations showed that the parameters of the runaway electrons depend on the amplitude and rise-time high-voltage pulse and gas pressure.

Decomposition of three volatile organic compounds by nanosecond pulsed corona discharge: Study of by-product formation and influence of high voltage pulse parameters

Increasing concerns over atmospheric pollution has motivated research into technologies able to remove volatile organic compounds (VOC’s) from gas streams. The aim of this paper is to understand the chemical and physical mechanisms implied in the decomposition of VOC’s in a filamentary nonthermal plasma discharge. Experiments have been carried out on three pollutants (propane, propene, and isopropyl alcohol) in dry air at atmospheric pressure using a wire to cylinder corona discharge generated by a homemade nanosecond rise time high voltage pulse generator. The resulting plasma efficiently destructs propane, propene, or isopropyl alcohol at a concentration of 500ppm with low specific input energies (less than 500J∕L), but the poor oxidation rate leads to the formation of numerous by-products (acetone, formaldehyde, formic acid, and methyl nitrate) whose concentration can reach some hundreds of ppm. We also investigated the effect of pulse parameters on VOC removal efficiency. Neither pulse peak value nor rise time (in the range of 4–12ns) appears to have a significant influence on the VOC decomposition rates. Therefore, we believe that the way the energy is deposited in the plasma does not modify the density of active species (radicals, ions) in the streamers. The production of energetic electrons is not enhanced by the external applied field, and the only effective parameter may be the local field in the streamer head, which is almost the same (around 500Td) whatever the voltage (above the inception value).

Generation of subnanosecond laser pulses by periodic Q-switching technique using a simple electrically triggered spark gap

The generation of subnanosecond Nd:YAG laser pulses by the technique of periodic Q-switching using a simple electrically triggered spark gap is described. The construction and some operating characteristics of the spark gap are given. The measurement of very short rise time high-voltage pulses using a V probe is also described.