Spark Gap Generator Research Articles

Testing and optimization of 3D-printed volumetric diffusor arrays for attenuation of blast noise

3D-printed volumetric diffusing array structures, composed of many arbitrarily shaped pillars in an optimized pattern, have previously been shown to be very effective for blast noise attenuation in a scale model experiment (Ochi et al., 2019). This work expands upon previous progress by investigating innovative optimization schemes for the array designs, and further testing these optimized arrays in scale model experiments with a spark gap generator operating as a surrogate blast noise source. Properties of the propagated signal, including directivity, duration, and spectral characteristics, are discussed, as well as how these properties depend on the choice of volumetric diffusor. Finally, the propagated waveform, spectra, and effective attenuation predicted using 2D-FDTD simulations are compared with the results of the experiment as a method of testing the validity of the simulations.

Utilizing a spark gap generator as an impulsive noise source for scale model experiments investigating novel metamaterial arrays

Utilizing a spark gap generator as an impulsive noise source for scale model experiments investigating novel metamaterial arrays

Peak-Power-Limited Frequency-Domain Microwave-Induced Thermoacoustic Imaging for Handheld Diagnostic and Screening Tools

Coherent frequency-domain microwave-induced thermoacoustic (TA) imaging is investigated as an alternative to the traditional pulsed-based TA imaging approaches that use extremely high-energy short excitation pulses, often produced by vacuum RF sources or spark-gap generators. It is shown that under peak-power limitation of the RF source, dictated by the goals of form factor and portability of this paper, the frequency-domain approach can achieve the required signal-to-noise ratio (SNR) without sacrificing resolution or other performance metrics. Theoretical and experimental comparison of the time-domain and frequency-domain TA methods is provided with the ultimate goal of implementing the imager with solid-state hardware. Using a microwave source with 120 W of peak power, frequency-domain TA demonstrates 27-dB SNR improvement over the pulse method while the average specific absorption ratio remains below 10 W/kg. Finally, we demonstrate TA images of multilayer relatively complex muscle-fat structures. To the best of our knowledge, these are the first TA images obtained with solid-state electronic sources.

The X(-Band) Files: An X-Band Microstrip Voltage-Controlled Oscillator with Wideband Tuning Range

Signal sources are essential devices for radar and communication systems. The demand for oscillators has existed for very long time. In 1888, Heinrich Hertz introduced the first known oscillator to prove Maxwell's equations experimentally [1]. He used a dipole as the frequency determining structure and a spark-gap generator as the signal source. His invention signaled the birth of wireless communications because Hertz confirmed the existence of electromagnetic radiation which was postulated by Michael Faraday and James Clerk Maxwell.

The first experiments on electrical safety

This paper discusses the experiments conducted by physicist and physician Arsenne d'Arsonval on the effect of sinusoidal ac on the body, well before the era of electronics. d'Arsonval's first experiments were on the effect of ac on muscle contraction using frog muscle. He contrived a most ingenious device, which displayed the voltage curve and the force of muscle contraction on a smoked-drum kymograph. By using this instrument, along with various alternators such as the Gramme machine, d'Arsonval was able to show that the muscular contraction force decreased with increasing frequency of the electric current. d'Arsonval then turned his attention to the effect of high-frequency ac on the human body. To this end, he created a spark-gap generator of the type described by Hertz in 1888. d'Arsonval demonstrated two important facts: 1) muscle contraction force decreased with increasing frequency of the current and 2) substantial current could be passed through the body and it produced a sensation of warmth. This he proved with conductive and capacitive coupling. By his experiments, d'Arsonval laid the foundation for two new medical techniques: 1) electrosurgery and 2) diathermy. Today both fields are well established in medicine

De forest and the first electrosurgical unit.

In the United States, Lee De Forest, who patented the first triode vacuum tube (audion) in 1907 and 1908, was experimenting with a high-frequency spark-gap generator for use in surgery and filed a U.S. patent application describing his work on 10 February 1907, which was issued on 17 December 1907. This device was the first electrosurgical unit, and there are no better words than his own in his patent for describing it; he stated: Be it known that I, Lee De Forest, a citizen of the United States, and a resident of New York, in the county of New York and State of New York, have invented a new and useful improvement in Cauteries, of which the following is a specification. My invention relates to devices for producing burning effects by means of high-frequency electrical currents, and more particularly to cauteries employed in surgery. (A cautery is a heated rod used to cut and coagulate living tissue.) I have discovered that when a conductor is attached to any part of a high-frequency oscillating circuit, the high-frequency electrical current passing into a body, for example, a human body, will produce a heating or burning effect at the point of contact of the electrode conveying such currents to said body, and that the intensity of said heating or burning effect is inversely proportional to the terminal area of said electrode. If therefore the electrode ends in a fine point or cutting edge, or relatively small area of other shape, an extremely intense burning effect may be obtained.

High-current and high-voltage pulsed testing of resistors

Three types of resistors have been tested to determine maximum usable power at pulsed high voltage and pulsed high current. Experiments were carried out using high-voltage cable generators, spark gap generators, and thyratron drivers. Pulse durations were varied from 0.7 /spl mu/s to 21 /spl mu/s. The pulse amplitudes were varied from 1 kV to 35 kV. The peak current reached was 3 kA. Metal film, carbon film, and carbon composition resistors of four different rated powers (0.25 W, 0.5 W, 1 W, and 2 W) have been tested. Data are given for the limiting pulsed power and energy for each type of resistor in nanosecond and microsecond time ranges. The experimental investigation of the threshold loading of the resistors in the high-current pulsed mode and in the high-voltage pulsed mode has shown that the process of destruction of resistors has specific features for each mode. The mechanisms of failure and destruction of resistors under the action of high-voltage and high-current pulses are discussed.

Cardiac Dysrhythmias Related to Extracorporeal Shock Wave Lithotripsy Using a Piezoelectric Lithotriptor in Patients with Kidney Stones

Shock waves delivered by a spark-gap generator during extracorporeal shock wave lithotripsy (ESWL) for kidney stones frequently cause cardiac arrhythmias. However, detailed data about the arrythmogenicity of this therapy using a piezoelectric lithotriptor are not available even though this type of machine is generally not considered to induce cardiac arrhythmias. The prevalence and nature of cardiac dysrhythmias during piezoelectric ESWL were assessed in 34 patients with kidney stones in whom cardiac disease other than dysrhythmias had been excluded. Each patient underwent 24-hour ambulatory electrocardiography (ECG) recording 2 to 3 days before ESWL. On the day of ESWL, ECG was performed continuously from 4 hours before and throughout the procedure. The relationship between ESWL-related dysrhythmias and autonomic neural activity was also evaluated by heart rate spectral analysis. Piezoelectric ESWL was found to elicit new or worsened tachyarrhythmia originating from the atria or ventricles or both in 20 patients (59%), atrial premature contractions in 4, ventricular premature contractions in 7, both types in 7, atrial and ventricular premature contractions plus extreme sinus bradycardia in 1, and neurally mediated sinus bradycardia and hypotension in 1. However, piezoelectric ESWL-related dysrhythmias were not related to the dysrhythmias seen in the usual life. Heart rate spectral analysis suggested that changes in autonomic neural activity were involved in the mechanism(s) of ESWL-related dysrhythmia. Although lethal dysrhythmias have not yet been encountered at our institution, patients at risk of sustained life-threatening cardiac dysrhythmias should be monitored closely even if ESWL for kidney stones is undertaken using a piezoelectric lithotriptor.

Cardiac Dysrhythmias Related to Extracorporeal Shock Wave Lithotripsy Using a Piezoelectric Lithotriptor in Patients with Kidney Stones

It is well known that, during extracorporeal shock wave lithotripsy (ESWL [dagger]) for kidney stones, shock wave delivered by a spark-gap generator frequently elicit cardiac arrhythmias. However, detailed data are lacking concerning the arrhythmogenesis of ESWL using a piezoelectric lithotriptor, even though this type of machine has generally been considered not to induce cardiac arrhythmia. Therefore, the prevalence and nature of cardiac dysrhythmias during piezoelectric ESWL were examined in 34 patients with kidney stones in whom cardiac disease other than dysrhythmia had been excluded. Each patient underwent 24-hour electrocardiographic recording 2 to 3 days before ESWL. On the day of ESWL electrocardiography was recorded continuously beginning from 4 hours before until the end of the procedure. The relationship between ESWL related dysrhythmia and autonomic neural activity was also evaluated by heart rate spectral analysis. Piezoelectric ESWL was found to elicit new or worsened tachyarrhythmia originating from the atria and/or ventricles in 20 patients (59 percent) and serious bradycardiac arrhythmia in 1. However, piezoelectric ESWL related dysrhythmias were not associated with the dysrhythmias in the daily life of the patients. Heart rate spectral analysis suggested that changes in autonomic neural activity were involved in the mechanism(s) of ESWL related dysrhythmia. Although lethal dysrhythmia has not yet occurred at this institution, it is considered that patients at risk for life threatening cardiac dysrhythmia should be monitored closely even if ESWL for kidney stones is done with a piezoelectric lithotriptor. [dagger] Dornier Medical Systems, Inc., Marietta, Georgia.

First Experience with the Lithoring in the Management of Urinary Stones

The Lithoring Multi-One is a lithotripter recently developed in Italy. Its main features are (1) spark gap generator with large ellipsoid, with tunable power for treatments with or without analgesia; (2) localization by fluoroscopy and ultrasounds without moving the patient; (3) isocentric variation of shock wave window, and (4) multifunctional table. It can treat both urinary and biliary stones. The first 50 patients were treated without anesthesia with an average of 1,700 shock waves at 19.2 kV. 37 patients had stones larger than 1 cm. 13 patients had ureteral stones. Two patients had complete staghorn stones. The disintegration rate was 97.9%, the overall stone-free rate at 3 months' follow-up was 83.3%, and the retreatment rate was 1.29 treatments for patients. No complication occurred.

Clinical and Materials Sciences

evices were used for gingival retraction prior to impression-taking procedures. The effects of these retraction methods upon blood pressure and loss of gingival tissue height were evaluated on three Rhesus monkeys. Chamfer finishing lines were prepared on all of the teeth and penetrating into the gingival sulcus. All the retraction devices were used to produce the desired amount of retraction which would allow an acceptable impression. Contralateral teeth, on which a chamfer was cut but no retraction performed were used as control teeth. The only retraction device which had no effect on blood pressure and caused no tissue loss was the nonepinephrine retraction cord. The 8% r-epinephrine string and the two electrosurgical devices caused elevated blood pressures. With the 8% r-epinephrine retraction cord, no tissue loss was observed and complete healing occurred within nine days. Both electrosurgical devices caused tissue loss. The fully rectified current device caused a slight loss in gingival tissue height, while the spark gap generator caused a marked amount of tissue height to be lost. The Hyfrecator should not be used for gingival retraction because of the tissue damage that results. It appears that the safest retraction device is the retraction cord, when used properly. Further research is recommended to establish the possible systemic effects of the electrosurgical techniques.

Applications of microwaves in scientific research

Microwaves are very short radio waves covering the range roughly between λ = 10 em. and 1 mm. wave lengths. This spectrum of the electromagnetic waves, which bridges light and radio waves, holds a great deal of scientific interest. The physicist is especially anxious to study the absorption spectra of gases, and the magnetic and dielectric properties of liquids and solids in the microwave region; astrophysicists are interested in measuring the microwave radiation coming from the sun, the stars and clouds of gas in space; the biologist wants to gain a better understanding of living matter by studying the behavior of biological tissues and bacteria in the radiation field of centimeter and millimeter wave lengths; and nuclear physicists harness microwaves to accelerate electrons and protons for bombarding nuclei and to study nuclear reactions. Before World War II comparatively little was known about the physical and scientific applications of microwaves. Although these waves have been produced to a limited extent for many years by means of spark gap generators, Barkhausen-Kurz tubes and magnetrons, the greatest advances in the field of microwave technique took place during the recent war as a result of the concentrated efforts of teams of scientists engaged in the development of microwave radar. Vastly improved new methods for the transmission, generation, reception and measurement of microwaves have provided the physicist with important new research tools. It is the aim of this paper to review the most important progress made in this new science of microwave physics.