High Pulse Repetition Research Articles

A Modular High-Voltage Pulse-Generator With Sequential Charging for Water Treatment Applications

High-voltage pulse-generators can be used effectively for bacterial decontamination in water treatment applications. Applying a pulsed electric field to the infected water sample guarantees killing of harmful germs and bacteria. In this paper, a modular high-voltage pulse-generator with sequential charging is proposed for water treatment via underwater pulsed streamer corona discharge. The proposed generator consists of series-connected modules similar to an arm of a modular multilevel converter. The modules’ capacitors are charged sequentially from a relatively low-voltage dc supply, then they are connected in series and discharged into the load. Two configurations are proposed in this paper, one for low repetitive pulse rate applications, and the other for high repetitive pulse rates. In the first topology, the equivalent resistance of the infected water sample is used as a charging resistance for the generator’s capacitors during the charging process. While in the second topology, the water resistance is bypassed during the charging process, and an external charging resistance with proper value is used instead. In this paper, detailed designs for the proposed pulse-generators are presented and validated by simulation results using MATLAB. A scaled down experimental setup has been built to show the viability of the proposed concept.

Nox reduction from biodiesel exhaust by plasma induced ozone injection supported by lignite waste adsorption

This paper explores the technique of ozone injection to induce reactions leading to NO conversion in a diesel engine exhaust and subsequent adsorption by lignite ash, an industrial waste from lignite coal fired power plants. Experimental investigations were carried out using a diesel engine fuelled by biodiesel, prepared from pongamia pinnata, a native Indian plant. Ozone is produced from dry air in a Dielectric Barrier Discharge (DBD) reactor by the application of high voltage. The choice of the high voltage was made after a comparative study between high frequency AC and unipolar repetitive pulse source, with the latter consuming lesser power for given ozone production. By injecting ozone, the higher composition of NO in biodiesel exhaust gets oxidized to higher oxides of nitrogen in general and NO2 in particular. This NO2 can be adsorbed in the lignite fly ash pellets as successfully demonstrated in this paper. This combined ozone injection-lignite ash adsorption technique has resulted in an overall removal efficiency of oxides of nitrogen (NOx) as high as 95% even under loaded conditions. A comparison has also been made between the ozone injection technique and direct plasma treatment of exhaust for NOx removal.

Effect of the pulse repetition rate on fiber-assisted tissue ablation

The effect of the pulse repetition rate on ablation performance was evaluated ex vivo at various fiber sweeping speeds for an effective 532-nm laser prostatectomy. Three pulse repetition rates (7.5, 15, and 30 kHz) at 100 W were delivered to bovine liver tissue at three sweeping speeds (2, 4, and 6 mm/s) to achieve bulky tissue removal. Ablation performance was quantitatively compared in terms of the ablation volume and the coagulation thickness. The lowest pulse repetition rate of 7.5 kHz attained the highest ablation volume (101.5 ± 12.0 mm3) and the thinnest coagulation (0.7 ± 0.1 mm) along with superficial carbonization. The highest pulse repetition rate of 30 kHz was associated with the least tissue removal (65.8 ± 5.0 mm3) and the deepest thermal denaturation (1.1 ± 0.2 mm). Quantitative evaluations of laser parameters can be instrumental in facilitating ablation efficiency and maintaining hemostatic coagulation during treatment of large-sized benign prostate hyperplasia.

High-Sensitivity In Situ Soot Particle Sensing in an Aero-Engine Exhaust Plume Using Long-Pulsed Fiber-Laser-Induced Incandescence

A method to produce spatially resolved images of the distribution of absorbing particles in the exhaust plume of a modified helicopter gas turbine engine is presented. Over a small region of the plume, in situ sensing of soot particles by laser-induced incandescence (LII) is demonstrated using fiber lasers with higher power ( $\sim 10$ W), longer pulse duration (>100 ns), and higher pulse repetition rates (>10 kHz) than the conventional LII. The sensitivity of the method is illustrated by the detection of ambient absorbing particles in background conditions with engine at rest. With a running engine, single-beam images are obtained in 0.01 s. The feasibility of using long-pulsed fiber lasers for soot particle concentration measurement is investigated using a representative laboratory system. The time-resolved LII behavior and the measurement linearity are investigated, demonstrating the suitability of using fiber lasers for soot particle measurement for aero-engine emissions. Results for normalized soot concentration are compared with extractive measurements illustrating good correlation across a range of engine speeds. This paper is the first step toward the development of a non-intrusive system for the measurement of 2-D soot concentration in the cross section of an aero-engine exhaust plume.

Effective laser driven proton acceleration from near critical density hydrogen plasma

AbstractRecent advances in the production of high repetition, high power, and short laser pulse have enabled the generation of high-energy proton beam, required for technology and other medical applications. Here we demonstrate the effective laser driven proton acceleration from near-critical density hydrogen plasma by employing the short and intense laser pulse through three-dimensional (3D) particle-in-cell (PIC) simulation. The generation of strong magnetic field is demonstrated by numerical results and scaled with the plasma density and the electric field of laser. 3D PIC simulation results show the ring shaped proton density distribution where the protons are accelerated along the laser axis with fairly low divergence accompanied by off-axis beam of ring-like shape.

Dense Plasma Focus: physics and applications (radiation material science, single-shot disclosure of hidden illegal objects, radiation biology and medicine, etc

The paper presents some outcomes obtained during the year of 2013 of the activity in the frame of the International Atomic Energy Agency Co-ordinated research project “Investigations of Materials under High Repetition and Intense Fusion-Relevant Pulses ”. The main results are related to the effects created at the interaction of powerful pulses of different types of radiation (soft and hard X-rays, hot plasma and fast ion streams, neutrons, etc. generated in Dense Plasma Focus (DPF) facilities) with various materials including those that are counted as perspective ones for their use in future thermonuclear reactors. Besides we discuss phenomena observed at the irradiation of biological test objects. We examine possible applications of nanosecond powerful pulses of neutrons to the aims of nuclear medicine and for disclosure of hidden illegal objects. Special attention is devoted to discussions of a possibility to create extremely large and enormously diminutive DPF devices and probabilities of their use in energetics, medicine and modern electronics.

Recyclable Metal Air Fuel Cells Using Sintered Magnesium Paste with Reduced Mg Nanoparticles by High-Repetitive Ns Pulse Laser Ablation in Liquid

An energy cycle using solar power and metals has been proposed. High repetitive laser pulses are generated by a solar-pumped laser or a laser generated using solar power, and the laser pulses are irradiated to metal oxides in liquid. We can obtain reduced metal nanoparticles with this method, and solar power is effectively stored as chemical energy. We succeeded in producing sintered Mg metal paste. The sintered Mg nanopaste reduced Mg nanoparticles from pure MgO or Mg(OH)2 powder, collected from used Mg air cells, by laser ablation in liquid using a high-repetitive ns pulse Nd:YAG laser. We also fabricated metal air fuel cells using sintered Mg plates as negative electrodes. Electricity was successfully produced from these cells. A light-emitting diode and a motor were connected to the Mg paste air fuel cells and the output voltage and current of the cells were measured. The observed output voltage was 1.4 V when they were connected to a low load, which is the same as conventional Mg air cells. Metal oxides were reduced with high efficiency and at a noticeably low cost by using lasers generated from solar energy. This makes it possible to recycle Mg plates. The new recyclable Mg paste air fuel cells are expected to become common power supplies with high-energy density and high output power.

Wet separation between palladium(II) and molybdenum(IV) ions by using laser-induced particle formation: Enhancement of recovery efficiency of palladium by laser condition

Abstract Metal separation by using laser-induced particle formation was applied to the recovery of Pd from a mixed solution with Mo. In this separation, the Pd ions in the mixed solution containing 1 vol% ethanol were selectively reduced by irradiation of pulsed laser (10 Hz repetition rate) and high-repetition-pulse (HRP) laser (30 kHz repetition rate) with the wavelength of 355 nm while keeping irradiation power constant. The laser-induced reduction resulted in the generation of the Pd neutrals, which is followed by the aggregation of Pd neutrals in the absence of a stabilizing agent. The generated Pd particles were recovered and separated from the Mo ions by filtration. ICP-AES analysis of the filtrate elucidated that the Pd metals were successfully separated from Mo with a high recovery efficiency (84%). The recovery efficiency of Pd was different in the irradiation between the pulsed and HRP lasers; the efficiency obtained using the pulsed laser was 12% higher than that from the HRP laser. XRD analyses demonstrated that the Pd particles subjected to pulsed laser irradiation were 30 times larger than those subjected to the HRP laser. Based on TEM observations, the sizes of the Pd primary particles were approximately 200 nm (pulsed laser) and

Numerical Analysis of Narrow Band Ultrasonic Wave Generation with High Repetition Pulse Laser and Laser Scanning

Although the easiest way to enhance ultrasonic energy generated with pulse laser is to increase laser output, excessive laser output causes damage of the surface. This study introduced an alternative way to generate burst signals without any damages at the surface using a newly developed high repetition pulse laser controlled by galvano mirrors. The calculation results using two-dimensional elastodynamic finite integration technique coupled with thermoelastic effect proved that burst wave of 1 MHz and its higher harmonics were generated while supressing excessive temperature rise using this technique. Moreover, significantly large displacements at the frequency range sufficiently lower than laser repetition rate were observed of the same order of displacements generated with one single shot with the same input energy.

Analysis and experimental study on formation conditions of large-scale barrier-free diffuse atmospheric pressure air plasmas in repetitive pulse mode

Atmospheric air diffuse plasmas have enormous application potential in various fields of science and technology. Without dielectric barrier, generating large-scale air diffuse plasmas is always a challenging issue. This paper discusses and analyses the formation mechanism of cold homogenous plasma. It is proposed that generating stable diffuse atmospheric plasmas in open air should meet the three conditions: high transient power with low average power, excitation in low average E-field with locally high E-field region, and multiple overlapping electron avalanches. Accordingly, an experimental configuration of generating large-scale barrier-free diffuse air plasmas is designed. Based on runaway electron theory, a low duty-ratio, high voltage repetitive nanosecond pulse generator is chosen as a discharge excitation source. Using the wire-electrodes with small curvature radius, the gaps with highly non-uniform E-field are structured. Experimental results show that the volume-scaleable, barrier-free, homogeneous air non-thermal plasmas have been obtained between the gap spacing with the copper-wire electrodes. The area of air cold plasmas has been up to hundreds of square centimeters. The proposed formation conditions of large-scale barrier-free diffuse air plasmas are proved to be reasonable and feasible.

Safety of Diagnostic Ultrasound No. 6. The Safety of Pulsed Doppler Ultrasound

There are two pulsed Doppler ultrasound including continuous wave (CW) Doppler and pulsed Doppler, where the safety is discussed in the pulsed Doppler, because of its higher ultrasound intensity, due to longer pulse and higher pulse repetition frequency than simple B-mode ultrasound, and obstetrical setting of ultrasound devices determines the thermal and mechanical indices below one in pulsed Doppler. Ultrasound user is responsible to ultrasound safety, where the user lowers the ultrasound thermal and mechanical indices below one, when indices are higher than one. The use of pulsed Doppler in the first trimester is regulated by ISUOG committee.

Graphene-based passively Q-switched Nd:KLu(WO4)2 eye-safe laser operating at 1,425 nm

With graphene as saturable absorber, an Nd:KLu(WO4)2 eye-safe laser operating at 1,425 nm is demonstrated. To the best of our knowledge, this is the first demonstration that an Nd:KLu(WO4)2 laser operates at the eye-safe 1.4-μm region. A maximum total average output power of 170 mW is obtained under the pump power of 9.6 W, corresponding to an optical–optical efficiency of 1.77 %. The minimum pulse width and the highest pulse repetition rate are 153 ns and 97 kHz, respectively. Also the characteristics of the graphene used as saturable absorber for a 1.4-μm laser were studied for the first time.

Development and Study on Transformer Characteristics of A High Repetition Pulse Generator

High repetition pulse/ high frequency generators are of great interest for scientific and technological applications, including high voltage devices. This paper addresses the design and development of a high repetition pulse generator using a PIC microcontroller (PIC 16F877A). The PIC microcontroller generates two PWM pulses to drive the IGBTs through the optocouplers, which can perform fast switching in high voltage devices with low switching losses. The voltage and current supplied by the optocouplers make it perfectly suitable for the driving operations of IGBTs. Experiments were carried out to test its efficiency, and the waveforms of high repetition pulse frequency were observed by oscilloscope. The results of its operation present that the system could be used in the frequency range 2kHz < f < 200kHz. The system was also simulated by a Matlab Simulink model, in which two types of transformer were introduced to predict its validity in real operation with high voltage devices. The simulated results of the designed pulse generator show that the ignition coil transformer is more suitable than other iron core transformers for a high voltage with high pulse frequency. The system could be easily integrated with other high voltage devices to produce high pulsed frequency high voltages.

Simulation of a CuBr–Ne–HBr laser with high pump pulse repetition frequencies

Comparative experimental and model investigations of the performance of a CuBr laser without and with HBr at high pump pulse repetition frequencies have been carried out. Analysis performed based on a numerical simulation has revealed the mechanism of improvement of the lasing characteristics of the laser operated with an active additive (HBr) both at conventional (10–20 kHz) and at increased pulse repetition frequencies (up to 100 kHz).

Investigation on repetition rate and pulse duration influences on ablation efficiency of metals using a high average power Yb-doped ultrafast laser

Ultrafast lasers provide an outstanding processing quality but their main drawback is the low removal rate per pulse compared to longer pulses. This limitation could be overcome by increasing both average power and repetition rate. In this paper, we report on the influence of high repetition rate and pulse duration on both ablation efficiency and processing quality on metals. All trials have been performed with a single tunable ultrafast laser (350 fs to 10ps).

Study of the Repetition Pulses Based on Hydrogen Thyratron

Repetition pulses with sub-microsecond arising time, high voltage and large current, have been widely utilized in the field of production and scientific research, in which the gas spark switch is usually selected because of the large state current and the high operating voltage. However, due to the recovery property of gas ionization, it is hard to get the repeated switch-on and switch-off at a high rate towards the conventional gas spark switch. Owing to the reliably triggering and faster arising time, the hydrogen thyratron is found to be more suitable for the switch to generate the repetition pulses at a high rate. In this paper we proposed a novel design of repetition pulses, in which it gets a several times high voltage output based on the inductive-adder, by using the hydrogen thyratron switch with a low operating voltage, and then we analyze the magnetic field distribution under the structure of the coaxial cable and describe the design of high voltage repetition pulses in details

Global Analysis of EnviSat Burst Echoes Over Inland Water

Satellite radar altimeters have an established and increasingly vital role in monitoring the Earth's surface inland water resources. This paper analyzes two years of EnviSat burst echoes (which have 3.9-m nominal along-track separation) over rivers, lakes, and ephemeral water globally to assess the increase in monitoring potential afforded by the higher pulse repetition frequency (PRF) of the next generation of synthetic aperture radar altimeters and investigate spatial burst correlation. Burst echoes at 1800 Hz are successfully retracked with no waveform averaging. The conclusion is that the higher PRF allows detection and measurement of water bodies on a far finer spatial scale because water is a very bright reflector at Ku-band and land in general is relatively poor, with pools of water a few tens of meters across being successfully identified.

2123 HOLMIUM:YAG OPTICAL FIBER BURNBACK VARIES WITH STONE COMPOSITION

You have accessJournal of UrologyStone Disease: Evaluation & Medical Management I1 Apr 20122123 HOLMIUM:YAG OPTICAL FIBER BURNBACK VARIES WITH STONE COMPOSITION Jennifer Castelbuono, Joel Teichman, and Bodo Knudsen Jennifer CastelbuonoJennifer Castelbuono Columbus, OH More articles by this author , Joel TeichmanJoel Teichman Vancouver, Canada More articles by this author , and Bodo KnudsenBodo Knudsen Columbus, OH More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2012.02.2292AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Optical fiber tip degradation (fiber burnback) occurs at variable rates during laser lithotripsy of renal stones. Prior research showed more fiber damage with calcium oxalate monohydrate (COM), calcium phosphate (CP), and struvite stones compared to uric acid stones. We hypothesize that the rate of fiber burnback varies with stone composition. METHODS An ex-vivo testing apparatus was used to bring a 240 μm core sized optical fiber into contact with stones of known composition (UA, CP, COM, and artificial Bego). Lead tape was used to ensure consistent pressure was applied to the stone. The holmium YAG laser was activated until 100 J were delivered. Settings of 400 mJ and 1500 mJ at 5Hz were tested for all stone compositions. The amount of fiber burnback was measured. Fiber energy transmission was measured before and after each trial. Multiple trials with each stone composition were performed. RESULTS Contact with COM and CP stones resulted in greater burnback than with UA stones at both 400 mJ and 1500 mJ (p < 0.05). Contact with Bego stones resulted in similar burnback to COM and CAP stones, but greater than UA stones (p < 0.05). For COM, CP, and Bego stone compositions, burnback increased at the higher pulse energy setting (p < 0.05). Pulse energy did not alter the rate of burnback with UA stones. Fiber energy transmission did not change. CONCLUSIONS Optical fiber burnback varies with stone composition and pulse energy setting with the exception of UA stones. Fiber burnback did not alter energy transmission. These findings are consistent with prior studies. A strategy of low pulse energy and high pulse repetition should minimize burnback while maintaining fragmentation efficiency. COHORT BURNBACK MEAN (μm) ENERGY TRANSMISSION (mJ) Bego (400 mJ) 0.148 535 Bego (1500 mJ) 0.787 481 Uric Acid (400 mJ) 0.026 515 Uric Acid (1500 mJ) 0.024 510 COM (400 mJ) 0.1 498 COM (1500 mJ) 0.671 500 CP (400 mJ) 0.175 511 CP (1500 mJ) 0.561 512 © 2012 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 187Issue 4SApril 2012Page: e857 Advertisement Copyright & Permissions© 2012 by American Urological Association Education and Research, Inc.MetricsAuthor Information Jennifer Castelbuono Columbus, OH More articles by this author Joel Teichman Vancouver, Canada More articles by this author Bodo Knudsen Columbus, OH More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Electrical Characteristics Investigation of Transient Plasma Ignition

A pseudo-spark based high repetition pulse generator is used, and a rapid charger (3μF) is used for repetitive discharge, and the frequency of typical discharge is 10 kHz. The pulse generator can provide pulse with duration of 1~2μs, which can be generated at 10~100 kHz maximum repetition rate in burst mode, with amplitudes up to 140 kV and 7 J of energy per ignition pulse. This paper studies the changing laws of voltage and current in TPI under different electrodes and discharge voltages. The result indicates that the use of screw thread electrode can increase the discharge times of TPI, reduce applied voltage without reducing the peak burst power. With the same time, TPI can raise the pulse energy and reduce pulse time by increasing voltage.

Ultra Stable, Industrial Green Tailored Pulse Fiber Laser with Diffraction-limited Beam Quality for Advanced Micromachining

We report on a novel pulsed fiber laser platform providing pulse shaping agility at high repetition rates and at a wavelength of 532 nm. The oscillator is based on the direct modulation of a seed laser diode followed by a chain of fiber amplifiers. Advanced Large Mode Area (LMA) fiber designs as well as proprietary techniques to mitigate non-linear effects enable output energy per pulse up to 100 μJ at 1064 nm with diffraction-limited beam quality and narrow line widths suitable for efficient frequency conversion. Ultra stable pulses with tailored pulse shapes were demonstrated in the green region of the spectrum at repetition rates higher than 200 kHz. Pulse durations between 2.5 ns and 640 ns are available, as well as pulse to pulse dynamic shape selection at repetition rates up to 1 MHz. The pulse energy stability at 532 nm is better than ± 1.5%, 3σ, over 10 000 pulses. Excellent beam characteristics were obtained. The M2 parameter is lower than 1.05, the beam waist astigmatism and beam waist asymmetry are below 10% and below 8% respectively, with high stability over time. We foresee that the small spot size, high repetition rate and pulse tailoring capability of this platform will provide advantages to practitioners who are developing novel, advanced processes in many industrially important applications.