Artykuły w czasopismach: „Pulse operation”

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Seol, Youbin, Minsu Choi, Hongyoung Chang i Shinjae You. "Study on OH Radical Production Depending on the Pulse Characteristics in an Atmospheric-Pressure Nanosecond-Pulsed Plasma Jet". Materials 16, nr 10 (19.05.2023): 3846. http://dx.doi.org/10.3390/ma16103846.

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Hydroxyl radicals (OH) play a crucial role in plasma-bio applications. As pulsed plasma operation is preferred, and even expanded to the nanosecond range, it is essential to study the relationship between OH radical production and pulse characteristics. In this study, we use optical emission spectroscopy to investigate OH radical production with nanosecond pulse characteristics. The experimental results reveal that longer pulses generate more OH radicals. To confirm the effect of pulse properties on OH radical generation, we conduct computational chemical simulations, focusing on two types of pulse properties: pulse instant power and pulse width. The simulation results show that, similar to the experimental results, longer pulses generate more OH radicals. In the nanosecond range, reaction time is critical for OH radical generation. In terms of chemical aspects, N2 metastable species mainly contribute to OH radical generation. It is a unique behavior observed in nanosecond range pulsed operation. Furthermore, humidity can turn over the tendency of OH radical production in nanosecond pulses. In a humid condition, shorter pulses are advantageous for generating OH radicals. Electrons play key roles in this condition and high instant power contributes to them.

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Шашкин, И. С., А. Ю. Лешко, Д. Н. Николаев, В. В. Шамахов, Н. А. Рудова, К. В. Бахвалов, А. В. Лютецкий i in. "Излучательные характеристики мощных полупроводниковых лазеров (1060 нм) с узким мезаполосковым контактом на основе асимметричных гетероструктур AlGaAs/GaAs с широким волноводом". Физика и техника полупроводников 54, nr 4 (2020): 408. http://dx.doi.org/10.21883/ftp.2020.04.49149.9333.

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Light characteristics of narrow-stripe lasers (5.5 m) based on asymmetric AlGaAs/GaAs heterostructures are studied. It was shown that the maximum optical power achieved under continuous-wave (CW) operation is limited by thermal heating and reaches 1695 mW at a current of 2350 mA at +25°C, and the maximum efficiency reaches 54.8 %. By reducing the operating temperature to -8°C, we were able to increase the maximum power to 2 W. A peak power of 2930 mW was obtained under pulsed operation (pulse width 240 ns, amplitude 4230 mA). It is shown there is a region of an “optical dip” in the power profile with a low-efficiency lasing of a train of pulses of sub-ns duration under pulsed operation.

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Godun, D. V., S. V. Bordusau i G. P. Budzko. "Output Current Control System of a High Voltage Electric Pulse Generator for Plasma Excitation". PLASMA PHYSICS AND TECHNOLOGY 6, nr 1 (2019): 7–9. http://dx.doi.org/10.14311/ppt.2019.1.7.

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A control and pulse discharge current limiting system integrated into an AC/DC converter and pulse modulator of a high voltage pulse generator have been developed. The peculiarity of such system\textquotesingle s operation is the stabilization of the power supplied to the discharge and the correction of the width of output electric pulses towards decrease upon reaching the specified pulsed current amplitude value. The system enables the pulse generator to work in the modes close to the ``short circuited load'' mode. In this case the driving module of a composite IGBT key performs the correction of the working pulse width and blocks the pulse generator operation if needed. The suggested circuit design solutions allow using the generator in a wide range of electric plasma-forming parameters' modes and working with various types of vacuum gas discharge systems.

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Irshad, Kashif. "Performance Improvement of Thermoelectric Air Cooler System by Using Variable-Pulse Current for Building Applications". Sustainability 13, nr 17 (28.08.2021): 9682. http://dx.doi.org/10.3390/su13179682.

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The thermoelectric air conditioning system (TE-AC) is a small, noiseless alternative to standard vapor compression refrigeration (VCR) systems. The cooling characteristics of a TE-AC system operating under two conditions, i.e., steady current and current pulses, are investigated in this study. This system consists of three thermoelectric modules, a heat sink, and an air circulation fan. The result shows that maximum temperature reduction in cooling side of TE-AC system was achieved at 6 A input current under steady state operation. The optimum performance of the TE-AC system under steady state operation depends upon the combined effect of the cooling load, Joule, Fourier, and Peltier heat. In TE-AC pulse operation, both current width and cooling load applied on the cold side of the thermoelectric module (TEMs) play an important role in achieving optimum cooling performance of the system. When normal input current operation (i.e., no current pulse) was compared to pulse-operated TE-AC system operation, it was found that pulse operation provides an additional average temperature reduction of 3–4 °C on the cold side of TEMs. Although on the hot side, it maintains a temperature in the range of 18 °C to 24 °C to reduce overshoot heat flux. The duration of operation is also important in determining pulse width and pulse amplitude. Minimum and overshoot peak temperature rises during each cycle for longer run operation. In the TE-AC system, the accumulated Joule heat during a current pulse frequently causes a temperature overshoot, which lasts much longer. As a result, the next current pulse was not released until the temperature of TE was restored to its initial value.

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Benaouda, Omar Fethi, Badreddine Babes, Mohamed Bouchakour, Sami Kahla i Azzedine Bendiabdellah. "Arc Welding Current Control Using Thyristor Based Three-Phase Rectifiers Applied to Gas Metal Arc Welding Connected to Grid Network". Journal Européen des Systèmes Automatisés 54, nr 2 (27.04.2021): 335–44. http://dx.doi.org/10.18280/jesa.540216.

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The purpose of the welding operation is to ensure the continuity of the materials to be assembled in large industrial sectors. This study aims to suggest a topology of the Thyristor based three-phase rectifiers applied to the Gas Metal Arc Welding (GMAW) process connected to the grid network, the output currents are controlled and using various pulsed forms such as square, annealing, and spike pulse operations and investigate and compare between the effects of the three references welding currents structures on the welding current, welding voltage, droplet diameter, and welding quality. To have the best pulse operation, the amplitude and frequency are kept the same for all operations, the application of meshing graphs in the references of welding currents structures, welding current, welding voltage, and droplet diameter can illustrate a clear comparison between them. The simulation results show that the square pulse operation is the best among them. The Single-Sided Amplitude Spectrum (SSAS) method is also applied to the welding current and droplet diameter of the three operations under slow and rapid droplet detachment rates to estimate the droplet detachment frequency. The results show the great success of the SSAS in estimating the precise frequency.

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Tikhomirov, S. A. "Femtosecond System with Pulse Pumping of Seed Laser and Amplifier by Using a Single Power Unit". Devices and Methods of Measurements 12, nr 1 (19.03.2021): 23–29. http://dx.doi.org/10.21122/2220-9506-2021-12-1-23-29.

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For several decades development of methods for generating ultrashort pulses has been an independent urgent scientific and technical problem. There is a constant improvement both in the methods of such pulses receiving and in methods of their use. The aim of this work was to investigate the possibility of realizing the coordinated operation of two fundamentally different types of pump lasers for the femtosecond oscillator and amplifier based on one single-lamp laser head and to create on this basis a compact high-power femtosecond system with pulsed pumping and one power unit.The practical implementation of two types of pulsed lasers (nano- and picosecond ones operating, respectively, in Q-switch and modelock regime) on a single laser head with two active elements and one pump lamp is carried out. The required synchronization in time the pump pulse femtosecond amplifier formation and quasi-stationary region of generated pulses in the output radiation of a femtosecond Ti:sapphire is obtained.On this basis a compact, pulse pumped monoblock laser system has been developed that can generate femtosecond pulses with a duration of 50–150 fs with an energy up to 1 mJ and a high enough pulse repetition rate (up to 1 kHz which is determined by the type of laser head and pump unit used). In the developed laser system a compact scheme of a stretcher-compressor with a single common diffraction grating is used.Laser systems of this type characterized by a relatively low cost due to the use of a single power supply unit for simultaneous pumping of the amplifier and oscillator, as well as lower requirements for the quality of optical elements and usage conditions due to the pulse mode of operation, are quite practical and can be used both in scientific research in the field of ultra-high-speed kinetic spectroscopy and nonlinear optics, as well as in numerous technical applications, particular in the precision processing of materials, as optical simulators of the action of heavy charged particles in testing the radiation resistance of integrated circuits and electronic modules.

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Zhang, Liqiang, Zhiyong Pan, Zhuang Zhuo i Yunzheng Wang. "Three Multiple-Pulse Operation States of an All-Normal-Dispersion Dissipative Soliton Fiber Laser". International Journal of Optics 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/169379.

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Multiple-pulse operation states of an all-normal-dispersion Yb-doped double-clad dissipative soliton fiber laser are investigated in this paper. The proposed laser can deliver harmonic mode-locked pulses, bound states of dissipative solitons, and dual-wavelength dual-pulses. Stable second-harmonic and third-harmonic mode-locked pulse trains are obtained with the output power of 1.39 W and 1.46 W, respectively, and the corresponding single pulse energies are 12.1 nJ and 8.5 nJ. With the adjustment of pump power and the wave plates, the fiber laser generates bound states of two or three dissipative solitons. Moreover, a dual-wavelength dual-pulse state is presented, where the output pulses from the nonlinear polarization rotation rejection port consists of the leading and trailing edges of the pulses circulating in the cavity.

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Xu, Nannan, Pengfei Ma, Shenggui Fu, Xinxin Shang, Shouzhen Jiang, Shuyun Wang, Dengwang Li i Huanian Zhang. "Tellurene-based saturable absorber to demonstrate large-energy dissipative soliton and noise-like pulse generations". Nanophotonics 9, nr 9 (12.02.2020): 2783–95. http://dx.doi.org/10.1515/nanoph-2019-0545.

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AbstractTwo-dimensional layered monoelemental materials (Xenes) with excellent optoelectronic properties have various property-related applications, such as energy, biomedicine, and optoelectronic devices. Xenes also show excellent performance in acting as saturable absorbers (SAs) for obtaining ultrafast laser operations. Few-layer tellurene as a typical Xenens exhibits distinct optoelectronic properties and promising practical application potential, and its nonlinear optical absorption characteristics and related ultrafast modulation applications have been investigated preliminarily. However, tellurene-based SAs to demonstrate large-energy mode-locked operations, which have special applications in industrial and scientific research areas, are seldom studied. In this work, we focus on the preparation of tellurene-based SAs and explore its applications in demonstrating large-energy mode-locked operations [dissipative soliton (DS) and noise-like pulses (NLP)]. For DS operation, the maximum average output power, pulse width, and largest pulse energy are 23.61 mW, 5.87 ps, and 1.94 nJ, respectively. NLP operation with a recorded average output power of 106.6 mW and a pulse energy of 8.76 nJ is also generated, which shows significant enhancement in comparison to previously reported Xenes-based works. Our contribution reveals the great potential and capacity of tellurene-based SAs in obtaining large-energy pulse operations and further promotes the explorative investigation of Xenes-based optoelectronic devices.

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Zhou, Yan, Keyun Zhang, Meisong Liao, Guoying Zhao i Yongzheng Fang. "Operating Vector Solitons with Chirped Sech Pulse Shapes". Photonics 9, nr 3 (28.02.2022): 143. http://dx.doi.org/10.3390/photonics9030143.

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In this paper, we report the theoretical results about operating vector solitons with chirped sech pulse shapes. In the operation, the shapes of temporal pulses and corresponding optical spectra in orthogonal directions will change, which are based on soliton parameters. When input orthogonal pulses have the same central wavelength of 1064 nm, the shift from the central wavelength always occurs for orthogonal pulses. When input orthogonal pulses have different central wavelengths of 1063 nm and 1065 nm, output pulse shapes and optical spectra with obvious multiple peak/dip structures can be achieved in orthogonal directions. Our theoretical results are meaningful for the study of vector soliton dynamics and have potential applications in optical communication and optical sensing.

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Łaszczych, Zbigniew, Mikołaj Krakowski i Grzegorz Soboń. "Mode-Locking Dynamics in an All-PM Figure-Nine Tm-Doped Fiber Laser". Applied Sciences 12, nr 20 (20.10.2022): 10613. http://dx.doi.org/10.3390/app122010613.

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We report a study on pulse dynamics in figure-nine Tm-doped all-polarization maintaining fiber laser. We analyzed laser operation from self-starting with multi-pulse dynamic to single-pulse operation by decreasing the pump power from the mode-locking threshold. By choosing a reliable setting of waveplates, our laser was generating pulses at the central wavelength of 1985 nm with a half-width of the spectrum, pulse duration, and pulse energy equal 6.4 nm, 650 fs, 177 pJ for the output port and 19.2 nm, 1279 fs, 57 pJ for the reject port in the single-pulse state. In the multi-pulse state, we recorded optical spectra, temporal waveforms, and average power at both exit ports. By analyzing temporal traces and output to reject port ratio power, we can distinguish between eight states of operation which follow an exact pattern. In the case of the single-pulse regime, we performed a further laser characterization, including relative intensity noise.

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Mohamed, M. M., T. Uchida i S. Minami. "A Pulse-Operated Microwave-Induced Plasma Source". Applied Spectroscopy 43, nr 1 (styczeń 1989): 129–34. http://dx.doi.org/10.1366/0003702894202058.

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A new pulse-operated microwave-induced plasma (MIP) source is described. To avoid operational difficulties of the MIP due to Joule heating and to obtain spectral emission lines of high peak intensities, one energizes the MIP source with a TM010 cavity with a microwave pulse of large peak power and short duration, which is superposed on a low-bias dc microwave. A peak power of 400 W, which is two times the maximum output ratings of a magnetron under a normal dc operation, can be generated by applying a −500 V pulse to the cathode of the magnetron operating under the bias mode. The pulsed-MIP requires no special cooling system since the mean power remains low during the entire operation. Some of the considerations taken into account in the design and construction of the microwave generator are presented. The electrical and spectral characteristics of the MIP source are also described in detail.

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Podstrigaev, Alexey S., i Alexander S. Lukiyanov. "The operating algorithm of the delay device processing time overlapped pulses in a matrix receiver". T-Comm 16, nr 3 (2022): 36–42. http://dx.doi.org/10.36724/2072-8735-2022-16-3-36-42.

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Matrix receiver from about the 1960s is used for wideband analysis of the signal environment (SE). Its use provides simultaneously a wide instantaneous analysis bandwidth, relatively high sensitivity, no signal gaps and the possibility of narrow-band processing of the output signal. However, there is a high probability of time-overlapping for pulses from pulse streams created by various radio emission sources in modern SE. When processing time-overlapped pulses in a classical matrix receiver, measurement ambiguities and abnormal errors occur. Therefore, multiple approaches are used to improve its efficiency in a complex SE. One such approach is based on installing a delay device to the wideband receiver's input. The principle of operation of the delay device consists of multiple signal transfers from the microwave range to the optical one and vice versa with the passage through fiber segments of various lengths. However, the operation algorithm of such a device has not been developed in detail. That's why our purpose is to substantiate and develop the algorithm for operating the delay device installed at the input of the matrix receiver to ensure the processing of time-overlapped pulses. In addition to the main algorithm for adapting the delay value to the pulse duration, we developed a nested algorithm for choosing a segment of the adjustable delay line. To store the pulse for the duration of processing by the receiver of previously received pulses, we developed a nested algorithm for executing the delay cycle. The use of the delay device operating following the proposed algorithm makes it possible to reduce the likelihood of measurement ambiguity and abnormal errors during the operation of the matrix receiver in the complex SE.

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Ichikawa, Tsubasa, Masamitsu Bando, Yasushi Kondo i Mikio Nakahara. "Geometric aspects of composite pulses". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, nr 1976 (13.10.2012): 4671–89. http://dx.doi.org/10.1098/rsta.2011.0358.

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Unitary operations acting on a quantum system must be robust against systematic errors in control parameters for reliable quantum computing. Composite pulse technique in nuclear magnetic resonance realizes such a robust operation by employing a sequence of possibly poor-quality pulses. In this study, we demonstrate that two kinds of composite pulses—one compensates for a pulse length error in a one-qubit system and the other compensates for a J -coupling error in a two-qubit system—have a vanishing dynamical phase and thereby can be seen as geometric quantum gates, which implement unitary gates by the holonomy associated with dynamics of cyclic vectors defined in the text.

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Pushkarev, A. I., Y. I. Isakova i I. P. Khaylov. "Stabilization of ion beam generation in a diode with self-magnetic insulation in double-pulse mode". Laser and Particle Beams 33, nr 2 (17.04.2015): 283–91. http://dx.doi.org/10.1017/s0263034615000385.

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AbstractThe paper presents the results of statistical studies of ion beam generation in different geometry diodes with explosive emission cathode in a mode of self-magnetic insulation. The experiments were carried out using the TEMP-4M pulsed ion beam accelerator during its operation in both unipolar pulse mode (100 ns, 250–300 kV) and bipolar-pulse mode with the first negative (300–600 ns, 100–150 kV) followed by a second positive (120 ns, 250–300 kV) pulse. It is found that the standard deviation of the total energy and energy density of the beam does not exceed 10–11%, while the same shot-to-shot variation in ion current density was found to be 20–30%. The mechanism of the energy density stabilization from pulse to pulse may be associated with the charge exchange between accelerated ions and stationary molecules and formation of accelerated neutrals. We observed a high correlation between the energy density (or total beam energy) and the duration of the first voltage pulse. We performed analysis of Blumlein statistical performance when the Blumlein was terminated with a resistive load and with a self-magnetically insulated ion diode. A characteristic feature of Blumlein operation in the double-pulse mode is an excellent reproducibility of breakdown of the preliminary spark gap, the variation in breakdown voltage is <2%. At the same time, the shot-to-shot variation in the breakdown voltage of the main spark gap in both bipolar- and unipolar pulse mode is 3–4 times higher than that for the preliminary spark gap. To improve the statistical performance of the main spark gap we used the first voltage pulse at the output of Blumlein to trigger the main spark gap. The new trigatron-type regime of the main spark gap operation showed a better reproducibility of the first pulse duration, with the time jitter not exceeding 10 ns in a set of 50 pulses.

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Mead, James B., i Andrew L. Pazmany. "Quadratic Phase Coding for High Duty Cycle Radar Operation". Journal of Atmospheric and Oceanic Technology 36, nr 6 (czerwiec 2019): 957–69. http://dx.doi.org/10.1175/jtech-d-18-0108.1.

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AbstractQuadratically varying phase codes applied from pulse to pulse can be used to impart a range-dependent frequency shift in the decoded signal of a pulsed radar. Radars employing such codes can operate at extremely high pulse repetition frequencies (PRFs) with overlaid signals from multiple echo trips separated in the spectral domain. When operating at high PRFs, the radar duty cycle can approach 50% in a single-antenna system. High duty cycle operation results in a substantial increase in average transmit power with a proportional increase in signal processing gain as compared to a conventional pulsed radar. The shortest quadratic phase code, or base code, has a length equal to the number of echo trips M that can be unambiguously resolved in the spectral domain. The decoded waveform is essentially free from range sidelobes under ideal conditions. However, amplitude and phase errors associated with nonideal phase coding result in range sidelobes that appear at all echo trips in the decoded signal. These sidelobes can be suppressed by using a composite phase code composed of a periodically repeating base phase code added to a much longer quadratic code with a proportionally slower phase variation. Meteorological data gathered with a Ka-band radar operating at 3.0-MHz PRF at 45% duty cycle are presented. A comparison of these data with data gathered in short-pulse mode at a duty cycle of 0.3% exhibited a 21-dB improvement in the Doppler spectrum signal-to-noise ratio, equal to the ratio of the respective duty cycles.

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Bagayev, S. N., V. A. Averchenko, I. A. Chekhonin, M. A. Chekhonin, I. M. Balmaev i I. B. Mekhov. "Coherent tunable diffractional pulse shaping and generation of the 0π-pulse in Rb vapor". Journal of Physics: Conference Series 2086, nr 1 (1.12.2021): 012133. http://dx.doi.org/10.1088/1742-6596/2086/1/012133.

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Abstract We have experimentally studied for the first time a new operation principle of the coherent diffractional pulse shaper (Rabi shaper). In the experiment, we observed an effect of tunable pulse shaping of nanosecond semiconductor laser pulse during the resonant pumping of the D2 line (780.24 nm) of 87Rb vapor in the range of self-diffraction angles φ = ± 4°. We observed the synthesis of nanosecond 0π-pulses at the small length of the nonlinear interaction 0.1…1 mm. We propose to use the Rabi shaper as an energy efficient tunable shaper of classical and single-photon wave packets. We analyze a possibility of the Rabi shaper operation in quantum systems with feedback.

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Gribacheva, V., i S. Shcherbakov. "THE COOLING SYSTEM OF THE PERIODIC PULSED REACTOR". PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. SERIES: NUCLEAR AND REACTOR CONSTANTS 2021, nr 2 (26.06.2021): 256–67. http://dx.doi.org/10.55176/2414-1038-2021-2-256-267.

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The paper proposes the configuration and composition equipment of the cooling system of the designed periodic pulsed reactor (PPR) of high power. The special features of the PPR are a small flow section, a large heating of the coolant in the power pulse and the impossibility of useful use of thermal energy in the periodic mode of operation. Liquid lithium is proposed as a coolant and heat is discharged through air heat exchangers (AHE). The goal was to achieve compactness and low power consumption, the ability to work with frequent stops and optimize the operation of equipment in pulse modes. For this purpose, high-temperature AHE with a small heat exchange surface and forced air cooling are used, the circulation circuit is divided into two parts - the reactor circuit and the AHE circuit with two circulation pumps and a common drain tank. The separation of the circuit allows to independently perform the operations of starting, stopping and heating the circuits in a periodic mode. The drain tank limits the composition of the equipment exposed to temperature pulses. Numerical studies of the temperature regime of the coolant in the equipment of the PDR cooling system are carried out. The calculations were performed using the TURBOFLOW code in two-dimensional terms for all the main elements of the equipment. Quasi-stationary (nominal and partial power levels) and pulse modes of operation are considered. Calculated characteristics for forced and natural air circulation are obtained. The limits of the air circulation modes under the conditions of non-freezing of the coolant are determined. The obtained values of the maximum temperatures of the coolant: in the pulsed mode is 750 °C, in the quasi-stationary mode - 490 °C with an average power of 15 MW, air flow of 150 m3/s and the size of the AHE in the plan of 5×5 m, 100 panels of 1.08×0.025×5 m.

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Wen, Song, Qiu-Xia Xiao, Zhao-Qiong Zhu, Li Chen, Ying Li, Qi-Hua Ran, Song Cao i Liu-Lin Xiong. "Application of Nalbuphine in Trigeminal Ganglion Pulse Radiofrequency Surgery in Patients with Postherpetic Neuralgia". Pain Research and Management 2021 (1.03.2021): 1–9. http://dx.doi.org/10.1155/2021/6623112.

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This study aimed to explore the application value of nalbuphine in pulsed radiofrequency operation of trigeminal ganglion in patients with postherpetic neuralgia (PHN). Thirty patients with PHN were randomly divided into the nalbuphine (Nalbu) group and ketorolac tromethamine (KT) group and received CT-guided pulsed radiofrequency surgery on trigeminal ganglion. The numeric rating scale (NRS) scores of patients were recorded at preoperative, intraoperative, and postoperative time points, before going to bed, and the next morning after the operation. In addition, the number of breakthrough pain before operation and within 24 hours after operation, the incidence of nausea and vomiting within 24 hours after surgery, and the patient’s sleep quality before and on the day after surgery were evaluated. The outcome data demonstrated that patients treated with nalbuphine had lower NRS scores after the pulse radiofrequency operation during and after the pulse radiofrequency operation compared to those with KT. In addition, nalbuphine effectively decreased the number of breakthrough pain, reduced the occurrence of nausea and vomiting after surgery, and improved the sleep quality. In conclusion, intramuscular injection of nalbuphine 30 min before trigeminal ganglion pulse radiofrequency surgery can be conducive to pain relief and improve the postoperative comfort of patients, providing an effective alternative for the alleviation of PHN in clinic.

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Bostanjoglo, O., F. Heinricht i F. Wünsch. "Performance of A Laser-Pulsed Thermal Electron Gun". Proceedings, annual meeting, Electron Microscopy Society of America 48, nr 1 (12.08.1990): 124–25. http://dx.doi.org/10.1017/s0424820100179373.

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High-speed electron microscopy strongly demands a high-brightness electron gun in order to increase the number of image forming electrons. A few years ago, a laser-pulsed high-brightness electron gun was introduced. Fig.1 shows the experimental set-up, A standard triode system was supplemented with a Nd:YAG laser, focussing optics and a modified anode, which incorporates the laser deflection mirror. The frequency doubled laser pulse (τ =5 ns, λ = 532 nm) is focused through a window onto the tip of the tungsten hairpin emitter. The laser treated area (≈ 100 μm diameter) is heated well above the melting point, which results in a strong thermal electron emission. Due to rapid heat-up and fast cool-down of the tungsten surface short electron pulses with a duration of 20 ns and a maximum current of 20 mA at 80 kV are emitted. A destruction of the tungsten wire is avoided, too. Laser energies used for the generation of electron pulses are in the range of 100 μJ. Due to these minor modification, the DC operation of the electron gun is not disabled, which allows a convenient adjustment in the DC mode and then switching into the pulsed operation mode. Fig.2 shows a typical electron pulse emitted by the gun. Shorter electron pulses up to 5 ns can be generated by a beam blanking unit.

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Ivanov, Pavel A., Oleg Kon'kov, Tatyana Samsonova, Alexander Potapov i Igor Grekhov. "Electrical Performance of 4H-SiC Based Drift Step Recovery Diodes". Materials Science Forum 858 (maj 2016): 761–64. http://dx.doi.org/10.4028/www.scientific.net/msf.858.761.

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Mesa-epitaxial 4H-SiC p+-p-no-n+-diodes were fabricated from commercial epitaxial wafers. Reverse recovery characteristics of the diodes were measured in pulse regimes to be relevant to operation of drift step recovery diodes (DSRDs) [1]. When injecting the minority carriers by forward current pulse followed by applying a reverse voltage pulse, the diodes are able to break the reverse current in a subnanosecond time (DSRD-mode). Different regimes of diode operation in DSRD-mode are investigated such as variable reverse voltage amplitude, forward current amplitude and duration, time delay between forward and reverse pulses.

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Lyu, Wenhao, Yuan Cheng, Jiayi An, Marcello Condorelli, Mario Pulvirenti, Giuseppe Compagnini, Xiaogang Wang, Bo Fu i Vittorio Scardaci. "Silver Nanoplate Composites as Nonlinear Saturable Absorbers for a Q-Switched Laser". Photonics 9, nr 11 (7.11.2022): 835. http://dx.doi.org/10.3390/photonics9110835.

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Metal nanomaterials have promising applications in ultrafast photonics due to their broadband operation, large third-order nonlinear susceptibility, and ultrafast recovery time. We realized a Q-switched pulsed erbium-doped fiber laser based on a silver nanoplate polyvinyl alcohol film as a saturable absorber. This film, with a modulation depth of 15.7%, was integrated into a fiber laser by means of a sandwich structure. We obtained Q-switched pulses in the 1.5-μm band, which plays an important role in telecommunications and atmospheric detection. Stable Q-switched pulses were obtained at the pump power of 135 mW, with a single pulse energy of 33.8 nJ, a pulse width of 2.3 μs, a repetition rate of 62.4 kHz, and a signal-to-noise ratio of about 45 dB. When increasing the pump power up to a maximum value of 246 mW, the maximum single pulse energy of 57.8 nJ was achieved. This study first demonstrates the potential of silver nanoplates as saturable absorbers in generating stable laser pulses with high energy.

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Anik Kumar, Mondol, Andrea Padovani, Luca Larcher, S. M. Raiyan Chowdhury i Md Zunaid Baten. "Pulse optimization and device engineering of 3D charge-trap flash for synaptic operation". Journal of Applied Physics 132, nr 11 (21.09.2022): 114501. http://dx.doi.org/10.1063/5.0100173.

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We investigate 3D charge-trap (CT) nand flash cells using device-physics based multi-scale simulations to explore their potential and optimum operating conditions as electronic synapses of the neuromorphic hardware. A set of figure of merits (FOMs) has been adopted to indicate their goodness of operation under incremental pulse inputs. The results of this study suggest that excellent synaptic FOMs can be attained from 3D CT nands by designing and calibrating the input pulse trains. The impact of variations of device dimensions on charge capture and release phenomena have been investigated and linked to output characteristics in order to obtain intuitive guidelines for attaining desired synaptic functionalities. By co-designing gate dielectric stack and input pulses, the threshold voltage (VT) of the 3D CT cell can be sequentially increased and decreased in a linear and symmetric fashion, providing a large number of distinct VT levels with good retention characteristics. Statistical simulations suggest that device-to-device variations of electrical responses have a negligible impact on the synaptic capabilities of these devices. It has also been shown that the incorporation of deeper traps through material engineering improves synaptic reliability of the 3D CT cells under prolonged operations.

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Kazakov, Andrey V., Efim M. Oks i Nikolay A. Panchenko. "Operating regimes of a constricted arc discharge in a forevacuum-pressure, plasma-cathode electron source of pulsed large-radius electron beams". Physics of Plasmas 29, nr 10 (październik 2022): 103108. http://dx.doi.org/10.1063/5.0102810.

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We have investigated the operating regimes of a pulsed constricted arc discharge in a forevacuum plasma-cathode electron source of large-radius electron beams. The configuration of the intermediate electrode (IE) with a constricting channel (CC) determines the maximum parameters (current and pulse duration) and operating regimes of the constricted arc. An IE with ceramic (aluminum nitride) CC and an IE with sectional tantalum CC, formed by several electrically insulated tantalum disks with co-axial holes, lead to an increase in the maximum parameters compared to an IE with metal CC. In particular, an IE with sectional tantalum CC provides the highest maximum parameters. The ceramic and sectional tantalum constricting channels also provide lower minimum pressure for which the constricted arc operates stably. When the pressure reaches a certain threshold value, which depends on arc current, a discharge system with IE with sectional tantalum CC provides stable operation for pulse duration up to 10 ms. An increase in pressure provides higher discharge current in the millisecond regime of the discharge operation. When the arc current reaches threshold values from 84 to 92 A (depending on gas pressure), a self-compressed (pinched) mode of operation of the constricted arc occurs. The pinched arc regime is characterized by the highest current and the longest pulse duration. The forevacuum electron source based on the constricted arc discharge with IE with sectional tantalum CC offers generation of low-energy (up to 8 keV) electron beam with current up to tens of amperes and pulse duration up to 10 ms.

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24

Toci, Guido, Zeudi Mazzotta, Luca Labate, François Mathieu, Matteo Vannini, Barbara Patrizi i Leonida A. Gizzi. "Conceptual Design of a Laser Driver for a Plasma Accelerator User Facility". Instruments 3, nr 3 (8.08.2019): 40. http://dx.doi.org/10.3390/instruments3030040.

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The purpose of the European project EuPRAXIA is to realize a novel plasma accelerator user facility. The laser driven approach sets requirements for a very high performance level for the laser system: pulse peak power in the petawatt range, pulse repetition rate of several tens of Hz, very high beam quality and overall stability of the system parameters, along with 24/7 operation availability for experiments. Only a few years ago these performances were considered unrealistic, but recent advances in laser technologies, in particular in the chirped pulse amplification (CPA) of ultrashort pulses and in high energy, high repetition rate pump lasers have changed this scenario. This paper discusses the conceptual design and the overall architecture of a laser system operating as the driver of a plasma acceleration facility for different applications. The laser consists of a multi-stage amplification chain based CPA Ti:Sapphire, using frequency doubled, diode laser pumped Nd or Yb solid state lasers as pump sources. Specific aspects related to the cooling strategy of the main amplifiers, the operation of pulse compressors at high average power, and the beam pointing diagnostics are addressed in detail.

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25

Cauffman, Stephen, Monica Blank, Philipp Borchard i Kevin Felch. "Adaptation of a Dual-Frequency 104/140 GHz Gyrotron for Operation at 175 GHz". EPJ Web of Conferences 203 (2019): 04004. http://dx.doi.org/10.1051/epjconf/201920304004.

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A dual-frequency gyrotron capable of operation in the TE28,7 cavity interaction mode at 140 GHz, or in the TE22,5 mode at 104 GHz, has been developed for use in electron cyclotron heating in the W7-X stellarator at IPP Greifswald. The gyrotron incorporates an internal converter design that has been numerically optimized to convert either of the two operating modes into a high-quality Gaussian output beam. During short-pulse factory testing, the gyrotron produced 900 kW at 140 GHz, and 520 kW at 104 GHz. After delivery to IPP, the gyrotron was conditioned to long-pulse operation at 140 GHz, demonstrating 30-minute pulses at several power levels up to 811 kW, and producing ten consecutive ten-minute pulses at 811 kW as well. After long-pulse capabilities were demonstrated at 140 GHz, IPP requested an analysis of the feasibility of operating the gyrotron (without internal modification) in an additional mode with a frequency near 175 GHz. Several potential interaction modes were evaluated to determine the required operating parameters for excitation of these modes, and to assess the expected interaction efficiency, output power, internal diffraction losses, and output beam quality. The most promising modes appear to be the TE33,9 (173 GHz) and the TE34,9 (176 GHz), which should generate 400-500 kW of RF in a suitable magnet capable of producing the necessary 7.1 T field required for operation at these higher frequencies. Because the existing gyrotron’s internal converter was not optimized for these modes, however, internal losses are expected to be higher than usual (up to 7%), and the output beam pattern will require external phase-correction in order to produce a Gaussian beam. A feasibility analysis for such external phase correction has been performed, demonstrating that a high-quality beam can be recovered using numerically synthesized external phase-correcting mirror surfaces.

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26

Isakova, Yulia I., Galina E. Kholodnaya i Alexander I. Pushkarev. "Influence of Cathode Diameter on the Operation of a Planar Diode with an Explosive Emission Cathode". Advances in High Energy Physics 2011 (2011): 1–14. http://dx.doi.org/10.1155/2011/649828.

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This paper presents the results of experimental investigations into the current-voltage characteristics of a planar diode with an explosive emission cathode made from graphite. Studies were performed using a TEU-500 pulsed electron accelerator (350–500 keV, 100 ns, 250 J per pulse). Duration of diode operation, in a mode when electron current is limited by the emissive ability of the graphite cathode, is 15–20 ns. The contribution of the cathode periphery to total electron current appears only as an increase in the emissive surface area due to an expansion of explosive plasma. Investigations of an ion diode with a graphite cathode (plane and focusing geometry) were also carried out. Experiments were performed using a TEMP-4M ion accelerator, which forms two nanosecond pulses: the first negative pulse (150–200 kV, 300–600 ns) followed by the second positive (250–300 kV, 150 ns). Total diode current in the first pulse is well described by the Child-Langmuir law for electron current at a constant rate of plasma expansion, equal to 1.3 cm/μs. It is shown that for an area of flat cathode over 25 cm2, the influence of edge contribution does not exceed measurement error of total diode electron current (10%).

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27

Sun, Yanwen, Franz-Josef Decker, James Turner, Sanghoon Song, Aymeric Robert i Diling Zhu. "Pulse intensity characterization of the LCLS nanosecond double-bunch mode of operation". Journal of Synchrotron Radiation 25, nr 3 (27.03.2018): 642–49. http://dx.doi.org/10.1107/s160057751800348x.

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The recent demonstration of the `nanosecond double-bunch' operation mode,i.e.two X-ray pulses separated in time between 0.35 and hundreds of nanoseconds and by increments of 0.35 ns, offers new opportunities to investigate ultrafast dynamics in diverse systems of interest. However, in order to reach its full potential, this mode of operation requires the precise characterization of the intensity of each X-ray pulse within each pulse pair for any time separation. Here, a transmissive single-shot diagnostic that achieves this goal for time separations larger than 0.7 ns with a precision better than 5% is presented. It also provides real-time monitoring feedback to help tune the accelerator parameters to deliver double pulse intensity distributions optimized for specific experimental goals.

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Hari Krishna Prasad, P., i L. Anjaneyulu. "Time Domain Auto Pulse Shaping Operation". IETE Journal of Education 59, nr 2 (3.07.2018): 62–69. http://dx.doi.org/10.1080/09747338.2018.1517616.

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Safranek, J., J. Corbett, X. Huang, T. Rabedeau, J. Schmerge i J. Sebek. "SPEAR3 Short-Pulse, Low-α Operation". Synchrotron Radiation News 26, nr 3 (maj 2013): 19–21. http://dx.doi.org/10.1080/08940886.2013.791211.

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Zecca, A. "Positron Microscopy: Pulse Microbeam in Operation". Europhysics News 26, nr 1 (1995): 10. http://dx.doi.org/10.1051/epn/19952601010.

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Kurlapova, K. V., i Sh S. Zeynalov. "EQUIPMENT FOR THE STUDY OF DIVISION PROCESSES". Bulletin of Dubna International University for Nature, Society, and Man. Series: Natural and engineering sciences, nr 4 (45) (30.12.2019): 11–16. http://dx.doi.org/10.37005/1818-0744-2019-4-11-16.

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This article is devoted to the study of the principles of operation of a pulsed ionization chamber, in which particles emitted from a target create a sequence of well-isolated current pulses (the distance between pulses is several times greater than their width). Firstly, using the Ramo-Shockley theorem, the mechanisms of forming signals on the electrodes of an ionization chamber with Frisch nets are considered, then it is shown how information on energy and spatial orientation of particles can be extracted from such signals using modern electronic pulse digitizers.

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32

Illy, Stefan, Konstantinos A. Avramidis, Gerd Gantenbein, Zisis Ioannidis, Jianbo Jin, Parth C. Kalaria, Ioannis Gr Pagonakis i in. "Recent Status and Future Prospects of Coaxial-Cavity Gyrotron Development at KIT". EPJ Web of Conferences 203 (2019): 04005. http://dx.doi.org/10.1051/epjconf/201920304005.

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Coaxial-cavity gyrotrons are microwave sources that can extend the possible power levels of hollow cavity gyrotrons significantly and make them attractive for future fusion experiments and power plants. KIT already demonstrated operation of a modular short-pulse 170 GHz coaxial-cavity gyrotron with an output power of 2.2 MW, operating in the TE34,19 mode. Today’s focus of KIT is the verification of this technology at longer pulses, which will prove the long-pulse capabilities also. At the moment, the current KIT prototype has been extended with cooling capabilities for all critical, highly loaded components of the tube and two new, different electron guns are available for operation. This paper will give an overview about the recent status and the future prospects connected to the coaxial-cavity gyrotron development at KIT, including both experimental and theoretical activities.

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33

Sojka, Lukasz, Lukasz Pajewski, Samir Lamrini, Mark Farries, Trevor M. Benson, Angela B. Seddon i Slawomir Sujecki. "Experimental Investigation of Actively Q-Switched Er3+:ZBLAN Fiber Laser Operating at around 2.8 µm". Sensors 20, nr 16 (18.08.2020): 4642. http://dx.doi.org/10.3390/s20164642.

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A diode-pumped Q-switched Er3+:ZBLAN double-clad, single-transverse mode fiber laser is practically realized. The Q-switched laser characteristics as a function of pump power, repetition rate, and fiber length are experimentally investigated. The results obtained show that the Q-switched operation with 46 µJ pulse energy, 56 ns long pulses, and 0.821 kW peak power is achieved at a pulse repetition rate of 10 kHz. To the best of our knowledge, this is the highest-ever demonstrated peak power emitted from an actively Q-switched, single-transverse mode Er3+:ZBLAN fiber laser operating near 2.8 µm.

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34

YATSUI, KIYOSHI, KOUICHI SHIMIYA, KATSUMI MASUGATA, MASAO SHIGETA i KAZUHIKO SHIBATA. "Characteristics of pulsed power generator by versatile inductive voltage adder". Laser and Particle Beams 23, nr 4 (październik 2005): 573–81. http://dx.doi.org/10.1017/s0263034605050779.

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A pulsed power generator by inductive voltage adder, versatile inductive voltage adder (VIVA-I), which features a high average potential gradient (2.5 MV/m), was designed and is currently in operation,. It was designed to produce an output pulse of 4 MV/60 ns by adding 2 MV pulses in two-stages of induction cells, where amorphous cores are installed. As a pulse forming line, we used a Blumlein line with the switching reversed, where cores are automatically biased due to the presence of prepulse. Good reproducibility was obtained even in the absence of the reset pulse. Within ∼40% of full charge voltage, pulsed power characteristics of Marx generator, pulse forming line (PFL), transmission line (TL), and induction cells were tested for three types of loads; open-circuit, dummy load of liquid (CuSO4) resistor, and electron beam diode. In the open-circuit test, ∼2.0 MV of output voltage was obtained with good reproducibility. Dependences of output voltage on diode impedances were evaluated by using various dummy loads, and the results were found as expected. An electron-beam diode was operated successfully, and ∼18 kA of beam current was obtained at the diode voltage of ∼1 MV.

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35

Modest, M. F. "Transient Model for CW and Pulsed Laser Machining of Ablating/Decomposing Materials—Approximate Analysis". Journal of Heat Transfer 118, nr 3 (1.08.1996): 774–80. http://dx.doi.org/10.1115/1.2822698.

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Approximate, quasi-one-dimensional conduction models have been developed to predict the changing shape of holes, single grooves, or overlapping grooves carved by ablation into a thick solid that is irradiated by a moving laser source. For CW or pulsed laser operation a simple integral method is presented, which predicts shapes and removal rates with an accuracy of a few percent, while requiring one order of magnitude less CPU time than a three-dimensional, numerical solution. For pulsed operation a “full-pulse” model is presented, computing the erosion from an entire pulse in a single step, and reducing computer time by another order of magnitude.

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36

Petkovšek, Rok, Vid Agrež, Jaka Petelin, Luka Černe, Udo Bünting i Boštjan Podobnik. "Pulses on Demand in Fibre and Hybrid Lasers". Strojniški vestnik – Journal of Mechanical Engineering 65, nr 11-12 (18.11.2019): 680–89. http://dx.doi.org/10.5545/sv-jme.2019.6352.

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This paper presents an investigation of pulse-on-demand operation in fibre and hybrid lasers. Two methods for efficient gain control that enable the generation of laser pulses at arbitrary times with controlled pulse parameters are presented. The method of direct modulation of the pump power in the high-power laser oscillator is shown to generate pulses with a duration in the nanosecond range, with repetition rates varying during operation from a single shot to over 1 MHz. An advanced method using a combination of marker and idler seeding a fibre amplifier chain is investigated. Such a system can easily achieve repetition rates of several tens of MHz. The lasers’ performances were successfully tested in a real environment on an industrial platform for laser transfer printing. Similar concepts were used for a laser source with ultrashort laser pulses (femtosecond range) on demand by using a mode-locked seed as a source and a solid-state amplifier to achieve high pulse energy and peak power.

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37

Hai, Le Hoang, Nguyen Dai Hung, Hoang Huu Hoa, Alex V. V. Quema i Nobuhiko Sarukura. "DURATION LIMIT OF LASER PULSES EMITTED FROM A Ce-DOPED CRYSTAL SHORT CAVITY". ASEAN Journal on Science and Technology for Development 24, nr 1&2 (15.11.2017): 177–83. http://dx.doi.org/10.29037/ajstd.205.

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Based on the rate equation set for broadband cavities, the dependence of pulse duration on cavity and pumping parameters is analyzed. The cavity uses a Ce-doped crystal as a gain medium. Computation results show the variation of the pulse width with the change of cavity length, mirror reflectivity, pumping energy and pumping pulse duration. A significant influence of multiple-pulse operation in limiting pulse duration is realized and a pulse-width of the order 200 ps is found to be the limit for the direct generation of ultraviolet single picosecond pulses from a Ce:LLF short cavity.

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38

de Orio, Roberto L., Johannes Ender, Simone Fiorentini, Wolfgang Goes, Siegfried Selberherr i Viktor Sverdlov. "Optimization of a Spin-Orbit Torque Switching Scheme Based on Micromagnetic Simulations and Reinforcement Learning". Micromachines 12, nr 4 (15.04.2021): 443. http://dx.doi.org/10.3390/mi12040443.

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Spin-orbit torque memory is a suitable candidate for next generation nonvolatile magnetoresistive random access memory. It combines high-speed operation with excellent endurance, being particularly promising for application in caches. In this work, a two-current pulse magnetic field-free spin-orbit torque switching scheme is combined with reinforcement learning in order to determine current pulse parameters leading to the fastest magnetization switching for the scheme. Based on micromagnetic simulations, it is shown that the switching probability strongly depends on the configuration of the current pulses for cell operation with sub-nanosecond timing. We demonstrate that the implemented reinforcement learning setup is able to determine an optimal pulse configuration to achieve a switching time in the order of 150 ps, which is 50% shorter than the time obtained with non-optimized pulse parameters. Reinforcement learning is a promising tool to automate and further optimize the switching characteristics of the two-pulse scheme. An analysis of the impact of material parameter variations has shown that deterministic switching can be ensured for all cells within the variation space, provided that the current densities of the applied pulses are properly adjusted.

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Abdollahi, Rohollah. "Pulse doubling in zigzag–connected autotransformer–based 12–pulse ac–dc converter for power quality improvement". Journal of Electrical Engineering 63, nr 6 (1.12.2012): 357–64. http://dx.doi.org/10.2478/v10187-012-0053-3.

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This paper presents a pulse doubling technique in a 12-pulse ac-dc converter which supplies direct torque controlled motor drives (DTCIMDs) in order to have better power quality conditions at the point of common coupling. The proposed technique increases the number of rectification pulses without significant changes in the installations and yields in harmonic reduction in both ac and dc sides. The 12-pulse rectified output voltage is accomplished via two paralleled six-pulse acdc converters each of them consisting of three-phase diode bridge rectifiers. An autotransformer is designed to supply the rectifiers. The design procedure of magnetics is in a way such that makes it suitable for retrofit applications where a six-pulse diode bridge rectifier is being utilized. Independent operation of paralleled diode-bridge rectifiers, i.e. dc-ripple re-injection methodology, requires a Zero Sequence Blocking Transformer (ZSBT). Finally, a tapped interphase reactor is connected at the output of ZSBT to double the pulse numbers of output voltage up to 24 pulses. The aforementioned structure improves power quality criteria at ac mains and makes them consistent with the IEEE-519 standard requirements for varying loads. Furthermore, near unity power factor is obtained for a wide range of DTCIMD operation. A comparison is made between 6-pulse, 12-pulse, and proposed converters from view point of power quality indices. Results show that input current total harmonic distortion (THD) is less than 5% for the proposed topology at various loads.

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40

Shcherbina, A. O., O. O. Lukovenkova i A. A. Solodchuk. "Adaptive Threshold Scheme for Pulse Detection under Condition of Background Nonstationary Noise". Journal of Physics: Conference Series 2096, nr 1 (1.11.2021): 012019. http://dx.doi.org/10.1088/1742-6596/2096/1/012019.

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Abstract The paper describes a new adaptive threshold scheme for detecting pulses in high-frequency signals against a background of non-stationary noise. The result of the scheme operation is to determine the pulse boundaries by comparing the signal amplitude-time parameters with the threshold. The threshold value is calculated in non-overlapping windows of fixed length and depends only on the background noise level. The detected pulses undergo additional shape checking, taking into account their characteristics. The parameters of the algorithms for detecting pulses and checking their shape can be adjusted for any type of high-frequency pulse signals. This threshold scheme is tuned to detect pulses in high frequency geoacoustic emission signals. The results of the scheme operation on an artificial signal and on fragments of a geoacoustic signal are given, a comparison is made between the proposed scheme and the previously used (outdated) one. The new threshold scheme proposed by the authors is less sensitive to the choice of the initial threshold value and it is more stable in operation. When processing 15-minute fragments of a geoacoustic signal, the new scheme correctly detects, on average, 5 times more pulses.

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41

Tarvainen, Olli, Dan Faircloth i Scott Lawrie. "Caesium balance of the ISIS H^- Penning ion source in long pulse operation". Journal of Instrumentation 18, nr 05 (1.05.2023): C05023. http://dx.doi.org/10.1088/1748-0221/18/05/c05023.

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Abstract We have developed a semi-empirical model predicting the equilibrium caesium coverage (in monolayers) and the resulting work function of the ISIS Penning ion source cathode (in eV) in long pulse operation. We use the caesium balance model to predict the temporal structure of the extracted H- beam current pulses and compare the model predictions to experimental data with 60 mA, 2 ms beam pulses at 50 Hz. The experimentally observed droop of the beam current is reproduced by the model. The results imply that extracting square beam pulses in the long pulse operation mode requires more efficient cathode cooling. We apply the model for 70 mA, 3 ms beam pulses at 14 Hz, relevant for ESSνSB project. We conclude that achieving these parameters requires reducing the cathode temperature by 200 °C, and ramping the discharge current to cancel the discharge voltage droop.

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42

Idehara, T., T. Saito, H. Mori, H. Tsuchiya, La Agusu i S. Mitsudo. "Long Pulse Operation of the THz Gyrotron with a Pulse Magnet". International Journal of Infrared and Millimeter Waves 29, nr 2 (29.11.2007): 131–41. http://dx.doi.org/10.1007/s10762-007-9312-y.

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Ueda, Ken-Ichi, Hajime Nishioka, Kazuhiko Kimura i Hiroshi Takuma. "Advanced techniques of high-efficiency pulse compression for KrF lasers". Laser and Particle Beams 11, nr 1 (marzec 1993): 31–42. http://dx.doi.org/10.1017/s0263034600006893.

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A couple of advanced techniques of high-efficiency pulse compression for KrF lasers have been developed in our laboratory. As is well known, electron beam-excited KrF lasers have a capability of large output energy of 100- to 1,000-ns pulse duration. However, high-efficiency operation under a short-pulse input is difficult to achieve because of the reaction kinetics and short lifetime of KrF excimers. For developing ultrahigh peak-power lasers, the efficient pulse compression of ns to ps and ps to fs pulses is essential. We demonstrated advanced techniques, Raman pulse compression in a transient Raman regime, and pulse compression in saturated amplifiers with saturable absorbers.

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44

Glotov, A. N., Yu V. Golubenko, V. A. Desyatskov i A. V. Stepanov. "Certain Features of Interaction Between Laser Radiation and Metals". Herald of the Bauman Moscow State Technical University. Series Instrument Engineering, nr 1 (130) (luty 2020): 15–32. http://dx.doi.org/10.18698/0236-3933-2020-1-15-32.

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The paper presents experimental investigation results concerning the problem of optimising the efficiency of interaction between laser radiation and metals. We used several types of Nd lasers featuring the desired combination of power, temporal and spatial radiation parameters as sources of the radiation required. To pump these lasers, we employed rectangular pulses at a periodicity eliminating effects characteristic of continuous-wave and pulsed laser operation modes. This limits the laser radiation parameters driving the interaction efficiency functions to strictly those parameters that match the single-pulse laser operation mode. Temporal radiation parameter variation involved measurements in the free-running and high-frequency Q-switching modes as well as adjusting pumping (lasing) pulse durations. Power parameter variation was implemented through altering radiation energy density over the irradiated surface. Spatial structure of the ablative radiation was varied by means of optical radiation transfer facilities and different laser emitters. The experimental investigation results allowed us to establish certain patterns concerning the interaction between laser radiation and metals as a function of radiation parameters listed

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45

Bedrin, Alexander G., Alexander P. Guryev, Valentin M. Gromovenko i Galina A. Sokolova. "Forcing Power Supply of a Xenon Flash Lamp to Create a High Power Irradiation Facility". Light & Engineering, nr 04-2022 (sierpień 2022): 56–62. http://dx.doi.org/10.33383/2021-118.

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The article describes the technical characteristics of the software-controlled power supply system for generation of second-long light pulses by means of INP‑16/580 xenon flash lamps. The amplitude-time characteristics of luminous emission in a quasi-arc mode of lamp operation are formed by computer control of temporal current pulse shape in case of large energy deposition overloads. Methods of optimisation of light and engineering characteristics were defined accounting for non-linearity of the load of the thyristor unit and ambiguity of the dependence of luminous radiation on discharge current. The data on maximum acceptable operation parameters of pulse lamps with mains supply and natural air cooling and the results of physical modelling of radiation pulses with complex shape are presented.

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46

Stark, Henning, Christian Grebing, Joachim Buldt, Arno Klenke i Jens Limpert. "Divided-pulse nonlinear compression in a multipass cell". Journal of Physics: Photonics 4, nr 3 (25.05.2022): 035001. http://dx.doi.org/10.1088/2515-7647/ac66ab.

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Abstract The pulse-energy and peak-power limitations of a gas-filled multipass cell (MPC) for nonlinear pulse compression are surpassed by applying a burst of four temporally separated pulses instead of a single one. The burst is generated by two birefringent crystals and contains 1 m J of energy per pulse replica. It is then spectrally broadened in an Argon-filled MPC and recombined into a single pulse by a second set of birefringent crystals. The combined pulse is compressed by chirped mirrors to a pulse duration of 32 f s and a pulse energy of 3.4 m J . An excellent passive stability and a high system efficiency of > 90% are reached. Using the 4-pulse burst, the overall output energy supported by the MPC is doubled in comparison to single-pulse operation.

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Калашникова, Наталия, Nataliya Kalashnikova, Елена Грядунова, Elena Gryadunova, Анжелика Журавлева, Anzhelika Zhuravleva, Мария Горина, Mariya Gorina, Андрей Горин i Andrey Gorin. "LUBRICANT TEMPERATURE INFLUENCE UPON PULSE HYDROPNEUMATIC DRIVE OPERATION". Bulletin of Bryansk state technical university 2016, nr 3 (30.09.2016): 76–82. http://dx.doi.org/10.12737/22013.

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A pulse hydropneumatic drive can make a percussive effect up to 15,000 J. A head carrying out a pulse effect (a blow) on an object is cocked in an operation position by liquid. At the same time occurs a compression of a working body (gas) in a gas accumulator. The pulse influence occurs because of head acceleration at the expense of a working body in a pneumatic accumulator. The operation of a pulse hydropneumatic drive depends on a number of parameters: viscosity and temperature of operating fluid, pressure of pneumatic accumulator initial charge and others. In the course of work oil becomes warm because of a high rate of travel in control equipment of a pulse drive in hydromains that results in changes in blow energy. A simulator describing stages and acceleration of the head of a pulse hydro-pneumatic drive. As a result of a numerical experiment carried out in the en-vironments of Mathcad and Matlab there are obtained dependences of blow energy upon working liquid tem-perature. To investigate the influence of different parameters of a pulse hydro-pneumatic drive upon its operation was designed and carried out a test bench which allows changing different parameters of a drive in a wide range. The experimental dependences of blow energy upon temperature of a working body and the dependences of blow energy upon working liquid viscosity are obtained. A comparative analysis of theoretical and experimental results which has given good convergence is carried out. The conclusions obtained: the operation of a pulse hydro-pneumatic drive is effected greatly both by the viscosity of a working body, and its temperature; the best values of head energy correspond to the mean viscosity of working liquid; to obtain a constant of blow energy it is necessary to use working liquids with stable viscosity at high tempera-tures: it is expedient that different additives should be used in working liquid to reduce a constant of friction and wear-resistance increase.

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Mohamad Rashid, Nur Nadhirah, Harith Ahmad, Mohammad Faizal Ismail, Muhammad Quisar Lokman, Siti Nur Fatin Zuikafly, Hafizal Yahaya, Nur Azmah Nordin, Wan Mohd Fazli Wan Nawawi i Fauzan Ahmad. "Nanotubes in Chitin Mode Locker for Passive Mode−Locked Fibre Laser in 2.0 µm Region". Photonics 10, nr 3 (28.02.2023): 257. http://dx.doi.org/10.3390/photonics10030257.

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This research demonstrated an ultrafast passively mode-locked thulium-holmium doped fibre laser (THDFL) using a carbon nanotube (CNT)-chitin composite film as a saturable absorber (SA). The CNTs were fabricated using ultrasonic-assisted liquid-phase exfoliation, and the chitin biopolymer was derived from oyster mushrooms (Pleurotus Ostreatus). The free-standing SA successfully performed a mode-locking operation at a threshold input pump power of 203 mW with an operating wavelength of 1908.53 nm. The generated mode-locked pulses had repetition rate, pulse width, and signal-to-noise ratio (SNR) values of 16 MHz, 1.1 ps, and 69 dB, respectively. The work demonstrates the potential of CNTs embedded in chitin biopolymer as a sustainable and environmentally friendly SA for a wide range of applications, particularly for pulsed lasers.

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Куропаткин, Ю. П., В. И. Нижегородцев, И. Н. Романов, К. В. Савченко, В. Д. Селемир, Е. В. Урлин, В. А. Фомичёв, А. А. Чинин i О. А. Шамро. "Мобильный ускоритель на базе безжелезного импульсного бетатрона для радиографирования динамических объектов". Журнал технической физики 92, nr 2 (2022): 297. http://dx.doi.org/10.21883/jtf.2022.02.52021.196-21.

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The paper concerns the mobile accelerator based on the ironless pulsed betaron. The accelerator is aimed to radiograph dynamic objects with a large optical thickness. It has a possibility to obtain up to three γ-pulses in one cycle of the acceleration. The accelerator operation description and results of its testing powering in a single-pulse mode are provided. The estimated boundary energy of an electron beam is equal to 60 MeV at the capacitance value of 1.8 mF of the storage of the betatron electromagnet pulsed power system. The thickness of the lead test object examined with γ-rays is 140 mm at 4 m from the tantalum target. The full width of the output γ-pulse at half maximum is equal to 120 ns. The dimension of the radiation source is 3×6 mm. The application of these accelerators within the radiographic complex will allow increasing the investigation efficiency due to the optimization of the hydrodynamic experiments geometry and the cost reduction.

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Ahn, Seung Joon, Chul Geun Park, J. S. Lim, K. H. Baik, Dae Wook Kim, Ho Seob Kim i Seung Joon Ahn. "Improvement of the Core Loss of SiFe by Optimizing the Operation Conditions of the Laser Scribing". Materials Science Forum 510-511 (marzec 2006): 194–97. http://dx.doi.org/10.4028/www.scientific.net/msf.510-511.194.

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The magnetic domain refinement was carried out by laser pulse scribing in order to reduce the core loss of SiFe. The laser pulses were generated by a Q-switched Nd:YAG laser, and the optical frequencies of the laser pulses were altered by using the SHG and the THG. The core losses were measured and analyzed to find optimal parameters of the laser treatment. The laser beam was focused with a spot size of 0.2 mm, and pulse energy of 10~30 mJ and the lines were scribed with a period of ~5 mm. The core loss was improved up to 19 % with the THG of Q-switched Nd:YAG laser in 3% SiFe.

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