Generation Of High-power Pulses Research Articles

Self-triggering topology for high-power nanosecond pulse generators based on avalanche transistors Marx bank circuits and linear transformer driver.

In recent years, several novel avalanche transistor-based power synthesis topologies have been proposed to improve the output performance of pulse generators based on avalanche transistors. The most promising is the topology based on avalanche transistors Marx Bank Circuits (MBCs) and linear transformer driver (LTD). However, it suffers from the same problems as other semiconductor switch-based LTD generators. The greater the number of LTD modules, the higher the requirements for synchronization and drive capability of the trigger system. This paper proposes a new self-triggering topology for pulse generators based on avalanche transistors MBCs and LTD, which significantly simplifies the entire generator's requirement for trigger system synchronization and driving capability. First, the circuit topology and its operation principle are introduced. Then, three prototypes with one trigger LTD module and three self-triggering LTD modules are developed. The output characteristics are experimentally investigated. The results verify the feasibility of the proposed topology. Finally, the output amplitude and the rise time are 3.35 kV/3.7ns, 4.12 kV/3.7ns, and 4.88 kV/4.0ns on a 25 Ω resistive load, respectively. All generators can operate at 1kHz. The topology proposed in the article maximally simplifies the requirements for synchronization and drive capability of the trigger system for generators based on avalanche transistor MBCs and LTD.

Generation of High Peak Power Pulses With Controllable Repetition Rate in Doubly Q-Switched Laser With AOM/SnSe2

By simultaneously employing self-made SnSe2 saturable absorber (SA) and an acous-to-optic modulator (AOM), a dual-loss-modulated Q-switched Nd:YVO4 laser with short pulse width, high peak power and adjustable pulse repetition rate is presented. The maximum pulse peak power of 37.57 KW with the minimum pulse duration of 5.52 ns were obtained under the pump power of 8 W and the pulse repetition rate of 5 kHz. The experimental results demonstrate that the dual-loss modulation technology with AOM and SnSe2 SA is a simple and efficient method to generate short pulses with high peak power and adjustable low repetition rates.

Comparative Studies of High-Voltage Diode-Dynistor Generators of High-Power Nanosecond Pulses

The results of comparative studies of two compact generators of nanosecond high-voltage pulses are presented. Both generators include an opening switch in the form of a block of drift step-recovery diodes (DSRDs) and a closing switch in the form of a block of shock-ionized dynistors (SIDs). The generators are designed according to two different schemes, but they have similar parameters of the output pulses on a load of <inline-formula> <tex-math notation="LaTeX">$50~\Omega $ </tex-math></inline-formula>: the amplitude of the output voltage is &#x007E; 30 kV, its rise time is &#x007E; 3 ns, and the output energy is &#x007E; 0.4 J. It is shown that it is possible to increase the output voltage and output energy of the generators.

Application of Two-Phase Immersion Cooling Technique for Performance Improvement of High Power and High Repetition Avalanche Transistorized Subnanosecond Pulse Generators

In this article, we show the feasibility of improving the performance of a high voltage and high repetition avalanche transistor pulse generator by applying a two-phase immersion cooling technique. The forced air cooling, single-phase immersion cooling, and two-phase immersion cooling techniques were applied to a 60-stage subnanosecond pulse generator. The experimental results indicate that the two-phase immersion cooling technique can effectively control the temperature rising of the avalanche transistor and, thus, reduce the time base jitter and voltage amplitude jitter. Five types of dielectric fluid with different boiling temperatures were comparatively studied. The FC-72 was finally adopted for the balanced performance on voltage amplitude and repetition rate. The two-phase immersion cooling technique could reduce the thermal resistance between the case and ambient and increase the maximum power from 330 to 876 mW. With this cooling method, the surface temperature of the transistor can be effectively controlled below 62 °C. The pulse generator could achieve outstanding performance with a voltage of 2350 V and a rise time of 180 ps. It can work stably at 200 kHz for more than 30 min, and the burst repetition rate could be 260 kHz within 1 min. This article offers new perspectives in the design of high repetitive avalanche transistorized subnanosecond generators.

High Power and Large-Energy Pulse Generation in an Erbium-Doped Fiber Laser by a Ferromagnetic Insulator-Cr2Si2Te6 Saturable Absorber.

Large-energy mode-locked fiber lasers are extensively studied due to their indispensable use in various fields and applications. Recently, ferromagnetic insulators have attracted tremendous research interest in ultra-fast photonics because of their unique ferromagnetic properties and typical layered structure. In our work, Cr2Si2Te6 nanosheets are prepared and utilized as a saturable absorber (SA) in a large-energy mode-locked erbium-doped fiber (EDF) laser. With a total cavity length of 240 m, a stable mode-locked operation characterized by maximum pulse energy as high as 244.76 nJ with a repetition rate of 847.64 kHz is achieved. When the cavity length is extended to 390 m, the output maximum pulse energy is successfully scaled up to 325.50 nJ. To our knowledge, this is the largest pulse energy and highest output power level to be achieved in mode-locked fiber lasers by two-dimensional (2D) material saturable absorbers (SAs) so far. This work not only makes a forward step to the investigation of the generation of large-energy pulses in mode-locked fiber lasers but also fully proves that the ferromagnetic insulator-Cr2Si2Te6 possesses an excellent nonlinear absorption property, antioxidant capacity in ambient conditions, as well as outstanding thermal stability, which enriches our insight into 2D materials.

High-power terahertz pulse generation from bias-free nanoantennas on graded composition InGaAs structures.

We present a bias-free photoconductive emitter that uses an array of nanoantennas on an InGaAs layer with a linearly graded Indium composition. The graded InGaAs structure creates a built-in electric field that extends through the entire photoconductive active region, enabling the efficient drift of the photo-generated electrons to the nanoantennas. The nanoantenna geometry is chosen so that surface plasmon waves are excited in response to a 1550 nm optical pump to maximize photo-generated carrier concentration near the nanoantennas, where the built-in electric field strength is maximized. With the combination of the plasmonic enhancement and built-in electric field, high-power terahertz pulses are generated without using any external bias voltage. We demonstrate the generation of terahertz pulses with 860 µW average power at an average optical pump power of 900 mW, exhibiting the highest radiation power compared to previously demonstrated telecommunication-compatible terahertz pulse emitters.

Compact and Integrated High-Power Pulse Generation and Forming System

This paper presents comprehensive analytical, numerical and experimental research of the compact and integrated high-power pulse generation and forming system based on the flux compression generator and the electro-explosive forming fuse. The paper includes the analysis of the presented solution, starting from the individual components studies, i.e., the separate flux compression generator tests in field conditions and the forming fuse laboratory test, through the formulation of the extended quasi-empirical components models aimed at enabling their optimal parameters determination at the early design stage and ending with the description of the integrated system studies in field conditions. Based on detailed research, it was possible to achieve very high parameters of the generated pulses, i.e., overvoltages of up to 340 kV with the available source power reaching 25 GW. A very high convergence of the simulation and the results of experimental research has been obtained. The parameters of the presented system have been compared with other literature solutions and the selected topology of the high power pulse generation and forming system has been distinguished against other available ones, e.g., based on Marx generators and forming lines.

Improved Auxiliary Triggering Topology for High-Power Nanosecond Pulse Generators Based on Avalanche Transistors

The avalanche transistor-based Marx circuit has great advantages in generating high-voltage nanosecond pulses. The introduction of auxiliary triggering topology (ATT) can reduce the damage probability of transistors in M × N-stage Marx bank circuits (MBCs). However, as the number of modified stages increases, the output voltage drops significantly, which makes it not achievable to adopt ATT at each stage. The transistors in nonmodified stages still have a certain failure rate when operating at a high repetition rate. Moreover, the previous ATT is only applicable in the negative polarity MBC. In this article, an improved ATT is proposed to solve the above problems. First, its operating principle is analyzed, and the feasibility of its application in both negative and positive MBCs is verified by simulations. Then, the effects of the improved ATT on M × N-stage MBCs are experimentally studied, and the results show that the improved ATT can be used in all stages of MBC without reducing the output voltage. It can also reduce the minimum operating voltage of transistors and widen the regulating range of output voltage. In addition, it can improve the synchronous conduction of parallel-connected transistors. Finally, two nanosecond pulse generators with positive and negative polarity, respectively, are developed and used to drive the atmospheric pressure plasma jet. The amplitude of output voltage can be adjusted in the range of 5-10 kV, measuring at the open end of a coaxial cable with 75 Ω impedance, and the maximum repetition rate is up to 7 kHz.

High-voltage pulse modulated radio frequency generator for dielectric barrier discharge combined with ultra-fast high power pulse generator

Dielectric barrier discharge is the electrical discharge between two electrodes separated by an insulating dielectric barrier. The discharge process typically uses a high-voltage alternating current in the range of several kilohertz to several gigahertz. A high-frequency and high-power pulse generator is required to drive the discharge process through the capacitance load. There are two main techniques to implement this type of generator: the forced and resonant modes. This work demonstrates the implementation of a programmable digital circuit based on a digital signal controller and a full H-bridge that combines the two topologies and can be used as a controller for dielectric barrier discharge with varying capacitance and structure. We integrated an ultra-fast, high-resolution, and high-power pulse generator into a radio frequency generator to drive high-pressure, supersonic, pulsed valves. The excitation based on our DBD and the combined generator produces cold plasma beams. The controller generates discharge voltages of up to 5 kV, in pulses of 10 to 50 μs wide, at rates of up to 1 kHz, while the discharge frequency ranges are from 1 to 3 MHz under a capacitive load of 100 pF. The power generator applies a current pulse of up to 20 A and voltage of up to 150 V.

Compact generators of high-power fast-rising pulses with closing switches in the form of reversely switched dynistors.

This paper presents the results of a study of reversely switched dynistors (RSDs) with an operating voltage of 2.3 kV and a structure diameter of 12mm in an unconventional mode, when they commutate current pulses with very short durations (a few microseconds). In this mode, we studied the dependence of the switching energy loss on the amount of charge that passes through the RSDs during the flow of the control current, which is reversed with respect to the main current. It is shown that a sufficiently powerful control action will result in the RSDs under study having a very low energy loss and being able to effectively commutate microsecond current pulses with an amplitude of >10 kA. It is found that if a rise time of the commutated current pulses is less than 200ns, the efficiency of theRSDswitching significantly decreases. The results concerning the use of the RSDs under study in high-voltage generators are presented. The generators are able to commutate a pulsed power of tens of MW in less than 1 µs at a repetition rate of hundreds of Hz. Finally, this paper suggests ways to increase the power of generators.

Switchable PNIPAm/PPyNT Hydrogel for Smart Supercapacitors: External Control of Capacitance for Pulsed Energy Generation or Prolongation of Discharge Time.

Supercapacitors based on nonresponsive polymer hydrogels are gaining significant attention due to their fabrication simplicity and high potential for wearable electronics. However, the use of smart hydrogels in supercapacitor design remains unexplored. In this work, a smart externally controlled supercapacitor based on a temperature-responsive hydrogel doped with polypyrrole nanotubes (PPyNTs) is proposed. The redistribution of PPyNTs in the poly(N-isopropylacrylamide) (PNIPAm) hydrogel can be reversibly controlled by light illumination or temperature increase, leading to on-demand formation/disruption of the nanotube conductive network, due to release/entrapping of the nanotubes from PNIPAm globule volume on surface. The switchable material was introduced in a supercapacitor design as an active and smart electrode, responsible for external control of charge transport and storage. The created device showed a switchable supercapacitor performance with an ability to significantly and rapidly change capacity under heating/cooling or light illumination. The external trigger was applied for static or dynamic control of supercapacitor behavior: prolongation of discharge time (with constant electric loading) or vice-versa pronounced acceleration of supercapacitor discharge. The proposed smart material-based supercapacitor can find a range of attractive applications in backup energy storage or high power pulse generation.

Generation of annular femtosecond few-cycle pulses by self-compression and spatial filtering in solid thin plates.

Annular-shaped femtosecond few-cycle pulses are generated by 40fs laser pulses propagating through 6 solid thin plates in numerical simulations as well as in experiments. The generation of such pulses takes advantage of the conical emission caused by plasma effect, which introduces continuously varying off-axis plasma density along the radial direction of the propagating beam. The negative dispersion induced by the plasma causes the pulse at particular radial location to be self-compressed and to form an annular beam of short pulse, which can be extracted simply by spatial filtering. Meanwhile, by adjusting the input pulse energy and position of each thin plate relative to the laser focus, we control the plasma density in thin plates which changes the ratio between ionization and effects providing positive dispersion, and obtain a higher compression ratio indicating that the scheme of solid thin plates has the flexibility to regulate the laser intensity so as to plasma density, thus the negative dispersion the pulse experiences during propagation. Few-cycle pulses as short as 8.8 fs are generated in experiments, meanwhile the shortest pulse duration found in the simulations is 5.0 fs, which corresponds to two optical cycles at its central wavelength 761 nm. This method has great potential in high-power few-cycle pulse generation.

Generation of high-power electromagnetic pulses and its application to radiation effect research: A review

<p indent=0mm>This study reviews the research progress of high-power electromagnetic pulse generation. It introduces the physical model, different technologies, and the experimental generation of ultrafast, ultrashort, and ultra-high-power electromagnetic pulses. Progress on the radiation effects of electromagnetic pulses and the measured damage thresholds of microcontroller and photo-electronic devices are also discussed. Finally, future research prospects in this field are suggested.

Low-impedance high-power pulsed generator based on forming line with built-in Tesla transformer.

In order to meet the application needs of gyromagnetic nonlinear transmission lines, a pulsed power generator is required to output short duration pulses with a fast rising edge in high repetitive-rate mode. In this paper, a low-impedance high-power pulsed generator based on the forming line with a built-in Tesla transformer is explored and developed. The generator includes a 14 Ω coaxial forming line, a SF6/N2 gas switch, and a resistive dummy load, which can steadily operate in 100Hz mode and suits the needs above. The pulsed forming line adopts transformer oil as the insulation medium and has a large shell radius and short length to reduce impedance. It has been verified by CST simulation that a relatively high coupling coefficient (0.93) can be achieved when the length-radius ratio is 3.2. The maximum forming line charging voltage is -600 kV in single-shot mode, while the charging voltage is -520 kV in repetitive-rate mode. The output pulse duration is 13ns with a 4ns rising edge, and its amplitude for a 10 Ω load is -220 kV at a repetition rate of 100Hz. The experimental results showed the feasibility of the low-impedance nanosecond periodically pulsed generator based on an oil forming line charged from the high-coupling Tesla transformer. These efforts expand the technical route of the pulse forming line with a built-in Tesla transformer and set a good foundation for its application in the future.

Current divider-based nanosecond high current pulse measuring systems

This paper presents the analysis of the new approach to the measurement methodology of significant values (in order of hundreds of kA) and huge steepness (in order of MA/μs) current pulses based on current dividers along with a comparison of the various types transducers suitability in measuring systems with such extreme parameters. Such dividers are used to extend the measurement ranges of current transducers with limited current conversion capabilities. The results of the selected current dividers field-circuit simulations have been presented, including their attributes and potential application as an important elements of the high-current measurement circuits. The physical prototypes of dividing systems have been verified using an experimental high-power pulse generation and forming system based on the flux compression generator and ultra-fast fuse-opening switch. As the additional aim of this study, the dividers current ratio error compensation method based on the general field-circuit model of current divider has been proposed.

Design of Compact Solid-State Modulator for High-Power Electromagnetic Pulse Generation

The proposed compact solid-state modulator for the generation of high-power electromagnetic (HPEM) pulses uses a lithium polymer battery as the input power source and is capable of achieving a 100-Hz pulse discharge rate with a peak voltage of 400 kV for 2 min. The developed pulse generator consists of two charging units. The primary charging unit is designed to work with 200-A battery current, which increases switching losses and temperature increments at the main switch. To compensate the problems, a half-bridge three-phase structure is connected to transformers via the proposed delta-star connection that decreases the turns ratio of the three-phase transformer effectively. Furthermore, the resonant components are intentionally placed on the secondary side of the three-phase transformer, which is characterized by low current and high voltage conditions. The secondary charging unit uses the resonance between the two capacitors, and the inductor must protect not only the controller, which is susceptible to HPEM pulse effects, but also the output rectifying diodes of the primary charging unit from the peak 20-kA pulse discharging effect. The design procedures and analysis are verified with simulations for each charging unit. The experimental results using various loads, including the actual tesla transformer, validate the system performance and confirm a 94% power efficiency with a peak power density of 431 W/L.

An in-band diode-end-pumped high-power and high-efficiency ultrashort pulse Nd:YVO4 bulk laser mode-locked by a frequency doubling LBO crystal

Nonlinear mirror (NLM) mode locking has also been verified to be an efficient technology for high-power ultrashort pulse laser generation. In this paper, we report on high-power and high-efficiency NLM mode-locked Nd:YVO4 laser with a 880-nm diode laser for in-band pumping, which has very rarely been investigated in the past. The achieved maximum average output power reached 6.76 W at an absorbed power of 13.82 W corresponding to a slope efficiency of 54.5%. Thanks to the used type I LBO crystal with small group velocity mismatch, the achieved pulse duration was as short as 6.5 ps. The results represent one of the best performances that ever achieved for NLM mode-locked Nd:YVO4 laser. NLM mode locking could be very promising for high-power ultrashort pulse generation in visible and middle infrared wavelengths, at which SESAMs are still not mature and the average output powers of ultrafast laser oscillators are also still limited to great extent.

High power and high repetition frequency sub-nanosecond pulse generator with two-phase immersion cooling technique.

In this paper, a 60-stage Marx circuit with the two-phase immersion cooling technique is presented. The performance parameters of the pulse generator with phase change immersion cooling and forced air cooling are compared. The results show that the maximum repetition rate is increased from 80 to 260 kHz, the pulse drift is significantly reduced from 900 to 200ps, and the temperature rise of transistors is controlled effectively to enhance the stability of the amplitude. We also studied the influence of temperature on the turn-on and turn-off processes of the transistors to show the importance of heat management under high repetition conditions. Finally, a pulse generator is developed with the repetition rate of 200 kHz, the rise time of 180ps, and the amplitude of 2350V on a matched 50 Ω resistive load, which can work for more than 30min.

A High-Power Pulse Generator Based on Pulse Forming Network and Linear Transformer

With the development of high-power microwave technology, the output power of the pulse generator is required more and more higher. In this paper, it is realized by increasing the output power of the module while the output impedance of the module changes little. The module of the generator is based on pulse forming network (PFN) and linear transformer (LT). Four Blumlein PFNs with arc-type configuration and 24 Ω characteristic impedance were connected symmetrically to the primary coil of the LTD and driven by two identical laser triggered spark switches to ensure four Blumlein PFNs synchronizing operation. On this basis, a two-stage high-power pulse generator based on PFN-LT is developed. The following technical parameters of the generator were achieved on a 12 Ω high-power solid resistor: output voltage amplitude of ∼250 kV and output power of ∼5.2 GW at a repetition rate of 5 Hz.

Generation of high-power few-cycle femtosecond IR pulses by double-chirp parametric amplification

We present an energy scalable configuration for the generation of high-power few-cycle femtosecond IR pulses based on the sequential parametric amplification of chirped radiation pulses at the idler (0.86 μm) and signal (1.39 μm) wavelengths from the multi-terawatt femtosecond laser system made at the Institute of Laser Physics, Siberian Branch of the Russian Academy of Sciences (ILP SB RAS). The configuration under consideration involves the sequential production of radiation pulses with centre wavelengths of 2.24, 3.56, and 7.25 μm. The conditions are determined for the generation of few-cycle pulses with a terawatt peak power in the 3.56 μm (15.8 fs, 1.5 cycles) and 7.25 μm (17.2 fs, shorter than one cycle) domains. The phase transfer between signal and idler waves in the double-chirp parametric amplification is investigated for the first time.