Trigger Pulse Research Articles

Low-Timing Jitter Single-Frequency Pulse Output from a Passively Q-Switched Monolithic Non-Planar Ring Oscillator

A low-timing jitter passively Q-switched monolithic non-planar ring oscillator (NPRO) with diffusion-bonded Cr4+: YAG in a single-frequency operation was realized. The pulse parameters were controlled by a Cr4+: YAG saturable absorber, while the single-frequency operation was ensured by the unidirectional ring cavity structure. The pulse trigger was actively provided by a gain switcher utilizing a composite pumping scheme. The dependence of the timing jitter between the output pulse and the trigger signal on the parameters of the composite pumping scheme was investigated both theoretically and experimentally. Using this approach, we achieved a single-frequency pulsed laser output with a timing jitter of 14.568 ns (RMS) at a repetition rate of 100 Hz corresponding to a pulse width of 5.99 ns. This novel Q-switched monolithic NPRO, which integrates the benefits of both active and passive Q-switching, results in a simple and reliable structure that achieves a low-timing jitter single-frequency pulse output.

Design and Validation of a Long-Range Streak-Tube Imaging Lidar System with High Ranging Accuracy

The Streak-Tube Imaging Lidar (STIL) has been widely used in high-precision measurement systems due to its ability to capture detailed spatial and temporal information. In this paper, we proposed a ranging measurement method that integrates a Time-to-Digital Converter (TDC) with a streak camera in a remote STIL system. In this method, the TDC accurately measures the trigger pulse time, while the streak camera captures high time-resolution images of the laser echo, thereby enhancing both measurement accuracy and range. A corresponding ranging model is developed for this method. To validate the system’s performance, an outdoor experiment covering a distance of up to 6 km was conducted. The results demonstrate that the system achieved a distance measurement accuracy of 0.1 m, highlighting its effectiveness in long-range applications. The experiment further confirms that the combination of STIL and TDC significantly enhances accuracy and range, making it suitable for various long-range, high-precision measurement tasks.

A compact solid-state high repetition rate trigger based on a spiral generator.

The trigger generator made with a spiral generator (SG) has the advantages of light weight, compact structure, and low cost and has promising applications in the pulsed power field. This paper introduces a compact solid-state high-voltage pulse trigger system based on an improved SG, which has improved repetition rate and lowered the demands for semiconductor switches' maximum current and current rise rate when compared with previous studies. The improvement is achieved by winding outward an additional layer of the passive layer and low-voltage metal strip, which realizes a significant reduction of the peak current and current rise rate of the discharge switch. The final dimension of the trigger is 25 × 10 × 10cm3, excluding the power supply. An experiment carried out in single shot mode shows that the peak value of the output pulse can reach 50kV with a leading edge of 57ns. Repetitive experiments were carried out up to 1kHz, with the peak voltage of the output pulse being 30.5kV, the leading edge being 48ns, and the jitter being 0.84ns. Finally, the generator is used to trigger a gas switch, and it works stably and reliably.

Amplification characteristics of N+2 lasing at multiple wavelengths generated by polarization-modulated femtosecond laser fields.

Multiple gain routes complicate the amplification behaviors of N2+ lasing. A direct comparison of the amplification processes of various lasing lines of N2+ is still lacking to date, mainly because the efficient generation of different lasing lines requires different experimental conditions. In this work, to overcome the limitation, we use an intense polarization-modulated femtosecond laser pulse to simultaneously produce high-intensity N2+ lasing signals at 391 nm and 428 nm, permitting us readily performing their time-domain characterizations. Our results show that the primary amplification of 428-nm lasing is always retarded by a few picoseconds with respect to the probe pulse while the amplification of 391-nm lasing can be basically completed within the probe pulse duration at a relatively high gas pressure, and besides, the time duration of the former sustains several times longer than that of the latter. These observations indicate the non-negligible contribution of the initial electronic coherence established by the pump laser, apart from the external triggering pulse. For the 391-nm lasing, the seed amplification and superradiance can fiercely interplay within the probe pulse duration. However, for the 428-nm lasing, its amplification is in essence Raman-assisted superfluorescence due to the lacking of the initial electronic coherence and a direct triggering pulse. Our findings not only shed light on the physics of N2+ lasing but also promote the relevant studies on the collective emissions in the cascaded multi-level molecular ion system.

A novel micro-capillary discharge plasma jet triggered gas switch.

To reduce the working coefficient and jitter of the three-electrode gas switch used in linear transformer drivers, a novel trigger method that uses a nanosecond pulse in cooperation with the microplasma jet generated by capillary discharge was developed. A microplasma jet was generated by the nanosecond trigger pulse and injected into the follow-up breakdown gap of the gas switch to decrease the working coefficient. The influence of capillary parameters on the development of the microplasma jet was simulated. The results showed that the microplasma jet significantly reduced the breakdown delay time, jitter, and working coefficient. Increasing the capillary length and decreasing the diameter results in better triggered breakdown performance. Furthermore, the gas switch triggered by a positive pulse exhibits a lower breakdown delay and jitter. Combined with the intensified charge coupled device's shooting results, it can be concluded that the microplasma jet has a distinct influence on streamer formation, which is important for improving the working performance of the gas switch.

Development of All Solid State Nanosecond Pulse Transformer Fault Detection Device Based on Marx Circuit

Abstract a nanosecond pulse generator with a fast leading edge for transformer fault diagnosis is developed. The device is composed of a full solid-state nanosecond pulse generator based on Marx circuit and with a tail cut switch and a field programmable logic gate array (FPGA) device. Among them, the nanosecond pulse source is mainly composed of DC power supply, control circuit and main circuit. The main circuit is a 9-level modular Marx circuit, using MOSFET as the main switch and tail cut switch; The control circuit generates a synchronous trigger pulse signal, which drives the MOSFET to work synchronously after being isolated through the optical fiber. The output nanosecond pulse voltage parameters are adjustable amplitude 0-8kv, pulse width 100˜1000ns, repetition frequency 1hz˜1000hz, rising edge 30ns and falling edge 40ns. The transformer fault diagnosis platform is built, and the transformer off-line and on-line fault diagnosis is carried out, which paves the way for further exploration of transformer fault diagnosis technology.

A false trigger pulse elimination circuit for low-frequency energy harvesting active rectifiers

Abstract In this article, a false trigger pulse elimination circuit is proposed to be used for a low-frequency energy harvesting active rectifier. It is divided into two-stage circuits, each stage almost including a switching signal generation circuit, a switching inverter, and an inverter to eliminate false triggering pulses on the rising edge and falling edge respectively. There is an edge detection circuit in each switching signal generation circuit, generating a switching signal that controls the switching inverter’s on-off behavior. This allows the inverter to achieve inverter output voltage clamping by turning off its inverter function and turning it into a switch that is only turned on at the high or low level. At the same time, a thyristor delay element is used to determine and adjust the effective level time of the switching signal, which can reach over 150 μs, completely covering the rising or falling edge false trigger pulse so that no GΩ-level resistors are needed in the low-frequency field. The results show that the low-frequency false trigger pulse elimination circuit proposed in this article can better eliminate false trigger pulses on both rising and falling edges. It can also achieve on-chip integration, reduce the power consumption of the self-adaptive delay compensation loop, and enhance the stability of the circuit.

Trigger transceiver and timing control system for ADITYA-U tokamak

The trigger transceiver and timing control system described in this study is developed to generate multiple triggers with varying delays to synchronize various subsystems with plasma discharges in the ADITYA Upgrade (ADITYA-U) tokamak (Ghosh et al., 2016) [1]. The Toroidal Field Power Supply (TFPS) is a fundamental component for each plasma discharge in the ADITYA-U, which generates a master trigger pulse for the particular discharge. The rise time of Toroidal Field Power Supply is 2 s and the loop voltage which is required to initiate the plasma discharge begins at 2.4 s after the master trigger. So the loop voltage is time-stamped at t = 0 and the master trigger from TFPS is time-stamped at t = −2.4 s and considered as a pre-trigger. Apart from this master trigger at t = −2.4 s, two more pre-trigger pulses, one at ∼ −40 ms and another at ∼ −4 ms, prior to the initiation of loop voltage trigger are generated by the power supply. These pre-trigger pulses generated by TFPS constitute the backbone of the entire discharge timing sequence, and they operate/control/initiate numerous ADITYA-U subsystems such as the gas puffing system, data acquisition system, radio frequency pre-ionization and heating system, plasma position control, and so on. So a suitable trigger generator system was needed to be developed in which three pre-trigger pulses (time stamped @ −2.4 s, −40 ms, and −4 ms prior to the loop voltage trigger) arriving from the TFPS may be selected and altered based on the experimental needs. To cater these requirements in ADITYA-U, a trigger transceiver and timing control system has been developed. The system has been successfully operated over ∼6000 discharges of ADITYA-U and functioned satisfactorily in all discharges in daily experiments with no failures. This study will discuss the detailed design elements and implementation of the Trigger Transceiver and Timing Control System for ADITYA-U plasma operations.

SMART CANE WITH OBSTACLES DETECTION

The project describes ultrasonic blind walking stick with the use of Arduino. According to World Health Organisation, 30 million peoples are permanently blind and 285 billion peoples with vision impairment. If u notice them, you can very well know about it they can’t walk without the help of other. One has to ask guidance to reach their destination. They have to face more struggles in their life daily life. Using this blind stick, a person can walk more confidently. This stick detects the object in front of the person and give response to the user by vibrating. So, the person can walk without any fear. This device will be best solution to overcome their difficulties. Generally, blind people use a traditional cane (known as white cane) for moving from one place to another. Activities like walking down the road, knowing and recognizing the presence of an obstacle in front of them, reading road signs etc. We represent a model of walking stick for blind people. This consists of GPS module, GPS Antenna, Arduino, ultrasonic sensor and buzzer. This stick can detect place and obstacles. The system employs a point-by-point approach to analyze the surrounding environment, providing real-time feedback to the user. Blind people consists of a large group of people in our society. Losing their eyesight has caused them inconvenience in performing daily tasks. Hence, smart cane had been developed in order to increase the life quality of a blind person. The purpose of this project is to design a smart cane with ultrasonic sensor and global system for mobile (GSM) for the blind. This embedded system mainly has mobility. For mobility system, it is equipped with ultrasonic sensor, HCSR04 and vibrating motor. Ultrasonic sensor will send the trigger pulse to detect obstacles. When an obstacle is detected, signals will be sent to vibrating motor and activate it. The vibrating motor will vibrate with different strengths according to the distance of the obstacle. The microcontroller used in this embedded system is Arduino UNO. The prototype of smart cane was built to increase the mobility of the blind people. Keywords— Signal processing, Internet of things, Ultrasonic sensor, visual impaired people

Improving Breath Detection From Pulsed-Flow Oxygen Sources Using a New Nasal Interface.

Patients with COPD and other lung diseases are treated with long-term oxygen therapy (LTOT). Portable oxygen sources are required to administer LTOT while maintaining patient autonomy. Existing portable oxygen equipment has limitations that can hinder patient mobility. A novel nasal interface is presented in this study, aiming to enhance breath detection and triggering efficiency of portable pulsed-flow oxygen devices, thereby improving patient mobility and independence. To examine the effectiveness of the new interface, 8 respiratory therapists participated in trials using different oxygen sources (tank with oxygen-conserving device, SimplyGo Mini portable oxygen concentrator [POC], and OxyGo NEXT POC) and breathing types (nasal and oral) while using either the new nasal interface or a standard cannula. Each trial was video recorded so participant breaths could be retroactively matched with a pulse/no-pulse response, and triggering success rates were calculated by dividing the number of oxygen pulses by the number of breaths in each trial. After each trial, volunteers were asked to rate their perceived breathing resistance. Nasal breathing consistently resulted in higher triggering success rates compared to oral breathing for pulsed-flow oxygen devices. POCs exhibited higher triggering success rates than did the oxygen tanks with conserving device. However, there were no significant differences in triggering success rates between the two POC models. The new nasal interface demonstrated improved triggering success rates compared to the standard cannula. Whereas the new nasal interface was associated with a slight increase in perceived breathing resistance during nasal breathing trials, participants reported manageable resistance levels when using the interface. This study demonstrates that the new nasal interface can improve triggering success rates of pulsed-flow oxygen devices during both nasal and oral breathing scenarios. Further research involving patient trials is recommended to understand the clinical implications of improved pulse triggering.

Numerical Investigation on the Mechanism of Solid Rocket Motor Instability Induced by Differences between On-Ground and In-Flight Conditions

A solid rocket motor (SRM) with a high aspect ratio that performs normally during ground tests may experience instability during flight. To address this issue, this study employs the pulse triggering method and the numerical approach of two-way fluid–structure interaction to investigate the mechanisms behind the SRM instability resulting from distinctions between on-ground and in-flight conditions. The results indicate that the main distinctions between the on-ground and in-flight conditions for SRMs are the strong constraints during the ground test, as well as aerodynamic forces and aerodynamic heating during flight. The strong constraints in the ground test effectively suppress structural vibrations by limiting displacements. In flight conditions, the aerodynamic heating reduces the strength of the SRM casing and aerodynamic forces provide sustained energy input for structural vibrations during flight. The mechanism for the ground/flight differences that induce SRM instability is that the structural natural frequencies are reduced by aerodynamic heating and the first-order acoustic frequency increased by the propellant regression approach reaches the resonance condition. Therefore, an instability factor Φ is proposed to represent the resonance relationship between the structural natural modes and the acoustic mode of SRMs. Furthermore, the closer the frequency of the aerodynamic forces is to the resonance frequency of the acoustic-structure coupling, the more pronounced the SRM instability.

Method of instantaneous signal synchronization of measuring pulse generators

The synchronization methods used in the pulse generators of the G5 measuring group in the external trigger mode are analyzed. The factors determining the error in the formation of time intervals in this mode have been studied. It is shown that the main source of errors in the formation of time intervals during external triggering of measuring pulse generators is the variation in the position of the clock generator reference pulses relative to the external trigger pulses. An analytical review of synchronization methods based on the sampling of time intervals by a multi-tap delay line as a pulse signal propagates along it is carried out. The method of instantaneous synchronization of output pulses is proposed, using sampling of the period of the reference pulses of the clock generator with a multi-tap delay line and fixing the position of the edge of the external trigger pulse within the period of the reference frequency by triggers that control the multiplexer, which connects the output of the multi-tap delay line to the output of the device, at which the edge of the next reference clock pulse generator lags by a minimum time from the front of the external trigger pulse. A device is presented that makes it possible to implement the proposed solution. The simulation of the device was carried out, illustrating the details of its functioning. Jitter was assessed on a prototype device using an integrated 5-tap delay line with a total delay of 20 ns. The method can be applied in measuring pulse generators and belongs to the field of pulse technology.

An accelerated modelling method of full-bridge modular multilevel converter considering dead-time

To avoid short-circuits of the same side switching of power converters, the dead time is of significance in the pulse trigger gating signal for full bridge modular multilevel converter (FB-MMC). However, the previous equivalent models use the binary resistance switching model to equivalent the switching state which is impossible to simulate the switching with dead time, and the detailed model (DM) with higher levels is time-consuming and inefficient in electromagnetic transient (EMT) simulation. To address this problem, based on the state-space averaging method, a speed-up average value model (AVM) of FB-MMC considering dead time is proposed. Firstly, the working state of FB-MMC is obtained through analysing the switching states with dead time and is classified into three cases according to the capacitor. Secondly, derived from state-space equation, the three cases are integrated into a unified model by introducing the duty cycle, and then the equivalent controlled source is used as the interface circuit between the external grid and capacitor. Finally, a 49-level two-terminal MMC-HVDC system consisting of FB-MMC is constructed in PSCAD / EMTDC simulations, showing that the proposed AVM compared with DM has high accuracy and operation efficiency.

Synapse-Mimicking Memristors Based on 3,6-Di(tpy)-9-Phenylcarbazole Unimer and Its Copolymer with Cobalt(II) Ions.

The title compound, unimer U (tpy stands for 2,2':6',2″-terpyridin-4'-yl end-group), by itself shows the memristor effect with a retention time of 18 h and persistence of 11 h. Its coordination copolymer with Co(II) ions, [CoU]n, exhibits multimodal resistance changes similar to the synaptic responses observed in biological systems. More than 320 cycles of potentiation and depression measured in continuous sequence occurred without observing a significant current change, confirming the operational stability and reproducibility of the device based on the [CoU]n polymer. The synaptic effect of a device with an indium tin oxide (ITO)/[CoU]n/top-electrode (TE) configuration is more pronounced for the device with TE = Au compared to devices with TE = Al or Ga. However, the latter TEs provide a cost-effective approach without any significant compromise in device plasticity. The detected changes in the synaptic weight, about 12% for pair-pulse facilitation and 80% for its depression, together with a millisecond trigger and reading pulses that decay exponentially on the time scale typical of neurosynapses, justify the device's ability to learn and memorize. These properties offer potential applications in neuromorphic computation and brain-inspired synaptic devices.

A fast and high‐accurate commutation failure identification method for LCC‐HVDC system

AbstractCommutation failure (CF) is one of the most common issues in line‐commuted converter‐based high voltage direct current systems (LCC‐HVDC), leading to critical power system security and stability problems. Accurate and rapid identification of CF is crucial to prevent subsequent CF in HVDC systems. However, the existing CF identification methods are lack of the required accuracy and speed. The relationship between bridge arm current, commutation voltage, and trigger pulse based on the commutation progress mechanism after the AC fault is analysed in this paper. A novel CF identification method is presented, which utilises the CF identification factor, enabling fast and high‐accurate identification without relying on the value of the extinction angle. The proposed method offers a simpler and more efficient implementation in engineering practice. Finally, the effectiveness of the proposed method is verified in both the standard International Council on Large Electric systems HVDC model and the Hardware in Loop test using practical project parameters. The results demonstrate that the proposed method can accurately and fast identify CF.

The influence mechanism of leakage inductance and distributed capacitance on nanosecond pulse transformer-type trigger

The pulse trigger generator exerts a significant impact on the Marx generator’s output pulse (OP). In this paper, a pulse transformer (PT)-type trigger device is intended to give a pulse of front steepness below 30 ns, a half-width of more than 300 ns, and a magnitude of 50 kV to a 4 MV Marx generator. A steepening circuit is modeled on the output side of the PT equivalent circuit to reduce the OP front steepness, establishing the model of a closed-core PT-type trigger generator. The influence of distributed capacitance and leakage inductance (parasitic parameters) of the PT winding on the OP magnitude, triggering delay time, and front steepness are analyzed, and the design scheme of the PT is decided accordingly. Then, the pulse trigger generator model is simulated, and the trigger pulses are obtained in accordance with the design index. The OP waveforms are tested using a newly developed pulse trigger device prototype.

Design and investigation of a capacitance-coupling pre-ionized sharpening switch.

The sharpening switch is one of the most important elements in the trigger generator, which is used to sharpen the front of the trigger pulse. The breakdown performance of the sharpening switch has an important influence on the output and stability of the trigger generator. In this paper, a novel 200kV capacitance-coupling pre-ionized sharpening switch, which can realize pre-ionization by dividing voltage through its own structural capacitances, is proposed and investigated. In order to obtain the optimal parameters of the pre-ionized sharpening switch, the influences of the electrode structure, electrode material, main gap distance, and pre-ionized gap distance on the breakdown performance are studied experimentally. The experimental results show that the electrode structure with a circular knife-edged cathode and a plate-shaped anode has the smallest breakdown jitter, followed by the needle-plate structure and the tapered ball-head structure. The stainless steel electrode has the smallest jitter, followed by graphite, aluminum, and brass electrodes. When the gap distances of the main gap and the pre-ionized gap are 13 and 1.5mm, respectively, the breakdown stability of the pre-ionized sharpening switch is the best. Under an input voltage pulse with a rise time of about one microsecond, the jitter of the capacitance-coupling pre-ionized sharpening switch with the optimal parameters is 6.08ns, which is about 0.6% of the rise time of the input pulse. The jitter decreases by 44.5% compared to the switch without pre-ionization. The rise time of the output pulse is sharpened to 17ns, corresponding to a voltage rise rate of more than 11 kV/ns.

Beam control system and output fine-tuning for safe and precise delivery of FLASH radiotherapy at a clinical linear accelerator.

We have previously adapted a clinical linear accelerator (Elekta Precise, Elekta AB) for ultra-high dose rate (UHDR) electron delivery. To enhance reliability in future clinical FLASH radiotherapy trials, the aim of this study was to introduce and evaluate an upgraded beam control system and beam tuning process for safe and precise UHDR delivery. The beam control system is designed to interrupt the beam based on 1) a preset number of monitor units (MUs) measured by a monitor detector, 2) a preset number of pulses measured by a pulse-counting diode, or 3) a preset delivery time. For UHDR delivery, an optocoupler facilitates external control of the accelerator's thyratron trigger pulses. A beam tuning process was established to maximize the output. We assessed the stability of the delivery, and the independent interruption capabilities of the three systems (monitor detector, pulse counter, and timer). Additionally, we explored a novel approach to enhance dosimetric precision in the delivery by synchronizing the trigger pulse with the charging cycle of the pulse forming network (PFN). Improved beam tuning of gun current and magnetron frequency resulted in average dose rates at the dose maximum at isocenter distance of >160 Gy/s or >200 Gy/s, with or without an external monitor chamber in the beam path, respectively. The delivery showed a good repeatability (standard deviation (SD) in total film dose of 2.2%) and reproducibility (SD in film dose of 2.6%). The estimated variation in DPP resulted in an SD of 1.7%. The output in the initial pulse depended on the PFN delay time. Over the course of 50 measurements employing PFN synchronization, the absolute percentage error between the delivered number of MUs calculated by the monitor detector and the preset MUs was 0.8 ± 0.6% (mean ± SD). We present an upgraded beam control system and beam tuning process for safe and stable UHDR electron delivery of hundreds of Gy/s at isocenter distance at a clinical linac. The system can interrupt the beam based on monitor units and utilize PFN synchronization for improved dosimetric precision in the dose delivery, representing an important advancement toward reliable clinical FLASH trials.

An experimental and numerical study: to investigate the switching characteristics of a field-distortion sparkgap switch in various SF6 admixtures

Pressurized sparkgap switch is one of the major components that is most commonly used in various pulsed-power systems and the stochastic closure time delay (t d ) and jitter (σ d ) in this gas discharge switch has substantial effect on the temporal characteristics of output pulse. Experimental investigations performed with various volumetric concentrations of SF6 in SF6-N2, SF6-dry air and SF6-Ar admixtures evidenced that the intrinsic parameters of the switch such as time delay and jitter were found to be strongly dependent on the nature of gas, volumetric concentration of SF6 in admixture and rate of rise of voltage (dV/dT) of applied trigger pulse for e.g. in SF6/N2 admixture experiments as the concentration of SF6 was increased from 5% to 50% the average time delay and jitter was consequently increased from 278 ns to 413 ns and 17 ns to 56 ns, respectively. The similar increasing trend was observed even in SF6/dry air and SF6/Ar admixture experiments. It was also observed in the investigation that the variation in time delay and jitter is relatively much lesser for the condition when fast rising trigger pulse having slew rates ∼500 V ns−1 is applied than that of trigger pulse with lower dV/dT of ∼3 V ns−1. To further corroborate the stochasticity of streamer discharge in experimented SF6 admixtures, numerical studies have also been carried out by using a Particle-In-Cell/Monte Carlo Collision (PIC/MCC) model. Our experimental and simulation results infer that SF6/Ar admixture with low SF6 concentration is a superior alternative than pure SF6 for pulsed power switching applications.

Simulation design and analysis 9-level H-bridge single phase stepdown cyclo inverter

This DC-to-AC voltage converter is designed for output frequency controlled by a 9-level cascade H-bridge cyclo inverter with pulse width adjustment. The aim of the study was to determine the pattern and format of the voltage, output frequency, and Total Harmonic Distortion index of a 9-level IGBT cyclo inverter. The method used is to build a unidirectional power converter design modeling into 9 alternating levels with cyclo converter-controlled frequency settings using the Simulink MATLAB tool. The cyclo converter section is constructed with two P and N converters in a parallel arrangement. The frequency and trigger pulse width of both converters control the output voltage and frequency format of the cyclo inverter. The test results show a series of ladder waves with an output frequency, of (1/2f, 1/3f, 1/4f, 1/5f, 1/6f, 1/7f, 1/8f, 1/9f, and 1/10f). The simulation results show that the nth input frequency divider waveform is characterized by the emergence of a number of step pulses of n positive half cycles and negative half cycles. The Total Harmonic Distortion Index gets bigger when the system circuit is designed at a low frequency. This modeling can be implemented into a prototype that is used for variable-speed DC motor drivers.