High voltage fracturing technology was widely used in the field of reservoir reconstruction due to its advantages of being clean, pollution-free, and high-efficiency. However, high-frequency circuit oscillation occurs...High voltage fracturing technology was widely used in the field of reservoir reconstruction due to its advantages of being clean, pollution-free, and high-efficiency. However, high-frequency circuit oscillation occurs during the underwater high voltage pulse discharge process, which brings security risks to the stability of the pulse fracturing system. In order to solve this problem, an underwater pulse power discharge system was established, the circuit oscillation generation conditions were analyzed and the circuit oscillation suppression method was proposed. Firstly, the system structure was introduced and the charging model of the energy storage capacitor was established by the state space average method. Next, the electrode high-voltage breakdown model was established through COMSOL software, the electrode breakdown process was analyzed according to the electron density distribution image, and the plasma channel impedance was estimated based on the conductivity simulation results. Then the underwater pulse power discharge process and the circuit oscillation generation condition were analyzed, and the circuit oscillation suppression strategy of using the thyristor to replace the gas spark switch was proposed. Finally, laboratory experiments were carried out to verify the precision of the theoretical model and the suppression effect of circuit oscillation. The experimental results show that the voltage variation of the energy storage capacitor, the impedance change of the pulse power discharge process, and the equivalent circuit in each discharge stage were consistent with the theoretical model. The proposed oscillation suppression strategy cannot only prevent the damage caused by circuit oscillation but also reduce the damping oscillation time by77.1%, which can greatly improve the stability of the system. This research has potential application value in the field of underwater pulse power discharge for reservoir reconstruction.展开更多
Triggered spark-gap switch is a popular discharge switch for pulse power systems.Previous studies have focused on planarizing this switch using thin film techniques in order to meet the requirements of compact size in...Triggered spark-gap switch is a popular discharge switch for pulse power systems.Previous studies have focused on planarizing this switch using thin film techniques in order to meet the requirements of compact size in the systems.Such switches are one-shot due to electrodes being too thin to sufficiently resist spark-erosion.Additionally,these switches did not employ any structures in securing internal gas composition,resulting in inconsistent performance under harsh atmospheres.In this work,a novel planar triggered spark-gap switch(PTS)with a hermetically sealed cavity was batched-prepared with printed circuit board(PCB)technology,to achieve reusability with low cost.The proposed PTS was inspected by micro-computed tomography to ensure PCB techniques meet the requirements of machining precision.The results from electrical experiments demonstrated that PCB PTS were consistent and reusable with lifespan over 20 times.The calculated switch voltage and circuit current were consistent with those derived from real-world measurements.Finally,PCB PTS was used to introduce hexanitrostilbene(HNS)pellets in a pulse power system to verify its performance.展开更多
A new concept of a coaxial plasma dynamic accelerator with a self-energized magnetic compressor coil to simulate the effects of space debris impact is demonstrated. A brief description is presented about the pulse pow...A new concept of a coaxial plasma dynamic accelerator with a self-energized magnetic compressor coil to simulate the effects of space debris impact is demonstrated. A brief description is presented about the pulse power supply system including the charging circuit, start switch and current transfer system along with some of the key techniques for this kind of accelerator. Using this accelerator configuration, ceramic beads of 100 μm in diameter were accelerated to a speed as high as 18 km/sec. The facility can be used in a laboratory setting to study impact phenomena on solar array materials, potential structural materials for use in space.展开更多
The long-pulse power-supply system equipped for the 4 MW beam-power ion source is comprised of three units at ASIPP(Institute of Plasma Physics, Chinese Academy of Sciences): one for the neutralbeam test stand and ...The long-pulse power-supply system equipped for the 4 MW beam-power ion source is comprised of three units at ASIPP(Institute of Plasma Physics, Chinese Academy of Sciences): one for the neutralbeam test stand and two for the EAST neutral-beam injectors(NBI-1 and NBI-2, respectively). Each power supply system consists of two low voltage and high current DC power supplies for plasma generation of the ion source, and two high voltage and high current DC power supplies for the accelerator grid system. The operation range of the NB power supply is about 80 percent of the design value, which is the safe and stable operation range. At the neutral-beam test stand, a hydrogen ion beam with a beam pulse of 150 s, beam power of 1.5 MW and beam energy of 50 ke V was achieved during the long-pulse testing experiments. The result shows that the power-supply system meets the requirements of the EAST-NBIs fully and lays a basis for achieving plasma heating.展开更多
Ammonia is one of the most important chemical raw materials in both manufacture and life of human.Traditionally Haber-Bosch method for ammonia synthesis involves high temperature and high pressure conditions,leading t...Ammonia is one of the most important chemical raw materials in both manufacture and life of human.Traditionally Haber-Bosch method for ammonia synthesis involves high temperature and high pressure conditions,leading to significant energy consumption and environmental pollution.Non-thermal plasma(NTP) is a promising alternative approach to ammonia synthesis at low temperature and atmospheric pressure.In this study,the synergistic effect of nanosecond pulsed dielectric barrier discharge(np-DBD) and Ni-MOF-74 catalyst was investigated in ammonia synthesis by utilizing nitrogen and hydrogen as feedstock.The results demonstrated that the plasma catalytic-synthesis process parameters play a crucial role in the synthesis process of ammonia.The highest ammonia synthesis rate of 5145.16 μmol·g^(-1)·h^(-1)with an energy efficiency of 1.27 g·kWh^(-1)was observed in the presence of the Ni-MOF-74 catalyst,which was3.7 times higher than that without Ni-MOF-74 catalyst.The synergistic effect of Ni-MOF-74catalyst and nanosecond pulsed plasma was explored by in-situ plasma discharge diagnostics.展开更多
Silicon carbide(SiC) emitter turn-off thyristors(ETOs) are very promising high power capacity semiconductor devices for high voltage and high power density power systems and pulse power applications. However,reports o...Silicon carbide(SiC) emitter turn-off thyristors(ETOs) are very promising high power capacity semiconductor devices for high voltage and high power density power systems and pulse power applications. However,reports on comparison of high voltage SiC GTOs and ETOs in pulse power applications have been rare. In this paper, a comprehensive study on a 6.5 kV SiC GTO and ETO are carried out to demonstrate the superior performance of the SiC ETO over the GTO in pulse power application. A 6.5 kV SiC ETO was designed and tested with a printed circuit board(PCB) integrated gate driver. The forward conduction characteristics of the SiC ETO and GTO in elevated temperatures are measured and compared, showing the excellent temperature coefficient of the SiC ETO’s output characteristics. Their turn-off characteristics with resistive load are measured and compared,demonstrating that the SiC ETO has much faster switching speed and smaller turn-off loss. Experimental results demonstrate that the SiC ETO has a better performance, especially with respect to its switching characteristics,making it a very competitive candidate for high power and pulse power applications.展开更多
A novel nanosecond pulsed power unit was developed for plasma treatment of wastewater, based on the theory of magnetic pulse compression and semiconductor opening switch (SOS). The peak value, rise time and pulse du...A novel nanosecond pulsed power unit was developed for plasma treatment of wastewater, based on the theory of magnetic pulse compression and semiconductor opening switch (SOS). The peak value, rise time and pulse duration of the output voltage were observed to be -51 kV, 60 ns and 120 ns, respectively. The concentrations of .OH generated by the novel nanosecond pulsed plasma power were determined using the method of high-performance liquid chromatography (HPLC). The results showed that the concentrations of .OH increased with the increase in peak voltage, and the generation rates of .OH were 4.1 ×10^-10 mol/s, 5.7× 10^-10 mol/s, and 7.7× 10^-10 mol/s at 30 kV, 35 kV, and 40 kV, respectively. The efficiency of OH generation was found to be independent of the input parameters for applied power, with an average value of 3.23×10^-12 mol/J obtained.展开更多
Dielectric barrier discharges(DBDs)have been widely used in ozone synthesis,materials surface treatment,and plasma medicine for their advantages of uniform discharge and high plasmachemical reactivity.To improve the r...Dielectric barrier discharges(DBDs)have been widely used in ozone synthesis,materials surface treatment,and plasma medicine for their advantages of uniform discharge and high plasmachemical reactivity.To improve the reactivity of DBDs,in this work,the O_(2) is added into Ar nanosecond(ns)pulsed and AC DBDs.The uniformity and discharge characteristics of Ar ns pulsed and AC DBDs with different O_(2) contents are investigated with optical and electrical diagnosis methods.The DBD uniformity is quantitatively analyzed by gray value standard deviation method.The electrical parameters are extracted from voltage and current waveforms separation to characterize the discharge processes and calculate electron density n_(e).The optical emission spectroscopy is measured to show the plasma reactivity and calculate the trend of electron temperature T_(e) with the ratio of two emission lines.It is found that the ns pulsed DBD has a much better uniformity than AC DBD for the fast rising and falling time.With the addition of O_(2),the uniformity of ns pulsed DBD gets worse for the space electric field distortion by O_(2)^(-),which promotes the filamentary formation.While,in AC DBD,the added O_(2) can reduce the intensity of filaments,which enhances the discharge uniformity.The ns pulsed DBD has a much higher instantaneous power and energy efficiency than AC DBD.The ratio of Ar emission intensities indicates that the T_(e) drops quickly with the addition of O_(2) both ns pulsed and AC DBDs and the ns pulsed DBD has an obvious higher T_(e) and n_(e) than AC DBD.The results are helpful for the realization of the reactive and uniform low temperature plasma sources.展开更多
We have developed a conceptual design of a 15-TW pulsed-power accelerator based on the linear-transformer-driver(LTD)architecture described by Stygar[W.A.Stygar et al.,Phys.Rev.ST Accel.Beams 18,110401(2015)].The driv...We have developed a conceptual design of a 15-TW pulsed-power accelerator based on the linear-transformer-driver(LTD)architecture described by Stygar[W.A.Stygar et al.,Phys.Rev.ST Accel.Beams 18,110401(2015)].The driver will allow multiple,high-energy-density experiments per day in a university environment and,at the same time,will enable both fundamental and integrated experiments that are scalable to larger facilities.In this design,many individual energy storage units(bricks),each composed of two capacitors and one switch,directly drive the target load without additional pulse compression.Ten LTD modules in parallel drive the load.Each module consists of 16 LTD cavities connected in series,where each cavity is powered by 22 bricks connected in parallel.This design stores up to 2.75 MJ and delivers up to 15 TW in 100 ns to the constant-impedance,water-insulated radial transmission lines.The transmission lines in turn deliver a peak current as high as 12.5 MA to the physics load.To maximize its experimental value and flexibility,the accelerator is coupled to a modern,multibeam laser facility(four beams with up to 5 kJ in 10 ns and one beam with up to 2.6 kJ in 100 ps or less)that can provide auxiliary heating of the physics load.The lasers also enable advanced diagnostic techniques such as X-ray Thomson scattering and multiframe and three-dimensional radiography.The coupled accelerator-laser facility will be the first of its kind and be capable of conducting unprecedented high-energy-densityephysics experiments.展开更多
Objective:The Holmium:yttrium-aluminum-garnet(Ho:YAG)laser is the standard lithotrite for ureteroscopy.This paper is to evaluate a Ho:YAG laser with a novel effect function in vitro,which allows a real-time variation ...Objective:The Holmium:yttrium-aluminum-garnet(Ho:YAG)laser is the standard lithotrite for ureteroscopy.This paper is to evaluate a Ho:YAG laser with a novel effect function in vitro,which allows a real-time variation of pulse duration and pulse peak power.Methods:Two types of phantom calculi with four degrees of hardness were made for fragmentation and retropulsion experiments.Fragmentation was analysed at 5(0.5 J/10 Hz),10(1 J/10 Hz),and 20(2 J/10 Hz)W in non-floating phantom calculi,retropulsion in an ureteral model at 10(1 J/10 Hz)and 20(2 J/10 Hz)W using floating phantom calculi.The effect function was set to 25%,50%,75%,and 100%of the maximum possible effect function at each power setting.Primary outcomes:fragmentation(mm^3),the distance of retropulsion(cm);5 measurements for each trial.Results:An increase of the effect feature(25%vs.100%),i.e.,an increase of pulse peak power and decrease of pulse duration,improved Ho:YAG laser fragmentation.This effect was remarkable in soft stone composition,while there was a trend for improved fragmentation with an increase of the effect feature in hard stone composition.Retropulsion increased with increasing effect function,independently of stone composition.The major limitations of the study are the use of artificial stones and the in vitro setup.Conclusion:Changes in pulse duration and pulse peak power may lead to improved stone fragmentation,most prominently in soft stones,but also lead to increased retropulsion.This new effect function may enhance Ho:YAG laser fragmentation when maximum power output is limited or retropulsion is excluded.展开更多
The superconducting tokamak HT-7U [1] has been designed by the Institute of Plasma Physics since 1998 and will be set up before 2003. The 1.2 MW /2.45 GHz HT-7U LHCD (Lower hybrid current drive) system which being the...The superconducting tokamak HT-7U [1] has been designed by the Institute of Plasma Physics since 1998 and will be set up before 2003. The 1.2 MW /2.45 GHz HT-7U LHCD (Lower hybrid current drive) system which being the most efficient non-induction device can heat the plasma and drive the plasma current has been efficiently in operation 'owl and a particular design of the 2.8 MW/-35 kV high-voltage DC power supply has been already completed and will apply to the klystron of LHCD on HT-7 and the future HT-7U, and the project of the power supply has been examined and approved professionally by an authorized group of high-level specialist in the institute of Plasma Physics. The detailed design of the power supply and the simulation results are referred in the paper.展开更多
The pulsed power supply(PPS)is one important component in the electromagnetic launch system.The inductive PPSs have attracted researchers’attentions with the major advantages of high energy storage density(over the c...The pulsed power supply(PPS)is one important component in the electromagnetic launch system.The inductive PPSs have attracted researchers’attentions with the major advantages of high energy storage density(over the capacitive PPSs)as well as simple structure and easy control(over the rotating mechanical PPSs).As for the inductive PPSs,the circuit topology of the basic module will directly determine the comprehensive performance of the whole system.From the perspectives of working principles,strengths,weaknesses,and comprehensive performance,this paper presents a historical and technical review of the major circuit topologies for the inductive PPSs.展开更多
High power switch is one of the most important components in pulsed power technology. The RSD (Reversely Switched Dynistor), turned on by a thin layer of an electron-hole plasma, is a high power semiconductor switch...High power switch is one of the most important components in pulsed power technology. The RSD (Reversely Switched Dynistor), turned on by a thin layer of an electron-hole plasma, is a high power semiconductor switch. In this study, the RSD turn-on conditions were investigated by numerical analysis and device simulation as well as the experiments conducted to validate the turn-on conditions. A design of a triggering high-voltage RSD is presented based on a saturable transformer.展开更多
An all solid-state pulsed power generator for plasma immersion ion implantation (PIII) is described. The pulsed power system is based on a Marx circuit configuration and semi- conductor switches, which have many adv...An all solid-state pulsed power generator for plasma immersion ion implantation (PIII) is described. The pulsed power system is based on a Marx circuit configuration and semi- conductor switches, which have many advantages in adjustable repetition frequency, pulse width modulation and long serving life compared with the conventional circuit category, tube-based technologies such as gridded vacuum tubes, thyratrons, pulse forming networks and transformers. The operation of PIII with pulse repetition frequencies up to 500 Hz has been achieved at a pulse voltage amplitude from 2 kV to 60 kV, with an adjustable pulse duration from 1 μs to 100 μs. The proposed system and its performance, as used to drive a plasma ion implantation chamber, are described in detail on the basis of the experimental results.展开更多
The discharge characteristics of the series surface/packed-bed discharge (SSPBD) reactor driven by bipolar pulse power were systemically investigated in this study. In order to evaluate the advantages of the SSPBD r...The discharge characteristics of the series surface/packed-bed discharge (SSPBD) reactor driven by bipolar pulse power were systemically investigated in this study. In order to evaluate the advantages of the SSPBD reactor, it was compared with traditional surface discharge (SD) reactor and packed-bed discharge (PBD) reactor in terms of the discharge voltage, discharge current, and ozone formation. The SSPBD reactor exhibited a faster rising time and lower tail voltage than the SD and PBD reactors. The distribution of the active species generated in differ- ent discharge regions of the SSPBD reactor was analyzed by optical emission spectra and ozone analysis. It was found that the packed-bed discharge region (3.5 mg/L), rather than the surface discharge region (1.3 mg/L) in the SSPBD reactor played a more important role in ozone gener- ation. The optical emission spectroscopy analysis indicated that more intense peaks of the active species (e.g. N2 and OI) in the optical emission spectra were observed in the packed-bed region.展开更多
Nanosecond-pulsed dielectric barrier discharge actuators with powered electrodes of different exposures were investigated numerically by using a newly proposed plasma kinetic model. The governing equations include the...Nanosecond-pulsed dielectric barrier discharge actuators with powered electrodes of different exposures were investigated numerically by using a newly proposed plasma kinetic model. The governing equations include the coupled continuity plasma discharge equation, drift-diffusion equation, electron energy equation, Poisson's equation, and the Navier–Stokes equations.Powered electrodes of three different exposures were simulated to understand the effect of surface exposure on plasma discharge and surrounding flow field. Our study showed that the fully exposed powered electrode resulted in earlier reduced electric field breakdown and more intensive discharge characteristics than partially exposed and rounded-exposed ones. Our study also showed that the reduced electric field and heat release concentrated near the right upper tip of the powered electrode. The fully exposed electrode also led to stronger shock wave, higher heating temperature, and larger heated area.展开更多
A combined method of granular activated carbon(GAC) adsorption and bipolar pulse dielectric barrier discharge(DBD) plasma regeneration was employed to degrade phenol in water.After being saturated with phenol,the ...A combined method of granular activated carbon(GAC) adsorption and bipolar pulse dielectric barrier discharge(DBD) plasma regeneration was employed to degrade phenol in water.After being saturated with phenol,the GAC was filled into the DBD reactor driven by bipolar pulse power for regeneration under various operating parameters.The results showed that different peak voltages,air flow rates,and GAC content can affect phenol decomposition and its major degradation intermediates,such as catechol,hydroquinone,and benzoquinone.The higher voltage and air support were conducive to the removal of phenol,and the proper water moisture of the GAC was 20%.The amount of H2 O2 on the GAC was quantitatively determined,and its laws of production were similar to phenol elimination.Under the optimized conditions,the elimination of phenol on the GAC was confirmed by Fourier transform infrared spectroscopy,and the total removal of organic carbons achieved 50.4%.Also,a possible degradation mechanism was proposed based on the HPLC analysis.Meanwhile,the regeneration efficiency of the GAC was improved with the discharge treatment time,which attained 88.5% after 100 min of DBD processing.展开更多
The highpower pulsed power supply system for the magnetic field of the HL-2A Tokamak is described in this paper. The total output power of its eight magnetic field power supply units of nearly 250 MW. Their highest DC...The highpower pulsed power supply system for the magnetic field of the HL-2A Tokamak is described in this paper. The total output power of its eight magnetic field power supply units of nearly 250 MW. Their highest DC output voltage and current are 3510 V and 45 kA, respectively. All the units are operated in a pulsed mode. The pulse duration is 5 s, and the cyclic period is 15 min. The power supply system consists mainly of pulsed flywheel motor generators, rectifying transformers, thyristor converters, diode rectifiers and switches. The system incorporates many key technologies-supply equalization with two generators and four diode bridges, constant-angle phase triggers with a wide frequency range, current equalization, a status detector for the high current 6-phase converter, and advanced monitoring based on a programmable logic computer and engineering parameter measurement. The experimental results show that the performance of the power supply system satisfies the requirements of HL-2A experiments very well.展开更多
Output-pulse shaping capability of a linear transformer driver (LTD) module under different conditions is studied, by conducting the whole circuit model simulation by using the PSPICE code. Results indicate that a h...Output-pulse shaping capability of a linear transformer driver (LTD) module under different conditions is studied, by conducting the whole circuit model simulation by using the PSPICE code. Results indicate that a higher impedance profile of the internal transmission line would lead to a wider adjustment range for the output current rise time and a narrower adjustment range for the current peak. The number of cavities in series has a positive effect on the output- pulse shaping capability of LTD. Such an improvement in the output-pulse shaping capability can primarily be ascribed to the increment in the axial electric length of LTD. For a triggering time interval longer than the time taken by a pulse to propagate through the length of one cavity, the output parameters of LTD could be improved significantly. The present insulating capability of gas switches and other elements in the LTD cavities may only tolerate a slightly longer deviation in the triggering time interval. It is feasible for the LTD module to reduce the output current rise time, though it is not useful to improve the peak power effectively.展开更多
The power dissipation characteristics of pulsed power switch reversely switched dynistors (RSDs) are investigated in this paper. According to the expressions of voltage on RSD, derived from the plasma bipolar drift ...The power dissipation characteristics of pulsed power switch reversely switched dynistors (RSDs) are investigated in this paper. According to the expressions of voltage on RSD, derived from the plasma bipolar drift model and the RLC circuit equations of RSD main loop, the simulation waveforms of current and voltage on RSD are acquired through iterative calculation by using the fourth order Runge-Kutta method, then the curve of transient power on RSD versus time is obtained. The result shows that the total dissipation on RSD is trivial compared with the pulse discharge energy and the commutation dissipation can be nearly ignored compared with the quasi-static dissipation. These characteristics can make the repetitive frequency of RSD increase largely. The experimental results prove the validity of simulation calculations. The influence factors on power dissipation are discussed. The power dissipation increases with the increase of the peak current and the n-base width and with the decrease of n-base doping concentration. In order to keep a low power dissipation, it is suggested that the n-base width should be smaller than 320μm when doping concentration is 1.0×10^14cm^-3 while the doping concentration should be higher than 5.8×10^13cm^-3 when n-base width is 270μm.展开更多
基金financially supported by the National Science and Technology Major Project(No.2016ZX05034004)。
文摘High voltage fracturing technology was widely used in the field of reservoir reconstruction due to its advantages of being clean, pollution-free, and high-efficiency. However, high-frequency circuit oscillation occurs during the underwater high voltage pulse discharge process, which brings security risks to the stability of the pulse fracturing system. In order to solve this problem, an underwater pulse power discharge system was established, the circuit oscillation generation conditions were analyzed and the circuit oscillation suppression method was proposed. Firstly, the system structure was introduced and the charging model of the energy storage capacitor was established by the state space average method. Next, the electrode high-voltage breakdown model was established through COMSOL software, the electrode breakdown process was analyzed according to the electron density distribution image, and the plasma channel impedance was estimated based on the conductivity simulation results. Then the underwater pulse power discharge process and the circuit oscillation generation condition were analyzed, and the circuit oscillation suppression strategy of using the thyristor to replace the gas spark switch was proposed. Finally, laboratory experiments were carried out to verify the precision of the theoretical model and the suppression effect of circuit oscillation. The experimental results show that the voltage variation of the energy storage capacitor, the impedance change of the pulse power discharge process, and the equivalent circuit in each discharge stage were consistent with the theoretical model. The proposed oscillation suppression strategy cannot only prevent the damage caused by circuit oscillation but also reduce the damping oscillation time by77.1%, which can greatly improve the stability of the system. This research has potential application value in the field of underwater pulse power discharge for reservoir reconstruction.
基金We gratefully acknowledge support from the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20151486).
文摘Triggered spark-gap switch is a popular discharge switch for pulse power systems.Previous studies have focused on planarizing this switch using thin film techniques in order to meet the requirements of compact size in the systems.Such switches are one-shot due to electrodes being too thin to sufficiently resist spark-erosion.Additionally,these switches did not employ any structures in securing internal gas composition,resulting in inconsistent performance under harsh atmospheres.In this work,a novel planar triggered spark-gap switch(PTS)with a hermetically sealed cavity was batched-prepared with printed circuit board(PCB)technology,to achieve reusability with low cost.The proposed PTS was inspected by micro-computed tomography to ensure PCB techniques meet the requirements of machining precision.The results from electrical experiments demonstrated that PCB PTS were consistent and reusable with lifespan over 20 times.The calculated switch voltage and circuit current were consistent with those derived from real-world measurements.Finally,PCB PTS was used to introduce hexanitrostilbene(HNS)pellets in a pulse power system to verify its performance.
基金the Programme for Scientific Instrument Development of the Chinese Academy of Sciences(No.y2003001)
文摘A new concept of a coaxial plasma dynamic accelerator with a self-energized magnetic compressor coil to simulate the effects of space debris impact is demonstrated. A brief description is presented about the pulse power supply system including the charging circuit, start switch and current transfer system along with some of the key techniques for this kind of accelerator. Using this accelerator configuration, ceramic beads of 100 μm in diameter were accelerated to a speed as high as 18 km/sec. The facility can be used in a laboratory setting to study impact phenomena on solar array materials, potential structural materials for use in space.
基金supported by the National Magnetic Confinement Fusion Science Program of China(No.2013GB101003)National Natural Science Foundation of China(No.11505225)Foundation of ASIPP(No.DSJJ-15-GC03)
文摘The long-pulse power-supply system equipped for the 4 MW beam-power ion source is comprised of three units at ASIPP(Institute of Plasma Physics, Chinese Academy of Sciences): one for the neutralbeam test stand and two for the EAST neutral-beam injectors(NBI-1 and NBI-2, respectively). Each power supply system consists of two low voltage and high current DC power supplies for plasma generation of the ion source, and two high voltage and high current DC power supplies for the accelerator grid system. The operation range of the NB power supply is about 80 percent of the design value, which is the safe and stable operation range. At the neutral-beam test stand, a hydrogen ion beam with a beam pulse of 150 s, beam power of 1.5 MW and beam energy of 50 ke V was achieved during the long-pulse testing experiments. The result shows that the power-supply system meets the requirements of the EAST-NBIs fully and lays a basis for achieving plasma heating.
基金the financial support from the Beijing Municipal Natural Science Foundation (No. 1242015)National Undergraduate Innovation and Entrepreneurship Training Program of China (No. 202310015019)Discipline Construction of Material Science and Engineering(Nos. 21090122014 and 21090123007)。
文摘Ammonia is one of the most important chemical raw materials in both manufacture and life of human.Traditionally Haber-Bosch method for ammonia synthesis involves high temperature and high pressure conditions,leading to significant energy consumption and environmental pollution.Non-thermal plasma(NTP) is a promising alternative approach to ammonia synthesis at low temperature and atmospheric pressure.In this study,the synergistic effect of nanosecond pulsed dielectric barrier discharge(np-DBD) and Ni-MOF-74 catalyst was investigated in ammonia synthesis by utilizing nitrogen and hydrogen as feedstock.The results demonstrated that the plasma catalytic-synthesis process parameters play a crucial role in the synthesis process of ammonia.The highest ammonia synthesis rate of 5145.16 μmol·g^(-1)·h^(-1)with an energy efficiency of 1.27 g·kWh^(-1)was observed in the presence of the Ni-MOF-74 catalyst,which was3.7 times higher than that without Ni-MOF-74 catalyst.The synergistic effect of Ni-MOF-74catalyst and nanosecond pulsed plasma was explored by in-situ plasma discharge diagnostics.
基金Project supported by the National Natural Science Foundation of China(No.51577054)the Science and Technology Major Project of Hunan Province(No.2017GK1020)
文摘Silicon carbide(SiC) emitter turn-off thyristors(ETOs) are very promising high power capacity semiconductor devices for high voltage and high power density power systems and pulse power applications. However,reports on comparison of high voltage SiC GTOs and ETOs in pulse power applications have been rare. In this paper, a comprehensive study on a 6.5 kV SiC GTO and ETO are carried out to demonstrate the superior performance of the SiC ETO over the GTO in pulse power application. A 6.5 kV SiC ETO was designed and tested with a printed circuit board(PCB) integrated gate driver. The forward conduction characteristics of the SiC ETO and GTO in elevated temperatures are measured and compared, showing the excellent temperature coefficient of the SiC ETO’s output characteristics. Their turn-off characteristics with resistive load are measured and compared,demonstrating that the SiC ETO has much faster switching speed and smaller turn-off loss. Experimental results demonstrate that the SiC ETO has a better performance, especially with respect to its switching characteristics,making it a very competitive candidate for high power and pulse power applications.
文摘A novel nanosecond pulsed power unit was developed for plasma treatment of wastewater, based on the theory of magnetic pulse compression and semiconductor opening switch (SOS). The peak value, rise time and pulse duration of the output voltage were observed to be -51 kV, 60 ns and 120 ns, respectively. The concentrations of .OH generated by the novel nanosecond pulsed plasma power were determined using the method of high-performance liquid chromatography (HPLC). The results showed that the concentrations of .OH increased with the increase in peak voltage, and the generation rates of .OH were 4.1 ×10^-10 mol/s, 5.7× 10^-10 mol/s, and 7.7× 10^-10 mol/s at 30 kV, 35 kV, and 40 kV, respectively. The efficiency of OH generation was found to be independent of the input parameters for applied power, with an average value of 3.23×10^-12 mol/J obtained.
基金supported by National Natural Science Foundation of China(Nos.52037004 and 51777091)。
文摘Dielectric barrier discharges(DBDs)have been widely used in ozone synthesis,materials surface treatment,and plasma medicine for their advantages of uniform discharge and high plasmachemical reactivity.To improve the reactivity of DBDs,in this work,the O_(2) is added into Ar nanosecond(ns)pulsed and AC DBDs.The uniformity and discharge characteristics of Ar ns pulsed and AC DBDs with different O_(2) contents are investigated with optical and electrical diagnosis methods.The DBD uniformity is quantitatively analyzed by gray value standard deviation method.The electrical parameters are extracted from voltage and current waveforms separation to characterize the discharge processes and calculate electron density n_(e).The optical emission spectroscopy is measured to show the plasma reactivity and calculate the trend of electron temperature T_(e) with the ratio of two emission lines.It is found that the ns pulsed DBD has a much better uniformity than AC DBD for the fast rising and falling time.With the addition of O_(2),the uniformity of ns pulsed DBD gets worse for the space electric field distortion by O_(2)^(-),which promotes the filamentary formation.While,in AC DBD,the added O_(2) can reduce the intensity of filaments,which enhances the discharge uniformity.The ns pulsed DBD has a much higher instantaneous power and energy efficiency than AC DBD.The ratio of Ar emission intensities indicates that the T_(e) drops quickly with the addition of O_(2) both ns pulsed and AC DBDs and the ns pulsed DBD has an obvious higher T_(e) and n_(e) than AC DBD.The results are helpful for the realization of the reactive and uniform low temperature plasma sources.
文摘We have developed a conceptual design of a 15-TW pulsed-power accelerator based on the linear-transformer-driver(LTD)architecture described by Stygar[W.A.Stygar et al.,Phys.Rev.ST Accel.Beams 18,110401(2015)].The driver will allow multiple,high-energy-density experiments per day in a university environment and,at the same time,will enable both fundamental and integrated experiments that are scalable to larger facilities.In this design,many individual energy storage units(bricks),each composed of two capacitors and one switch,directly drive the target load without additional pulse compression.Ten LTD modules in parallel drive the load.Each module consists of 16 LTD cavities connected in series,where each cavity is powered by 22 bricks connected in parallel.This design stores up to 2.75 MJ and delivers up to 15 TW in 100 ns to the constant-impedance,water-insulated radial transmission lines.The transmission lines in turn deliver a peak current as high as 12.5 MA to the physics load.To maximize its experimental value and flexibility,the accelerator is coupled to a modern,multibeam laser facility(four beams with up to 5 kJ in 10 ns and one beam with up to 2.6 kJ in 100 ps or less)that can provide auxiliary heating of the physics load.The lasers also enable advanced diagnostic techniques such as X-ray Thomson scattering and multiframe and three-dimensional radiography.The coupled accelerator-laser facility will be the first of its kind and be capable of conducting unprecedented high-energy-densityephysics experiments.
文摘Objective:The Holmium:yttrium-aluminum-garnet(Ho:YAG)laser is the standard lithotrite for ureteroscopy.This paper is to evaluate a Ho:YAG laser with a novel effect function in vitro,which allows a real-time variation of pulse duration and pulse peak power.Methods:Two types of phantom calculi with four degrees of hardness were made for fragmentation and retropulsion experiments.Fragmentation was analysed at 5(0.5 J/10 Hz),10(1 J/10 Hz),and 20(2 J/10 Hz)W in non-floating phantom calculi,retropulsion in an ureteral model at 10(1 J/10 Hz)and 20(2 J/10 Hz)W using floating phantom calculi.The effect function was set to 25%,50%,75%,and 100%of the maximum possible effect function at each power setting.Primary outcomes:fragmentation(mm^3),the distance of retropulsion(cm);5 measurements for each trial.Results:An increase of the effect feature(25%vs.100%),i.e.,an increase of pulse peak power and decrease of pulse duration,improved Ho:YAG laser fragmentation.This effect was remarkable in soft stone composition,while there was a trend for improved fragmentation with an increase of the effect feature in hard stone composition.Retropulsion increased with increasing effect function,independently of stone composition.The major limitations of the study are the use of artificial stones and the in vitro setup.Conclusion:Changes in pulse duration and pulse peak power may lead to improved stone fragmentation,most prominently in soft stones,but also lead to increased retropulsion.This new effect function may enhance Ho:YAG laser fragmentation when maximum power output is limited or retropulsion is excluded.
文摘The superconducting tokamak HT-7U [1] has been designed by the Institute of Plasma Physics since 1998 and will be set up before 2003. The 1.2 MW /2.45 GHz HT-7U LHCD (Lower hybrid current drive) system which being the most efficient non-induction device can heat the plasma and drive the plasma current has been efficiently in operation 'owl and a particular design of the 2.8 MW/-35 kV high-voltage DC power supply has been already completed and will apply to the klystron of LHCD on HT-7 and the future HT-7U, and the project of the power supply has been examined and approved professionally by an authorized group of high-level specialist in the institute of Plasma Physics. The detailed design of the power supply and the simulation results are referred in the paper.
基金This work was supported in part by the National Natural Science Foundation of China under Grant 50877039in part by the Tsinghua University Initiative Scientific Research Program under Grant No.20121087927(Corresponding author:Xinjie Yu).
文摘The pulsed power supply(PPS)is one important component in the electromagnetic launch system.The inductive PPSs have attracted researchers’attentions with the major advantages of high energy storage density(over the capacitive PPSs)as well as simple structure and easy control(over the rotating mechanical PPSs).As for the inductive PPSs,the circuit topology of the basic module will directly determine the comprehensive performance of the whole system.From the perspectives of working principles,strengths,weaknesses,and comprehensive performance,this paper presents a historical and technical review of the major circuit topologies for the inductive PPSs.
基金supported by the National Natural Science Foundation of China (Nos.50277016,50577028)Specialized Research Fund for the Doctoral Program of Higher Education (No.20050487044)
文摘High power switch is one of the most important components in pulsed power technology. The RSD (Reversely Switched Dynistor), turned on by a thin layer of an electron-hole plasma, is a high power semiconductor switch. In this study, the RSD turn-on conditions were investigated by numerical analysis and device simulation as well as the experiments conducted to validate the turn-on conditions. A design of a triggering high-voltage RSD is presented based on a saturable transformer.
基金supported by National Natural Science Foundation of China (Nos. 50437020, 10675049)
文摘An all solid-state pulsed power generator for plasma immersion ion implantation (PIII) is described. The pulsed power system is based on a Marx circuit configuration and semi- conductor switches, which have many advantages in adjustable repetition frequency, pulse width modulation and long serving life compared with the conventional circuit category, tube-based technologies such as gridded vacuum tubes, thyratrons, pulse forming networks and transformers. The operation of PIII with pulse repetition frequencies up to 500 Hz has been achieved at a pulse voltage amplitude from 2 kV to 60 kV, with an adjustable pulse duration from 1 μs to 100 μs. The proposed system and its performance, as used to drive a plasma ion implantation chamber, are described in detail on the basis of the experimental results.
基金supported by National Natural Science Foundation of China (No.51177007)the Joint Funds of National Natural Science Foundation of China (No.U1462105)Dalian University of Technology Fundamental Research Fund of China (No.DUT15RC(3)030)
文摘The discharge characteristics of the series surface/packed-bed discharge (SSPBD) reactor driven by bipolar pulse power were systemically investigated in this study. In order to evaluate the advantages of the SSPBD reactor, it was compared with traditional surface discharge (SD) reactor and packed-bed discharge (PBD) reactor in terms of the discharge voltage, discharge current, and ozone formation. The SSPBD reactor exhibited a faster rising time and lower tail voltage than the SD and PBD reactors. The distribution of the active species generated in differ- ent discharge regions of the SSPBD reactor was analyzed by optical emission spectra and ozone analysis. It was found that the packed-bed discharge region (3.5 mg/L), rather than the surface discharge region (1.3 mg/L) in the SSPBD reactor played a more important role in ozone gener- ation. The optical emission spectroscopy analysis indicated that more intense peaks of the active species (e.g. N2 and OI) in the optical emission spectra were observed in the packed-bed region.
基金supported by National Natural Science Foundation of China(11472221)funded by the 111 project of China
文摘Nanosecond-pulsed dielectric barrier discharge actuators with powered electrodes of different exposures were investigated numerically by using a newly proposed plasma kinetic model. The governing equations include the coupled continuity plasma discharge equation, drift-diffusion equation, electron energy equation, Poisson's equation, and the Navier–Stokes equations.Powered electrodes of three different exposures were simulated to understand the effect of surface exposure on plasma discharge and surrounding flow field. Our study showed that the fully exposed powered electrode resulted in earlier reduced electric field breakdown and more intensive discharge characteristics than partially exposed and rounded-exposed ones. Our study also showed that the reduced electric field and heat release concentrated near the right upper tip of the powered electrode. The fully exposed electrode also led to stronger shock wave, higher heating temperature, and larger heated area.
基金financially supported by National Natural Science Foundation of China(Project No.51608468)the Natural Science Foundation of Hebei Province(Project Nos.B2015203303 and B2015203300)+3 种基金the China Postdoctoral Science Foundation(Project Nos.2015M580216 and 2016M601285)the Youth Teacher Independent Research Program of Yanshan University(Project No.15LGA013)the Hebei Province Preferred Postdoctoral Science Foundation(B2016003019)the Open Foundation of Key Laboratory of Industrial Ecology and Environmental Engineering(MOE)
文摘A combined method of granular activated carbon(GAC) adsorption and bipolar pulse dielectric barrier discharge(DBD) plasma regeneration was employed to degrade phenol in water.After being saturated with phenol,the GAC was filled into the DBD reactor driven by bipolar pulse power for regeneration under various operating parameters.The results showed that different peak voltages,air flow rates,and GAC content can affect phenol decomposition and its major degradation intermediates,such as catechol,hydroquinone,and benzoquinone.The higher voltage and air support were conducive to the removal of phenol,and the proper water moisture of the GAC was 20%.The amount of H2 O2 on the GAC was quantitatively determined,and its laws of production were similar to phenol elimination.Under the optimized conditions,the elimination of phenol on the GAC was confirmed by Fourier transform infrared spectroscopy,and the total removal of organic carbons achieved 50.4%.Also,a possible degradation mechanism was proposed based on the HPLC analysis.Meanwhile,the regeneration efficiency of the GAC was improved with the discharge treatment time,which attained 88.5% after 100 min of DBD processing.
文摘The highpower pulsed power supply system for the magnetic field of the HL-2A Tokamak is described in this paper. The total output power of its eight magnetic field power supply units of nearly 250 MW. Their highest DC output voltage and current are 3510 V and 45 kA, respectively. All the units are operated in a pulsed mode. The pulse duration is 5 s, and the cyclic period is 15 min. The power supply system consists mainly of pulsed flywheel motor generators, rectifying transformers, thyristor converters, diode rectifiers and switches. The system incorporates many key technologies-supply equalization with two generators and four diode bridges, constant-angle phase triggers with a wide frequency range, current equalization, a status detector for the high current 6-phase converter, and advanced monitoring based on a programmable logic computer and engineering parameter measurement. The experimental results show that the performance of the power supply system satisfies the requirements of HL-2A experiments very well.
基金supported by National Natural Science Foundation of China (Nos. 50637010, 51077111)the State Key Laboratory of Electrical Insulation and Power Equipment of Xi'an Jiaotong University of China (EIPE 09207)
文摘Output-pulse shaping capability of a linear transformer driver (LTD) module under different conditions is studied, by conducting the whole circuit model simulation by using the PSPICE code. Results indicate that a higher impedance profile of the internal transmission line would lead to a wider adjustment range for the output current rise time and a narrower adjustment range for the current peak. The number of cavities in series has a positive effect on the output- pulse shaping capability of LTD. Such an improvement in the output-pulse shaping capability can primarily be ascribed to the increment in the axial electric length of LTD. For a triggering time interval longer than the time taken by a pulse to propagate through the length of one cavity, the output parameters of LTD could be improved significantly. The present insulating capability of gas switches and other elements in the LTD cavities may only tolerate a slightly longer deviation in the triggering time interval. It is feasible for the LTD module to reduce the output current rise time, though it is not useful to improve the peak power effectively.
基金supported by the National Natural Science Foundation of China (Grant Nos 50277016 and 50577028)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No 20050487044)
文摘The power dissipation characteristics of pulsed power switch reversely switched dynistors (RSDs) are investigated in this paper. According to the expressions of voltage on RSD, derived from the plasma bipolar drift model and the RLC circuit equations of RSD main loop, the simulation waveforms of current and voltage on RSD are acquired through iterative calculation by using the fourth order Runge-Kutta method, then the curve of transient power on RSD versus time is obtained. The result shows that the total dissipation on RSD is trivial compared with the pulse discharge energy and the commutation dissipation can be nearly ignored compared with the quasi-static dissipation. These characteristics can make the repetitive frequency of RSD increase largely. The experimental results prove the validity of simulation calculations. The influence factors on power dissipation are discussed. The power dissipation increases with the increase of the peak current and the n-base width and with the decrease of n-base doping concentration. In order to keep a low power dissipation, it is suggested that the n-base width should be smaller than 320μm when doping concentration is 1.0×10^14cm^-3 while the doping concentration should be higher than 5.8×10^13cm^-3 when n-base width is 270μm.