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This paper discusses the development and analysis of a transfer function model of the peaking capacitor and peaking switch for an input from Marx generator and an output across load. The effect of variations of gap distance, pressure, peaking capacitor, and the input pulse rise time on the rise time of the output pulse is simulated using this model. For a given geometry, the modeling gives an optimum input pulse rise time and the effect of variation of peaking capacitor on various output parameters. The results obtained from modeling are validated with the experimental results.

A new computational model to understand the mechanism of discharges along the gas/solid interface at high voltage and high pressure is made based on the models of explosive electron emission, secondary emission, and neutral gas ionization by using finite-difference time domain-based particle-in-cell code. The charge particle movement at different durations is obtained at a pressure of 1 atmosphere. The profiles of phase space, the net charge density along the gap, and the effect of the dielectric on the characteristics of the gas discharge are presented. The ionization coefficient (α) and drift velocity (ve) calculated from simulation data closely match with the existing experimental results.

We present a study of the shot-to-shot variation in frequency of a reflex-triode virtual cathode oscillator with respect to peak diode voltage, current, impedance, and perveance. The typical electron-beam parameters were 185 kV, 7 kA, and 300 ns, with a current density of a few hundreds of amperes per square centimeter. The one-way analysis of variance was employed to examine the statistical correlation of the diode voltage, current, impedance, and perveance with the emitted microwave frequency. It was shown that the microwave dominant frequency variation is statistically correlated only with the peak diode current. However, the secondary emitted frequency is not statistically correlated with any of the electron-beam diode parameters.

To study the effect of explosive field emission cathodes on high power microwave generation, experiments were conducted on a reflex triode virtual cathode oscillator. Experimental results with cathodes made of graphite, stainless steel nails, and carbon fiber (needle type) are presented. The experiments have been performed at the 1 kJ Marx generator (200 kV, 300 ns, and 9 kA). The experimentally obtained electron beam diode perveance has been compared with the one-dimensional Child-Langmuir law. The cathode plasma expansion velocity has been calculated from the perveance data. It was found that the carbon fiber cathode has the lowest cathode plasma expansion velocity of 1.7 cm/μs. The radiated high power microwave has maximum field strength and pulse duration for the graphite cathode. It was found that the reflex triode virtual cathode oscillator radiates a single microwave frequency with the multiple needle cathodes for a shorter (

The paper describes the procedure for selection of electromagnetic parameters which govern the Electromagnetic Welding (EMW) process. EMW is a specific application of electromagnetic Forming (EMF). The metallic bodies get deformed and eventually collide to get welded. Hence it is classified as deformation bond. It is observed that the parameters such as input electrical energy, ringing frequency, coil geometry, coil conductor section, job material and it's configuration play a very important role in achieving the welding. In addition to this, the separation distance between the two colliding bodies (plates in the present case) is also a crucial parameter. These parameters together decide the resultant collision velocity. The collision velocity in turn decides the strength of weld joint. The procedure is formulated based on computational and experimental observations as applied to 1 and 2 mm thick aluminium plates. This procedure could be extended for other materials and their combinations (such as similar or dissimilar and of different dimensions).

This paper discusses the modeling of a peaking switch to study the reduction in rise time for the subnanosecond duration pulses. The effect of the various shapes of input pulse, inductance, and interelectrode distance on the output voltage and wave shape is discussed in this paper. The modeling has been carried out using the electromagnetic and microwave modeling software of Computer Simulation Technology.

This paper describes the experiments conducted for the development of a solid state pulse power modulator using low cost Mn-Zn ferrite cores. These ferrite cores although have restricted magnetic parameters, gave promising results for use in pulsed power systems. The experience gained has revealed that such low cost ferrite can be used in the development of pulse power modulators.

This paper presents the design and development of a repetitive Marx generator rated at 1 kJ, 300 kV, 12 kA, and 10 Hz and which is suitable to drive the load directly. Bipolar charging of a Marx generator scheme has been adopted to get the following: 1) faster rise time and 2) relatively low charging voltage. The faster rise time is due to the reduced number of spark gaps down to six for 12 in-series capacitors (0.15 μF and 50 kV) of a six-stage bipolar-charging Marx generator. Interstage inductive charging further enhances the efficiency of the overall system as compared to resistive charging. The generator is characterized by an aqueous resistive load for both polarities at the output voltage. Output voltages of the same magnitude have been achieved for both polarities. The matched impedance is found to be 25 Ω for which a suitable reflex triode is designed. Intense electron beams and high-power microwaves have been generated using this Marx generator and reflex triode system. Experimental results demonstrating the Marx generator and the reflex triode operation are presented and discussed.

In Electromagnetic Welding process, the electromagnetic parameters govern the welding process. The collision velocity is the crucial parameter that decides the quality o f the weld joint. The EMW process is comparatively less effici ent for low electrical conductivity metals. However, the efficienc y of the process can be improved by using high electrical conductivity metals, such as copper, aluminum (named as 'drivers') which are placed adjacent to the job piece. In this paper, the perfo rmance of different driver materials is analyzed. This exercise is important from the point of view of minimization of input energy. The computation of the collision velocity is carried out by commercial software's. The results are verified with experim ental observations. The job pieces chosen are flat strips of alumin um, copper and S.S. Needless to say, the conclusions drawn are applicable to any other geometry. Since the EM forming process precedes the EMW process, the conclusions are also applicable in the case of the former process.

The most fundamental issues in virtual cathode oscillator (vircator)-based high-power microwave devices are efficiency improvement and oscillation frequency control. We present a study of the time-dependent behavior of the oscillation frequency of a reflex-triode vircator for various anode-cathode (AK) gaps. The typical electron-beam parameters were 200 kV, 4 kA, and 300 ns, with a current density of a few hundreds of amperes per square centimeter. Time-dependent frequency analysis is applied to the output signal of the vircator to investigate the time evolution of the emitted frequency spectrum for various AK gaps. We find that the dominant frequency peak is less affected by shot-to-shot fluctuations of diode voltage and current than the other frequency components. In addition, the time of occurrence of the dominant and secondary frequency peaks varies on a shot-to-shot basis. The highest microwave power is emitted when all the power is delivered into a single frequency with minimal mode hopping.

Electromagnetic welding (EMW) is a specific application of E lectromagnetic Forming (EMF), owing to the fact that the latter very often than not precedes the former, which means that the metallic parts to be welded get deformed before getting welded. This is a new application of electromagnetic field. This being so, there are not much efforts made for the electrical characterization of the equipment to improve it 's performance. The electrical parameter of the system are a nalyzed in detail in this paper for welding of aluminum strips of 1 mm and 2 mm thickness (width = 400 mm and length = 550 mm). The two bodies (to be welded) have necessarily to be separated from each other so that they acquire sufficient velocity bef ore collision. The collision velocity is the important paramet er in this process. The variation in collision velocity is co mputed for a range of separation distances. The optimum separation distance and minimum energy required for welding is computed and experimentally verified. The paper summarizes the analy sis comprising of computational work, substantiated by data for mechanical strength tests and the study of microstructure. The correlation between the quality of weld and collision velocity has been established.

The KALI-1000 pulse power system has been used to generate single-pulse nanosecond-duration high-power microwaves from an axial virtual cathode oscillator. The typical electron beam parameters were 250 kV, 15 kA, and 100 ns, with a current density of a few hundreds of amperes per square centimeter. The shot-to-shot variation of the microwave pulsewidth was studied for various anode-cathode gaps and two different cathode materials (velvet and graphite). Results indicated that the average microwave pulsewidth for a diode with a graphite cathode increased as the anode-cathode gap was increased. The one-way analysis of variance was employed to examine the statistical correlation between the diode voltage, current, perveance, and the microwave pulsewidth for various diode gaps and for two different cathode materials. It was shown that the microwave pulsewidth variations are not statistically correlated with the diode voltage, current, and perveance.

In Electromagnetic Welding (EMW) process, the capacitive energy is the source of input energy. The tool that is used for welding comprises of an electromagnetic coil. The job piece to be welded is placed in close proximity with the coil. The welding is achieved by impact, when the colliding job pieces are accelerated towards each other by the Lorentz force. The electromagnetic and mechanical properties/ parameters of the equipment, tool and the job govern the overall welding process. We have described a procedure to calculate the capacitive input energies for jobs of different sizes. Data is given for welding of strips of aluminium, copper and S.S. in similar and dissimilar combinations. Since the EMW technique is used in limited applications, this type of data is not available. We have validated our model with some data available in the literature. It is hoped that, this information will help the designer, to select and standardize the system and process parameters.

KALI-1000 pulse power system has been used to generate single pulse nanosecond duration high-power microwaves (HPM) from a virtual cathode oscillator (VIRCATOR) device. HPM power measurements were carried out using a transmitting-receiving system in the presence of intense high frequency (a few MHz) electromagnetic noise. Initially, the diode detector output signal could not be recorded due to the high noise level persisting in the ambiance. It was found that the HPM pulse can be successfully detected using wide band antenna, RF cable and diode detector set-up in the presence of significant electromagnetic noise. Estimated microwave peak power was ∼59.8 dBm (∼1 kW) at 7 m distance from the VIRCATOR window. Peak amplitude of the HPM signal varies on shot-to-shot basis. Duration of the HPM pulse (FWHM) also varies from 52 ns to 94 ns for different shots.

This paper discusses the experiments conducted for the development of 50 kV, 10 A, 10 mus duration, and rise time of 2 mus solid state pulse power modulator using toroidal amorphous steel core and low cost IGBT switches. The experiments revealed (i) the need for new design methodologies based on energy transfer between the electrical and magnetic systems and (ii) the success of low-cost switching circuit.

Intense gigawatt relativistic electron beam generation studies were carried out with a Perspex cathode holder. Purpose of the dielectric cathode holder was to minimize the prepulse voltage across the diode. The typical electron beam parameter was 180 kV, 26 kA, 100 ns, with a few hundreds of ampere per square centimeter current density. It was found that corrugated Perspex of length ges35 mm can eliminate the prepulse voltage but affects the rise time of the diode voltage. The diode voltage and current waveforms were analyzed with the bipolar space-charge limited flow model. The anode and cathode plasma expansion velocities were calculated using the perveance data. The plasma expands at 5.1 cm/mus for 18-mm anode-cathode gap and the plasma velocity increases for larger gap. Inserting a dielectric at the cathode holder could be a very effective method to reduce prepulse voltage at the electron beam diode, but it increases the rise time of the diode voltage and reduces the effective electron beam pulsewidth. The prepulse voltage reduces significantly (les10%) when an inductance is added to the charging circuit of the Blumlein line.

This study was conducted to evaluate the efficacy of using hybrid technology of ozone pulsed UV to decontaminate Salmonella on spices such as chilli and pepper. The effect of ozone in combination with UV was tested against the pure culture of Salmonella. The results indicated that 0.2 ppm concentration of ozone was very effective in reducing (2 log reduction) the Salmonella population. Effect of ozone and extended duration of UV on Salmonella showed a significant reduction at 0.2 ppm (5 log), 0.8 ppm (2 log) and 1.4 ppm (5 log) along with 20 min of extended UV exposure. Inactivation of Salmonella in chilli (six trials) and their log reduction by ozone with extended UV indicated a significant reduction of 1 log at 1.4 ppm conc. of ozone and 15 min of exposure time along with 30mins of UV exposure. Similarly 2 log reduction of Salmonella was observed in pepper. Analysis of moisture, ash and fat content of ozone treated and non treated spice samples indicated that they are not significant to each other. The results demonstrated that the hybrid technology of ozone pulsed UV is an effective alternative microbial reduction technique for spices.

A numerical model employing FDTD based particle-in-cell code (PIC) is used to study the discharge mechanism across a gas /solid interface. The simulation is carried out with and without an insulator in the anode cathode gap at a pressure of latmosphere and a ramp voltage with a rise time of 5ns and pulse duration of 50ns is used as the input pulse. The profiles of electron densities, avalanche growth, phase profile of electrons, and the gap voltage are calculated with and without an insulator to study the mechanism of discharge in presence of an insulator. Spacer efficiency of 81% is obtained which closely agrees with the existing experimental data.

In this article a novel way of synchronizing the critical component for pulsed power applications is described: the spark gap switch. The circuit design of a synchronized spark-gap switch circuit is discussed. The circuit uses a combination of one master spark gap, and a set of inductor and capacitors to synchronize two spark gaps. Critical issues for circuit design are presented together with experimental results. It is observed that the synchronization achieved in terms of switch jitter between two spark gaps is of the order of 1–5ns. Measurements were performed with 30– 34 kV average switching voltage with 30–40ns pulse rise.

In this article a novel way of synchronizing two parallel connected sparkgap switches with accuracies of 1–5 ns for high frequency pulsed power applications is described. The circuit design of a synchronized sparkgap switch circuit is discussed. The circuit uses a combination of one master sparkgap and a set of inductor and capacitors to synchronize two sparkgaps and can be controlled via an IGBT switch. Critical issues for circuit design are presented together with analytical calculations and simulations. Experimental verification of the novel topology is carried out in a prototype experimental setup. Results showing nanosecond level of accuracy in synchronization are reported in this paper along with simulations and analysis.

This paper is intended to report design methodology and implementation experiments of solid state based triggering arrangement for MARX generator of KALI-5000 (1MV, 40kA, 100nS) pulsed power system. The 15 stage bipolar MARX generator of KALI-5000 system is triggered using three triggered sparkgaps. An IGBT based trigger supply is used to trigger the first spark gap and consecutive two sparkgaps are triggered by using internally generated trigger pulses. Optically isolated arrangements are provided for human interface. Whole assembly is tested with dummy copper sulphate load and an excellent triggering range of 7–12kV is achieved. Circuit diagram, analysis and experimental results are presented in the paper.

This paper presents the work being conducted in our laboratory on direct driving of HPM load using opening switch consisting of electrically exploding wire array. Using the opening switch, desired voltage profile required for driving the load has been achieved and HPM has been generated along with making the complete system compact and portable which otherwise is difficult to envisage.

A Flash X-ray diode has been designed and developed for generation of single shot, nanosecond duration x-rays from KALI-5000 Pulse Power System (0.8–1 MV, 40 kA, 100 ns). The typical electron beam parameter was 500 kV, 8 kA, 100 ns, with a few hundreds of A/cm current density. The spot size for different diode configurations varied from 4 mm to 2 mm. X-ray radiograph of various metal objects were taken on X-ray films. The diode voltage and current waveforms were analyzed with the space-charge limited flow model. The anode and cathode plasma expansion velocities were calculated using the perveance data and varies from 2.5–3.3 cm/μs. Time integrated x-ray dose was measured using pen dosemeter and the on-axis dose was 10 mR at 1m distance from the window. The radiograph of stainless steel objects shows good resolution.

In recent years, pulsed power systems have gained importance for the pulsed electron beam generation for industrial and defense applications. High voltage Energy storage capacitors were being used widely worldwide for the pulsed power system in electric field. In case of capacitive energy storage system, the size of the system is decided by capacitor size which depends on dielectric strength and relative permittivity of the dielectric material. Similarly, an inductor can also be used to store energy in magnetic field to generate pulsed power system by making use of an opening switch. This paper discusses the initial experimental results of inductive energy storage pulsed power system being developed in the division.

Rogowski coils have been used for decades for non-invasive current measurement when other probe, such as current shunts, current transformers are impracticable. The measurement of diode beam current in pulse power system under vacuum and high voltage are challenging task which requires development of Rogowski coil for specific applications. They operate in large radiation fields, under intense electron bombardment and at high di/dt. The Rogowski coil has been developed and calibrated to detect nano second pulsed currents from 10kA to 100kA with wide bandwidth and sensitivity. This paper describes Calibration of Rogowski coil used for measuring KALI-1000 pulsed power system[1] relativistic electron beam current. Rogowski coi designed and fabricated using damping resistor technique is also described.

Experiments were carried out to generate intense relativistic electron beams and High Power Microwaves (HPM) with reflex triode geometry from 1 kJ pulse power system. The typical electron beam parameters were 300 kV, 12 kA, and 300 ns, with a current density of a few hundreds of amperes per square centimeter. We present a power optimization study of the HPM generated from the reflex-triode vircator for various anode-cathode (AK) gaps. A horn antenna setup with diode detector and attenuators was used to measure the microwave power. The HPM frequency was measured with a D-dot probe along with a high band width oscilloscope. It was found that the microwave power and E-field peaks at 15 mm AK Gap and the frequency at this gap is 2.2 GHz. The highest microwave power is emitted when all the power is delivered into a single frequency with minimal mode hopping.

In recent years pulsed power activity has gained wide spread importance in the field of defense & research. With involvement of energy storage capacitors, inductors, the generation, and consequent effective utilization of magnetic fields becomes inevitable in these spheres of research. Interaction process using magnetic fields has tremendous importance in every domain of physics. The present work involves a reliable measurement of pulsed magnetic field with search coil (inductive principle) and a novel method of calibrating the same. Both experimental and simulation results are presented, which are in close agreement.

A 6 MW peak, 24 kW average power Sband Klystron is under development at CEERI, Pilani under an MoU between BARC and CEERI. The design of the klystron has been completed. The electron gun has been designed using TRAK and MAGIC codes. RF cavities have been designed using HFSS and CST Microwave Studio while the complete beam wave interaction simulation has been done using MAGIC code. The thermal design of collector and RF window has been done using ANSYS code. A Gun Collector Test Module (GCTM) was developed before making actual klystron to validate gun perveance and thermal design of collector. A high voltage solid state pulsed modulator has been installed for performance evaluation of the tube. The paper will cover the design aspects of the tube and experimental test results of GCTM and klystron.

Pulse modulators generate high power pulses which are used for various industrial applications. This paper discusses the numerical validation of pulse transformer used in a pulse modulator wherein the pulse is created by switching on a capacitor in parallel to the pulse transformer using a solid state switch. The pulse transformer is connected to resistive load. The numerical validation was undertaken to understand the effects of air gap in the assembled pulse transformer.

This paper presents the experimental results of a repetitive Marx generator being developed at BARC. Effect of lead inductance, sparkgaps' alignment, charging inductor, ground inductor and shielding has been studied. Two types of configurations have been adopted in order to reduce the erected Marx inductance and results are compared. In this Marx generator plus-minus charging scheme was adopted for both test setups. Each setup comprised of 2-stage Marx with 4 series capacitors (each rated for 0.15 microfarad, 40nH, 50kV) while discharging giving 0.375 microfarads capacitance. In one of the scheme Type-I, all spark gaps were aligned in line of sight arrangements and successive discharge path were assembled in a zigzag manner so that the induced magnetic field gets cancelled out and effective inductance is reduced. This scheme was terminated to an aqueous load and critical matched condition was achieved at 12 ohm. This scheme had effective capacitance of 0.0375 microfarads, wave shape in lower voltage i.e. 10–15kV charging level. During experiments effect of load was also seen which gave half the open voltage to matched load [z=√(L/C)] and in critical damping condition voltage was 0.7 times of open circuit voltage. These data will be used for developing a 6-stage 1.2 kJ Marx generator for 20 pps burst output. Presently testing is limited to 2pps due to charging power supply limitations. Thus the results can be summarized as follows: (i) line of sight and ultra violet triggering is not effective for a distance of 200mm, (ii) cancellation of induced magnetic field is not effective at 5kA current peak at 100mm distance, (iii) longer length leads in smaller diameter is preferable over larger diameter with smaller length assembly with zigzag leads for giving shorter pulse, higher current and faster rise time.

A pulse power system (1 MV, 5 0kA, and 100 ns) based on dual polarity charged Marx generator and Blumlein pulse forming line (PFL) was built to generate high power microwaves. This paper describes the inherent prepulse present with the Blumlein configuration and the mitigation strategies adopted. Further, a qualitative attempt to verify the generation of high power microwave output on the system is presented.

A design approach giving the optimum number of stages in a magnetic pulse compression circuit and gain per stage is given. The limitation on the maximum gain per stage is discussed. The total system volume minimization is done by considering the energy storage capacitor volume and magnetic core volume at each stage. At the end of this paper, the design of a magnetic pulse compression based linear induction accelerator of 200 kV, 5 kA, and 100 ns with a repetition rate of 100 Hz is discussed with its experimental results.

A pulse power system (1 MV, 50 kA, and 100 ns) based on Marx generator and Blumlein pulse forming line has been studied for characterization of a general system. Total erected Marx inductance and series resistance are calculated from modular testing of Marx generator and testing of Marx generator with Blumlein. The complete pulse power system has been tested with the termination of a liquid resistor load for finding the Blumlein characteristic impedance. Equivalent electrical circuits during the charging and discharging of the Blumlein are constructed from the characterized parameters of the system. These equivalent circuits can be used in the analysis of prepulse voltage and droop in the flat top of the main pulse in the pulse power systems based on Marx generator and Blumlein.

Intense relativistic electron beam diode has been operated without a prepulse switch. A bipolar prepulse of peak 60 kV voltage has been recorded at the diode voltage. Prepulse generated plasma expands and lowers the impedance of the diode. For small gap prepulse generated plasma completely fills the anode cathode gap and the diode behaves as plasma filled diode. It has been observed that electron beam can be generated without encountering the closure problem if the anode cathode gap is kept larger than that estimated by the Child Langmuir relation. At a large gap the beam parameters obtained are 420 KeV, 22 kA, 100 ns. Intense electron beam diode behavior was studied for various anode cathode gaps and voltages in presence of prepulse. From the experimentally obtained values of perveance an upper limit was set up for the Marx voltage (or anode cathode voltage) and lower limit for the anode cathode gap in order to avoid the gap closure problem and the diode can be operated with a better shot to shot reproducibility.

Summary form only given. The high intensity pulsed electron beam of KALI-5000 system is used to develop a flash X-ray source. The KALI-5000 system is capable of generating intense relativistic electron beam (IREB) of 1MeV, 60 kA and 100 ns when connected to impedance matched electron beam diode. This system is operated in 6 GW, 100 ns duration to produce the Bremsstrahlung flash X-ray on a tantalum target of planner anode-cathode geometry. The axial and the radial dose distribution are characterized using CaSO4: Dy TLDs (thermoluminescent dosimeter) as well as using the optical densitometer to measure the dose distribution of the exposed X-ray film. The measured dose distribution by TLDs and the optical densitometer plus X-ray film matches within plusmn5%.

This paper presents modelling and analysis of peaking switch used in Marx generator, such that the rise time of the pulse produced by the Marx generator is reduced substantially. Towards this FEMM (Finite Element Methods Magnetics) software is used for the field modelling of the switch and MATLAB for circuit modelling to observe the rise time. The switch has to produce pulse with sub-nanosecond rise time, hence the electrode distance has to be minimum. This switch can withstand high voltage only under high pressure. A mathematical model is simulated in MATLAB to see the performance under high pressure.

An inductive energy storage pulse power system is being developed in BARC, India. Simple, compact, and robust opening switches, capable of generating hundreds of kV, are key elements in the development of inductive energy storage pulsed power sources. It employs an inductive energy storage and opening switch power conditioning techniques with high energy density capacitors as the primary energy store. The energy stored in the capacitor bank is transferred to an air cored storage inductor in 5.5 μs through wire fuses. By optimizing the exploding wire parameters, a compact, robust, high voltage pulse power system, capable of generating reproducibly 240 kV, is developed. This paper presents the full details of the system along with the experimental data.

Temporal jitter in a magnetic pulse compression based copper vapor laser (CVL) system is analyzed by considering ripple present in the input dc power supply and ripple present in the magnetic core resetting power supply. It is shown that the jitter is a function of the ratio of operating voltage to the designed voltage, percentage ripple, and the total propagation delay of the magnetic pulse compression circuit. Experimental results from a CVL system operating at a repetition rate of 9 kHz are presented.

The research results of the explosive field emission cathode plasma expansion velocity and the initial emission area in the planar diode configuration with cathodes made of graphite, stainless steel, polymer velvet, carbon coated, and carbon fiber (needle type) cathodes are presented. The experiments have been performed at the electron accelerator LIA-200 (200 kV, 100 ns, and 4 kA). The diode voltage has been varied from 28–225 kV, whereas the current density has been varied from 86–928 A/cm2 with 100 ns pulse duration. The experimentally obtained electron beam diode perveance has been compared with the 1 dimensional Child-Langmuir- law. It was found that initially only a part of the cathode take part in the emission process. The plasma expands at 1.7–5.2 cm/μs for 4 mm anode-cathode gap for various cathode materials. It was found that the plasma expansion velocity increases with the decrease in the cathode diameter. At the beginning of the accelerating pulse, the entire cathode area participates in the e...

This paper presents a new high voltage pulse shaping methodology for pulsed power applications. The aim is to generate high voltage square pulse across anode cathode gap of e-beam diodes. The non-linear time varying perveance characteristics of e-beam diodes are used for shaping of output voltage pulse across it, generated directly from Marx generator. Analytically, it has been shown in the paper that under certain conditions, if achieved, Marx generator feeding an e-beam diode can produce a square-like pulse at the output, without any extra pulse shaping arrangements. Experimental results to support the analysis are also presented in the paper.

LCL resonant converter based repetitive capacitor charging power supply (CCPS) is designed and developed in the division. The LCL converter acts as a constant current source when switching frequency is equal to the resonant frequency. When both resonant inductors' values of LCL converter are same, it results in inherent zero current switching (ZCS) in switches. In this paper, ac analysis with fundamental frequency approximation of LCL resonant tank circuit, frequency dependent of current gain converter followed by design, development, simulation, and practical result is described. Effect of change in switching frequency and resonant frequency and change in resonant inductors ratio on CCPS will be discussed. An efficient CCPS of average output power of 1.2 kJ/s, output voltage 3 kV, and 300 Hz repetition rate is developed in the division. The performance of this CCPS has been evaluated in the laboratory by charging several values of load capacitance at various repetition rates. These results indicate that this design is very feasible for use in capacitor-charging applications.

Intense electron beam generation studies were carried out using polymer velvet as a cathode material. The typical electron beam parameters were 250 kV, 15 kA, 100 ns, with a few hundred A cm−2 current density. The cathode plasma expansion velocity and the effective initial emission area have been calculated using the perveance data. It was found that the gap closure velocity and the initial emission areas vary randomly on a shot-to-shot basis. In comparison with a graphite cathode, the gap closure velocity of the velvet cathode is less for lower diode gaps, but is much higher for the larger accelerating gaps. One-way analysis of variance was employed to examine the statistical correlation between the diode voltage, current, plasma velocity and the effective emission area for various diode gaps and for two different cathode materials. It was shown that the mean diode voltage, current, plasma velocity and the effective emission area are different for graphite and velvet cathodes whereas the statistical variations of diode voltage and plasma expansion velocities are not cathode material dependent. However, the mean effective emission area is cathode material dependent as are the variances.

Repetitive Pulsed Power Technology is being developed keeping in mind the potential applications of this technology in material modifications, disinfections of water, timber, and food pasteurization etc. BARC has indigenously developed a Linear Induction Accelerator (LIA-200) rated for 200 kV, 4 kA, 100 ns, 10 Hz. The satisfactory performance of all the sub-systems includ- ing solid state power modulator, amorphous core based pulsed transformers, magnetic switches, water capacitors, water pulse- forming line, induction adder and field-emission diode have been demonstrated. This paper presents some design details and operational results of this pulsed power system. It also highlights the need for further research and development to build reliable and eco- nomic high-average power systems for industrial applications.

High power microwave (HPM) generation studies were carried out in KALI-5000 pulse power system. The intense relativistic electron beam was utilized to generate HPMs using a coaxial virtual cathode oscillator. The typical electron beam parameters were 350 kV, 25 kA, and 100 ns, with a few hundreds of ampere per centimeter square current density. Microwaves were generated with graphite and polymer velvet cathode at various diode voltage, current, and accelerating gaps. A horn antenna setup with diode detector and attenuators was used to measure the microwave power. It was observed that the microwave power increases with the diode voltage and current and reduces with the accelerating gap. It was found that both the peak power and width of the microwave pulse is larger for the velvet cathode compared to the graphite cathode. In a coaxial vircator, velvet cathode is superior to the graphite cathode due to its shorter turn on time and better electron beam uniformity.

Intense electron beam generation studies were carried out in high power cylindrical diode to investigate the effect of the accelerating gap and diode voltage on the electron beam current. The diode voltage has been varied from 130 to 356 kV, whereas the current density has been varied from 87 to 391 A/cm2 with 100 ns pulse duration. The experimentally obtained electron beam current in the cylindrical diode has been compared with the Langmuir–Blodgett law. It was found that the diode current can be explained by a model of anode and cathode plasma expanding toward each other. However, the diode voltage and current do not follow the bipolar space-charge limited flow model. It was also found that initially only a part of the cathode take part in the emission process. The plasma expands at 4.2 cm/μs for 1.7 cm anode-cathode gap and the plasma velocity decreases for smaller gaps. The electrode plasma expansion velocity of the cylindrical diode is much smaller as compared with the planar diode for the same accel...

Electron cyclotron resonance (ECR) proton source at 50 keV, 50 mA has been designed, developed, and commissioned for the low energy high intensity proton accelerator (LEHIPA). Plasma characterization of this source has been performed. ECR plasma was generated with 400-1100 W of microwave power at 2.45 GHz, with hydrogen as working gas. Microwave was fed in the plasma chamber through quartz window. Plasma density and temperature was studied under various operating conditions, such as microwave power and gas pressure. Langmuir probe was used for plasma characterization using current voltage variation. The typical hydrogen plasma density and electron temperature measured were 7x10(11) cm(-3) and 6 eV, respectively. The total ion beam current of 42 mA was extracted, with three-electrode extraction geometry, at 40 keV of beam energy. The extracted ion current was studied as a function of microwave power and gas pressure. Depending on source pressure and discharge power, more than 30% total gas efficiency was achieved. The optimization of the source is under progress to meet the requirement of long time operation. The source will be used as an injector for continuous wave radio frequency quadrupole, a part of 20 MeV LEHIPA. The required rms normalized emittance of this source is less than 0.2 pi mm mrad. The simulated value of normalized emittance is well within this limit and will be measured shortly. This paper presents the study of plasma parameters, first beam results, and the status of ECR proton source.

A pulse power system (1 MV, 50 kA, and 100 ns) based on Marx generator and Blumlein pulse forming line has been built for generating high power microwaves. The Blumlein configuration poses a prepulse problem and hence the diode gap had to be increased to match the diode impedance to the Blumlein impedance during the main pulse. A simple method to eliminate prepulse voltage using a vacuum sparkgap and a resistor is given. Another fundamental approach of increasing the inductance of Marx generator to minimize the prepulse voltage is also presented. Experimental results for both of these configurations are given.

High power electron beam generation studies were carried out in a planar diode configuration to investigate the effect of the accelerating gap, diode voltage, and anode-cathode materials on the electrode plasma expansion. The diode voltage has been varied from 145–428 kV, whereas the current density has been varied from 208–2215 A/cm2 with 100 ns pulse duration. It was found that the diode voltage and current follow the bipolar space-charge limited flow model. The anode and cathode plasma expansion velocities were calculated using the perveance data. The plasma expands at 11 cm/μs for 34 mm anode-cathode gap and the plasma velocity decreases for smaller gaps. It was found that the plasma expansion velocity increases significantly due to the cathode edge contribution and the edge contribution is particularly important during the beginning and the end of the accelerating pulse when the diode voltage and the corresponding electric field are comparatively low. It was also observed that the diode current incre...

The shot to shot variation in perveance of a planar diode with explosive emission graphite cathode in a range of accelerating gaps 3–12 mm is investigated experimentally. The typical electron beam parameters were 200 kV, 12 kA, 100 ns, with a few hundreds of A/cm2 current density. The diode perveance remains less than the Child–Langmuir value, indicating that only a fraction of the cathode take part in the emission process. A simple statistical analysis of the diode perveance shows that the shot to shot variation is more pronounced for the later part of the accelerating pulse. The cathode plasma expansion velocity and the effective initial emission area have been calculated from the perveance data. It was found that the plasma expansion velocity varies from 3 to 6.5 cm/μs. The mean expansion velocity and the standard deviation increase with the increase in the accelerating gap. The initial emission areas also varies randomly on a shot to shot basis and at the beginning of the accelerating pulse only 4%–35...

Intense gigawatt relativistic electron beam generation studies were carried out in the presence of prepulse. Electron beams were generated using planar and annular graphite cathodes of various diameters at a fixed 25mm anode-cathode gap. For the planar cathode, the beam parameters obtained are 340keV, 24kA, and 100ns at a 680A∕cm2 current density. With an annular cathode, 346keV, 10kA, and 100ns electron beam could be generated at a 3.4kA∕cm2 current density. The peak electric field in the diode varies from 58to138kV∕cm. A bipolar prepulse voltage has been recorded at the diode for both the cathodes. The amplitude of the negative prepulse voltage varies with the Marx generator voltage but the time duration remains same. The positive prepulse voltage varies both in amplitude and time duration with the Marx generator voltage. Some shot to shot variation in the diode voltage and current were recorded for the annular cathode due to the nonreproducibility of the prepulse generated plasma. It was found that the...