Rishi Verma

• PhD
• Researcher at Bhabha Atomic Research Centre

The Zr2Co phase, characterized by higher lattice parameter and unit cell volume, is a preferable material for hydrogen storage as well as non evaporable getter. Sintered pellets of zirconium and cobalt have been prepared by conventional ceramic techniques out of high pure powders. The sintering process has been carried out under vacuum rather than...

Sulphur Hexafluoride (SF<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub>) gas is a potent greenhouse gas, and there has been research into more environmentally friendly gases as a replacement to SF<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</s...

In this paper, the effect of driving current profile on efficient utilization and conversion of stored electrical energy into kinetic energy of the projectile has been investigated for electromagnetic railgun systems. It has been experimentally evidenced and also corroborated by simulation results that the acceleration efficiency of railgun launche...

The absorption process of deuterium in titanium was studied in titanium film produced in two different types of copper substrate, one was a polished copper substrate and the other one was chemically etched copper substrate. Titanium film was produced by thermal evaporation method. It was activated at a temperature of 500 °C followed by deuteration...

Pressurized sparkgap switch is one of the major components that is most commonly used in various pulsed-power systems and the stochastic closure time delay (td) and jitter (σd) in this gas discharge switch has substantial effect on the temporal characteristics of output pulse. Experimental investigations performed with various volumetric concentrat...

The impact of the gas mixing ratio on the insulation strength refers to the synergistic behavior of mixed gas. In this work, synergistic effects of various SF6 admix (SF6/N2, SF6/dry air, and SF6/Ar) are tested using HV co-axial sparkgap switch with different % by vol of SF6 under nonuniform field background (point-plane configuration). The experim...

RF LINAC accelerator is a 9MeV system which can be operated up to 200Hz Prf. Its beam diameter is 8mm which fall on the Tantalum (High Z element) target to produce High energy Bremsstrahlung X-ray radiation. This high energy X-ray can be used for Cargo scanning or neutron radiography by utilizing neutrons produce from (ϒ, n) nuclear reaction by usi...

A modular electromagnetic railgun accelerator facility named “RAFTAR” (i.e., Railgun Accelerator Facility for Technology and Research) has been commissioned and its performance has been characterized for high velocity impact testing on materials in a single-shot mode. In the first tests, RAFTAR demonstrated an acceleration of more than 1000 m/s for...

NEWS LETTER : ISSN: 0976-2108 The article presents the experimental results of developed electromagnetic railgun including its design parameters. The 1.2 meter long rectangular bore railgun launches 6.8g aluminum armature at an exit velocity of 525m/s . The interference fit between rail and armature interface is selected 1mm. Further the impact of...

Sparkgap are most widely used closing switches in various high-voltage pulsed power systems and its reliable operation at desired voltage level is very essential. Conventionally by adjusting the filling gas pressure inside sparkgap switch, breakdown voltage level is altered but switching characteristics such as stability in hold-off voltage at vari...

Titanium thin film was prepared on copper substrate by thermal evaporation method. Gettering property of titanium film for deuterium was studied for different values of temperature, pressure and time. The studies were carried out in an ultra high vacuum system. The substrate was mounted in the vacuum system on a heater whose temperature was control...

This paper is a sequel to the 1998 review paper “Scientific status of the Dense Plasma Focus” with 16 authors belonging to 16 nations, whose initiative led to the establishment of the International Center for Dense Magnetized Plasmas (ICDMP) in the year 2000. Its focus is on understanding the principal defining characteristic features of the plasma...

Zirconium and beryllium fast-neutron activation detectors are used to investigate the fusion neutron emission from the NX3 Plasma Focus (PF) device operated in deuterium gas, with 7.2 kJ bank energy. Both Zr and Be activation cross-sections increase with energy, but with different trends, enabling an effective neutron energy Eneff to be inferred fr...

The paper exhibits the simulation and experimental results of Pulse sharpening switch along with a 250 kV High Voltage Pulse Transformer for generation of high voltage fast risetime short duration pulse. The Pulse transformer is employed to charge the Pulse forming line integrated with Pulse sharpening switch. The Pulse sharpening switch is a two e...

Zirconium based alloys are proved to be a good material for hydrogen storage as well as a vacuum pump. A non evaporable getter pump based on St 172 was tested for deuterium storage capacity in a sealed off vacuum device. The vacuum in the range of ultra high vacuum was maintained by the getter pump by gettering. Initial vacuum was created by a turb...

The design details and performance characterization results of a newly developed plasma focus based compact and portable system (0.5 m × 0.5 m ×1.2 m, weighing ≈100 kg) that produces an average neutron yield of ∼2 × 10^8 neutrons/shot (of fast D-D neutrons with typical energy ∼2.45 MeV) at ∼1.8 kJ energy discharge are reported. From the detailed a...

This paper specifically talks about optimized design strategy of sub-kilo Joule Dense plasma focus (PF) fusion device in a full-fledged systematic manner. Recently, there are many pulsed power groups working in design and development of various PF devices in the range of sub-kilo joule energy. Few of them are publishing with the optimized operating...

An experiment was conducted at college of agriculture, Nagpur during 2006-07 on comparative study the different methods of composting by using wheat straw. The experiment was laid out by randomized block design in seven treatments and replicated thrice. The different methods of composting were significant effect on granule size, humic substances, r...

A 200 kJ pulsed power system (PPS) has been built up to drive pulsed plasma devices. This PPS consists of two 100 kJ capacitor bank modules, each comprising of five capacitors of each 178 μF, a discharge switch, and a pulse-shaping unit. When both the banks are charged simultaneously to -15 kV using full charging technique, it delivers a peak curre...

The present investigation was carried out at the Vegetable Research Farm, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh (India) during Rabi of the year 2009 and 2010 on alluvial soil to assess the effect of Pseudomonas fluorescens and humic acid in combination with three different levels of mineral fertilizer...

A study was conducted at Department of Agronomy, Rajasthan College of Agriculture, Udaipur during 2011 and 2012 crop season to assess the effect of weed management practices and level of fertility with emphasis on improving the productivity and quality of quality protein maize. The treatments were laid out in split-plot design with maize weed manag...

The results of characterization experiments carried out on a newly developed dense plasma focus device based intense pulsed neutron source with efficient and compact pulsed power system are reported. Its high current sealed pseudospark switch based low inductance capacitor bank with maximum stored energy of ∼10 kJ is segregated into four modules of...

A sub-kilo-Joule plasma focus device (FMPF-3, 14 kV/235 J) was operated with deuterium–krypton admixtures (of 1, 2 and 5 % Kr by volume) to study the influence of admixture ratio on neutron yield (Y n). Experiments were performed for different insulator sleeve lengths and cathode geometries. The results reveal that for a carefully optimized electro...

The results of a miniature plasma focus are presented in this paper which is operated with energy less than or equal to 150 J. The miniature plasma focus is driven by a small capacitor bank and the peak current delivered in the focus is 75-80 kA. The deuterium gas is filled with a pressure range of 5-7 mbar inside the plasma focus chamber. The quar...

A field experiment was conducted on loamy sand soil during rabi, 2009-10 to find out the effect of irrigation and mulching practices on quality, N uptake, water use efficiency and economics of fennel. Results revealed that application of 6 irrigations significantly increased the essential oil content, protein content in seed, nitrogen content in se...

A field experiment was conducted during the summer season of the year 2009 at Anand Agricultural University, Anand, Gujarat to study the influence of irrigation scheduling (IW: CPE ratios) and plant growth regulators on growth, yield and yield attributes of summer cluster bean. Sixteen treatment combinations consisting of four levels of irrigation...

A field experiment was conducted during the summer season of the year 2009 at Anand Agricultural University, Anand, Gujarat to study the influence of irrigatio n scheduling (IW: CPE ratios) and plant growth regulators on growth, yield and yield attributes of summer cluster bean. Sixteen treatment combinations consisting of four levels of irrigation...

India is a highly populated country under the category of developing nations. The protein requirement of most of the people is fulfilling through pulses. Production of pulse crops and their yield stagnation last so many years. It has been estimated that India's population would reach 1.68 billion by 2030 from the present level of 1.21 billion. Acco...

A range of plasma focus machines from the 200 J FMPF3 through the 2 kJ NX2 to the 20 kJ NX3 are operated at the National Institute of Education in Singapore. The neutron yield Yn versus pressure P curves for these machines have been measured and published. We use the Lee code to compute these Yn versus P curve for each machine after fitting a compu...

The design, construction and operational characteristics of a portable flash X-ray source driven by battery-powered compact Marx is reported. The novel configuration of compact Marx utilizes hollow capacitors in successive stages to enhance the erection reliability. The characteristic impedance of this system is ∼200Ω. At discharge of ∼22kV, >200kV...

Railgap switches are connected to transfer energy from high energy capacitor bank to enable large coulomb transfer in distributed monde in 1.2MJ capacitor bank 'RUDRA' at Energetics & Electromagnetics Division, BARC, Visakhapatnam. The total energy stored in the 1.2MJ bank is segmented in to six modules (of 200kJ each) capable of delivering 3.6MA o...

The performance of railgap switch critically relies upon multichannel breakdown between the extended electrodes (rails) in order to ensure distributed current transfer along electrode length and to minimize the switch inductance. The initiation of several simultaneous arc channels along the switch length depends on the gap triggering technique and...

The results of a pulse power generator driving an axial virtual cathode oscillator are being presented in this paper as a source of high power microwave (HPM) radiations. The electron beam generator is also modified to attain the intense X-ray burst. The pulse power generator used for these applications is common and is having 10 ohms as its charac...

A Marx generator delivers high power electrical pulse in very short duration and can be configured to be compact. This ultrafast coaxial Marx generator has also been developed without pulse shaping/peaking circuit. The results of 5-stage ultrafast coaxial Marx generator has a rise time of 800ps, maximum output voltage 75kv, pulse width(FWHM) of 1.5...

A field experiment was conducted rabi season 2009-10 at Agricultural Research Farm, BHU, Varanasi, on alluvial soils to assessed the effects of concentrate organic manure and levels of inorganic fertilizers on microbial dynamics in alluvium soil. The maximum bacterial, fungal and actinomycetes population were recorded The total bacterial counts ran...

Characterization results of high-power microwave radiation, from an axial vircator driven by pulsed electron beam accelerator AMBICA-600 are reported in this paper. We present a study on variation in pulsed microwave power output and dominant frequency by discretely varying anode-cathode (A-C) gap. While keeping the cathode diameter fixed at 40 mm,...

AlON nanolayers are synthesized on Al substrate by the irradiation of energetic nitrogen ions using plasma focusing. Samples are exposed to multiple (5, 10, 15, 20 and 25) focus shots. Ion energy and ion number density range from 80 keV to 1.4 MeV and 5.6×1019 m-3 to 1.3×1019 m-3, respectively. Moreover, the effect of continuous annealing (473 K an...

This manuscript focuses on the effect of concentrate organic manure (wellgrow grain and wellgrow soil) and different levels of nutrients on growth and yield component of wheat under different levels of fertility. Significant improvement in terms of growth parameters like plant height, number of tillers, dry matter production and number of productiv...

AlON nanolayers are synthesized on Al substrate by the irradiation of energetic nitrogen ions using plasma focusing. Samples are exposed to multiple (5, 10, 15, 20 and 25) focus shots. Ion energy and ion number density range from 80 keV to 1.4 MeV and 5.6£1019 m¡3 to 1.3£1019 m¡3, respectively. Moreover, the effect of continuous annealing (473 K an...

This paper reports the results of characterization and optimization experiments carried out on a newly developed NX-3 dense plasma focus device (20 kJ at 20 kV, a quarter time period of ~ 3 μs, and 10 kJ/600 kA at 14 kV) at the Plasma Radiation Source Laboratory, NIE, Nanyang Technological University, Singapore. Initial experiments were conducted w...

A low impedance Marx generator was developed, which will serve as a test bed for Vacuum diodes of various electrode materials and geometries. The vacuum diodes will be used for high power microwave generation. The generator is capable to supply ~3GW of pulsed power to the vacuum diodes which is sufficient enough to produce plasma within the diode f...

Short duration, high power pulses with fast rise time and good flat-top are essentially required for driving pulsed electron beam diodes. To attain this objective, a dual resonant Tesla transformer based pulsed power accelerator 'AMBICA-600' has been developed. In this newly developed system, a coaxial water line is charged through single turn Tesl...

A compact 180 kV electron beam system is designed for high power microwave generation. The electron beam system is consists of a secondary energy storage device, which can deliver energy to the load at faster rate than usual primary energy storage system such as tesla transformers or marx generator. The short duration, high voltage pulse with fast...

For the generation of microwaves, Electron beam devices operating in vacuum are most widely used. For pulsed and high power microwave generation, Virtual cathode oscillators (VIRCATORs) are said to be simple in operation and construction. They are generally driven by a pulsed power source which gives high input powers to the Vircator connected as l...

A high performance high repetition rate plasma focus device with significant time averaged neutron yield and greater shot to shot reproducibility could be a highly valuable neutron source for Homeland Security applications. The single module fast miniature plasma focus ‘FMPF-2’ (2.4 μF, 56 ± 3 nH, 89 kA @ 14.0 kV, T/4~575 ns) was upgraded to four m...

The experimental results of an air-core pulse transformer are presented, which is very compact (<10 Kg in weight) and is primed by a capacitor bank that is fabricated in such a way that the capacitor bank with its switch takes the shape of single-turn rectangular shaped primary of the transformer. A high voltage capacitor assembly (pulse-forming-li...

form only given. The research and development of compact repetitive miniature plasma focus devices, with stored energy from few tens to few hundred joules, is becoming increasingly important because of their potential applications as portable neutron source for explosive and contraband material detection. In this paper, we report the neutron emissi...

form only given. Preliminary experimental results of a new, high energy, dense plasma focus device NX-3 that has recently been made operational at Plasma Radiation Source Lab, NIE, Nanyang Technological University, Singapore is reported. The NX-3 capacitor bank stores 20kJ energy in eight modules (of 2.5kJ each) and cumulatively delivers peak curre...

The fast pulsed electric discharge current drives all physical processes in the plasma focus device; in turn all physical processes in the focus affect the current waveform. Thus the discharge current waveform is the most important indicator of plasma focus performance. This underlies the importance of properly measuring, processing and interpretin...

Highly crystalline AlN films are deposited on Si substrate by the bombardment of charge particles emanating from plasma focus device. Deposition of AlN films are carried out for multiple focus shots at room temperature. Numbers of ions (1.3×1019–5.6×1019m−3) are emitted during one focus shot. X-rays diffraction results reveal that an amorphous and...

Preliminary experimental results of an axially extracted virtual cathode oscillator (vircator) built on the low impedance pulsed electron beam accelerator AMBICA-600 is reported. The AMBICA-600 pulsed power system mainly comprises of a coaxial waterline charged from single turn Tesla transformer. Waterline has impedance of ~5Ω and generates pulse w...

Highly crystalline AlN films are deposited on Si substrate by the bombardment of charge particles emanating from plasma focus device. Deposition of AlN films are carried out for multiple focus shots at room temperature. Numbers of ions (1.3_1019–5.6_1019 m_3) are emitted during one focus shot. X-rays diffraction results reveal that anamorphous and...

Compact Marx generators are known for delivering high power in very short duration and do not require any separate pulse shaping components. The design and operation of 10 stage coaxial Marx generator with fast rise time of 2.4 ns, maximum voltage 300 kV, pulse width 20 ns, energy 4.2 J and impedance 71 Ω has been presented. The Marx generator is c...

The time-integrated imaging of pinched plasma column in the NX2 plasma focus device is performed using a general-purpose digital SLR camera with neutral density filters (ND 0.9). Although it is very simple, some useful information is obtained from the pinch phase of plasma focus device, and the images are compared with the neutron yield, electron,...

Nanostructured multiphase Ti(C,N)/a-C films were deposited using a 3.3kJ pulsed plasma focus device onto silicon (100) substrates at room temperature. The plasma focus device, fitted with solid titanium anode instead of usual hollow copper anode, was operated with nitrogen and Ar/CH4 as the filling gas. Films were deposited with different number of...

Diamond-like carbon (DLC) films were deposited on Si (1 0 0) substrate using a low energy (219 J) repetitive (1 Hz) miniature plasma focus device. DLC thin film samples were deposited using 10, 20, 50, 100 and 200 focus shots with hydrogen as filling gas at 0.25 mbar. The deposited samples were analyzed by XRD, Raman Spectroscopy, SEM and XPS. XRD...

The Dense Plasma Focus (DPF) was independently discovered by J. Mather1 and N. V. Filippov2 in the early 60's. The DPF represents one of the most interesting and important applications of plasma physics to fusion and multi-radiation sources1-4. Nearly forty years of experiments have demonstrated the ability of (even table-top) DPF devices to produc...

The Letter reports the first ever application of low energy miniature plasma focus device as a deposition facility for nanostructured thin films. We demonstrate successful utilization of a 120 J fast miniature plasma focus device as a novel facility for the deposition of magnetically soft FeCo thin films. Different gas types and the substrate mater...

In this paper, we report the experimental demonstration of enhancement in time averaged neutron yield by an order of magnitude, using the fast miniature plasma focus FMPF-2 in repetitive mode. The newly developed FMPF-2 device (2.4 µF, 56 nH, 13.8 kV, T/4 ~ 575 ns) operates up to 10 Hz in the quasi-continuous mode. Using pure deuterium as the fuell...

A repetitive NX2 dense plasma focus (DPF) device, operating at a low voltage of 8 kV with a stored energy of capacitor bank in the sub-kilojoule range (~880 J), was successfully used to deposit nanostructured magnetic CoPt thin films. The samples were synthesized at different filling hydrogen gas pressures and using different numbers of plasma focu...

In this Letter we report the effect of two different cathode structures – tubular and squirrel cage, on neutron output from a miniature plasma focus device. The squirrel cage cathode is typical of most DPF sources, with an outer, tubular envelope that serves as a vacuum housing, but does not carry current. The tubular cathode carries the return cur...

Summary form only given. A table top miniature plasma focus device FMPF-1 has been successfully used as a portable, pulsed hard X-ray source for fast radiography applications. It has 2.4 muF capacitor bank formed by 4 capacitors, operates at _14 kV charging voltage and delivers ~80 kA peak discharge current in a quarter time period of ~400 ns. The...

In order to gain insight into the possible neutron production mechanism in sub-kilojoule miniature plasma foci, the anisotropy in neutron and hard x-ray emissions from a newly developed fast miniature plasma focus device (2.4 µF, 27 nH, T/4 ~ 400 ns, 12–15 kV, 170–270 J, total mass ~25 kg) is investigated. The system produces an average neutron yie...

High energy ions and energetic plasma irradiation of aluminum cathode inserts have been accomplished in nitrogen and argon filled plasma focus device. The Filippov-type plasma focus facility, Dena, with 288 μF capacitor bank and charging voltage of 25 kV (90 kJ maximum storage energy) was first optimized for strong ion beam generation for nitrogen...

The effect of varied concentrations of deuterium-krypton (D2–Kr) admixture on the neutron emission of a fast miniature plasma focus device was investigated. It was found that a judicious concentration of Kr in D2 can significantly enhance the neutron yield. The maximum average neutron yield of (1±0.27)×104 n/shot for pure D2 filling at 3 mbars was...

As a first step toward the development of a compact and portable, quasi-continuous pulsed neutron source, we have demonstrated a 'fast miniature plasma focus (PF) device' as a compact nuclear fusion apparatus. The system operates with deuterium gas and produces an average neutron yield (Y90°) of (1 ± 0.27) × 104 neutrons/shot at ~70 kA peak dischar...

Uniform FePt nanoparticles were synthesized through nanostructuring of pulsed laser deposited FePt thin films by single shot H+ ion irradiation using a plasma focus device. The annealing temperature required for phase transition from low Ku face-centred cubic to high Ku face-centred tetragonal, for ion irradiated samples, is simultaneously lowered...

In a 200 J fast miniature plasma focus device about 17- and 10-fold increase in x-ray yield in spectral ranges of 0.9–1.6 keV and 3.2–7.7 keV, respectively, have been obtained with deuterium-krypton (D2–Kr) admixture at operating pressures of ⩽ 0.4 mbar. In the pressure range of >0.4–1.4 mbar, about twofold magnification in average x-ray yield alon...

The UNU-ICTP plasma focus with a significantly longer than conventional anode can still be a reasonably good neon soft x-ray (SXR) source. The highest average neon SXR yield of 3.3 J was achieved at 3 mbar. The time difference between the two first peaks of the voltage probe signal at the radial collapse phase was found to be inversely related to t...

We report the design and development of insulated gate bipolar junction transistor based high performance driver for operating thyratrons in grounded grid mode. With careful design, the driver meets the specification of trigger output pulse rise time less than 30 ns, jitter less than +/-1 ns, and time delay less than 160 ns. It produces a -600 V pu...

The increased interest in pulsed power field applications has generated the need for development of compact and remotely operated chargers driven by rechargeable batteries. With this objective, a compact and portable dc to dc Converter has been developed which has an output rating of 100 kV, 0.4 mA. The high voltage generation scheme uses a hybrid...

Conventionally, Marx generators are used for the production of short duration, high voltage pulses but since many discharge gap switches are utilized for stepping up the voltage, there are many disadvantages. Here, an alternative and much simpler technique for the multiplication of nanosecond high voltage pulses has been presented in which multipli...

Pinch experiments like Magnetized Target Fusion (MTF) and Dense Plasma Focus require for their operation fast rising high power and high energy pulses. To perform such experiments, an 1.2MJ Capacitor Bank capable of delivering 3.6MA of peak current with 5 to 7μs rise time has been designed and commissioned. The major application of bank is focused...

Summary form only given. In proposed paper, the design of a modular, robust, high-voltage impulse power supply for pulsed power applications is put into practice and analyzed. The capacitor is charged to a voltage variable between 5 to 20 kV to be successively discharged on the inductor. Associated protection circuits are described in detail. The a...

The technology used for the intense relativistic electron beam production has advanced significantly and is wide spread in use for variety of pulsed power applications generating several mega-watts of beam power. The production of such intense electron beam begins from electron source. In various applications of intense pulsed electron beams such a...

A slow-wave delay line type air-core (nonmagnetic Nylon former) current transformer fabricated using silver epoxy for the measurement of currents of long pulse durations and few nanoseconds rise times is reported in this article. The advantage of using silver epoxy is that it fills all the voids between coil and shield and enhances the proximity of...

There are various plasma applications of MTF in which very high currents are delivered using modules of capacitor banks to a single load as per the load requirement. Moreover there are other applications too, in which the large number of transmission lines feed a load from a single high-energy capacitor because of their well-defined current ratings...

An alternative approach for applications requiring production of intense electron beam without using conventional configuration of Marx/Tesla accompanying Pulse Forming Line has been explored. The developed portable system utilizes four stage Blumlein pulse forming network made from inexpensive commercially available URM-67 coaxial cables having ch...

A compact pulsed power system, which is reported in this paper, is designed for conducting relativistic-electron-beam characterization experiments in the space-charge limited flow. The experiments are conducted for various cathode materials like graphite and velvet and also for various anode transparencies and geometries by making them of thin foil...

Summary form only given. The design procedure, fabrication details and experimental results of a high-energy capacitor bank is reported in this paper. The bank consists of 8 capacitors connected in parallel, each having a capacitance of 178 muF giving a total of 1424 muF. The bank is charged at 15 kV using a 28 kV power supply which charges the cap...

Blumlein generator is a flexible transmission line based device which is well suited for high voltage pulse generation with time durations ranging from few nanoseconds to microseconds. Its well defined output impedance and degree of flexibility to obtain defined pulse shapes with fixed voltage gain makes it suitable for large variety of pulsed powe...

Electromagnetic interference (EMI) related malfunctioning of equipment containing electronic control devices has become a serious problem these days, as it couples to wires and PCB's in the equipment, reflecting and resonating and then being amplified by an IC finally resulting in malfunction. In order to test and simulate the immunity of electroni...

The technology used for the intense relativistic electron beam production has advanced significantly and is wide spread in use for variety of pulsed power applications generating several mega-watts of beam power. The production of such intense electron beams begins from electron source. In majority of applications the main requirement for electron...

Summary form only given. Plasma focus is important tool for plasma physicists for understanding dense magnetized plasma. Recently Plasma focus attracted the attention of the plasma research community for its use in pulsed radiation applications. The emitted neutrons can be applied to perform radiographs and substance analysis, taking advantage of t...