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Nagesh, K. V.

Paper Title Page
THPMA064 Development of a 200keV Linear Induction Accelerator 720
 
  • K. V. Nagesh, S. Acharya, R. Agarwal, D. P. Chakravarthy, S. Mitra, K. C. Mittal, D. D. Praveen Kumar, R. N. Rajan, S. R. Raul, P. C. Saroj, A. S. Sharma, D. K. Sharma
    BARC, Mumbai
  
  Electron Linear Induction Accelerator (LIA) are for applications for applications in High Power Microwaves (HPM), high gradient accelerators, flash X-Ray radiography (FXR), flue gas clean-up, detoxification of chemicals, cross-linking of polymers, sterilization of food and medical devices, etc. The LIA-200 being developed at APPD/BARC consists of three main phases of pulse compression and voltage amplification, viz; (i)solid-state pulse modulator uses semiconductor devices, (ii)Pulse compression and voltage amplification stages, steps up to 200kV, 5 micro-seconds and compresses these pulses to 75kV, 10kA, 50ns in five stage and (iii)three induction cavities in ADDER mode for relativistic electron beam generation, with matched impedance of 5 ohms. Metglas cores have been used in the switches, cavities and pulse transformers. Deminaralized water capacitors and water transmission lines have been used for low impedance energy storage and compactness. The complete system has been assembled and ready for commissioning. LIA system will be operated from a PLC based control system which is under testing.  
THPMA065 Theoretical Analysis of the Recovery Times in Low Pressure Sparkgaps - Positive Ion Diffusion Method 723
 
  • K. V. Nagesh, K. V. Nagesh
    BARC, Mumbai
  
  The recovery characteristics of the low-pressure sparkgaps in the time interval of 300*s to 50ms, for hydrogen, argon and deuterium gases,had shown thatthat the breakdown voltage under second pulse is higher than the breakdown voltage under first pulse along the left hand side of Paschen's characteristics and defined as over recovery (>100% recovery). An attempt has been made to calculate and analyze the recovery times of low pressure sparkgaps based on diffusion of positive ions here. The recovery times are calculated based on the reported data of plasma diffusion rates. The spherical ambipolar and free diffusion recovery times are generally in good agreement with the experimental recovery times at higher pressures. The cylindrical ambipolar and free diffusion recovery times are an order of magnitude lower than spherical diffusion recovery times. The recovery times are not in good agreement for positive polarity experimental recovery times. The theoretical calculation of recovery times, comparison of calculated and experimental recovery times and discussions are presented in this paper.  
THPMA065 Theoretical Analysis of the Recovery Times in Low Pressure Sparkgaps - Positive Ion Diffusion Method 723
 
  • K. V. Nagesh, K. V. Nagesh
    BARC, Mumbai
  
  The recovery characteristics of the low-pressure sparkgaps in the time interval of 300*s to 50ms, for hydrogen, argon and deuterium gases,had shown thatthat the breakdown voltage under second pulse is higher than the breakdown voltage under first pulse along the left hand side of Paschen's characteristics and defined as over recovery (>100% recovery). An attempt has been made to calculate and analyze the recovery times of low pressure sparkgaps based on diffusion of positive ions here. The recovery times are calculated based on the reported data of plasma diffusion rates. The spherical ambipolar and free diffusion recovery times are generally in good agreement with the experimental recovery times at higher pressures. The cylindrical ambipolar and free diffusion recovery times are an order of magnitude lower than spherical diffusion recovery times. The recovery times are not in good agreement for positive polarity experimental recovery times. The theoretical calculation of recovery times, comparison of calculated and experimental recovery times and discussions are presented in this paper.  
THPMA066 Theoretical Analysis of the Recovery Times In Low Pressure Sparkgaps- Anode Temperature Decay Method 726
 
  • K. V. Nagesh, K. V. Nagesh
    BARC, Mumbai
  
  The recovery characteristics of the low-pressure sparkgaps in the time interval of 300*s to 50ms, with stainless steel electrodes, in the pressure range of 1 to 40Pa, for gap spacings of 2.5mm and 10mm, have been determined experimentally for hydrogen, argon and deuterium gases. Presently there are no methods ideally suitable for calculation of recovery times of low pressure sparkgaps. However an attempt has been made to analyze the recovery times of low pressure sparkgaps by anode temperature rise and decay method based on liquid and solid vapour phases here. The recovery times are calculated based on the reported data of anode drops. The solid phase recovery times are generally in good agreement with the experimental recovery times with higher load currents. The liquid phase recovery times are an order of magnitude low compared to the experimental recovery times. The recovery times are not in good agreement for positive polarity experimental recovery times due to non-uniformity in the gap. The theoretical calculation of liquid and solid phase recovery times, comparison of calculated / experimental recovery times and discussions are presented in this paper.  
THPMA066 Theoretical Analysis of the Recovery Times In Low Pressure Sparkgaps- Anode Temperature Decay Method 726
 
  • K. V. Nagesh, K. V. Nagesh
    BARC, Mumbai
  
  The recovery characteristics of the low-pressure sparkgaps in the time interval of 300*s to 50ms, with stainless steel electrodes, in the pressure range of 1 to 40Pa, for gap spacings of 2.5mm and 10mm, have been determined experimentally for hydrogen, argon and deuterium gases. Presently there are no methods ideally suitable for calculation of recovery times of low pressure sparkgaps. However an attempt has been made to analyze the recovery times of low pressure sparkgaps by anode temperature rise and decay method based on liquid and solid vapour phases here. The recovery times are calculated based on the reported data of anode drops. The solid phase recovery times are generally in good agreement with the experimental recovery times with higher load currents. The liquid phase recovery times are an order of magnitude low compared to the experimental recovery times. The recovery times are not in good agreement for positive polarity experimental recovery times due to non-uniformity in the gap. The theoretical calculation of liquid and solid phase recovery times, comparison of calculated / experimental recovery times and discussions are presented in this paper.  
THPMA070 Characterisation of Amorphous Magnetic Material with Multiple Pulse Excitation 732
 
  • A. S. Sharma, S. Acharya, K. V. Nagesh
    BARC, Mumbai
  • U. Kumar, G. R. Nagabhushana
    IISC, Bangalore
  
  An experimental investigation for the understanding of magnetic core saturation behaviour under pulse excitation is presented in this paper. The effect of repetitive shots, after resetting, on the magnetic properties of toroidal amorphous core of size 160/240/25 mm is reported. This study is made using 20kV, 20, and 200ns square pulse source, to realize the various steps which an amorphous core undergoes on saturation as well as corresponding changes in magnetic parameters viz. magnetization force, total flux swing and relative permeability. The most significant effect of pulsing is seen at higher values of operating flux, compared to lower flux regimes. Effects of number of turns and input power level to the core are also shown in this paper. It has been shown that the total energy required to saturate the core in multiple pulses is less if peak input is smaller than that in case of higher peak pulse excitation. Keyword: amorphous core, multiple pulses, effect of turns, pulse excitation  
THPMA071 Study of Insulation Coordination in the Presence of Multiple Dielectric Materials 735
 
  • S. Mitra, D. P. Chakravarthy, K. V. Nagesh, D. D. Praveen Kumar, A. K. Ray, A. S. Sharma
    BARC, Mumbai
  
  Use of various dielectric materials for insulation is inevitable in high voltage systems. Choosing a particular insulating material (solid, liquid, and gas) depends on various factors like the nature of the system, insulation level required, dielectric strength and thermal & mechanical stress handling capability of the material. Besides the surface break down strength of two material interfaces plays important role in the high voltage design considerations of the system. This paper critically analyses the field stress in high voltage points in presence of multiple dielectric media, in particular on the existing system of Kilo Ampere Linear Injector (KALI – 5000) system. In this paper, local field enhancement phenomenon due to presence of different solid and liquid dielectrics is evaluated. Mathematical derivations of the percentage increment of field, at the critical point, due to presence of hybrid dielectric materials, are calculated for planar, spherical and cylindrical geometry of the high voltage elements. 2-D simulations of the same to support the mathematical calculations are done using MAXWELL SV software.  
THPMA043 Development of 3 MeV, 30 kW DC Electron Accelerator at EBC, Kharghar 682
 
  • K. C. Mittal, S. Acharya, R. Agarwal, R. Barnwal, D. P. Chakravarthy, A. S. Chawala, A. R. Chindarkar, S. R. Ghodke, B. S. Israel, A. Jain, D. Jayaprakash, M. K. Kumar, M. K. Kumar, R. L. Mishra, K. V. Nagesh, K. Nanu, M. K. Pandey, G. P. Puthran, R. N. Rajan, S. R. Raul, A. K. Ray, P. C. Saroj, D. K. Sharma, V. Sharma, R. Shilendra, S. K. Suneet, S. B. Supriya, D. P. Suryaprakash
    BARC, Mumbai
  
  A 3 MeV, 30 kW DC industrial electron accelerator has been designed and is in advanced stage of development at EBC, Kharghar, Navi Mumbai. Electron beam at 5 keV is generated in electron gun with LaB6 cathode and is injected into accelerating column at a vacuum of 10-7 torr. After acceleration, the beam is scanned and taken out in air through a 100 cm X 7 cm titanium window for radiation processing applications. The high voltage accelerating power supply is based on a capacitive coupled parallel fed voltage multiplier scheme operating at 120 kHz. A 50 kW oscillator feeds power to high voltage multiplier column. The electron gun, accelerating column and high voltage multiplier column are housed in accelerator tank filled with SF6 gas insulation at 6 kg/sq.cm. The accelerator is located in a RCC building with product conveyor for handling products. A central computerized control system is adopted for operation of the accelerator. Accelerator is in the advance stage of commissioning. This paper describes the design details and current status of the accelerator and its various subsystems.