Vivek Yadav

An improved magnetic field simulator - MAGFLD

An improved two-dimensional simulator MAGFLD has been developed which is useful for the design and simulation of periodic permanent magnet (PPM) focusing system for linear beam tubes. At present, input is possible only through the input file, which is very simple and user friendly. A complete PPM circuit is generated using the coordinates of first pole piece, first magnet, gun adapter (if the structure is a-periodic) and the region of computation. Small mesh units of either square or rectangular shapes can be used with mesh refinement capability in one or more regions in any or both directions for better accuracy of the solution. Materials with different magnetic permeability can be modeled by defining a characteristic value for each mesh point of the geometry. The effective potential value at each point in the region of interest is calculated based on the vector potential model by using the 5-point finite difference method and the solution is achieved by over relaxation technique for faster convergence. This package has an interface with EGUN to model the electron gun and collector under the influence of magnetic field. Versatile color graphics are capable of plotting both axial magnetic field and flux lines along with the magnetic circuit. MAGFLD has been validated against some published data and experimental results.

P3-1: Design of 42 GHz, 200 kW Gyrotron

The design of 42 GHz, 200 kW Gyrotron has been carried out using in-house and commercially available softwares. A triode type MIG has been designed using EGUN code and three in house developed codes MIGSYN, GINTMESH and MIGANS respectively. A weakly tapered interaction cavity has been designed to excite TE03 operation mode. A software GCAVSYN has been developed to synthesize the cavity geometry and selection of the operating mode. The cold cavity analysis was carried out using commercially available PIC code MAGIC. An axial output power above 200 kW has been obtained at the guiding magnetic field 1.60T–1.65T. The behavior of generated rf power in beam tunnel has been simulated using the CST Microwave Studio and Ansoft HFSS. The different lossy ceramics have been studied for reflection, transmission and absorption. A good agreement has been found in the simulated results from both the software. The design of collector has been optimized to achieve the maximum beam spread.

Electron Beam Emission and Interaction in 0.3-THz Gyrotron for Second Harmonic, CW Operation

This paper describes the design of a 0.3-THz gyrotron at second harmonic operation. The interaction cavity design and the beam-wave interaction computation are carried out for TE0,6 mode by using the particle-in-cell electromagnetic simulation approach. The simulation results confirm > 6-kW output power with efficiency ~ 17% by using an electron beam with accelerating voltage 20 kV and current 2.0 A. To achieve the required electron beam parameters, a triode magnetron injection gun is designed. The transverse-to-axial velocity ratio (α), 1.27 and the transverse velocity spread <; 4% are realized. Considering the fabrication and operation of the device, the parametric analysis is also performed.

Towards the design of 100 kW, 95 GHz gyrotron for active denial system application

The design work for 95 GHz, 100 kW gyrotron for Active Denial System (ADS) application is presented. The mode selection is performed considering the various technical constraints. Particle-in-Cell code is used for the beam-wave interaction computation and cavity design. In addition, the designs of electron beam source, collector and RF window are also discussed. The design results confirm the RF power >100 kW with ≈50 % tube efficiency.

High-Frequency Transmission Characteristics of Inert Coolant Liquids for High-Power Gyrotron Windows

The frequency response of dielectric properties of coolant liquids used in the gyrotron RF window is measured. FC-40, FC-75, and CCl4 are considered for the measurements due to their reported application in gyrotron and excellent dielectric properties required for high-power RF transmission. A performance probe kit based on the reflection method is used for measurements in wide frequency range from 200 MHz to 50 GHz. Vector network analyzer (VNA) is used as the RF source as well as receiver. The dielectric constant and loss tangent are calculated directly by using the scattering matrix data obtained from the VNA. Further, ac conductivity and relaxation time are also computed by using measured data of loss tangent and dielectric constant.

Cold cavity analysis for 35 GHz gyrotron interaction cavity using free space method

The interaction cavity simulated, designed and fabricated for the 35 GHz gyrotron is verified experimentally. Free space method for the Q value and resonant frequency measurement is used in the experiments. The WR22 waveguide based antenna system, Agilent Vector Network Analyzer are used as the experimental set-up in the cavity measurement. The simulation results for the same cavity are also obtained by using the electromagnetic simulator MAGIC for the comparison.

Prevalence of HIV and syphilis infections among men who have sex with men attending an integrated counseling and testing centre at Agra: Comparison with studies in other regions of India

Abstract Men who have sex with men (MSMs) are a group of high-risk individuals in India, who have remained neglected for a long time. Stigma, discrimination and laws criminalizing sex between men undermine access to HIV/AIDS and other health care services. In this study, we determined the seroprevalence and risk factors for HIV and syphilis infections among a group of MSMs attending an Integrated Counseling & Testing Centre (ICTC) at Agra during 2009–11. The results have been compared with those in other regions of the country. There were 277 MSMs registered with a nongovernmental organization (NGO), Khushi, involved in a Targeted Intervention (TI) project, who were tested for HIV and venereal disease research laboratory (VDRL) infections. Sociodemographic profile, risk factors, sexual identity, general health care access, and previous HIV and/or sexually transmitted infection (STI) testing, etc., were documented. The prevalence of HIV and syphilis infections among the MSMs are 11.9% (33/277) and 11.1% (31/277), respectively. There were 74% of them in the age group of 15–35 years, illiterate, and having no specific job. Alcohol, drug abuse, and high-risk behavior were common as they preferred to be in groups. There were 70% of HIV-positive MSMs, and 87% of those having sexually transmitted diseases (STDs) were unmarried and had multiple partners. Some of the MSMs were married and in bisexual relationships, and they might serve as an important bridge population between men and women. High prevalence of HIV and STDs in this group emphasizes the need for public health interventions aimed at reduction of risky behavior, education and counseling to urge them to seek health care advice when needed.

Analysis of parasitic mode oscillations for 95 GHz gyrotron beam tunnel

The analysis for the parasitic mode excitation is performed for gyrotron beam tunnel. Scattering matrix simulations are performed for the initial design of the beam tunnel. Here only the symmetric TE modes are observed due to the week damping inside the tunnel. Various approaches are used for investigation of parasitic mode excitations.

Estimation of permittivity and loss tangent of high frequency ceramics using free space method

In this paper, the results of permittivity and loss tangent measurements of high frequency ceramics are presented. The free space method is used to measure the permittivity and loss tangent of different ceramics in the millimeter wave band (110 GHz-125 GHz).

Design of 28 GHz, 200 kW Gyrotron for ECRH Applications

Abstract This paper presents the design of 28 GHz, 200 kW gyrotron for Indian TOKAMAK system. The paper reports the designs of interaction cavity, magnetron injection gun and RF window. EGUN code is used for the optimization of electron gun parameters. TE03 mode is selected as the operating mode by using the in-house developed code GCOMS. The simulation and optimization of the cavity parameters are carried out by using the Particle-in-cell, three dimensional (3-D)-electromagnetic simulation code MAGIC. The output power more than 250 kW is achieved.