Lalit Mohan Joshi

• PhD
• Principal Investigator at Central Electronics Engineering Research Institute

A 352.2 MHz klystron with an output power of 100 kW CW is under development at CSIR-CEERI for charged particle accelerator application. The paper presents various design results achieved through simulation of the electron gun, radio frequency (RF) interaction structure and collector for the device. Based on the design results, a beam stick tube has...

High CW power klystrons are having wide applications in various accelerator based systems and ongoing research in the area of high energy physics as a source of microwave power. Thermal analysis of collector for a klystron designer becomes very critical for high CW power tubes, as the energy in the spent electron beam may lead to damage of collecto...

The multiple-beam klystrons (MBKs) are well known for some distinct performance advantages over their single-beam versions. The advantages of the MBKs include higher average power, relatively lower operating voltages, higher bandwidth, and low individual beam current. However, the design of the MBKs is more extensive and requires thorough and caref...

The paper reports the theoretical approach and computer-aided design results for a 350 MHz, 100 kW (CW) inductive output tube. The design considerations and methodologies employed for electromagnetic simulation of individual electron gun and RF cavity assemblies and that of their combined assembly were presented. The electron gun parameters namely...

Inductive Output Tube (IOT) is an amplifier that usually operates in UHF range. It is an electron tube whose basic structure is similar to conventional vacuum devices. This device is widely used in broadcast applications but is now being explored for scientific applications also specifically, particle accelerators and fusion plasmaheating purposes....

The klystron is a well-known microwaveamplifier which uses kinetic energy of an electron beam for amplification of the RF signal. There are some limitations of conventional single beam klystron such as high operating voltage, low efficiency and bulky size at higher power levels, which are very effectively handled in Multi Beam Klystron (MBK) that u...

The paper deals with the simulation and analysis of pillbox type RF window for high power S-band klystron. Numerical simulation of RF window has been performed by using -wave wizard code. The impedance matching technique has been used for the designing of pillbox type RF window. The simulation results have been validated through cold testing of fe...

This study is all about the evolution of inductive output tube (IOT) and its significance in the current scenario. The historical review with timeline is briefly discussed. The basic design considerations and operating principle of IOT have been described. This tube is opted for many applications these days over other conventional vacuum tubes for...

In this paper, a computer aided study of the re-entrant cavity structures, which are of practical utility and widely employed in klystrons, has been done. For these cavities, the behavioral aspects of the cavity parameters are studied by changing the gaps and the drift tube profile. The URMEL group of computer code has been employed for this purpos...

In this paper, a detailed design procedure for designing a thin disc pill-box type microwave window, operating in narrow frequency range at S-band and at a power level of 5 MW, has been given. The design criteria and a generalised design flow chart have been presented and discussed in detail. A method has been suggested for quicker experimental opt...

AD/E band, 1 kW CW four cavity klystron tube has been successfully developed at the Central Electronics Engineering Research Institute (CEERI), Pilani. The main building blocks of this tube are electron gun, magnetic focussing system, RF cavities and collector. Design of each of these has been worked out and is presented in this paper.

The paper describes voltage break down phenomenon and preventive measures in components of 250 KW CW, C band klystron under development at CEERI Pilani. The klystron operates at a beam voltage of 50 kV and delivers 250 kW RF power at 5GHz frequency. The klystron consists of several key components and regions, which are subject to high electrical st...

The multiple beam klystrons (MBK) offer some distinct advantages over their single beam versions including higher average power, relatively lower operating voltages, higher bandwidth and low individual beam current. In this paper the design of the radio frequency (RF) section of a multiple beam klystron working in the J band frequency range is pres...

Sheet Beam Klystron (SBK) is a device employing rectangular/elliptical cross section beam. The barbell cavity for SBK has been designed providing uniform flat electric field profile across the width of the cavity. The loop coupling arrangement has also been designed using CST Microwave studio software tool and optimized for maximum return loss. The...

The paper presents the design and development of collector for C-band 250 kW high power klystron. The design criteria for the collector assembly is selection of material, vacuum and high temperature compatibility, proper electron beam dispersion, minimum back scattering of electrons and thermal design for proper cooling at high power dissipation. A...

This article describes the computer-aided design of the RF-cavity for a S-band klystron operating at 2856 MHz. State-of-the-art electromagnetic simulation tools SUPERFISH, CST Microwave studio, HFSS and MAGIC have been used for cavity design. After finalising the geometrical details of the cavity through simulation, it has been fabricated and chara...

This paper is concerned with the design of rectangular radio frequency (RF) cavities for a miniature multiple beam Klystron. The proposed multiple beam klystron will have four beamlets, each carries 64mA current. The RF cavities under design will be compatible with a multiple beam electron gun under development in CEERI. This work is in continuatio...

The present paper deals with the designing and simulation of electron gun, collector and electromagnet for 250kW CW, 5GHz klystron. The assembled structure named as Gun collector test module (GCTM) is also designed to validate the gun perveance and thermal design of collector. The electron beam optics is designed in TRAK 1D code and MAGIC2D code. B...

Klystron is microwave power amplifier widely used as RF source in particle accelerators, thermonuclear reactors and radars. The re-entrant cavity structures are widely used in klystron. They play a prominent role in deciding the performance of the device. Its design is carried out using SUPERFISH and MAGIC. The fabrication of cavities was carried o...

The radiation performance of broadband circularly polarized gap-coupled arrangement of rectangular patches is reported in this article. This arrangement of patches is designed on glass epoxy FR-4 substrate. The considered structure consists of three rectangular patches having separation “d” between them. The central designed patch is excited throug...

During past fifteen years, tremendous growth in the field of microwaves, millimeter waves and Terahertz frequency region has been realized in India. The growth of R&D activities in these areas has attracted many multinational companies to start new ventures. The research funding for these activities are mainly provided by government agencies but ma...

The design of the aperture in the pole piece of a multi-beam confined-flow electron gun has been studied using the commercially available code OPERA 3D and validated the results using the CST particle studio, and the OmniTrak simulation tools. The results obtained by these tools are in good agreement with respect to the beam-waist radius and the th...

Conventional microwave tubes generally use cylindrical electron beam coaxial to RF interaction circuit for generation or amplification of microwave signals. Many performance limitations these tubes in respect of band width, efficiency, voltage break have been addressed by emerging multi-beam technology which uses several low perveance electron beam...

The klystron is a microwave tube capable to produce very high power that find wide use in communication, radar, material processing, particle accelerators and thermonuclear fusion reactors. The RF section has an important role in deciding the RF performance of the tube, such as its gain, band width, efficiency etc. The RF section is a integration o...

This paper gives a new design for the cavity of Sheet beam Klystron (SBK) which has lot of advantages as well as some design challenges. This cavity design employs dielectric loading for flat field across the beam.

A 6 MW peak, 24 kW average power S-band 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 simulati...

The radiation performance of a compact gap-coupled assembly of patches forming the geometry of elliptical patch antenna is simulated and tested using glass epoxy FR4 substrate material. This assembly is achieved by cutting a conventional elliptical patch antenna geometry into three independent patches through two narrow slits parallel to minor axis...

This work presents the thermal and structural analysis of collector for multi beam klystron (MBK) using convective heat transfer method for cooling of collector. The structural deformation and developed stresses along both the axial and radial directions, due to temperature distribution, has been simulated. The results has also been compared with d...

The radiation performance of a circular patch microstrip antenna having a concentric diamond shape slot has been presented in this paper. The side lengths and angles of the inserted diamond shape slot have been optimized to achieve a single layer multi frequency microstrip antenna applicable for C band space communication systems. For simulation wo...

The paper presents the design fabrication and cold testing of vacuum RF window for C-band 250 kW CW power klystron. The electromagnetic simulation of the window has been carried out using the CST microwave studio software. The proposed window is designed for 5 GHz operating frequency for handling 250 kW of RF power. In the proposed window geometry,...

The radiation performance of a right triangular microstrip antenna (RTMA) having two parallel narrow slits is simulated using IE 3D software, and later this antenna is designed on glass epoxy FR-4 substrate with an air gap and tested in free space. The slit length, width, and thickness of air gap are optimized to attain best performance from the mo...

Klystron is vacuum electron device operating in microwave range of frequencies. It is used as power amplifier in a variety of systems including radars, particle accelerators and thermonuclear reactors. With the availability of very reliable design codes, it is now possible to optimize the design and develop a tube with minimum iterations in fabrica...

A 3.7 GHz., 120 kW (pulsed), lower hybrid current drive (LHCD) system is employed to drive non-inductive plasma current in ADITYA tokamak. The rf power is coupled to the plasma through grill antenna and is placed in vacuum environment. A vacuum break between the pressurized transmission line and the grill antenna is achieved with the help of a mult...

The paper deals with the design fabrication and cold testing of vacuum RF window for C-band 250 kW CW power klystron. The simulation of the window has been carried out using the CST microwave studio software. The proposed window is designed for 5 GHz operating frequency for handling 250 kW of RF power. In the proposed window geometry, metallized al...

In multi-beam klystron (MBK), several electron beams are used to interact with the RF signal in a single interaction structure. MBK has a number of advantages over single beam klystron. As it uses several low perveance beams, for the same overall perveance, the beam voltage is substantially lower than single beam klystron for same RF output power.

The paper presents design, analysis and electromagnetic simulation of asymmetric structure of pillbox type RF window for S-band high power applications. This study is motivated by 6 MW pulse peak and 24 kW average power S band klystron project. Asymmetrical pill box type RF window structure is a new approach for matching reduced waveguide in one si...

In multi-beam Klystron (MBK),several electron beams are used to interact with the r.f. signal in a single interaction structure. MBK has a number of advantages over single beam klystron. As it uses several low perveance beams, for the same overall perveance, the beam voltage is substantially lower than single beam klystron for same DC input power....

Klystron is microwave power amplifier widely used as RF source in particle accelerators, thermonuclear reactors and radars. A precise simulation of beam-wave interaction in klystron is useful not only to understand itpsilas operation but also in development of tube with minimum iterations in fabrication. For this purpose a 1-D code AJDISK has been...

This paper describes different applications of alumina ceramics in the form of metal-alumina vacuum tight seals for development of 5 MW klystron. The klystron is a high power microwave amplifier operated at 2856 MHz with 5 MW rf output power. The klystron tubes with ceramic-metal seals are more rigid and are capable of handling relatively large pow...