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The M-type Strontium Hexaferrite SrFe12O19 particles were prepared by a Self propagating High temperature Synthesis (SHS) route. Precursors were heated under two different conditions: microwave heating for 30 minutes and sintered at 950°C for 4 hrs. The dielectric properties: dielectric constant (ε'), dielectric loss (tan δ) and ac conductivity (σac) were measured at room temperature in the frequency...
This article describes the development and alignment of multi-stage depressed collector which is used in TWT application by using Twymann-Green Interferometry technique. A unique methodological approach is used to develop a better efficient system design layout for the alignment process for an assembly of MSD collectors. In view demand of a high power and high efficiency traveling wave tubes for space...
A compact generator based on Tesla transformer for application in plasma opening switch has been developed. This system will be used to produce microwave for plasma-microwave interaction studies. Overall dimension of this system is 6 feet by 4 feet. This system is designed to operate with up to 350 kV on water pulsed forming line to generate 75 kA, 40 ns pulse, which further will be compressed in...
Reliability of cathodes is critical for the reliability of traveling wave tubes. Accordingly, the reliability test and life prediction of diodes can provide useful information for cathode and TWT reliability evaluation. In this paper, a simple cathode life prediction method considering the evolving of heater power and perveance is presented. The method is applied on the reliability test data for some...
Accurate and fast SUNRAY-2.5D code has been developed for multi-signal large signal analysis of a complete helix TWT. Ring model of electron beam was used and relativistic equations of motion were solved with variable focusing field, circuit loss and pitch profiles. Improved expressions of the circuit field and induced voltages were developed. Complete RF output and beam performance including higher...
The helix TWT in which the dielectric supports with varying along area of interaction ε are used is suggested. The law of varying ε have maintained the necessary for high efficiency distribution of slowing of helix with constant pitch.
Two types (type-A and type-B) of the S-band high-power broadband multi-beam klystrons are being developed in the Institute of Electronics, Chinese Academy of Sciences (IECAS). Type-A adopts a coil focusing system, and type-B has a Periodic Reverse Permanent Magnet (PRPM) focusing system. Five tubes have been manufactured and tested to date. Test results show that both MBKs have the RF peak output...
Key performance characteristics that guide the selection of an amplifier for various applications are gain, power, linearity, and efficiency. In this paper, these parameters are contrasted for two amplifier configurations: a single-beam amplifier with stages placed in series vs. a multi-beam amplifier with cascading stages. Based on MAGIC-3D simulations, while gain and efficiency are comparable, the...
The vacuum system of the K=130 Room Temperature Cyclotron (RTC) (operational since 1978) has been recently modernized and the same of the Kbend=520 Superconducting Cyclotron (SCC), currently under commissioning, is being deployed for remote monitoring and control. The vacuum system of RTC is designed to achieve and maintain vacuum level of 2×10-6 mbar inside 23 m3 volume of Resonator tank and DEE...
Effective control of power absorption in tokamaks and stellarators could be achieved by the frequency tuning of ECH&CD power delivered by high-power gyrotrons. In this report some results of the development of a frequency tunable gyrotron with fused-silica Brewster window are presented. Excitation of several modes at 1 MW power level in the range of frequencies from 131 to 146.5 GHz is achieved...
We demonstrate that on considering an electric-field longitudinal profile in the shape of a two-level transition curve the monotron conversion efficiency can attain values in excess of 30%, 1.5 times as high as that obtained from the conventional uniform field distribution. This is accomplished by using two cavities electromagnetically coupled by an annular slit crossed by an electron stream. A two-cavity...
In this paper, the self-consistent large-signal formulation is used to study the beam-wave interaction mechanism in a gyrotron oscillator. The nonlinear interaction has been computed by solving the set of self-consistent nonlinear equations along the interaction length using numerical method. Consequently, the computation of energy, phase, output power, and efficiency of a gyrotron is made. The computed...
This paper describes the simulation of a single stage depressed collector using PIERCE and CST Studio including secondary electron emission effects. This collector was developed and integrated with a linear beam tube. The experimental efficiency of the collector agrees well with the simulated efficiency of the collector. The thermal analysis of the collector also has been carried out using ANSYS and...
In this paper we report precision MEMS Fabrication using novel LIGA technique for 0.22 THz micro-metallic staggered double-vane TWT circuits. For this high aspect ratio structure negative tone photo-resist KMPR was used. The entire fabrication process starting from spin coating, UV-lithography, electroforming and mold removal processing was fully characterized. Finally, the high tolerance TWT structure...
The paper presents the design of a MOU for the coaxial ITER gyrotron. Corrugated waveguides are used to transmit the high power mm-waves generated by gyrotrons to the plasma for Electron Cyclotron Resonance Heating (ECRH) and Current Drive (CD). The MOU contains two focusing mirrors, which are used to convert the gyrotron output into a Gaussian distribution with optimal parameters to improve the coupling...
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.
The sheet beam klystron (SBK) is characterized by a large rectangular drift tube, which allows the use of a high current, low voltage beam, resulting in a low beam current density, and hence high efficiency and the possibility of Periodic Permanent Magnet (PPM) focusing. Our research group has designed a 5-Cavity X-Band SBK recently. In this paper, we discusses the general design of this X-Band SBK...
In order to exploit the cavity resonance effect for enhancing the power conversion efficiency of coaxial vircators, a modification in the drift region is proposed. The modification introduces geometrical parameters which can be varied to change the structure and strength of modes inside the vircator. These cavity parameters have been optimized using particle-in-cell (PIC) simulation to increase the...
The dispersion equation for free electromagnetic waves guided by an anisotropically conducting open tape helix is derived from the exact solution of a homogenous boundary value problem for Maxwell's equations without invoking any a priori assumption about the tape-current distribution. The approximate dispersion curve tends to be close to the dominant-mode sheath-helix dispersion curve in the middle...
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