Mukesh Kumar Alaria

Design and Development of Helix Slow-Wave Structure for Ku-Band TWT

A helix slow-wave structure (SWS) for a high-efficiency (electronic efficiency >; 25%) Ku-band 140-W space traveling-wave tube (TWT) has been designed. The cold circuit parameters of helix SWS, like propagation constant and on-axis interaction impedance, were determined using 3-D electromagnetic field simulators ANSOFT-HFSS and CST-MWS, and those were validated with the experimental results. The in-house developed large-signal code SUNRAY-1D was used to design a complete helix SWS in two sections with sever and taper to achieve desired output power, gain, efficiency, and other linearity parameters like phase shift, AM/PM factor, and I/M components. The simulated RF performance of the Ku-band 140-W helix TWT was validated with the experimental results. A close agreement between the simulated and experimental results has been found.

Design of Single-Disk RF Window for High-Power Gyrotron

In this paper, the electrical design of the water-edge-cooled single-disk chemical-vapor-deposited-diamond window for the 120-GHz 1-MW gyrotron has been carried out using the CST Microwave Studio. The return loss (S11) and transmission loss (S21) of the 120-GHz gyrotron window have been obtained as -37.3 dB and -0.04 dB, respectively. The thermal analysis of the RF window for the 1-MW gyrotron has also been carried out using ANSYS software and discussed in this paper. The thermal analysis of the window, during extreme case of operation, has been carried out. The temperature range on the disk surface has been found to be 50°C-150°C.

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.

DESIGN AND CHARACTERIZATION OF HELIX SLOW WAVE STRUCTURE FOR KU-BAND SPACE TWT

A helix slow-wave structure (SWS) for a high e-ciency Ku-band 140W space TWT has been designed. Cold circuit parameters of helix SWS like propagation constant and on axis interaction impedance were determined using 3-D electromagnetic fleld simulators ANSOFT-HFSS and CST-MWS and validated with the experimental results. In-house developed large-signal code SUNRAY- 1D was used to design the complete helix SWS in 2-section with sever and taper to achieve desired output power, gain, e-ciency, and other linearity parameters such as phase shift, AM/PM factor, I/M components. Simulated RF performance of the Ku-band 140W helix TWT was validated with the experimental results. A close agreement between the simulated and experimental results has been found.

P2-12: Thermal analysis of slow wave structure for a space helix TWT

In this paper thermal analysis of the slow-wave structure for Ku-band helix space TWT has been carried out using ANSYS software v.10.1. To evaluate the thermal aspects of the helix slow-wave structure with three APBN support rods and barrel assembly, the related studies of the slow-wave structure assembly with six turn, ten turn and sixteen turn of helix for the Ku-band 140 W space TWT during extreme case of operation, i.e. at saturation and with perfectly rigid base-plate at 80 °C have been carried out. The CPU time on Pentium-4, window XP system with 512 MB RAM was 45 minutes for six turn, one hour for ten turn of helix.

P3-14: Effect of beam tunnel geometry on electron beam parameters for 42 GHz Gyrotron

A triode type Magnetron Injection Gun (MIG) for a 200kW, 42GHz Gyrotron has been designed by using commercially available code EGUN. The design optimization of the beam tunnel has been done with the help of 3-D simulation software CST-Microwave Studio. This paper presents the effect of beam tunnel geometry on the electron beam parameters for 42 GHz gyrotron.

Electron Beam Misalignment Study of MIG for 42 GHz, 200 kW Gyrotron

Abstract This paper presents the electron beam misalignment study with respect to cathode position and cathode magnetic field of 42 GHz, 200 kW gyrotron. The performance of gyrotron is affected with the misalignment of cathode position. The simulation results confirm the tolerance of cathode misalignment with respect to the design parameters such as the transverse-to-axial velocity ratio, the maximum transverse velocity spread, etc.

Evaluation of Cathode Heater Assembly for 42 GHz, 200 kW Gyrotron

Abstract In this paper, the evaluation of cathode-heater assembly of magnetron injection gun (MIG) for 42 GHz, 200 kW gyrotron is presented. The cathode-heater assembly is purchased from M/S SEMICON.The cathode-heater assembly is experimentally studied in three different conditions; in a belljar system, during vacuum processing of MIG and during MIG testing to ensure the required rise of cathode surface temperature for pre-set heater power.

Analysis of interaction structure for ka-band GYRO-TWT

Summary form only given. In GYRO-TWT, the RF wave propagates in the smooth wall cylindrical waveguide structure with a speed greater than the speed of a light. Such type of interactions structure used in gyro-TWTs are not capable of providing fairly wide device bandwidth due to rapid change in group velocity with frequency, at or near the cut off frequency of waveguide, which causes a narrow band coalescence between beam mode line and waveguide mode dispersion hyperbola. Wider bandwidths are achievable from this device using special type of loaded waveguides. The analysis has shown that the shape of the dispersion characteristics depends on the disc thickness, though not as much as it does on the disc-hole radius and the structure periodicity. The prediction of the effect of the structure or disc parameters on the control of the structure dispersion characteristics and their shape by the analysis ignoring the finite disc thickness more or less continues to hold good when the analysis is improvised by including the finite disc thickness. However, the improved analysis has further added to the prediction that, out of the parameters, namely, the structure periodicity, the disc-hole radius and the disc thickness, while the structure periodicity continues to be the most effective, the disc thickness proves to be the least effective, in controlling the dispersion shape, more precisely, in widening the frequency range of the straight-line portion of the dispersion characteristics. A decrease in the value of the structure periodicity has led to the widening of this frequency range. As for the disc-hole radius, it has to be optimised for maximising the frequency range of the straight-line portion of the dispersion characteristics.

Dielectric properties measurements of FC-75

In this paper the results of dielectric properties measurements of FC-75 (Fluoro Carbon-75) are presented, which is used in the double disk RF window of gyrotron as a coolant. The dielectric constant, the dielectric loss, the a.c. conductivity and the relaxation time are measured from 1 GHz to 50 GHz. The measurement procedure is based on reflection method. The measurements were performed by dielectric probe kit by using 50 GHz Vector Network Analyzer. The experimental results are in good agreement with design aspects of gyrotron RF window.