1. HPRFM-2013
Simulation Studies on a 10 kW CW Magnetron for Industrial Application
S.K. Vyas, N Shekhawat, S Maurya, V.V.P. Singh
MWT Division, Central Electronics Engineering Research Institute (Council of Scientific and Industrial Research (CSIR)), CEERI, Pilani, Rajasthan ,(India)
Fig A
Abstract
Simulation model of Magnetron
Design Equations of magnetron
This paper presents 3D electromagnetic simulation and analysis of 10 vane ring strapped 2.45 GHz 10kW CW industrial magnetron using CST microwave studio and MAGIC3D. The resonant circuit of the magnetron is vane type with double ring strapping. The output coupler is coaxial with central conductor end-terminated at one of the vanes. The RF window is a thin coaxial alumina disc. A procedure was laid out to synthesize the magnetron using analytical & empirical equations and spread sheet (Microsoft excel sheet). The dimensional parameters of the resonant system of this magnetron thus obtained were used in the simulation using PC based CST microwave studio and MAGIC3D to predict the frequency of pi-mode, Q values, field distributions etc. Some of the results of simulations are given in fig and Table 2. The simulation model shown in fig 1 represents the cold test model of the magnetron, which includes vanes, double ring straps, coaxial output coupler, etc. The results indicate the effectiveness of the synthesis procedure as it took only few iteration to optimize the dimensions to achieve desired pi-mode frequency, i.e., 2.45GHz. Dispersion curves for unstrapped and single & double strap cases have been computed.
Cell length =0.205*λ cm
Strap width = * λ cm
Strap height =0.0066* λ cm
Fig. 1: CST 3D Model Of Magnetron
Eigen Mode Simulation of Magnetron using MAGIC 3D And CST Microwave Studio
Table 1: Simulation Parameter
Simulation Parameter
Value
Anode radius
0.773 cm
Anode Voltage
12.7 kV
Anode Current
1.1 A
Cathode radius
0.340 cm
Anode height cm
Cell height cm
Number of van 10
Van thickness cm
Van length
2.12 cm
Inner strap radius cm
Outer strap radius cm
Strap width
0.14 cm
Strap height
0.080 cm
Fig.3: Electric Field Plot on Curve
Fig.2:Vector plot of Electric Field For Simple Anode Block
Fig.4:Vector plot of Electric Field For Single Strapped Magnetron
Fig.6 : Counter plot of electric field for Simple Anode Block
Fig.7:Vector plot of Electric Field For Double Strapped Magnetron
Fig.5 : Counter plot of electric field for Single strapped Magnetron
Fig.5 : Counter plot of electric field for Double strapped Magnetron
Dispersion Curve of Magnetron
Cold Test Result
Fig.9 : Dispersion Curve of simple
Anode Block
Fig.10 : Dispersion Curve of Single Strapped Magnetron
Fig .12: 3D Model of Magnetron RF Window
Fig.14 : RL Value With frequency
Table 2: Simulation Result
Parameter
Value F
2.459 GHz ∆F
10 MHz RL
2.70 dB
1/2RL
1.14 dB
VSWR
6.485 QL
245 Qo
1833
QEXT
282
Efficiency
86.6%
Fig .13: S11 Of Magnetron RF Window
Fig.11 : Dispersion Curve of Double Strapped Magnetron
Conclusion
Acknowledgement
A spread sheet to calculate initial design parameters was developed. Using the sheet parameters such as anode radius, cathode radius, vane thickness, cell radius, strap dimensions etc., were calculated. Output coaxial coupler and window were designed using CST MWS. The entire magnetron geometry was modelled using CST MWS and MAGIC3D softwares. The pi mode frequency computed is 2.459GHz. The dispersion curve computed shows the excellent mode seperation between pi mode and other adjucent modes. The cold test results obtained using CST confirms the virtual prototyping of the 10kW magnetron. The tube will be actually fabricated and tested to validate the design as a next step.
This work is being carried out under a CSIR network project PSC-0101, supported by CSIR, New Delhi, India.