Design of a coaxial re-entrant cavity based interaction circuit for a high-power multiple-beam klystron

Ashok Bansiwal, P Shalini, V Nallasamy, Sushil Raina, G Viswam and S K Datta
Microwave Tube Research and Development Centre, DRDO, Ministry of Defence, Near BEL North Gate, Jalahalli PO, Bangalore-560 013, India

RF design of a high gain re-entrant cavity based interaction circuit for a high power Multiple-beam Klystron (MBK) has been presented. The operating frequency of the Klystron lies in S-band. Coaxial double re-entrant cavities have been used in interaction circuits. Cavity operates in TM₀₂₀ mode and total six number of cavities were used for the interaction circuit to achieve the desired gain of more than 50dB.  Initial dimensions of the cavity were obtained using analytical formulations. Then, cold circuit parameters of coaxial re-entrant cavities were  computed and optimized using the eigen mode solver of CST studio. Studies were carried out for tuning of resonant frequency using inductive screw tuning mechanism and also for tuning of loaded quality factor of the cavities by loading them using lossy buttons. RF performance of the interaction circuit was analysed through Particle-In-Cell (PIC) simulation. Peak output power of more than 97.78 dBm (6.0 MW) and power gain of more than 50 dB could be achieved through the simulations. Further, 4 MHz bandwidth could also be obtained. © Anita Publications. All rights reserved.
Doi: XXX
Keywords: Cavity interaction circuit, Coaxial double re-entrant cavity, Higher order mode cavity, High power Klystron, Multiple-beam Klystron, PIC simulation

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