@article{thottappan_singh_jain_2013,  title={Analysis and PIC simulation of a Gyrotron travelling wave tube amplifier},  volume={12},  ISSN={2179-1074},  url={https://doi.org/10.1590/S2179-10742013000200006},  DOI={10.1590/S2179-10742013000200006},  number={2},  journal={Journal of Microwaves, Optoelectronics and Electromagnetic Applications},  publisher={Sociedade Brasileira de Microondas e Optoeletrônica e Sociedade Brasileira de Eletromagnetismo},  author={Thottappan, M. and Singh, Surya Prakash and Jain, P.K.},  year={2013},  month={Dec},  pages={307–324} }