Patents

Multi-beam Klystrons (MBKs) have already established itself as a front runner in the modern technologies of high power microwave tubes due to its ability to provide high output power at considerably lower beam voltage. Additionally, lower magnetic field is required to focus multiple number of electron beams of low current density making the tube lighter than a conventional single beam klystron. For providing passage to the electron beams, there should be multiple number drift tubes in each resonant cavity. The authors in CSIR-CEERI are trying to develop a 4-beam MBK, whose operating frequency will be 17.6GHz and peak output power will be 300W. The diametrically opposite drift tubes, of 0.5mm radius, should be at a distance of 15mm and the adjacent drift tubes should lie at an angle of 90°. In this process, a novel technique has been adopted to design the resonant cavities. The resonant cavities were observed to have the following distinguished features: a) All the gaps of the four drift tubes inside the cavity were coupled by the same magnetic field. So, a single tuner was found to be sufficient to perturb the magnetic field for tuning the cavity. Such a technique is desirable for MBK cavities operating at high power and higher order mode due to significant separation between the cathodes. b) Mode separation between 1st and 2nd mode was noticeably higher than conventional MBK cavities. c) From the fabrication point of view, it is much easier to assemble the cavities since there are no separate nose cones, thus limiting the brazing operations to the joining of the central conductor and the end plates to the cavity cylinder.