Applications of advanced materials technologies to vacuum electronic devices

Power Absorption by Thin Films on Microwave Windows

“…1(b). In the regime where , the thin film is modeled as a lumped resistor , given by (1) From the transmission line model, the fraction of the incident RF power that is absorbed by the thin film ( ) is given by [15] (2) in terms of the normalized film thickness, . The length scale in (2) The power absorption curve in Fig.…”

“…The mechanical stresses in the window due to thermal gradients can cause window failure [1]- [3] even if localized failure initiators [4] such as multipactor [5]- [10] (which is of concern only for frequencies below 30 GHz) are ignored. It is therefore important to be able to estimate the amount of power absorbed in the window in order to design an effective thermal management system.…”

Design considerations for no discharge in space TWTs for long life & reliable satellite communication

“…Space-borne TWTs are required at frequencies from L-band (1.5GHz) to V-band (60GHz) and now extended up to W-band (94GHz) and power level up to 250 watts. Tube technologies for space TWTs [3][4][5][6] have been consistently developed that have led to decisive improvements in space TWT efficiency and thermal performance. Space TWTs have been developed to the point where they possess the RF power output and efficiency, and the reliability, to meet the 15-year (uninterrupted) service life requirements of orbital systems.…”

High heat flux thermal management of microfabricated upper millimeter-wave vacuum electronic devices

“…Although high, it is within the range of aggressive liquid cooling technologies such as microchannel coolers. Such coolers at these flux levels and even higher are being investigated for cooling solid state [2] and vacuum electronic devices [3].…”