Stephen D. Russell

By Narayan R. Joshi, Stephen D. Russell, Ayax D. Ramirez and David W. Brock

Part of the book: Acoustic Emission

By Narayan R. Joshi, Ayax D. Ramirez, Stephen D. Russell and David W. Brock

Microwave tubes used in high-power radar and communications systems are expensive and have an operating life of a few thousand hours. When one fails, it is generally impossible to determine the sequence of events that contributed to its failure. Previous investigators have designed microprocessor-based systems with as many as 11 sensors to monitor tube performance, provide tube protection, and record a comprehensive tube failure history. These systems are limited by the small amount of time available during the tube’s interpulse period for data buffering and fault analysis. They work well if the microwave tube is operated with 200 or fewer pulses per second. However, many tubes are operated at up to 1000 pulses per second. In this effort, an alternative nondestructive testing technique using acoustic emission (AE) was used for in-situ monitoring of normal and abnormal performance of radar tubes, including a magnetron, a klystron, and a traveling wave tube amplifier. This technique captures changes in radio frequency (RF) output pulses due to irregular operation and it is a real-time instantaneous in-situ indicator of the performance of microwave radar tubes. It also offers the possibility of developing built-in prognostic capabilities within the radar system to provide advanced warning of a system malfunction. Understanding the sequence of events leading to a tube failure allows for better maintenance, extends the operating life of the system, and results in significant cost avoidance.

Part of the book: Acoustic Emission Technology for High Power Microwave Radar Tubes

By Ayax D. Ramirez, Stephen D. Russell, David W. Brock and Narayan R. Joshi

Each year, nearly $100 M is spent replacing high-power microwave tubes in the fleet. In many cases (estimated at over 25%), tubes that are operating perfectly are inadvertently replaced because there are insufficient in-situ monitoring equipment available to diagnose specific problems within the system. High-power microwave vacuum tubes used in radar or communications systems have minimal condition-based maintenance capability and no means to identify specific component failures. This chapter presents the results from a system that uses cathode current and acoustic emission sensors combined as a virtual sensor to locate and classify microwave transmitter failures. Data will be shown which differentiate the failure mode from subsystems on a radar klystron and from a communications system magnetron. The use of the integrated condition assessment system (ICAS) to acquire and track virtual sensor data will also be described. These results offer promise of a low-cost, nonintrusive system to monitor microwave transmitters, which correctly identifies component failures avoiding incorrect replacement of high-value klystrons, magnetrons, or traveling wave tubes. This advanced technique also offers the possibility of developing built-in prognostic capabilities within the radar system to provide advanced warning of a system malfunction.

Part of the book: Acoustics of Materials