An experimental test station for multistage depressed collectors

An experimental test station developed to characterize Multistage Depressed Collector (MDC) performance is being utilized for helix traveling wave tube (TWT) MDC design. The test station consists of two components; a four stage demountable test module and a spent beam measurement module. With the demountable test module, measurements of the thermal dissipation and recovered power of each stage are monitored in real-time during dc and rf operations via a computer-controlled automatic data acquisition system. Collector efficiency under varying tube operating parameters can be evaluated. The spent beam measurement module characterizes the velocity distribution of the rf modulated beam at the collector entrance plane. Mounted on an XYZ positioning system, a beam probe measures the transverse and axial velocity components using electrostatic retarding and deflection plates. The measured data is used as input to Varian´s beam optics collector design computer program. A description of this test station is presented in this paper.