LOW-NOISE MICROWAVE TUBES
Abstract
A traveling-wave tube was built which used a beam extracted from a lithium plasma. The plasma was produced by mixing the electrons from an L-cathode and the ions from heated Beta-eucryptite. The tube had a noise factor of 5.7 db, considered a low value in view of the fact that little transformer optimization was possible and that the L-cathode was operated at 1500 K. These conditions are remediable. An improved cesium hollow cathode was developed which employs a slit-feed, for controlled cesium flow, and a filter. This structure was incorporated into a standard TWT and is ready for noise tests. DC studies of this plasma cathode showed it to be capable of delivering 100-150 muA of extracted beam current with an electron temperature of only 750 K. Pinhole studies were made of beams from conventional TWT guns. It was found that near conditions of low-noise operation a virtual cathode formed between the cathode and first anode. Virtual cathode effects intentionally produced between the second and third anodes were found to exhibit sharp transitions and hysteresis only if ions were present. Pinhole measurements of electron temperature showed that the temperature was proportional to current density; thus, with positive beam-forming voltages, the beam edge was always hotter than the beam core. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 15, 1961
- Accession Number
- AD0267301
Entities
People
- A.l. Eichenbaum
- S. Bloom
Organizations
- Sarnoff Corporation