Measurement of Barium Evaporation from a Dispenser Cathode Using Laser-Induced Fluorescence
Abstract
The rate of evaporation of barium atoms from a thermionic dispenser cathode is measured as a function of cathode temperature and operating time using laser-induced fluorescence techniques. A continuous wave dye laser is tuned to the 5535 A barium I transition, the laser beam is aimed over an operating cathode, and the resulting fluorescence is measured using photon counting techniques. The evaporation rate is then calculated from the measured fluorescent intensity. The results indicate that for the Semicon type S cathode under test the evaporation rate increases until the cathode temperature reaches 1200 K, above which the rate decreases, possibly due to self absorption of the fluorescent photons inside the test cell. The lifetime data indicates that, after a high evaporation rate for the first 30 hours of operation, the evaporation rate decreases and becomes approximately constant at 7.11 x 10 to the 9th power atoms/sec for the 420 hour duration of the lifetime test. The cathode heater failed at 430 hours.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1982
- Accession Number
- ADA124727
Entities
People
- Eugene F. Kasper
Organizations
- Air Force Institute of Technology