THALLIUM BEAM TUBE RESEARCH.
Abstract
Studies were made of hot surface ionizers for thallium. Only tungsten, operated at a temperature of 1200 K to 1250 K in an atmosphere of about 10 to the -7 power torr of oxygen, was found to ionize thallium atoms suitably for use in an atomic frequency standard. Investigation of cylindrical cavities with coaxial center sections showed that interference between the desired mode and suppressed modes nearly degenerate with it make design of a satisfactory cavity difficult. Cavities with shorter end sections are less subject to such degeneracies. A thallium beam tube was designed and built using the oxidized tungsten ionizer and double resonance beam optics with hexapole state selector. It performed according to expectations. The resonance frequency of the transition was measured with the prototype thallium beam tube to be 21, 310, 833, 946.4 + and - 1.2 Hz in agreement with previously measured values within the error of the measurement. Calculation of the error in the apparent resonance frequency caused by the use of the double resonance method shows that the error may be unacceptably large, or not, depending on the details of the distribution of times of flight of atoms through the apparatus, which is generally not known. The time average of the frequency error can be made zero by running the two low frequency resonance coils at different frequencies. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1966
- Accession Number
- AD0800172
Entities
People
- Richard F. Lacey