The theory of a free electron method for measuring e/m0 isdescribed. This method consists essentially in the use of a welldefined, rotating, high-frequency magnetic field as a phasing valveto determine the velocity of an electron stream. Use of the relativistically correct energy equation then yields e/m0, if thepotential of the electron stream is known. As shown below theuse of a resonant cavity operating in the TM110 mode, approximatelyproduces such a field.
The apparatus which was designed and constructed to supportthe cavity, maintain high-vacuum, provide radio-frequency, produceand measure the electron beam, and measure the parameter of internetis described. Included also are circuit diagram of the variouscontrol and measurement electronic circuits.
Finally, data are given which determine essentially theresolving power of the instrument. Estimates are made as to theprobable ultimate accuracy of the measurement. It is shown thatan accuracy of 1 part in 10,000 should be easily obtainable in a given run, and that accuracies of several parts in 100,000 shouldbe possible with more data.
