Page:Design and Calibration of a New Apparatus to Measure the Specific Electronic Charge.pdf/3

 ABSTRACT

The theory of a free electron method for measuring e/m0 is described. This method consists essentially in the use of a well defined, rotating, high-frequency magnetic field as a phasing valve to determine the velocity of an electron stream. Use of the relativistically correct energy equation then yields e/m0, if the potential of the electron stream is known. As shown below the use of a resonant cavity operating in the TM110 mode, approximately produces such a field.

The apparatus which was designed and constructed to support the cavity, maintain high-vacuum, provide radio-frequency, produce and measure the electron beam, and measure the parameter of interest is described. Included also are circuit diagrams of the various control and measurement electronic circuits.

Finally, data are given which determine essentially the resolving power of the instrument. Estimates are made as to the probable ultimate accuracy of the measurement. It is shown that an accuracy of 1 part in 10,000 should be easily obtainable in a given run, and that accuracies of several parts in 100,000 should be possible with more data.