BEAM ANALYZER. III. BEAM ANALYSIS IN A CIRCULARLY DEFLECTING SYSTEM
ILLINOIS UNIV AT URBANA ELECTRICAL ENGINEERING RESEARCH LAB
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A description is given of an application of a circularly deflecting system to an analysis of an HF modulated electron beam with respect to its density and velocity distribution. The deflecting system was designed for circularly deflecting an HF modulated electron beam having the same frequency as the beam is modulated with, in order to obtain a conversion of each phase element somewhere on the beam into a separable geometrical deflection angle element. The development shows that the chromatic aberrations of the deflecting system can be utilized so that this system may serve both as a phase writer system and as a velocity spectrograph. Experiments were carried out in which the bunching action in the drift region of a velocity modulated electron beam was made accessible to direct observation. The results were recorded photographically. Since a calibrated modulator provided the ac component of the velocity of the electrons in the beam, a comparison with a first-order bunching theory was possible. Observations and theory agree as long as the effects have their cause in the action along the long drift space. In the vicinity of bunches, space charge effects begin to play a somewhat distorting role. The occurrence of such phenomena is directly observable on the screen and can be studied later on the photographic plate.
- Particle Accelerators