EXPERIMENTELLE UNTERSUCHUNG EINES PERIODISCHELEKTROSTATISCHEN FOKUSSIERUNGSSYSTEMS.

A periodic electrostatic focusing system built from perforated disks was submitted to an investigation by electron rays with the serveance of 8. 10** minus **8. . . 10** minus **6 A/V**3**/**2 and the capacity of 0. 2. . . 20 W. The experiments were carried out in vacua from 5. 10** minus 7 to 10** minus **4 torr in order to make photographic representation of the beam form possible. It was found that despite its simple design the focusing system can be maintained stable. It follows that it can be considered as practically applicable in cases of low capacities. Optimization of the input arrangements, elimination of the secondary emission, and development of a closed electrode system can result in a substantial increase of transmission.