Development of the beam separation test device to evaluate the electric field of non-destructive electrostatic septum

Abstract Slow extraction is utilized for various nuclear and particle physics experiments and radiology in synchrotrons. A beam loss at a septum electrode induces equipment activation and damage. We have been developing a non-destructive electrostatic septum to solve this issue. To experimentally evaluate a 2-D electric field distribution of the new septum, an electric field measurement device named the beam separation test device was invented. The device consists of a prototype septum, horizontal and vertical wire scanners, and an electron gun installed on a movable stage fixed to a drive unit. This device measures the electric field by injecting an electron beam into the electric field and measuring the bending angle of the beam orbit. In order to increase the number of measurement points, we designed an additional optics system to be placed downstream of the electron gun for a narrow beam. In addition, we designed a beam dump that reduces secondary electron emission by utilizing energy loss when particles collide with materials. According to calculations of secondary electron emission, this beam dump can reduce secondary-emission into the chamber by up to 98%.