Simulation of an electron source based calibrating system for an ionisation profile monitor

Measurements have shown that the gain of the imaging system of the Ionisation Profile Monitor (IPM) changes over time, in a non-homogenous way. This ageing effect is caused by changes in the Micro Channel Plate (MCP) channel wall secondary emission coefficient, due to electron scrubbing. The MCP is only capable of emitting a limited number of electrons during its lifetime, and after a large number of electrons have been emitted, the gain is gradually reduced. To measure this ageing effect, and to be able to compensate for it, a remote controlled, built-in calibration system was developed. An Electron Generator Plate (EGP) produced was used as the electron emitter for the calibration system. In this paper, computer simulations of the system is presented. Promising results were obtained from these simulations. Results from experiments conducted at low magnetic fields, coincide with the results of the simulations. Both simulations and experiments indicate that the proposed calibration system should not deteriorate the performance of the IPM during beam profile measurements. (authors)