Design, Simulation and Testing of a 2D Electron Source Based Calibrating System for a Proton Beam Ionisation Profile Monitor

In this thesis the design of a calibration system, that measures the gain of the imaging system in the IPM, is discussed. Such a system is needed, as measurements have shown that the gain of the imaging system changes over time, in a non-homogenous way [1, 2]. This ageing effect is caused by changes in the 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 [3]. To measure this ageing effect, and to be able to compensate for it, a remote controlled, built-in calibration system was developed. Two sources were considered as electron emitters for the calibration, a heated wire grid and an EGP from Burle, Inc. [4] Previous test [2], and simulations presented in this thesis, showed that the wire grid would not produce an electron intensity at the MCP which was homogenous enough to be used for calibration purposes. Promising results were obtained from simulations and experiments with the EGP. However, without a magnetic field available in the experimental setup, no final conclusions about the accuracy of the proposed calibration system can be given. The results of the simulations for low magnetic fields, coincide with what was found in the experimental data. However, to obtain an electron distribution which can be used for calibration purposes, a magnetic field of 1000 Gauss or more is recommended. This suggests that further test should be conducted in a setup with a magnetic field available. This will reveal if the system, as predicted by the simulations for high magnetic fields, can be used for calibration purposes. Both simulations and experiments indicate that the proposed calibration system should not deteriorate the performance of the IPM during beam profile measurements. Simulations showed that the homogeneity of the electric field in operation mode will in fact improve with the calibration system implemented, compared to the original design. This should eventually be verified during actual beam profile measurements.