Calibration of Thomson parabola—MCP assembly for multi-MeV ion spectroscopy

Abstract

We report on the absolute calibration of a micro channel plate (MCP) detector, installed as detector in a Thomson parabola spectrometer. The calibration delivers the relation between a registered count numbers in the CCD camera (on which the MCP phosphor screen is imaged) as a result of the impact of an ion beam onto the MCP. The particle response of the whole detection system was evaluated by using laser accelerated ions with proton energies up to 3 MeV and carbon ion energies up to 16 MeV. In order to obtain an absolute measurement of the number of ions incident on the MCP detector, slotted CR-39 track detector was installed in front of the MCP. The signal registered on the MCP due to ions propagating through the CR-39 slots is compared to the number of particles counted on the adjacent CR-39 stripes after the etching. The calibration of the response of MCP has been extended to higher energy ions and protons on the basis of a simple model validated by comparison with the calibration data. This sensitive detection set-up makes it possible to measure in a single laser shot the ion spectrum in absolute terms.