Abstract
We present an approach to experimentally investigate the nonlinear response of phosphor screen (PS) module applied in velocity-map-imaging spectrometry under the condition of microchannel plate (MCP) module working in an appropriate amplifier voltage to ensure a constant unsaturation gain. Our approach, taking the Photek's VID240 detector system as an example, is based on the measurements of the position spectra of 87Rb+ photoion pulses with well-determined numbers of ions and duration times at various voltage differences (Uf) between MCP and PS modules. The measured spectra allow us to obtain the relationship between the two-dimensional distribution of luminescence (the luminescence intensity in the kth pixel) and the total number of ions in one pulse at a given Uf value. The obtained relationship leads to the luminescence efficiency and the acceptable limit of input ion flux density (the maximal number of ions arriving at MCP per unit time per unit area to avoid the nonlinear response) for a particular PS to be determined.
Published Version
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