The verification of the large dynamic range readout design for the charge detector of the very large area γ-rays space telescope.

This article focuses on the design and verification of a large dynamic range readout system for the charge detector of the Very Large Area γ-rays Space Telescope (VLAST), a successor to the DArk Matter Particle Explorer (DAMPE). The charge detector aims to measure cosmic ray nuclei from protons up to ultra-heavy ions, including elements up to lead (Pb, Z=82) and beyond, requiring a dynamic range of about five orders of magnitude. The proposed readout design utilizes signals from three dynodes of a Hamamatsu R4443 photomultiplier tube to cover this range, and a prototype detector was tested using cosmic ray muons, ultraviolet laser pulses, and relativistic heavy ion beams at CERN. Test results confirm that the multi-dynode readout effectively spans the required dynamic range, with dynodes 8 and 5 providing clear ion separation up to iodine (Z=53), while dynode 2 covers heavier ions but with reduced resolution; future improvements include adjusting dynode selection and adding light attenuation to optimize performance for ultra-heavy ion detection.