Design and tests of the prototype beam monitor of the CSR external target experiment

A prototype beam monitor was designed to provide tracking information for heavy-ion projectiles for the cool storage ring (CSR) external target experiment (CEE) at the Heavy Ion Research Facility in Lanzhou (HIRFL). High granularity and direct charge sensing are the main features of this device. It measures the beam position in a two-dimensional (2D) plane transverse to the beam direction on an event-by-event basis. The current design consists of two field cages inside a single vessel that operates independently and has electrical drift fields in orthogonal directions. Preliminary tests of the prototype were performed using a $${{}^{241}\mathrm{Am}}$$ $$\alpha$$ source. The results show that a spatial resolution of less than 40  $${\upmu \mathrm{m}}$$ and a time resolution of less than 600 ns can be achieved.