Design and preliminary characterization of a novel silicon charge sensor for the gaseous beam monitor at the CSR external-target experiment

Within the project of building a beam monitor for the CSR external-target experiment (CEE) at HIRFL, charge sensors that are used in the gaseous ionization detector and in line with the Topmetal principle, are being developed and studied. It integrates in the same chip a topmost metal, which senses the drifting charges, and the readout circuitry. This paper presents the design and preliminary characterization of the first full-sized Topmetal-CEE chip, the Topmetal-CEEv1, which follows this design principle while tailored to the CEE physics programs. It features an enlarged 1 mm × 89μm topmost metal per pixel, in-pixel discrimination and sparsified readout, as well as an amplitude measurement with the Time-over-Threshold (TOT) method. The studies are carried out with the injected pulses and the α particles from 241Am. The major functionalities of the chip are verified. Its performance pertaining to the usage as charge sensing and readout chip in the beam monitor of CEE are also preliminarily evaluated. It will be used in the upgraded prototype of the beam monitor, superseding the common-purpose Topmetal-II- chip.