A Low-Noise CMOS Pixel Direct Charge Sensor, Topmetal-II

• Main Authors: An, Mangmang, Chen, Chufeng, Gao, Chaosong, Han, Mikyung, Ji, Rong, Li, Xiaoting, Mei, Yuan, Sun, Quan, Sun, Xiangming, Wang, Kai, Xiao, Le, Yang, Ping, Zhou, Wei
• Format: Journal Article
• Language: English
• Published: 22-12-2015
• Subjects: Physics - Instrumentation and Detectors
• DOI: 10.48550/arxiv.1509.08611

Nuclear Instruments and Methods in Physics Research A 810 (2016)
144-150 We report the design and characterization of a CMOS pixel direct charge
sensor, Topmetal-II-, fabricated in a standard 0.35um CMOS Integrated Circuit
process. The sensor utilizes exposed metal patches on top of each pixel to
directly collect charge. Each pixel contains a low-noise charge-sensitive
preamplifier to establish the analog signal and a discriminator with tunable
threshold to generate hits. The analog signal from each pixel is accessible
through time-shared multiplexing over the entire array. Hits are read out
digitally through a column-based priority logic structure. Tests show that the
sensor achieved a <15e- analog noise and a 200e- minimum threshold for digital
readout per pixel. The sensor is capable of detecting both electrons and ions
drifting in gas. These characteristics enable its use as the charge readout
device in future Time Projection Chambers without gaseous gain mechanism, which
has unique advantages in low background and low rate-density experiments.