128 channels of multi-gigasample-per-second waveform sampling and digitization in a 10 cm × 10 cm × 8 cm package

Abstract

Extremely fast timing from Microchannel Plate PhotoMultiplier Tubes (MCP-PMTs) and multi-gigasample per second (GSa/s) waveform sampling ASICs will allow precision timing to play a pivotal role in the next-generation of Ring Imaging CHerenkov (RICH) detectors. The Instrumentation Development Laboratory at the University of Hawai'i has developed a prototype of the electronics to instrument the Imaging Time of Propagation (iTOP) counter for the Belle II detector at KEK in Tsukuba, Japan. The front-end electronics modules consist of an array of waveform sampling / digitizing ASICs controlled by an FPGA. The ASICs digitize signals from an array of multi-anode MCP-PMTs coupled to a quartz radiator bar. Readout and control are done via multi-gigabit-per-second fiber optic links to a custom back-end, where Digital Signal Processors (DSPs) correct for unwanted artifacts in the data before performing feature extraction. Variants of the modules will be used in other applications in addition to Belle II, including a tabletop neutrino detector, beam size monitoring at SuperKEKB, readout of wavelength shifting fibers for the Belle II K L /μ system, and a Focusing Detection of Internally Reflected Cherenkov (fDIRC) prototype. Important aspects of the system include thermal management problems in a very compact module, as well as the expected lifetime of the module in the intended high radiation environment(s). Our experiences running these modules as standalone entities with a pulser/laser on the bench have fed into the design of the next version of each component in the system. Cosmic ray tests and running a full system at a Fermilab beam test in late 2011 have contributed to our understanding of needed improvements for the system as a whole.