128 channel waveform sampling digitizer/readout in the TOP counter for the Belle II upgrade

Abstract

Extremely fast Micro-Channel 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. We have developed a second prototype of the electronics to instrument the Time of Propagation (TOP) 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 FPGAs with embedded microprocessor cores. The ASICs digitize amplified signals from an array of multi-anode MCP-PMTs coupled to a quartz radiator bar. Online feature-extraction is performed directly on the front-end via digital signal processing. Readout and control are done via multi-gigabit per second fiber optic links to a custom back-end. A previous generation of these modules has been running in a prototype Focusing Detection of Internally Reflected Cherenkov (FDIRC) counter mounted in a Cosmic-Ray Stand (CRT) at SLAC continuously for over 12 months. The most recent version was taken to a beam test at the LEPS experiment at the Japanese SPring-8 facility in mid-2013. These experiences have influenced the design of the next set of ASICs and PCBs for the front-end.

Commissioning and First Running Experiences with the TOP Barrel PID Detector in the Belle II Experiment

“…The signals of all 8192 MCP channels in the system are acquired by custom Ice Ray Sampler ver. X (IRSX) ASICs, which are continuously sampling into a switched capacitor array at 2.7 GSa/s [4]. The buffer depth of 10 µs allows the digitisation and data transfer of dynamically determined groups of samples upon arrival of an external trigger without incurring deadtime in the acquisition.…”

Belle II iTOP Optics: Design, Construction and Performance

“…This includes the newly designed iTOP (imaging-Time-Of-Propogation) counter [4][5][6][7], which is the particle identification counter in the barrel region. It consists of a 2.7 m long quartz optics for the radiation and propogation of the Cherenkov light, an array of micro-channel-plate photo-multiplier tubes (MCP-PMT) [8] for photon detection, and wave-sampling front-end readout electronics [9,10]. This article describes the design, construction and performance of the optics for the iTOP counter.…”

Development of Belle-II TOP detector and its MCP-PMT

“…2). The PMT signal is read out by a newly developed ASIC [4] with GHz analog bandwidth, high performance waveform recording, to achieve pico-second level timing measurement.…”