The Belle II Time-Of-Propagation detector is a novel particle
identification detector based on the measurement of the propagation
time of Cherenkov photons inside a fused silica bar, rather than their
impact point on a surface like in RICH and DIRC counters. Similar
designs have been proposed for other experiments such LHCb and PANDA,
but at the moment TOP is the only operational detector of this kind.
The Cherenkov radiation is emitted in thin fused silica bars that also
act a light guides, allowing the radiation to reach an array of micro-
channel-plate photomultipliers located at one end of the bars. The
photomultiplier signal is digitized by zero-deadtime waveform sampling
ASIC with time resolution of 20 ps. The waveform features like timing,
amplitude and intergral are exctracted online using a Xilinx Zynq FPGA-
First collisions were recorded in spring 2018, and now Belle II is
entering it high-luminosity phase. We will describe the status of the
detector after three years of operation, its performance and the
outlook for possible upgrades.