  TORCH is a large-area, high-precision time-of-flight (ToF) detector designed
to provide charged-particle identification in the 2-20 GeV$/c$ momentum range.
Prompt Cherenkov photons emitted by charged hadrons as they traverse a 10mm
quartz radiator are propagated to the periphery of the detector, where they are
focused onto an array of micro-channel plate photomultiplier tubes (MCP-PMTs).
The position and arrival times of the photons are used to infer the particles'
time of entry in the radiator, to identify hadrons based on their ToF. The
MCP-PMTs were developed with an industrial partner to satisfy the stringent
requirements of the TORCH detector. The requirements include a finely segmented
anode, excellent time resolution, and a long lifetime. Over an approximately
10m flight distance, the difference in ToF between a kaon and a pion with
10GeV$/c$ momentum is 35ps, leading to a 10-15ps per track timing resolution
requirement. On average 30 photons per hadron are detected, which translates to
a single-photon time resolution of 70ps. The TORCH research and development
program aims to demonstrate the validity of the detector concept through
laboratory and beam tests, results from which are presented. A timing
resolution of 70-100ps was reached in beam tests, approaching the TORCH design
goal. Laboratory timing tests consist of operating the MCP-PMTs coupled to the
TORCH readout electronics. A time resolution of about 50ps was measured,
meeting the TORCH target timing resolution.
