Demonstration of a 25-picosecond single-photon time resolution with gaseous photomultiplication

Photosensitive gaseous detectors with a simple photoelectron multiplication mechanism of resistive plate chambers (RPCs) are expected to have both a large photocoverage and an excellent time resolution and to be low-cost. To demonstrate the time resolution of the RPC-based photodetectors, we built a prototype detector with a LaB${}_6$ photocathode. It was tested with a picosecond pulse laser and the intrinsic time resolution for single photons was measured to be $25.0\pm 1.1$ ps at a gain of $3.3\times {10}^6$.