  To meet the need for a high counting rate and high time resolution in future
high-energy physics experiments, a prototype of a gas photodetector with an RPC
structure was developed. Garfield++ simulated the detector's performance, and
the single photoelectron performance of different mixed gases was tested with
an ultraviolet laser. The detector uses a low resistivity ($\sim1.4\cdot
10^{10} \Omega\cdot cm$) float glass so that its rate capability is
significantly higher than that of ordinary float glass($10^{12}\sim10^{14}
\Omega\cdot cm$), the laser test results show that in MRPC
gas($R134a/iC_{4}H_{10}/SF_{6}(85/10/5)$), the single photoelectron time
resolution is best to reach 20.3 ps at a gas gain of $7\cdot 10^{6}$.
Increasing the proportion of $iC_{4}H_{10}$ can effectively reduce the
probability of photon feedback, without changing the time resolution and
maximum gain. In addition to being applied to high-precision time measurement
scenarios (eg:T0, TOF), the detector can also quantitatively test the single
photoelectron performance of different gases and will be used to find
eco-friendly MRPC gases.
