1：Experimental Design and Method Selection:

The study uses a two-stage simulation approach. First, GEANT4 (version

2：4) is employed to simulate the conversion of 511 keV photons into electrons in a layered structure of lead converters and MRPC gas gaps. Second, a custom Monte Carlo code is developed to simulate the avalanche formation and signal generation in the MRPC, including ionization, electron multiplication, and charge induction on pick-up strips. Sample Selection and Data Sources:

The input consists of back-to-back 511 keV photon pairs, simulating positron annihilation events. Materials include lead converters, glass electrodes (700 μm thick), and a gas mixture of C2F4H2/i-C4H10/SF6 (85/5/10). Experimental validation uses a 22Na source emitting 511 keV photons.

3：0). Experimental validation uses a 22Na source emitting 511 keV photons. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: GEANT4 simulation toolkit, custom Monte Carlo code, six-gap MRPC prototype (16 cm x 10 cm with 200 μm gas gaps), float glass electrodes (600 μm thick from GSI, Germany), gas mixture of R-134a and iso-butane (95/5), plastic scintillator (5 cm x

4：2 cm), and high-voltage supply. Experimental Procedures and Operational Workflow:

For simulation, photon pairs are generated and passed through converter layers; conversion electrons are tracked to gas gaps. Avalanche formation is simulated with probability distributions, and signal induction is calculated with a charge threshold of 20 fC. For experiments, the MRPC is tested with a 22Na source, coincidences are measured with a scintillator, and time differences are recorded.

5：Data Analysis Methods:

Efficiency is calculated as ratios of detected to incident photons. Time resolution is derived from standard deviations of avalanche growth time distributions. Position resolution is estimated from time differences for extended sources using Gaussian spreads.