  The midsize single-phase liquid argon prototype detector, operating at the
surface laboratory, is designed to measure scintillation light emitted by the
liquid argon (LAr). The detector employs 42 8-inch photomultiplier tubes (PMT)
to collect the light. By analyzing the waveform of the signal, important
detector characteristics such as the slow decay time constant that
characterizes the purity of the liquid argon can be obtained. To describe the
signal waveform, a model that considers the TPB re-emission process and the
signal reflection effects based on the principles of liquid argon light
emission, including fast and slow components of light decay, is used. The TPB
re-emission process is introduced using a three-exponential time structure.
Additionally, experimental results provide comprehensive validation for a
post-peak hump structure, which is attributed to signal reflection.
