The PMT detector is used to transform light signals reflected from the target into electric signals. When the light signals are just transmitted by light source, the pulse-widths are ~10 ns and the pulse-energies are less than 75mJ. After the
light pulses are reflected back to the detector, because of the impact of atmospheric turbulence and atmospheric scattering, the pulse-widths increase to 20ns and the pulse-energies reduce to 10-17J. The reflective light is too weak, and a high gain and high sensitive PMT module from HAMAMASU is chosen. The PMT has radiant sensitivity of 3.9 ×104 A/W. Under the experimental conditions, it can output current signals with amplitude of 5~25μA. In addition, the radiant sensitivity can be changed via a voltage control port.