High-time-resolution imaging of transient discharge processes without fixed triggering

Higher time resolution imaging is vital for exploring the microscopic mechanisms of the discharge process. The transient processes of discharge phenomena occur in a short time, and the onset cannot be predicted in advance, thus not providing a trigger mechanism for conventional high-speed imaging methods. Here, the authors propose a high-time-resolution imaging method with 55-ps time resolution and single-photon detection sensitivity. First, the current signal generated by the discharge itself with a rising edge of only a few tens of nanoseconds combined with a high-speed sensing and signal-processing device is used to solve the high-speed triggering problem, and then the single-photon avalanche detector array operating in time-correlated single-photon counting mode combined with computational imaging techniques is used to obtain the evolution of the negative corona discharge at atmospheric pressure in air on the ps time scale, and finally, the time-dependent curves of the discharge photon number at different experimental voltages with different curvature radii are analysed. The method opens up new possibilities for imaging other high-speed dynamic processes without a fixed trigger signal.