Real-time Non-destructive Electro-optic Sampling Study on Laser Wakefield Acceleration

Laser wakefield acceleration (LWFA)1 has been studied intensively due to the inherent ultrashort bunch duration (fs) and large acceleration gradient (GV/cm) over conventional accelerators. This regime is considered promising on construction of compact table-top X-ray free electron lasers (XFEL) which have broad application in ultrafast process studies2. The generation of XFEL relies on the process of self-amplification of spontaneous emission (SASE)3, which requires electron beam with extremely high current, low energy spread, and low emittance to cause micro-bunching. Also, the jitter issue in the pump-probe experiment is dependent on the electron injection timing. During LWFA experiment, it is essential to establish real time electron bunch temporal diagnostics to monitor the electron pulse duration and arrival time.We present LWFA study via single-shot non-destructive electro-optic (EO) sampling4 technique for the first time. The electron spectra and divergence information had been detected simultaneously with electron bunch temporal signal. In the experiment, we observed stable and earlier electron pulse arrival time with higher plasma density. At density above 3×1019cm-3, multi-bunch signal was frequently observed. In addition, we achieved high quality electron bunch with divergence <1 mrad and energy spread