1. Introduction . In recent years, there has been an increasing interest in the application of high-repetition-rate (>1 kHz) lasers for laser-plasma acceleration [ 1 – 3 ]. In general, the peak power of high repetition rate laser systems is limited to about 1 TW or sub-TW, and they can be used for various applications such as the ultrafast electron diffraction [ 4 , 5 ], electron beam radiotherapy [ 6 , 7 ], etc. In the case of laser-plasma acceleration by high repetition rate l...