Measurement of femtosecond laser-driven X-ray focal spot with repetition frequency

In order to obtain focal spot size and spatial resolution of X-ray driven by the ultra-intense laser, a new method was designed to diagnose with a 0.2-m-thick knife-edge attached two different meshes, one copper mesh of 400 meshes and another nickel of 394 line pairs per centimeter. The X-ray was obtained by X-ray CCD. Tisapphire laser (1 J/40 fs/10 Hz) with an intensity of approximately 4.41018 W/cm2 shot the disc Cu target by repetition frequency. The experiment was carried out successfully on a 25 TW laser device at CAEP, in which the first focal spot and the X-ray image of the meshes were both obtained. The estimated focal spot of the X-ray was 43 m, and the estimated spatial resolution was 34 m. The results showed that the method of knife-edge and two meshes was suitable for the measurement of focal spot size of X-ray driven by ultra-intense laser.