Direct high power laser diagnostic technique on focused electron bunch

In laser produced plasma (LPP) EUV source, high intensity pulse CO₂ laser is essential for plasma generation. To achieve high conversion efficiency and stable EUV power, we would like to measure a laser profile in the interaction point. However, there is no way to measure directly the laser profile of such a high intensity laser at the focus point. Therefore, we have been developing the direct high power laser diagnostic technique based on laser Compton scattering (LCS). LCS signal by using focused electron beam shows 1D laser profile. 2D laser profile can be reconstructed by one-dimensional laser profiles from various angles using computer tomography (CT). This method is suitable for high intensity laser, but very small spot size of electron beam is required. To obtain small spot size, we used S-band Cs-Te photocathode RF-Gun and specially designed solenoid lens at Waseda University. We already succeeded in observing minimum beam size of about 20μm rms and this is adequate to scan the CO2 laser. In this conference, we will report the result of the laser Compton scattering with pulse CO2 laser, the preparatory experiment in measuring a metal wire cross section and the present progresses.