High power enhancement cavities for generation of XUV and X-ray radiation of high brilliance

In this contribution we present an enhancement cavity designed such that the spot sizes on all mirrors are increased significantly with respect to a standard bow-tie resonator. This is achieved by operating an all-curved mirror resonator (ACR) close to the border of its stability range. In Fig. 1, a standard design resonator (SR) in the stability range center, consisting of 4 mirrors with equal radii of curvature (300 mm). For comparison, the repetition rate of both resonator designs was set to 250 MHz, with two pulses circulating inside the cavity, and the focus radius to 30 μm. Fig. 1c shows the spot sizes on the mirrors. In the ACR the spot area is increased by more than 14 times with respect to the SR, suggesting that at the same intensity on the mirrors an average power higher by more than an order of magnitude can be achieved. In conjunction with a modified version of the CPA system described, which is planned to seed our ACR, Mega-Watt circulating average powers for ultrashort MHz-repetition-rate pulses come into reach for the first time.