In situ performance tests of soft-x-ray multilayer mirrors exposed to synchrotron radiation from a bending magnet

The performance of soft-x-ray multilayer mirrors of Mo/Si, Rh/Si, and Ru/Si has been tested in situ during ~ 15-h exposure to white synchrotron radiation from a bending magnet of the Photon Factory (Tsukuba, Japan) ring. The power density on the sample surface was ~ 0.14 W/mm(2). The tests were made by measuring the intensity of the reflected beam from the test mirrors with a detector unit consisting of a carbon filter and an aluminum cathode. The detector unit served as an effective narrow-band detector for the intense radiation of 85-105 eV reflected from the test mirrors. The Mo/Si and Rh/Si multilayer mirrors were found to be quite stable against continuous irradiation, whereas the Ru/Si multilayer mirror showed a definite decrease in the reflected-beam intensity.