Absolute reflectivity measurements at 4479 Å of sputter deposited multilayer x-ray mirrors

Multilayer x-ray mirrors have been deposited using a dc triode sputtering system, which incorporates an accurate method of thickness monitoring based on the dependence of the deposition rate on the target current. Thickness can be controlled with an accuracy of better than 0.1 A. High efficiency W-C and Ni-C multilayer mirrors have been synthesized and tested at 1.54-A (CuKoalpha) and 44.79-A (CKalpha). Absolute reflectivity measurements at lambda = 44.79-A (CKalpha) have been carried out. In this case the incident beam is previously polarized by a premonochromator equipped with a pair of parallel-plane multilayer mirrors fixed at an angle close to the Brewster (theta ? 45 degrees ). Thus the measured reflectivities are not affected by a progressive variation of the P-component.