A secondary X-ray analyser using a flat ring-shaped radially graded multilayer

A new type of efficient energy analyser specialised for thin film studies is suggested. The key feature of the analyser is the use of a ring-shaped, flat multilayer with d-spacing linearly increasing with radius. At small angles of diffraction, a gradual extension of multilayer period ensures isochromatic Bragg reflection of divergent X-rays emitted by the sample. The main advantages of this kind of secondary analyser are as follows: (1) a rather large acceptance angle (0.1–0.3 sr); (2) good energy resolution (2–3%) and (3) easy tuning in a wide energy range. The instrument is particularly suited for grazing-exit fluorescence X-ray absorption fine structure (XAFS) and XMCD studies with spatial resolution. A prototype graded W/Si multilayer with a change of period of about 30% was fabricated and tested. Preliminary results taken with the K fluorescence emission of copper film are presented to demonstrate feasibility of the analyser.