Reflectometer based on two monochromators RSM-500 and LHT-30

General description

The chambers with these monochromators form two different arms of the setup, each of which is used for its own spectral range. In total, the reflectometer provides radiation in a wide spectral range of 4–200 nm. Both arms are connected to the central chamber, in which the goniometer is located. In the first arm, in which the RSM-500 monochromator is located, the radiation source is an X-ray tube with replaceable anodes. The monochromator itself is built according to the Rowland X-ray optical scheme with a spherical diffraction grating and allows certifying samples in the range of 4–25 nm. In particular, the use of silicon and aluminum targets in the X-ray tube allows measuring mirrors at λ=13.5 nm and 17.1 nm, respectively. In the arm with the LHT-30 monochromator, a gas-discharge tube is used as a source. In the LHT-30, a toroidal diffraction grating is used as a dispersion element. The spectral range of this device is 30–200 nm. Hydrogen, helium, nitrogen, oxygen, and argon are used as working gases. For example, using helium, it is possible to measure the angular dependences of the reflection coefficients of samples on the spectral line of 30.4 nm. Thus, this setup allows measuring samples in both the MR and VUV ranges without changing the diffraction grating or the basic scheme of monochromators.

In the arm with the LHT-30 monochromator, a gas discharge tube is used as a source. In the LHT-30, a toroidal diffraction grating is used as a dispersion element. The spectral range of this device is 30–200 nm. Hydrogen, helium, nitrogen, oxygen, and argon are used as working gases. For example, using helium, it is possible to measure the angular dependences of the reflection coefficients of samples on the spectral line of 30.4 nm. Thus, this setup allows you to measure samples in both the MR and VUV ranges without changing the diffraction grating or the basic scheme of the monochromators.

The goniometer has six degrees of freedom (variable parameters α, δ, η, θ, φ, and ψ) and allows measurements of fairly massive samples (flat, spherical, aspherical) with a maximum diameter of 300 mm.

A CsI photocathode suitable for studies in the entire range is used as a radiation receiver when measuring filters and multilayer mirrors. Secondary electron multipliers of the VEU-6 type are used to register photoelectrons. Monitor radiation receivers with grid photocathodes are installed on the input beams of both channels to control the input beam intensity. All reflectometer chambers are continuously pumped out by a vacuum system that provides the vacuum necessary for radiation propagation without absorption, as well as higher vacuum requirements necessary for stable operation of secondary electron multipliers and an X-ray tube. The reflectometer design allows for replacement of test objects and adjustment manipulations without breaking the vacuum directly on the X-ray beam. All reflectometer mechanisms are driven by 8 stepper motors.

Basic characteristics of movements provided by a goniometer

External appearance of the reflectometer based on two monochromators RSM-500 and LHT-30

Scheme of a reflectometer based on two monochromators RSM-500 and LHT-30