OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 The works [53–54] describe monochromators in which the principle of indirect cooling of optical elements is realized (Fig. 27). Its essence consists of heat transfer from the heated crystal to a tightly pressed cooler, and the cooling liquid is pumped through its internal channels. Fig. 27. Scheme of indirect cooling of the monochromator crystal. Red arrows show the heat flow from the crystal to the cooling channels with liquid nitrogen (according to [54]) When designing monochromators, it is also necessary to take into account the aspects related to the effects of vibration “pollution”. This refers to vibrations of the ground, electrical appliances and other equipment. The consequence of this effect is the fluctuations of the beam position on the optical elements and the specimen. The vibration of optical elements leads to a violation of the alignment of the device, which prevents the achievement of its optimal parameters [56]. Factors contributing to the manifestation of deformation and vibrations of monochromator elements are related to the influence of thermal load, the impact of clamps on crystals or X-ray mirrors, and vibrations caused by the cooling system. In [57] the peculiarities of vibrations arising during the operation of the monochromator due to the thermal effect of the beam on the crystal are analyzed. When the thermal effect on crystals and X-ray mirrors is not critical, cooling of optical elements is not required. Additional information about monochromators Monochromator is an optical-mechanical device with a wide range of requirements. Equipment designer determine technical solutions that ensure reliable operation of the monochromator with observing accuracy indicators. At the same time, standard solutions are used in designing most devices. For example, goniometric devices are used for crystal rotation, shown schematically in Fig. 28. In practice, different variants of goniometer installation are possible. Fig. 29 shows the schemes of devices with horizontally and vertically oriented axes of rotation. Fig. 22 shows a monochromator illustrating another technical solution related to crystal control. In this device, one of the crystals (the second one) is fixed stationary, and the other is connected with a moving mechanism, which allows fixing the beam offset. In practice, other variants of providing movements on monochromators are also realized. Both optical elements or just one of it can be movable. The schemes of beam reflection in both vertical and horizontal planes are proposed. The final solution is determined by the device designers and depends on the set of tasks to be solved at the beamline. Monochromators containing several pairs of crystals [58, 59] of different geometric shapes have been proposed for using as a part of stations. Fig. 30 shows the scheme of the monochromator described in [58]. The red arrow highlights the incoming beam of synchrotron radiation. In order to adjust to the
RkJQdWJsaXNoZXIy MTk0ODM1