ALBA Synchrotron
MINERVA follows the optical layout of XPBF 2.0 and is sketched in Figure 2. It shows the three main components of the beamline: the multilayer monochromator enclosed in the optics hutch, the sample chamber inside a temperature-controlled enclosure, and the detector tower. One can find the distribution of the following optical elements:
- The source is one bending magnet of the ALBA storage ring.
- A filter unit consisting of one Si3N4 membrane coated with a thin Al deposition. This filter removes the visible light reflected by the M1 mirror.
- The front-end elements. The last component of the front-end is the trigger unit, which is placed at the first element of the optics hutch.
- A toroidal mirror (M1) with a multilayer coating. The mirror deflects the beam inboard, with a total deflection angle of 14 degrees (nominal incidence angle of 7 degrees from mirror surface). It collimates the beam in both the horizontal and vertical planes. Its reflective surface has a multilayer coating that selects a narrow bandwidth of the incoming radiation at the nominal energy of 1.0 keV.
- A set of pinholes, of several sizes, ranging from 10 µm to 500 µm in diameter. These apertures allow reducing the size of the beam that reaches the sample to a smaller well-defined diameter. The pinholes are installed on a motor actuated linear feedthrough, in a 4 way cross vacuum chamber.
- A photon beam shutter which includes a fluorescent screen beam diagnostic unit that allows visualizing the beam right upstream sample station.
- A valve equipped with Si3N4 window, which separates the upstream UHV section from the downstream HV.
- A four-blade slit system. The four blades are motorized and encoded, and allow for apertures from fully closed to more than 10 mm in aperture, both horizontally and vertically.
- The sample station, which includes an in-vacuum hexapod and 2 linear stages for vertical and horizontal translations. The mechanical arrangement allows positioning the mirror modules (MM) under test at the right position and orientation with respect to the incoming beam.
- A flight-tube, which links the sample station to the detector. The flight-tube preserves the vacuum along the 12 meters long beam path between the MM and the detection system. It can adapt its position to the range of the different deflection angles (its orientation from the floor can range from horizontal to about 7 degrees upwards). In addition, its adjustable length can compensate motion of the detection system position.
The imaging detector consists of a fluorescent screen coated at a viewport at the downstream flange of the flight-tube and imaged by a visible light 2-dimensional visible camera. To allow for the different deflection of the mirror modules, the detector is mounted on a support tower that allows changing its height from 1.4 m from the floor to about 2.7 m. Also for calibration purposes, the direct beam (not deflected by any MM) can be accessed.