Geometrical description (not to scale) of approach for detection (a) when a grating is removed from the beam path to measure the direct beam and (b) when grating is mounted within the beam path to lead to matter-wave scattering. Red arrows and purple-shaded regions show the beam path and detection regime covered by rotating mass-spectrometer, respectively. (c) An angular distribution of direct He beam as a function of the detector angle \(\Theta\) measured at T0 = 50 K and P0 = 26 bar. Here, the detector angle is measured with respect to the one end of the rotating detector. (d) The He atomic beams scattered from the square wave grating with a 400-\(\mu\)m period and a 10-\(\mu\)m strip width are measured as a function of detection angle \(\theta\). The reflection and the diffraction peaks appear when the grating is located within the beam path as shown in b. For a sake of clarity, the detection angle is defined from the plane of \(x=0\) (see Fig. 5), including the grating surface.