Simulation Project SANS-2: Detector

The detector is a circular PSD, diameter 64 cm, with a pixel size of \(8 \times 8\) mm\(^2\), placed in an evacuated tank that begins 0.5~m after the second slit. The distance between the second slit and the detector is either \(L_d = 3\) m or \(L_d = 6\) m. Calculate and simulate the size of the direct beam for \(L_c = L_d = 3\) m and \(L_c = L_d = 6\) m.

Place a circular beamstop of an appropriate diameter just before the detector to avoid the direct beam. Control whether this beamstop blocks the whole of the direct beam.

McStas hint

As preliminary treatment of isotropic SANS data, one would normally perform an average of the measured \(d \sigma / d \Omega ({\bf q})\) for positions of the detector with equal value of \(|{\bf q}|\). This corresponds to a radial average of the pixels in concentric circles. The monitor component PSD_monitor_rad performs this radial average. Perform the simulation with this component at the detector position.