Figure 3
Schematic showing shutter opening for the parallel and perpendicular shutter designs for a sample of size equal to that of the slit opening. Closing of the shutter is identical except for a reverse of the order. The beam is drawn in yellow. In the parallel geometry the beam is perpendicular to the plane of the figure. For the perpendicular geometry both the views perpendicular and parallel to the beam are shown. Note that in the perpendicular design the peripheral speed is half of that of the parallel design for a given opening time, as both the entrance and the exit apertures of the tunnel truncate the beam. In the parallel design the projection of the chopper slit scans through the sample, whereas in the perpendicular design the slit opening remains centered on the sample. |