Ewald's sphare

The sieve is an Ewald's sphere and the straight metal wires are 2D reciprocal rods. The diffracted electrons propagate from the center of the Ewald's sphere (sieve) to the crossing points of the 2D reciprocal rods(metal wires) and the Ewald's sphere(sieve) indicated by beads.  

To say precisely, the wave number of the 15keV electron is approximately 60Å-1,  and the distance between the adjacent 2D reciprocal rods is typically 1Å-1. The radius of the sieve below is 6cm and the distance of the metal wires is 1cm. To reproduce the actual ratio of the Ewald's sphere and 2D reciprocal rods in RHEED experiments, the diameter of the sieve should be 6 times bigger than the one used below, or the distance between the metal wires should be 10 times smaller than the distance below. Because I couldn't  find such big  hemispherical sieve in kitchen ware shops, I just used the small one to reproduce the Ewald's sphere and 2D reciprocal rods in RHEED experiments sacrificing accuracy.