Purpose

The sieve slit is a collimator plate with array of holes that select events with specific angles. With a point target and recognition of the correlations of the focal plane parameters, these events separated into specific holes are used to optimize the angular reconstruction matrices.

On the same plate, an open collimator is made to basically match the Enge spectrometer acceptances in order to minimize the particles that may hit the irons inside the spectrometer.

There is also an un-collimated opening on the plate. This is an option in case a study of the blocking effect of the bremsstrahlung and Mollor electrons is needed using the lower edge.