This will keep the spectrometer field constant, but survey of spectrometer angle and pointing is neccessary. Changing the spectrometer field. This works fine if the optics of the spectrometer scales with field. The collimators are quite effective to stop electrons. For long target, if they intersect the edge of the collimator they may loose anything between 0 and 360MeV, polluting the high E miss region of interest.
More studies are neccessary.
Akio studied different methods for a luminosity normalization. We don't have. A single third arm detector may have background problems. It seems we still have no striking idea, but c.1. will link luminosities for fixed HRSE setting, and c.2. may work if the target density does not vary too much with changes in fan speed, beam current, and raster size. The next meeting will be end of July.