A MEASUREMENT OF pp SPIN CORRELATION COEFFICIENTS AT

Data taking for CE42 was completed in February 1996. The experiment utilized the Wisconsin/IUCF polarized target1 which has been used by CE35 to measure spin correlation coefficients in pp elastic scattering at 200 MeV at angles 10" 5 O,, 5 35" [Ref. 21. The target cell and detector system are shown in Fig. 1. For ease of tuning and to be less susceptible to shifts in beam position during either the up or the down ramp, which in turn could cause background due to scattering off the cell walls, the cell opening was increased from 8 x 8 mm2 (CE35) to 10x10 mm2. Even though the increased cell diameter causes the target to be thinner by approximately a factor of two, the decrease in time-averaged luminosity is only a few percent, because the ring acceptance (which is determined by the target cell) has been increased. This behaviour has been expected from the results of a dedicated experiment to inverstigate the interplay between cell size, target thickness, ring acceptance and luminosity.