Increase beampipe diameter in BWL to increase minimum beam stay clear

In the 153rd FCC-ee optics meeting, the aperture bottleneck was found in the last two dipoles upstream of the IP. Especially at the H operation mode, the bottleneck was close to the aperture requirement from top-up injection, and a larger beam screen in this region was studied. Increasing the radius from 35mm to 45mm increases the beam stay clear from 14 sigma to 18 sigma. This change was discussed with R. Kersevan and appears in principle feasible. The overall length of the wider beam pipe section remains to be studied, as well as the impact on the SR background in the experiment.