Mitigation measures for extraction losses (M. Giovannozzi) - Discussion
 
It was asked if a bunched-beam extraction is still a possibility. Massimo answered that this option should be ruled out following the numerous tests performed in the past. The barrier bucket option might remain, but it would create four gaps in the longitudinal SPS structure and that will be a problem for the fixed-target experiments (although it would not be a problem for CNGS or for neutrino experiments in general).
Roland asked what would be the impact of the dummy-septum in SS15 on the shielding that will be added in SS16 during the LS1. Massimo answered that it should be considered when investigating the dummy-septum option, but in principle it should not have any impact.
Simone added that the situation should be improved by the dummy septum but this does not imply a reduction of the foreseen shielding increase.
Roland wondered that the dummy septum in SS15 would become the hottest part of the PS. Simone answered that the dummy septum will improve the situation in SS16 and in SS15 the situation will be mitigated by the added local shielding around the dummy septum.
Massimo warned that the fluctuations in fixed point positions would certainly worsen the situation in terms of losses. In reply to a question by Brennan, Massimo stated that the average loss rate measured during the 2010 MTE run, i.e., 5 %, should be used for estimating the irradiation of the SS15 and the surroundings. Simone commented that the shielding to be added in SS16 only make the shielding in that section in conformity with the shielding in other parts of the tunnel: indeed the shielding is “depressed” in that section from the construction of the tunnel. The civil engineering interventions will be done such as in the future will be possible to increase even more the shielding by 50 cm of earth if necessary.
Laurent asked if the dummy septum would be installed during the LS1 or before. Massimo replied that it will never be ready before that. Only some beam tests could be performed before and in particular tests for the hybrid-MTE option.
Rende asked if a two-month shutdown would not be enough to install the dummy septum. Massimo answered that even if the gamma-jump quadrupoles could be moved, the construction of the dummy septum could not be finished before the LS1.