A Pion Collector Based on Superconducting Solenoids : A Feasibility Study for the ESSnuSB

The European Spallation Sour e Neutrino Super-Beam project (ESSnuSB) plans to use the powerful proton beam from the ESS linac to produce a neutrino super beam in a dedicated target. The super beam must consist of either muon neutrinos or muon antineutrinos and be directed towards an underground detector 540 km from the source. A neutrino horn based on a magnetic toroid is normally employed for colle ting the pions that emerge from the target and soon after emit neutrinos as they decay. However, the horn cannot accept the nominal pulse from the linac due to ohmic heating from the high current driving the structure. As an alternative, we have studied the use of solenoids for pion colle tion. The solenoids, that would be made superconducting for continuous operation, are however blind to the pion charge wherefore a charge separation stage is needed. This report describes our efforts of combining solenoid and dipole fields in order to collect pions from the target and separate the pion charges before they have time to decay. The study indicates that focusing with solenoids is possible, but that simultaneous charge separation can only be achieved with limited efficiency and acceptance in terms of pion divergence and momentum. Further studies are required for full understanding of the limitations.ESSnuS