Required modifications of the ESS accelerator architecture for ESSnuSB

This report is a summary of major modifications to the ESS nominal linac layout, which are needed to enable the operation of the ESS linac as 5 MW proton driver for the ESSnuSB initiative in addition to its regular operation as 5 MW ESS proton source. A draft costing is also provided using extrapolations from the ESS official cost numbers and values, which are familiar to the authors. This assessment was made during a visit by F Gerigk (CERN) and E Montesinos (CERN) to ESS on 1 – 2 June 2016 together with staff members of ESS. The visit took place on the initiative and with the support of the University of Uppsala (Tord Ekelöf). We are very grateful to Mamad Eshraqi who organized our visit at ESS and who made it possible for us to discuss with the relevant ESS experts and work package leaders. In the following we start with the charge for the review, the considered ESSnuSB scenarios, an executive summary and then a detailed list of findings, comments and recommendations ordered by subject.