SPS Slow Extraction Losses and Activation: Challenges and Possibilities for Improvement

In 2015 the highest integrated number of protons in the history of the North Area was slow extracted from the CERN Super Proton Synchrotron (SPS) for the Fixed Target physics programme. At well over 1.10¹⁹ protons on target (POT), this represented the highest annual figure at SPS for almost two decades, since the West Area Neutrino Facility was operational some 20 years ago. The high intensity POT requests have continued into 2016-17 and look set to do so for the foreseeable future, especially in view of the proposed SPS Beam Dump Facility and experiments, e.g. SHiP*, which are requesting up to 4·10¹⁹ POT per year. Without significant improvements, the attainable annual POT will be limited to well below the total the SPS machine could deliver, due to activation of accelerator equipment and associated personnel dose limitations. In this contribution, the issues arising from the recent high activation levels are discussed along with the steps taken to understand, manage and mitigate these issues. The research avenues being actively pursued to improve the slow extraction related beam loss for present operation and future requests are outlined, and their relative merits discussed.