  These proceedings collate lectures given at the twenty-fifth specialized
course organised by the CERN Accelerator School (CAS). The course was held in
Bilbao, Spain from 24 May to 2 June 2011, in collaboration with ESS Bilbao. The
course covered the background accelerator physics, different types of particle
accelerators and the underlying accelerator systems and technologies, all from
the perspective of high beam power. The participants pursued one of six case
studies in order to get "hands-on" experience of the issues connected with high
power machines.
