Beam loss is a critical issue in high-intensity accelerators, and much effort
is expended during both the design and operation phases to minimize the loss
and to keep it to manageable levels. As new accelerators become ever more
powerful, beam loss becomes even more critical. Linacs for H- ion beams, such
as the one at the Oak Ridge Spallation Neutron Source, have many more loss
mechanisms compared to H+ (proton) linacs, such as the one being designed for
the European Spallation Neutron Source. Interesting H- beam loss mechanisms
include residual gas stripping, H+ capture and acceleration, field stripping,
black-body radiation and the recently discovered intra-beam stripping
mechanism. Beam halo formation, and ion source or RF turn on/off transients,
are examples of beam loss mechanisms that are common for both H+ and H-
accelerators. Machine protection systems play an important role in limiting the
beam loss.Comment: 24 pages, contribution to the 2014 Joint International Accelerator
School: Beam Loss and Accelerator Protection, Newport Beach, CA, USA , 5-14
Nov 201