Compact hadron sources and linacs for societal applications

CERN Linac4 was formally approved in 2007 in the framework of the LHC Injector Upgrade Project with the purpose of removing the first intensity bottleneck in the chain of CERN LHC injectors. Linac4 was inaugurated in 2017 and became the sole proton injector at CERN in 2020. The experience and know-how built over a decade through the Linac4 project has subsequently been applied to accelerators for societal applications via the Medical Application Office and the Knowledge Transfer Group at CERN. In this paper, we discuss the specific needs of accelerators for societal applications in terms of compactness, portability, and operability. We describe the specific beam dynamics that allow meeting those challenges and illustrate a few examples realized for medical applications and the analysis of fine art.