The Major Issues for CLIC Accelerating and Transfer Structure Development

Both main-linac accelerating structures and drive-linac decelerating structures, the latter referred to as 'transfer structures', are being developed by the CLIC study. Both types of structures have extremely demanding high-gradient, high-power and wakefield performance requirements. Extensive theoretical, computational and experimental studies and developments have been necessary to progress towards the realization of these structures. The main challenges, their interplay and progress in developing the two structures are summarized in this article.