own decelerator sector, synchronized with the arrival of the Main Beam. The use of low-frequency (1 GHz), long-pulse-length (148 μs) klystrons for accelerating the Drive Beam and the beam recombination makes it more convenient than using klystrons to directly accelerate the Main Beam. Test facilities The main technology challenges of the CLIC accelerator design have been successfully addressed in various test facilities. The Drive Beam production and recombination, and the two-beam acceleration concept were demonstrated at the CLIC Test Facility 3 (CTF3). X-band high-power klystron-based RF sources were built in stages at the high-gradient X-band test facility (XBOX), CERN. These facilities provide the RF power and infrastructure required for the conditioning and verification of the performance of CLIC accelerating structures, and other X-band based projects. Additional X-band high-gradient tests are being carried out at the NEXTEF facility at KEK and at SLAC, a new test stand is being commissioned at Tsinghua University and further test stands are being constructed at INFN Frascati and SINAP in Shanghai. CLIC detector A state-of-the-art detector is essential to profit from the complete physics potential of CLIC. The current detector design, named CLICdet, has been optimised via full simulation studies and R&D activities.<ref name="detector_R_and_D"></ref> The detector follows the standard design of grand particle detectors at high energy colliders: a cylindrical detector volume with a layered configuration, surrounding the beam axis. CLICdet would have dimensions of ~13 x 12 m (height x length) and weigh ~8000 tonnes. Detector Layers CLICdet consists of four main layers of increasing radius: vertex and tracking system, calorimeters, solenoid magnet, and muon detector. The vertex and tracking system is located at the innermost region of CLICdet and aims to detect the position and momenta of particles with minimum adverse impact on their energy and trajectory. The vertex detector is cylindrical with three double layers of detector materials at increasing radii and has three segmented disks at each end in a spiral configuration to aid air flow cooling. These are assumed to be made of 25x25 μm2 silicon pixels of thickness 50 μm, and the aim is to have a single point resolution of 3 μm. The tracking system is made of silicon sensor modules expected to be 200 μm thick. The calorimeters surround the vertex and tracking system and aim to measure the energy of particles via absorption. The electromagnetic calorimeter (ECAL) consists of ~40 layers of silicon/tungsten in a sandwich