thumb|Compact Linear Collider project
The Compact Linear Collider (CLIC) is a concept for a future linear particle accelerator that aims to explore the next energy frontier. CLIC would collide electrons with positrons and is currently the only mature option for a multi-TeV linear collider. The accelerator would be between long, more than ten times longer than the existing Stanford Linear Accelerator (SLAC) in California, US. CLIC is proposed to be built at CERN, across the border between France and Switzerland near Geneva, with first beams starting by the time the Large Hadron Collider (LHC) has finished operations around 2035. complemented by an updated energy staging scenario in 2016. Additional detailed studies of the physics case for CLIC, an advanced design of the accelerator complex and the detector, as well as numerous R&D results are summarised in a recent series of CERN Yellow Reports. However, the LHC can only partially answer questions about the true nature of this particle, such as its composite/fundamental nature, coupling strengths, and possible role in an extended electroweak sector. The 380 GeV stage of CLIC allows, for example, accurate model-independent measurements of Higgs boson couplings to fermions and bosons through the Higgsstrahlung and WW-fusion production processes. The second and third stages give access to phenomena such as the top-Yukawa coupling, rare Higgs decays and the Higgs self-coupling. The CLIC linear collider plans to have an extensive top quark physics programme. A major aim of this programme would be a threshold scan around the top quark pair-production threshold (~350 GeV) to precisely determine the mass and other significant properties of the top quark. For this scan, CLIC currently plans to devote 10% of the running time of the first stage, collecting 100 fb<sup>−1</sup>. Direct pair production of particles up to a mass of 1.5 TeV, and single particle production up to a mass of 3 TeV is possible at CLIC. Due to the clean environment of electron-positron colliders, CLIC would be able to measure the properties of these potential new particles to a very high precision. On the other hand, this research has also indicated that quantum gravity or perturbative quantum field theory will become strongly coupled before 1 PeV, leading to other new physics in the TeVs. The high accelerating gradient and the target BDR value (3 × 10<sup>−7</sup> pulse<sup>−1</sup>m<sup>−1</sup>) drive most of the beam parameters and machine design.
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|+<small> Key parameters of the CLIC energy stages.
alt=|thumb|400x400px|Overall layout of the CLIC accelerator complex for the 3 TeV stage, in which one can identify the two Drive Beam and two Main Beam injector complexes The [[positrons for the main beam are produced by sending a 5 GeV electron beam on a tungsten target. After an initial acceleration up to 2.86 GeV, both electrons and positrons enter damping rings for emittance reduction by radiation damping. Both beams are then further accelerated to 9 GeV in a common booster linac. Long transfer lines transport the two beams to the beginning of the main linacs where they are accelerated up to 1.5 TeV before going into the Beam Delivery System (BDS), which squeezes and brings the beams into collision. The two beams collide at the IP with 20 mrad crossing angle in the horizontal plane. 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
thumb|CLIC detector with cut out and labels |alt=|280x280px
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. 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 × 12 m (height × 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. To allow for effective air cooling, the average power consumption of the Silicon sensors in the vertex detector needs to be lowered. Therefore, these sensors will operate via a current-based power pulsing scheme: switching the sensors from a high to low power consumption state whenever possible, corresponding to the 50 Hz bunch train crossing rate.
Status
, approximately two percent of the CERN annual budget is invested in the development of CLIC technologies. The first stage of CLIC with a length of around is currently estimated at a cost of six billion CHF. as well as the status of the CLIC accelerator and detector projects.
The update of the ESPP is a community-wide process, which is expected to conclude in May 2020 with the publication of a strategy document.
Detailed information on the CLIC project is available in CERN Yellow Reports, on the CLIC potential for New Physics,