The Compact Linear Collider (CLIC) - 2018 Summary Report

The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^-$ collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and implementation aspects of the accelerator and the detector. CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively. CLIC uses a two-beam acceleration scheme, in which 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments and system tests have resulted in an increased energy efficiency (power around 170 MW) for the 380 GeV stage, together with a reduced cost estimate at the level of 6 billion CHF. The detector concept has been refined using improved software tools. Significant progress has been made on detector technology developments for the tracking and calorimetry systems. A wide range of CLIC physics studies has been conducted, both through full detector simulations and parametric studies, together providing a broad overview of the CLIC physics potential. Each of the three energy stages adds cornerstones of the full CLIC physics programme, such as Higgs width and couplings, top-quark properties, Higgs self-coupling, direct searches, and many precision electroweak measurements. The interpretation of the combined results gives crucial and accurate insight into new physics, largely complementary to LHC and HL-LHC. The construction of the first CLIC energy stage could start by 2026. First beams would be available by 2035, marking the beginning of a broad CLIC physics programme spanning 25-30 years

Estimate of Longitudinal Space-Charge in the ATF2 Final Focus

The ATF2 project at KEK in Japan is an essential part of the R&D effort for the future linear collider projects. One of the main goals of this R&D is to prove that it is possible to provide the nanometre beamsizes required for these colliders. The final goal of the ATF2 project is a beam size of 37 nm, while the current achievement is 65 nm. One explanation for this discrepancy could be longitudinal space-charge, which we estimate in this note

Beam-Gas Simulations for 2009 LHC Running and First Comparisons with Data

This notes describes the calculations made for the pressure maps, beam-gas events and lifetime for comparison to the first machine running at the end of 2009 at a beam energy of 450 GeV. This includes a full set of pressure maps and equations to calculate beam-gas. The beam-gas loss rates around the machine, and the expected flux of beam-gas induced background particles into the LHCb and ALICE experiments are calculated. Wherever possible at this early state, the consistency ofthe measured beam-gas rates and the simulations is assessed

Staircase and saw-tooth field emission steps from nanopatterned n-type GaSb surfaces

High resolution field emission experiments from nanopatterned GaSb surfaces consisting of densely packed nanocones prepared by low ion-beam-energy sputtering are presented. Both uncovered and metal-covered nanopatterned surfaces were studied. Surprisingly, the field emission takes place by regular steps in the field emitted current. Depending on the field, the steps are either regular, flat, plateaus, or saw-tooth shaped. To the author’s knowledge, this is the first time that such results have been reported. Each discrete jump in the field emission may be understood in terms of resonant tunneling through an extended surface space charge region in an n-type, high aspect ratio, single GaSb nanocone. The staircase shape may be understood from the spatial distribution of the aspect ratio of the cones

Tuning of the Compact Linear Collider Beam Delivery System

Tuning the Compact Linear Collider (CLIC) BeamDelivery System (BDS), and in particular the Final Focus (FF), is a challenging task. In simulations without misalignments, the goal is to reach 120%o f the nominal luminosity target, in order to allow for 10% loss due to static imperfections, and another 10% loss from dynamic imperfections. Various approaches have been considered to correct the magnet misalignments, including 1-1 correction, Dispersion Free Steering (DFS), and several minimization methods utilizing multipole movers. In this paper we report on the recent advancements towards a feasible tuning approach that reaches the required luminosity target

Measurements of Chromatic Coupling in the LHC

Chromatic coupling was regularly measured in the LHC throughout 2012. A first beam-based correction of chromatic coupling was applied during a dedicated MD. In this note we summarise the measurements and results showing a significant reduction in the chromatic coupling for both beams