[Paper Review] CERN Yellow Reports: Monographs, Vol 4 (2018): The Compact Linear Collider (CLIC) – Project Implementation Plan

Markus Aicheler|arXiv (Cornell University)|Jan 21, 2019

Particle Accelerators and Free-Electron Lasers106 references72 citations

TL;DR

The CLIC Project Implementation Plan outlines a staged, TeV-scale linear collider using a two-beam acceleration scheme with 12 GHz normal-conducting structures powered by a high-current drive beam, achieving 170 MW power consumption and a cost estimate of ~6 billion CHF for the 380 GeV stage. The design enables precision Higgs and top-quark measurements and direct searches for new physics over a 25–30 year physics program, with first beams possible by 2035.

ABSTRACT

The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^-$ collider under development by international collaborations hosted by CERN. This document provides an overview of the design, technology, and implementation aspects of the CLIC accelerator. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, for a site length ranging between 11 km and 50 km. CLIC uses a Two-Beam acceleration scheme, in which normal-conducting high-gradient 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 insignificant progress in recent years. Moreover, this has led to an increased energy efficiency and reduced power consumption of around 170 MW for the 380 GeV stage, together with a reduced cost estimate of approximately 6 billion CHF. The construction of the first CLIC energy stage could start as early as 2026 and first beams would be available by 2035, marking the beginning of a physics programme spanning 25-30 years and providing excellent sensitivity to Beyond Standard Model physics, through direct searches and via a broad set of precision measurements of Standard Model processes, particularly in the Higgs and top-quark sectors.

Motivation & Objective

• To present a comprehensive implementation plan for the Compact Linear Collider (CLIC), a future TeV-scale e+e− collider under development at CERN.
• To detail the technical design, technology choices, and system integration required for CLIC's staged construction and operation.
• To optimize CLIC's performance, energy efficiency, and cost through advanced accelerator physics and engineering developments.
• To evaluate the feasibility of a klystron-based alternative for the initial 380 GeV stage, reducing technical risk and enabling earlier deployment.
• To define a long-term upgrade path to 1.5 TeV and 3 TeV center-of-mass energies with enhanced luminosity and physics reach.

Proposed method

• Adopt a two-beam acceleration scheme where a high-current drive beam powers normal-conducting 12 GHz accelerating structures in the main beam linac.
• Implement a staged construction approach with three energy stages: 380 GeV, 1.5 TeV, and 3 TeV, each with increasing linac length (11–50 km).
• Use a klystron-based alternative for the 380 GeV stage, replacing the drive beam with X-band klystrons to reduce complexity and accelerate deployment.
• Integrate advanced beam dynamics, vacuum, survey, alignment, and ground motion mitigation systems to maintain nanometer-scale beam stability.
• Apply superconducting damping wigglers and permanent magnet-based dipole systems to minimize emittance and reduce power consumption.
• Implement a comprehensive controls, beam instrumentation, and machine protection system to ensure safe and stable operation.

Experimental results

Research questions

• RQ1 What is the optimal design for a high-luminosity, TeV-scale linear collider that balances physics performance, cost, and technical feasibility?
• RQ2 How can two-beam acceleration with 12 GHz structures and a drive beam achieve the required accelerating gradient and efficiency?
• RQ3 What are the performance and cost implications of using klystrons instead of the drive beam for the initial 380 GeV stage?
• RQ4 How can beam emittance, stability, and alignment be maintained over 11–50 km of linac under dynamic ground motion and magnetic field disturbances?
• RQ5 What is the long-term upgrade path to 3 TeV with high luminosity (L∗ = 6 m) while maintaining energy efficiency and system reliability?

Key findings

• The 380 GeV stage of CLIC achieves a power consumption of approximately 170 MW, a significant reduction from earlier estimates, due to optimized RF systems and energy recovery.
• The cost estimate for the 380 GeV stage is approximately 6 billion CHF, reflecting substantial progress in system integration and technology development.
• The klystron-based alternative for the 380 GeV stage is technically viable and reduces technical risk, enabling a potential start of construction as early as 2026.
• First beams at CLIC are projected for 2035, with a full physics program spanning 25–30 years, offering high-precision measurements in the Higgs and top-quark sectors.
• The design supports a luminosity of 6 × 10^30 cm⁻²s⁻¹ at 3 TeV with L∗ = 6 m, enabling sensitivity to new physics beyond the Standard Model.
• System-level studies confirm that the beam delivery system, vacuum, and ground motion mitigation can meet the stringent requirements for nanometer-scale beam stability.