In response to the 2013 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) study was launched, as an international collaboration hosted by CERN. This study covers a highest-luminosity high-energy lepton collider (FCC-ee) and an energy-frontier hadron collider (FCC-hh), which could, successively, be installed in the same 100 km tunnel. The scientific capabilities of the integrated FCC programme would serve the worldwide community throughout the 21st century. The FCC study also investigates an LHC energy upgrade, using FCC-hh technology. This document constitutes the second volume of the FCC Conceptual Design Report, devoted to the electron-positron collider FCC-ee. After summarizing the physics discovery opportunities, it presents the accelerator design, performance reach, a staged operation scenario, the underlying technologies, civil engineering, technical infrastructure, and an implementation plan. FCC-ee can be built with today’s technology. Most of the FCC-ee infrastructure could be reused for FCC-hh. Combining concepts from past and present lepton colliders and adding a few novel elements, the FCC-ee design promises outstandingly high luminosity. This will make the FCC-ee a unique precision instrument to study the heaviest known particles (Z, W and H bosons and the top quark), offering great direct and indirect sensitivity to new physics.

/pdf/fcc-ee-the-lepton-collider-future-circular-collider-61xh2cg09w.pdf

FCC-ee: The Lepton Collider: Future Circular Collider Conceptual Design Report Volume 2

Particle physics has arrived at an important moment of its history. The discovery of the Higgs boson, with a mass of 125 GeV, completes the matrix of particles and interactions that has constituted the “Standard Model” for several decades. This model is a consistent and predictive theory, which has so far proven successful at describing all phenomena accessible to collider experiments. However, several experimental facts do require the extension of the Standard Model and explanations are needed for observations such as the abundance of matter over antimatter, the striking evidence for dark matter and the non-zero neutrino masses. Theoretical issues such as the hierarchy problem, and, more in general, the dynamical origin of the Higgs mechanism, do likewise point to the existence of physics beyond the Standard Model. This report contains the description of a novel research infrastructure based on a highest-energy hadron collider with a centre-of-mass collision energy of 100 TeV and an integrated luminosity of at least a factor of 5 larger than the HL-LHC. It will extend the current energy frontier by almost an order of magnitude. The mass reach for direct discovery will reach several tens of TeV, and allow, for example, to produce new particles whose existence could be indirectly exposed by precision measurements during the earlier preceding e+e– collider phase. This collider will also precisely measure the Higgs self-coupling and thoroughly explore the dynamics of electroweak symmetry breaking at the TeV scale, to elucidate the nature of the electroweak phase transition. WIMPs as thermal dark matter candidates will be discovered, or ruled out. As a single project, this particle collider infrastructure will serve the world-wide physics community for about 25 years and, in combination with a lepton collider (see FCC conceptual design report volume 2), will provide a research tool until the end of the 21st century. Collision energies beyond 100 TeV can be considered when using high-temperature superconductors. The European Strategy for Particle Physics (ESPP) update 2013 stated “To stay at the forefront of particle physics, Europe needs to be in a position to propose an ambitious post-LHC accelerator project at CERN by the time of the next Strategy update”. The FCC study has implemented the ESPP recommendation by developing a long-term vision for an “accelerator project in a global context”. This document describes the detailed design and preparation of a construction project for a post-LHC circular energy frontier collider “in collaboration with national institutes, laboratories and universities worldwide”, and enhanced by a strong participation of industrial partners. Now, a coordinated preparation effort can be based on a core of an ever-growing consortium of already more than 135 institutes worldwide. The technology for constructing a high-energy circular hadron collider can be brought to the technology readiness level required for constructing within the coming ten years through a focused R&D programme. The FCC-hh concept comprises in the baseline scenario a power-saving, low-temperature superconducting magnet system based on an evolution of the Nb3Sn technology pioneered at the HL-LHC, an energy-efficient cryogenic refrigeration infrastructure based on a neon-helium (Nelium) light gas mixture, a high-reliability and low loss cryogen distribution infrastructure based on Invar, high-power distributed beam transfer using superconducting elements and local magnet energy recovery and re-use technologies that are already gradually introduced at other CERN accelerators. On a longer timescale, high-temperature superconductors can be developed together with industrial partners to achieve an even more energy efficient particle collider or to reach even higher collision energies.The re-use of the LHC and its injector chain, which also serve for a concurrently running physics programme, is an essential lever to come to an overall sustainable research infrastructure at the energy frontier. Strategic R&D for FCC-hh aims at minimising construction cost and energy consumption, while maximising the socio-economic impact. It will mitigate technology-related risks and ensure that industry can benefit from an acceptable utility. Concerning the implementation, a preparatory phase of about eight years is both necessary and adequate to establish the project governance and organisation structures, to build the international machine and experiment consortia, to develop a territorial implantation plan in agreement with the host-states’ requirements, to optimise the disposal of land and underground volumes, and to prepare the civil engineering project. Such a large-scale, international fundamental research infrastructure, tightly involving industrial partners and providing training at all education levels, will be a strong motor of economic and societal development in all participating nations. The FCC study has implemented a set of actions towards a coherent vision for the world-wide high-energy and particle physics community, providing a collaborative framework for topically complementary and geographically well-balanced contributions. This conceptual design report lays the foundation for a subsequent infrastructure preparatory and technical design phase.

/pdf/fcc-hh-the-hadron-collider-3zjqrxf0o5.pdf

FCC-hh: The Hadron Collider

Calorimetry plays a crucial role in modern experimental physics. Calorimeters are essential tools to extract physics in accelerator and non-accelerator experiments. The physics phenomena at the base of cascading processes in matter and the basic principles of calorimeters operation are reviewed at the light of data obtained from running experiments or from sets of dedicated measurements and the constraints from physics requirements. From this understanding comes the possibility of building powerful calorimetric systems with the optimal performances required by future experiments at high-energy and ultrahigh-energy regimes.

https://iopscience.iop.org/article/10.1088/0034-4885/63/4/202/pdf

Physics of cascading shower generation and propagation in matter: principles of high-energy, ultrahigh-energy and compensating calorimetry

We study the coil layouts of superconducting dipoles for particle accelerators based on the sector geometry. We show that a simple model based on a sector coil with a wedge allows us to derive an equation giving the short sample field as a function of the aperture, coil width, cable properties, and superconducting material. The equation agrees well with the actual results of several dipole coils that have been built in the past 30 years. The improvements due to the grading technique and the iron yoke are also studied. The proposed equation can be used as a benchmark to judge the efficiency of the coil design, and to carry out a global optimization of an accelerator layout.

/pdf/electromagnetic-design-of-superconducting-dipoles-based-on-2u59x0i0zw.pdf

Electromagnetic design of superconducting dipoles based on sector coils

To meet the present-day rate and radiation dose requirements, one would like to have a scintillator with the high radiation resistance of pure silica glass and the short fluorescence decay time of organic fluors. The new technology of sol-gel glass production permits the preparation of organic/inorganic composite materials by doping the silica gels with organic fluors. The procedure of production of monolithic organic/inorganic composite materials, such as 2-(4-tertbutylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole/SiO2, p-terphenyl/SiO2, p-quaterphenyl/SiO2, and 3-hydroxyflavone/SiO2, and the associated characterization techniques are described. The efficiency of light production, the light attenuation, the time width of light pulse, and the radiation resistance of the scintillating sol-gel glass are discussed. Preliminary results indicate that this technical advance will permit the creation of new materials with potential application such as particle detectors which are both radiation hard and fast.

Fast, Radiation‐Hard Scintillating Detector: A Potential Application for Sol‐Gel Glass

At Fermilab we have operated a production line for the fabrication of 901 21 foot long superconducting dipoles for use in the Energy Saver/Doubler. At any one time 772 of these dipoles are installed in the accelerator and 62 in beamlines; the remainder are spares. Magnetic field data are now available for most of these dipoles; in this paper we present some of these data which show that we have been able to maintain the necessary consistency in field quality throughout the production process. Specifically we report harmonic field coefficients, showing that the mechanical design permits substantial reduction of the magnitudes of the normal and skew quadrupole harmonic coefficients; field shape profiles; integral field data; and field angle data. Details of the measurement apparatus and procedures are described elsewhere.

/pdf/magnetic-field-properties-of-fermilab-energy-saver-dipoles-137clb3b7o.pdf

Magnetic Field Properties of Fermilab Energy Saver Dipoles

The measurement system and procedures used to test more than 900 superconducting dipole magnets and more than 275 superconducting quadrupole magnets for the Fermilab Energy Saver are described. The system is designed to measure nearly all parameters relevant to the use of the magnets in the accelerator including maximum field capability and precision field measurements. The performance of the instrumentation with regard to precision, reliability, and operational needs for high volume testing will be described. Previous reports have described the measurement system used during development of the Saver magnets from which this system has evolved.

/pdf/report-on-the-production-magnet-measurement-system-for-the-1isx4awrz4.pdf

Report on the Production Magnet Measurement System for the Fermilab Energy Saver Superconducting Dipoles and Quadrupoles

A 4 × 4 array of SCG1-C scintillation glass counters of 20.5 radiation lengths was exposed to positrons in the energy range 1–25 GeV. The energy resolution of the array was measured both with and without a 3.5 radiation length SCG1-C scintillation glass active converter and 0.2 radiation length shower position hodoscopes. The absolute number of photons produced by 1 GeV showers, the optical attenuation length for the light produced by showers, the fraction of the total light output due to Cherenkov light relative to scintillation light, and the radiation darkening have also been measured for the SCG1-C scintillation glass.

/pdf/a-measurement-of-the-energy-resolution-and-related-1q2jg3mga5.pdf

A measurement of the energy resolution and related properties of an SCG1-C scintillation glass shower counter array for 1–25 GeV positrons

The beam abort system proposed' for the Fermilab Tevatron Accelerator will extract the proton beam from the ring in a single turn (-20~s) and direct it to an external beam dump. It is the function of the beamdump to absorb the unwanted beam and limit the excapingradiation to levels that are acceptable to the surrounding populace and apparatus. In addition, it is clearly desirable that it be maintenance free and have a lifetime equal to that of the accelerator, lo-20 years. A beam dump that is expected to meet these requirements hasbeen designed and constructed. We describe below the detailed design of the dump, including considerations leading to the choice of materials.

https://epaper.kek.jp/p81/pdf/pac1981_2774.pdf

A High Intensity Beam Dump for the Tevatron Beam Abort System

A fixed frequency RF accelerating resonator has been built and tested for the Fermilab Energy Saver. Table I shows the design parameters and prototype resonator test results. The resonator features a high permeability nickel alloy resistor which damps unwanted modes and corona rolls designed with the aid of the computer code SUPERFISH. In bench measurements, the prototype resonator has achieved peak accelerating voltages of 500 kV for a 1% duty cycle and CW operation at 360 kV. The prototype has also been successfully operated with beam in the FNAL Main Ring.

F. Turkot

Papers

Magnetic Field Properties of Fermilab Energy Saver Dipoles

Report on the Production Magnet Measurement System for the Fermilab Energy Saver Superconducting Dipoles and Quadrupoles

A measurement of the energy resolution and related properties of an SCG1-C scintillation glass shower counter array for 1–25 GeV positrons

A High Intensity Beam Dump for the Tevatron Beam Abort System

Energy Saver Prototype Accelerating Resonator