Volume 1 of the FCC Feasibility Report presents an overview of the physics case, experimental programme, and detector concepts for the Future Circular Collider (FCC). This volume outlines how FCC would address some of the most profound open questions in particle physics, from precision studies of the Higgs and EW bosons and of the top quark, to the exploration of physics beyond the Standard Model. The report reviews the experimental opportunities offered by the staged implementation of FCC, beginning with an electron-positron collider (FCC-ee), operating at several centre-of-mass energies, followed by a hadron collider (FCC-hh). Benchmark examples are given of the expected physics performance, in terms of precision and sensitivity to new phenomena, of each collider stage. Detector requirements and conceptual designs for FCC-ee experiments are discussed, as are the specific demands that the physics programme imposes on the accelerator in the domains of the calibration of the collision energy, and the interface region between the accelerator and the detector. The report also highlights advances in detector, software and computing technologies, as well as the theoretical tools/reconstruction techniques that will enable the precision measurements and discovery potential of the FCC experimental programme. The content and structure of this report are guided by the scope and priorities defined in the mandate of the FCC Feasibility Study. It is therefore not intended to serve as an exhaustive review of the full physics potential of FCC. Several topics, already covered in earlier reports such as the FCC CDR, are not reiterated here or are addressed only briefly, in alignment with the study’s focus. This volume reflects the outcome of a global collaborative effort involving hundreds of scientists and institutions, aided by a dedicated community-building coordination, and provides a targeted assessment of the scientific opportunities and experimental foundations of the FCC programme.

Temperature dependent fracture properties of NiTi-based Shape Memory Alloys (SMAs), within the pseudoelastic regime, were analyzed. In particular, the effective Stress Intensity Factor (SIF) was estimated, at different values of the testing temperature, by a fitting of the William’s expansion series, based on Digital Image Correlation (DIC) measurements. It was found that temperature plays an important role on SIF and on critical fast fracture conditions. As a consequence, Linear Elastic Fracture Mechanics (LEFM) approaches are not suitable to predict fracture properties of SMAs, as they do not consider the effects of temperature. On the contrary, good agreements between DIC results and the predictions of an ad-hoc analytical model were observed. In fact, the model takes into account the whole thermo mechanical loading condition, including both mechanical load and temperature. Results revealed that crack tip stress-induced transformations do not represent a toughening effect and this is a completely novel result within the SMA community. Furthremore, it was demonstrated that the analytical model can be actually used to define a temperature independent fracture toughness parameter. Therefore, a new approach is proposed, based on the analytical model, where both mechanical load and temperature are considered as loading parameters in SIF computation.

The whole low-to-high cycle fatigue behavior of a pseudoelastic NiTi SMA was analyzed. Global and local strains measurements were carried out by an extensometer and digital image correlation. Significant differences were observed at the two scales, due to the localized nature of stress-induced transformations. Local mechanisms play a crucial role on fatigue damage and have a direct effect on the Z-shaped strain-life curves observed in previous works. The effective nature of this unusual behavior was revealed by systematic analysis of local strain. Finally, strain decomposition was made and data were analyzed by a recent modified Coffin–Manson approach.

Novel Nickel–Titanium (NiTi)-based shape memory alloy (SMA) pipe couplers were designed and developed. They are suitable for room-temperature ultrahigh vacuum (UHV) systems and provide a quick and compact solution at reasonable cost. Their use is particularly interesting for restricted-access areas of particle accelerators as their installation/dismounting can be performed remotely by temperature variations. A NiTi SMA with suitable composition was selected. NiTi couplers with different diameters in the range 30–135 mm were manufactured and thermo-mechanically trained to exhibit a proper two-way shape memory behaviour which comply with the strict operative constraints for coupling applications in room temperature vacuum sectors. The connectors are easily implementable as they were designed to be compatible with commercially available flanges (DN16, DN25, DN100) used worldwide in vacuum systems. The effect of the SMA joint geometry on the thermo-mechanical response and vacuum performance was investigated by numerical studies and experimental analyses such as strain-gauge, extensometer and leak-tightness tests performed under different operating conditions including static axial loads and multiple thermal cycles. It was demonstrated that NiTi-based connectors can be thermally mounted upon heating and can guarantee the leak tightness of the vacuum pipe within a suitable temperature window. The thermal dismounting was also verified by cooling the couplers down to subzero temperatures (lower than −40 °C). Possible use of these connections at European Organization for Nuclear Research (CERN) is foreseen in vacuum assemblies installed in high radioactive areas, like those nearby particle collision points and beam collimators. Thanks to their compactness, SMA couplers are also of great interest for connecting beam pipes with small aperture such as those studied for the electron–positron future circular collider (FCC-ee) and next-generation synchrotron light facilities.