Innovative applications of strong crystalline field effects to particle accelerators and detectors

It is well known that the electromagnetic interactions between high-energy particles and solid matter undergo substantial modifications when the latter is crystalline and its lattice axes are almost parallel to the incident beam direction. In particular, a strong enhancement to both bremsstrahlung (by electrons and positrons) and pair production (by photons) occurs in high-$Z$, high-density oriented crystals, owing to the coherent interactions of multi-$\mathrm{GeV}$ particles with the crystalline lattice axes. The interest in the experimental investigation of this enhancement has grown stronger in recent years. The focus is twofold: to fully characterise these coherent effects in order to widen the knowledge of the interactions between particles and matter, and to exploit them in the development of next-generation tools for high-energy physics. The work presented in this thesis delves into several experimental studies regarding the interactions of high-energy electrons and photons with the strong lattice field of oriented tungsten (W) and lead tungstate (PWO) crystals, which serve as the cornerstone of the design of three applications of paramount interest: an optimised positron source for the future lepton collider (e.g., the FCC-$ee$), a high-efficiency photon converter for the neutral kaon beamline of the HIKE experiment at the CERN SPS and an ultra-compact, high-performance homogeneous electromagnetic calorimeter for forward-geometry accelerator-based experiments and space-borne $\gamma$-ray telescopes.