Electromagnetic interaction is one of the four fundamental forces of nature.
Since this originates from the coupling between a photon and a charged particle, electromagnetic waves of relevant frequency can be a common tool to investigate or control various objects in the world. In this seminar, we will discuss the applications of Radio Frequency (RF) or microwaves to particle physics, condensed matter, and accelerator projects.
First, an application to particle physics will be presented. The RF is a probe for spectroscopy of the hyperfine structure of positronium, a bound state of an electron and a positron, which is an important object to study bound-state Quantum Electrodynamics (QED). The seminar will focus on a high-power microwave system at 203 GHz composed of a gyrotron oscillator and a Fabry-Pérot resonant cavity. Using a similar setup and a SIS-mixer, we also tried Light-Shining-through-a-Wall (LSW) searching for an extra U(1) gauge boson beyond the Standard Model.
Secondly, we will switch over to the application to superconductors. The RF is a probe to understand the electromagnetic response of quantum many body systems. Niobium-coated copper resonant cavities developed at CERN have suffered from well-known non-linear surface resistance so called Q-slope problem. In recently designed and fabricated cavities, we observed interesting behaviors which require reconsideration of conventional models of the surface resistance of superconductors, including trapped-flux oscillation and linear response theory in the non-equilibrium statistical mechanics.
Finally, we will discuss the application to an accelerator project at CERN. Here, the RF is a driving force to accelerate charged particles. Some project-driven achievements in the superconducting Linac for heavy ions (HIE-ISOLDE project) will be discussed. A serious accelerator project requires an intensive collaboration with experts in different fields, such as superconducting RF physicist, beam dynamics, alignment, clean room assembly, mechanical engineers, LLRF engineers (digital circuit), cryogenics, vacuum, and beam operators. The collaboration eventually provided fruitful beam times for a lot of users from the nuclear physics community.