Physics Experiments using Quantum Beams Pioneered by a Superconducting Transition-Edge Sensor Microcalorimeter Array

Synopsis: An array of superconducting transition-edge sensor (TES) microcalorimeters is an attractive detector in research fields where high precision measurements are required. This paper introduces two examples of applying a 240-pixel TES microcalorimeter array (TES detector) to physics experiments using quantum beams. The first application is a series of experiments involving the precise X-ray spectroscopy of exotic atoms using three types of charged-particle beams (i.e., pion, kaon, and muon) at large-scale proton accelerator facilities: Paul Scherrer Institute and J-PARC. The improvement in measurement accuracy by an order of magnitude has brought about great progress in research on exotic atoms. The second application is an atomic-molecule collision experiment using atomic or molecular beams with a cryogenic electrostatic ion storage ring at RIKEN. This is the world's first attempt to apply a TES detector to the detection of "neutral low-energy atoms and molecules" instead of "photons", aiming to use it as a new high-resolution mass spectrometer.