Nuclear charge radii are an important tool for testing nuclear models and serve as key inputs for precision experiments. While optical isotope shift data can provide charge radii differences, absolute reference radii are typically obtained from muonic atom spectroscopy, where the muon's large mass enhances nuclear finite size effects. Most stable nuclei have hadve been measured through x-ray spectroscopy, and recent laser spectroscopy on muonic hydrogen and helium has achieved the highest accuracy. However, other light elements remain out of reach for laser spectroscopy, and in addition, radiative nuclei were out of reach all together.

At the Paul Scherrer Institute a new high-precision x-ray spectroscopy effort was initiated using advanced Metallic Magnetic Calorimeters, aiming to enhance the accuracy of charge radii measurements for light nuclei by an order of magnitude. A proof-of-principle campaign took place at the Paul Scherrer Institute (PSI) in 2023, a first physics beam-time is ongoing this month. In addition, a method was developed to measured targeted long-lived isotopes with a novel hydrogen-deuterium transfer cell. I will give an overview of these experimental efforts.