The superconducting sensors need a temperature below 25 milli Kelvin. This is achieved by using a He4-He3 dilution refrigerator, pictured here. It is similar to those used for quantum computers. Credit: Régis Decker / HZB A major new tool for X-ray research has entered service at BESSY II. Developed through a collaboration between HZB, MPI-CEC (Mühlheim-an-der-Ruhr, Germany), and NIST (Boulder CO, USA), the instrument is the first and only TES spectrometer operating at a synchrotron facility in