Laboratory-scale production of tunable, narrow-bandwidth x-rays in the clinical energy regime

The Munich Compact Light Source (MuCLS) is part of a new class of X-ray sources based on inverse Compton scattering. A compact laboratory-scale electron storage ring stores electrons with energies from 29 MeV up to 45 MeV. These electrons collide with an infrared laser pulse from the enhancement cavity, capable of storing up to 300 kW of optical power, resulting in X-rays ranging from 15 keV to 35 keV.¹ The unique properties of the MuCLS beam enable a wide range of medical and biological applications: its narrow tunable spectrum allows for artifact-free quantitative computed tomography (CT)² as well as targeting K-edges for coronary angiography³ and absorption spectroscopy.⁴ Its relatively high flux density supports studies in radiation therapy,⁵ high-resolution micro-CT, and dynamic imaging of processes such as phase-contrast imaging of small animals, specifically focusing on respiratory processes.⁶ Additionally, the partial coherence of MuCLS is essential for phase-contrast and dark-field imaging applications: it enables grating-based phase-contrast radiography⁷ and tomography of larger specimens,⁸ as well as directional dark-field imaging.⁹ Despite its significant potential, the MuCLS is currently constrained by its X-ray energy, which impedes the observation of high-density or strongly absorbing materials^{10, 11} and limits penetration depth.¹² Enhancing the X-ray energy could considerably benefit various fields, enabling the detailed observation of denser bone structures and advancing research in geology and material science. Consequently, our project aims to upgrade the MuCLS enhancement cavity to operate at half the current wavelength in the green spectral region, potentially doubling the X-ray energy output.