The ESRF Upgrade Program EBS:
new horizons for time-resolved X-ray imaging

　The current and future ESRF X-ray imaging beamlines offer unique instruments for studying complex systems from the microscale to the nanoscale. Each beamline developed a specific focus in terms of application fields and corresponding observed variables, experimental techniques and energy range. These capabilities have been strongly enhanced by the ESRF Upgrade Program. Phase I (finished) enabled scientists using the ESRF to access a new generation of beamlines while Phase II - EBS (Extremely Brilliant Source) focuses on a major upgrade of the ESRF storage ring. A (r)evolution reaching towards new frontiers in X-ray imaging is anticipated.

　The potential of hard X-ray imaging to tackle scientific questions especially related to materials sciences can be substantially increased when the dimension time is accessible. Nowadays, unprecedented temporal resolution with hard X-ray imaging can be reached at synchrotron light sources thanks to high-speed CMOS cameras: with exposure times short enough to exploit the pulsed time-structure of the European Synchrotron Radiation Facility, mechanically induced cracks in glass and Si wafers could be depicted. By operating the storage ring of the ESRF in single-bunch mode with its correspondingly increased electron bunch charge density per singlet, the polychromatic photon flux density at insertion-device beamlines is sufficient to capture hard X-ray images exploiting the light from a single bunch (the corresponding bunch length is 140 ps FWHM). Hence, hard X-ray imaging with absorption contrast as well as phase contrast depicting processes in real time on the picosecond scale is nowadays accessible. Common bunch-rates are in the MHz regime (1.4 MHz and 5.6 MHz in case of ESRF). Additionally, direct transmission with diffraction imaging can be combined to track, for example, crack propagation in Si wafers in real-time. This gives access to information about the crack morphology and time evolution of the related strain in a simultaneous manner.

　We will outline concepts to reach MHz imaging rates with hard synchrotron radiation, discuss challenges and highlight recent applications. Future developments and their potential in the frame of the proposed upgrade of storage rings around the globe will be discussed.