SOPHIE - A new endstation for high-resolution soft X-ray ptychography

Spurred by the recent upgrade of many synchrotron light sources to a diffraction limited storage ring (DLSR) design, able to deliver highly coherent X-ray radiation to beamlines, and the availability of fast computational resources, soft X-ray ptychography is rapidly becoming a key synchrotron-based imaging technique, allowing for the routine acquisition of high-resolution images in fields ranging from condensed matter physics to chemistry, environmental, and life sciences. Ptychography is a coherent diffractive imaging (CDI) technique that relies on the acquisition of diffraction patterns in far field conditions by a 2D pixelated detector with a high dynamic range. In ptychography, the phase problem of CDI is solved by guaranteeing an overlap of the illumination of the sample in neighboring points of the scan, providing a constraint to the iterative phase recovery algorithm in real space. 

Ptychography allows, in principle, for the acquisition of high-resolution (<10nm at soft X-ray energies) images. However, to achieve the best spatial resolutions, at the theoretical limits of the technique (i.e. solid angle intercepted by the detector), special attention needs to be dedicated to the positioning precision of the sample, whilst allowing, at the same time, for flexibility in the sample mounting to accomodate the requirements of the user community. The SOft X-ray Ptychography Highly Integrated Endstation (SOPHIE) was developed to meet both of these goals. The endstation was designed and assembled at PSI, and commissioned at the SoftiMAX beamline of the MaxIV DLSR during the SLS 2.0 upgrade shutdown. The quality of the acquired ptychography images has exceeded the design expectations, allowing for routine imaging of nanoparticle samples with sub-5nm spatial resolutions. Meanwhile, the SOPHIE endstation is back at the SLS, and will be installed and commissioned at the SIM beamline, with the goal of opening the endstation for user beamtime applications from the second semester of 2026.

The design and performance overview of the SOPHIE endstation has been published in Review of Scientific Instruments.