0428同步年報-2021-全

Facility Status 103 Fig. 1 : (a) Active mirror. (b) Variance of slope error measured by LTP in the metrology laboratory. (c) Mirror chamber equipped with the AM and LTP. Soft X-ray Nanoscopy Beamline at Taiwan Photon Source A soft X-ray nanoscopy beamline is at present under construction at Taiwan Photon Source port 27. Powered by elliptically polarized undulator EPU66 and a newly designed active-mirror plane-grating monochromator (AMPGM), the TPS 27A nanoscopy beamline is capable of delivering a photon beam with high energy-resolving power at a constant beam size. Here we report the construction status of beamline TPS 27A and two microscopy stations that it hosts; scanning transmission X-ray microscope (STXM) and photoelectron microscope (PRINS; P hotoelectron R elated I maging and N ano- S pectroscopy). Despite the progress of beamline construction being slowed by numerous delays caused by the COVID-19 pandemic, we expect that this beamline will move into the commission phase by the end of 2022. Beamline TPS 27A The optical design of TPS 27A has photons coming through the entrance slit, reflected by an AM, and dispersed with a PGM before being focused onto the exit slit. In a conventional PGM system that works with a mirror of fixed curvature, its optimized focal length must be a function of the photon energy. As a result, it is difficult to maintain the beam size constant for all photon energies at a position- fixed exit without sacrificing the resolving power. This dilemma is overcome in TPS 27A that incorporates an AM system in which the mirror curvature is adjustable. The challenge of having an AM system is that bending a mirror is never trivial, not to mention that the curvature of the mirror must remain well defined during operation. To fine-tune the slope error of the mirror surface and to provide reliable feedback, the beamline construction team at the NSRRC developed two high-precision techniques for the AM system—a highly precise 25-actuator optical surface bender and a long-trace profiler (LTP). 1,2 Figure 1(a) shows a photograph of an AM system that has a mirror held on top of a high-precision 25-actuator optical surface bender. The variance of slope error of the AM measured by LTP in the metrology laboratory is shown in Fig. 1(b) . As depicted in Fig. 1(b) , the large slope error (black curve) is significantly suppressed (red curve) after the actuators are turned on. Figure 1(c) shows how the LTP is mounted on the mirror chamber. After the exit slit, the beam sizes are further adjusted with either a Fresnel zone plate or active Kirkpatrick-Baez mirrors according to the needs of the endstations. Figure 2 is a recent photograph of TPS 27A with the STXM at 27A1 . TPS 27A1 STXM Station After implementing several improvements in 2021, the scanning transmission X-ray microscope at TPS 27A1 designed in-house has been designated as the major commission endstation for beamline TPS 27A . Based on the photon-in photon-out mechanism, the microscope aims to work on X-ray absorption spectra and nano-imaging through a combination of multiple scanning stages, photon detectors, and focusing optics such as a zone plate (ZP) and order-sorting aperture. 2D images with a spatial resolution better than 30 nm can be recorded pixel-by-pixel by collecting the transmitted photons at each scanning point. To achieve high spatial resolution, it is critical to place vibration, mechanical and thermal stabilities under control. A 304 stainless-steel vacuum chamber with a baseplate of thickness of 55 mm is designed and attached to a 1950-kg epoxy granite via six rigid and adjustable (a) (b) (c)