Abstract:
Synchrotron radiation newS, Vol. 32, No. 5, 2019 13 Table 1: Ambient data acquisition settings used for all facilities. The APS facility data were included from a separate study, which is the reason for the increased resolution and averaging as compared to the other facilities. Introduction Nanofocusing of X-rays to ever smaller spot sizes requires increasingly stringent requirements for the stability of X-ray microscopes and X-ray nanoprobes. With X-ray optics now capable of focusing X-rays to spot sizes of 10 nm and below, and diffraction-limited mirrors enabling long and very long working distances, high thermal and vibrational stability are vital to achieve the positioning and scanning stability consistent with the small spot sizes. As an example of the metrics and approaches employed to create a sufficiently stable environment for X-ray nanoprobes, we present a study performed to guide specification of the experimental station of a new hard X-ray nanoprobe that will be built at the Advanced Photon Source (APS). The measurements analyze how existing facilities have approached low-vibration environments and, as such, are more broadly applicable to X-ray nanofocusing facilities. As part of the Advanced Photon Source Upgrade (APSU), a new In Situ Nanoprobe beamline (ISN beamline) will be constructed [1]. The ISN instrument will focus hard X-rays to a spot size as small as 20 nm, while providing a working distance of 50 mm. This is achieved by using a nanofocusing Kirkpatrick-Baez mirror (n-KB) system with large acceptance of 1 mm and with high numerical aperture. To achieve stable relative positioning of the KB system with respect to the sample, a positioning stability of less than 2 nm, and an angular stability of 5 nrad of both n-KB and sample positioners, are required. The ISN beamline is designed as a long beamline, with the ISN instrument positioned in a Long Beamline Building (LBB) at 220 m from the X-ray source in the APS storage ring. The long propagation path provides the large lateral coherence length required to fill the acceptance of the n-KB system and, in turn, provides the long working distance that enables broad in-situ studies. The LBB will be built downstream of APS sectors 19-ID and 20-ID, and house both the ISN endstation and the High-Energy X-ray Microscope (HEXM) endstation, as well as offices, laboratories, and related services. Construction of a new building offers the opportunity to design the ISN endstation with appropriate thermal and vibration specifications. To derive design requirements for the satellite building, we have measured and analyzed vibrations at several vibration isolated facilities that house scanning probe, electron microscope, and X-ray nanoprobe instruments. Vibration studies of isolated facilities for high-resolution X-ray, electron, and scanning probe instruments To quantify the stability needs for the ISN enclosure and develop approaches to achieve them, we studied three facilities at Argonne National Laboratory (ANL) and Brookhaven National Laboratory (BNL), and compared them to the level of ambient floor vibrations at the APS experimental floor. The facilities are the Scanning Probe Microscopy (SPM) facility of the Center for Nanoscale Materials (CNM), APS; the Sub-Angstrom Microscopy and Microanalysis (SAMM) facility at CNM [2]; and the Hard X-ray Nanoprobe (HXN) at BNL [3]. These isolated laboratories were chosen specifically for their efforts to mitigate vibrations for high-resolution imaging and analysis. All facilities used isolated concrete slabs for vibration mitigation.
