A simple vacuum sample chamber for small-angle X-ray scattering at Beijing synchrotron radiation facility

Abstract

A vacuum sample chamber for SAXS measurement of solutions was developed to improve the signal-to-noise ratio of the instrument at Beijing Synchrotron Radiation Facility (BSRF). We developed a vacuum sample chamber which could be connected to the upstream and the downstream vacuum tubes by bellows. Horizontal and vertical linear slides were mounted in the vacuum chamber to adjust the sample position by 35 mm in the horizontal and vertical directions to align the sample in the light path. The liquid sample holder of the chamber was sealed with polyimide film by squeezing instead of gluing to avoid the potential influence of sealant on the solution. The chamber had been used for SAXS measurements of water and bovine serum albumin solution at BSRF. The results showed that the background scattering intensity in air was much higher than that in vacuum, especially in the small-angle area near the beamstop. When the q value is 0.142 nm−1, 1.01 nm−1 and 1.25 nm−1, the background scattering intensity in air is 45, 6.8 and 4.6 times of that in vacuum, respectively. And the background-subtracted scattering curves of bovine serum albumin solution (10 mg/ml) in air and vacuum differ in intensity by a factor of about 2. When the q value is 2 nm−1, the signal-to-noise ratios of scattering intensity of BSA in air and vacuum are 0.79 and 8.51, respectively. We designed a simple vacuum sample chamber to be used on the SAXS instrument at 1W2A station of BSRF. The scattering of the background and protein solution in air and vacuum was tested and compared, and the signal-to-noise ratio was clearly improved.