Design and stability performance of a cradle type cryo-cooled monochromator at Shanghai Synchrotron Radiation Facility

Abstract

The mechanical design and stability performance of a dedicated double crystal monochromator (DCM) which has been commissioned in beamline BL02U2 at Shanghai Synchrotron Radiation Facility are presented. Details of the cradle type crystal angular adjustment mechanism design is given. The vibration response and relative stability performance of the DCM are systematically investigated at ambient temperature and under liquid nitrogen circulation condition respectively, whose vibrational spectra analyses coincide with each other highly. Furthermore, the X-ray beam stability at sample position is performed by a quadrant CVD-diamond beam position monitor (QBPM) in the end station. In summary, the dedicated monochromator achieves a relative pitch vibration of 31.5 nrad (Root-Mean-Square, RMS) in 0.1-100 Hz bandwidth at the liquid nitrogen (LN2) flow rate of 2.4 L min −1, which is of a good stability performance.