Silicon-nitride-based entrance slit design for the high-power-density monochromator in TPS 45A

Details of the design and operational status of the silicon-nitride-based entrance slit installed in the Taiwan Photon Source (TPS) 45A beamline are given. The slit is a diamond blade edge etched onto a copper slit part, which is in thermal contact with the silicon nitride base. A stable slit opening smaller than 4 µm is achieved in TPS 45A. The beam size at the slit has a full width at half-maximum of 3 µm in the vertical direction with a power of 20 W. Additionally, a hard stop made of invar is incorporated to control the thermal expansion displacement. The slit reduces the size and increases the stability of the source of the monochromator. Consequently, a higher energy resolution and excellent beamline stability are achieved.