(a) Front-end layout of the TPS 13A beamline, featured with the X-ray beam position monitors 1 and 2 (XBPM1 and XBPM2), high-heat-load slits, and microslits. Panels (b) and (c) are typical beam positions traced in the horizontal and vertical directions by XBPM-1 with 1 µm resolution. Periodic beam-position fluctuations of 5–30 µm correspond to the TPS top-up injections of period 4 min. Also shown in the same time interval is a relatively large beam-position shifting during an occasional change of the IU24 gap. (d) Schematics of the microslits, comprising four independent tungsten blades, H1, H2, V1 and V2, separated closely along the beam path for better heat dissipation through individual contacts with copper blocks (colored in orange). The two water-cooled slits of slit1 and slit2 after XBPM2 are optionally used to reduce stray irradiation, hence heat-load on the downstream DCM/DMM. The abbreviations used in (a) are PAB (photon absorber), MGV (metal gate valve), FCV (fast closing valve), DI water (deionized water), CP-Air (compressed air pressure), XBPM (X-ray photon beam position monitor), HMS (heavy metal shutter), IPA-C and IP# (ion pumps) and GV (gate valve).