We present a two-carriage, air-bearing system on a common ceramic support beam designed to utilize multiple modes of long-trace-profiler (LTP) operation, with movable and stationary optical sensors for both coherent and incoherent light probes, dubbed the LTP-2020. Measurements with different movable and stationary sensors integrated in the LTP-2020 system allow on-bench round-robin comparisons for ensuring high-accuracy metrology of x-ray optics. In the case of variable-line-spacing (VLS) gratings, one sensor can characterize the zero-order surface, and the second, in Littrow configuration, can record diffraction angle changes without introducing uncertainty of the mutual alignment between tools. We also aspire to preserve the major advantage of the current ALS LTP-II with the capability of raising and lowering the ceramic beam with the carriages and sensors. This design allows characterization of unmounted optical substrates, as well as multi-element optical systems and large mirror assemblies, such as bendable x-ray mirrors. The modular design of the LTP-2020 gantry system together with reconfigurable optical sensors mounted to separate carriages allows operation for scanning optical surfaces at three native orientations: face-up, side-facing, face-down. We also discuss the gantry system motion control algorithms and software that enable us to perform sophisticated data acquisition based on advanced optimal scanning strategies for anti-correlation of temporal drift and systematic errors. Experimental data illustrating the high performance of the developed gantry system is also presented. This work was supported in part by the U. S. Department of Energy under contract number DE-AC02-05CH11231.
|