Towards a new generation long trace profiler LTP-2020: optical design of pencil beam interferometry sensor

Conference · Tue Oct 03 04:00:00 EDT 2023 · Advances in Metrology for X-Ray and EUV Optics X

DOI:https://doi.org/10.1117/12.2677418· OSTI ID:2370362

Takacs, Peter Z.; Lacey, Ian; Yashchuk, Valeriy V.

Improvements in the quality of synchrotron beamline x-ray optics required for next-generation light sources (e.g. the ALS Upgrade project) drive the need to improve the performance of the metrology instrumentation used to measure these components. The Long Trace Profiler (LTP) that is in use at many synchrotron metrology laboratories around the world has some known issues that affect the accuracy of its measurements. The main error source is optical path difference (OPD) phase error introduced into the probe beam by inhomogeneities in the glass components used in the optical head. We have developed a new optical head design, LTP-2020, that replaces the cube polarizing beamsplitter (PBS) with a thin wedge plate polarizing beamsplitter (WPBS) and replaces the cemented doublet lens with an aspheric singlet. Both of these components significantly reduce the glass volume traversed by the laser probe beam. Careful attention to ghost ray interference produced by back reflection from optical surfaces is necessary to minimize distortion in the primary image that translates into systematic error in the slope angle measurement. We make extensive use of a commercial raytracing program to model the back reflections and adjust component parameters as necessary to minimize distortion. Deliberate misalignment of components is necessary to make the system perform correctly. Stringent requirements are placed on the 45◦ incidence coatings on the WPBS and on the normal incidence coatings on the lens and camera window elements. We encourage our colleagues who wish to upgrade their current LTP systems to join us in the procurement of these custom optical components.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-BES)
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 2370362
• Conference Information: Journal Name: Advances in Metrology for X-Ray and EUV Optics X Journal Volume: 12695
• Country of Publication: United States
• Language: English