First Steps Toward the Development of a Straight-Line Reference Alignment System for Future Accelerators at CERN Using Pseudo-Nondiffracting Layer Beams

TL;DR

This study evaluates a novel pseudo-nondiffracting Layer beam-based alignment system for CERN accelerators, demonstrating high precision and potential for radiation-hard sensors suitable for high-radiation environments.

Contribution

It introduces a new alignment sensor system using Layer beams with experimental validation and proposes solutions for noise reduction and radiation-hard sensor development.

Findings

Alignment RMSE less than 30 μm

Displacement measurement standard deviation of 4.3 μm

Fiber matrix sensor RMSE below 1.3 μm

Abstract

This paper presents experimental results that allow for the performance evaluation of a straight-line reference alignment system based on pseudo-nondiffracting Layer beams. Sensors, developed specifically for this system, feature four linear CMOS chips and a square aperture. This allows for simultaneous measurements along the beam path without disrupting the laser reference. Measurements, conducted over a distance of 2 m from the first to the last sensor, were compared with a laser tracker measurement to assess the sensor performance. The alignment reference generated by the Layer Beams exhibited a repeatability and reproducibility root-mean-square error (RMSE) of less than 30 ${\mu}$m. The relative alignment precision for a known displacement was validated with a standard deviation of 4.3 ${\mu}$m. The results highlight the underlying sources of noise, which are induced mainly by the cover glass, the protective film of the pixels, and the dark noise of the CMOS chips. Solutions to address these challenges are proposed. Additionally, a proof-of-concept for future development of a radiation-hard sensor utilizing optical fiber matrices is demonstrated. The RMSE of the reference position detection introduced by the fiber matrix remained below 1.3 ${\mu}$m. This would allow the sensor to be used reliably in high-radiation environments typical for accelerator facilities. This study serves as a foundational step toward developing a robust straight-line reference alignment system based on pseudo-nondiffracting Layer beams intended for deployment in the accelerator facilities.