Abstract

Several state-of-the-art metrology measurement methods have been investigated and combined for a fiducialization of accelerator components in the micrometric regime. The PACMAN project at CERN applied stretched-wire measurement methods to Compact Linear Collider quadrupole and cavity beam position monitor prototypes, to locate their magnetic, respectively, electromagnetic, axis using a dedicated test stand and to determine the position of the wire with respect to external alignment targets (fiducials) testing different methods, such as coordinate measuring machine measurements and microtriangulation. Further studies have been performed using a nanopositioning system, verifying the absolute accuracy and repeatability of the fiducialization method within a few micrometers.

Highlights

  • Fiducialization is one of the key steps in the alignment of components for particle accelerators, such as magnets, accelerating structures, beam diagnostic devices, etc. [1]

  • The reference axis is defined in different ways depending on the function of the component; e.g., it is the magnetic center axis in the case of a quadrupole magnet or the electromagnetic symmetry axis for a beam position monitor (BPM) or an accelerating structure (AS)—in other words, a symmetry axis of the component that matches the nominal beam trajectory but not necessarily the mechanical symmetry axis

  • Reasons:(i) on the main beam quadrupole (MBQ) side, the complementary mounted element refers to the four magnet poles that are affected by the precision of the four magnet quadrant assembly, and (ii) on the BPM side, the complementary mounted element is aligned with respect to the BPM external surface, since there is no access for metrology measurements to the BPM internal surface

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Summary

INTRODUCTION

Fiducialization is one of the key steps in the alignment of components for particle accelerators, such as magnets, accelerating structures, beam diagnostic devices, etc. [1]. The aim of the PACMAN project, a study on particle accelerator components’ metrology and alignment to the nanometer scale, lies in the development of novel methods and tools, allowing the fiducialization of different types of accelerator components simultaneously within the environment of a 3D coordinate measuring machine (CMM). This project aims to improve the efficiency and accuracy of the process in view of the large number of components needed in the CLIC accelerator [3,4].

Prealignment requirements
Description and objectives of the Final PACMAN Alignment Bench
The quadrupole magnet
The BPM
The stretched-wire displacement system
The nanopositioning system
Alignment targets and stretched wire
ASSEMBLY AND PREPARATION OF THE SYSTEMS
Mechanical alignment of components
Compatibility of the microtriangulation system in the CMM environment
Impact of the magnet current on the position of the magnetic axis
Offset between magnetic and mechanical axes of the quadrupole
Magnetic axis
Electrical axis
Microtriangulation vs CMM measurements
Nanopositioning measurements
PERSPECTIVES
A portable alternative to CMM measurements
Findings
CONCLUSION

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