rf measurements and tuning of the 1-meter-long 750 MHz radio-frequency quadrupole for artwork analysis

TL;DR

This paper details the low-power RF measurements and tuning process of a 750 MHz PIXE-RFQ at CERN, achieving precise field and frequency alignment using a novel algorithm, with results closely matching design specifications.

Contribution

Introduces a novel algorithm for simultaneous RF field and frequency tuning of a 750 MHz RFQ using direct response matrix measurements.

Findings

Successful RF tuning in two steps with high accuracy

Good agreement between measurements and design values

Effective measurement of module quality factors and coupling

Abstract

The 750 MHz PIXE-RFQ (radio-frequency quadrupole), developed and built at CERN, provides 2 MeV protons over a length of one meter for proton-induced X-ray emission analysis (PIXE) of cultural heritage artwork. In this paper, we report low-power rf measurements and tuning of the PIXE-RFQ, which have been completed mid-2020. Using a novel algorithm based on direct measurements of the response matrix, field and frequency could tuned at the same time in only two steps to satisfying accuracy. Additionally, we report measurements of single modules, quality factors, and coupling strength. In all cases, very good agreement between rf measurement and design values was observed.