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

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 be 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.

Automated summary

The 750 MHz PIXE-RFQ developed and built by CERN provides 2 MeV protons for proton-induced X-ray emission analysis of cultural heritage artwork over a length of one meter. The low-power rf measurements and tuning have been completed, achieving satisfying accuracy. Good agreement between rf measurement and design values was observed for single modules, quality factors, and coupling strength measurements.