Abstract
The proton-induced x-ray emission (PIXE) is the most commonly used ion beam analysis technique. It allows for nondestructive quantitative elemental characterization and is used in a variety of fields, particularly for the diagnosis of cultural heritage artwork. To provide mobile access to PIXE, a compact transportable radio frequency quadrupole (RFQ) linac has been designed and is being built at CERN. The PIXE RFQ has a length of only one meter and accelerates a proton beam to an energy of 2 MeV. This paper covers various rf design studies for the RFQ operating at 750 MHz. We show simulation results regarding cavity, equipment, and coupler geometry. Thermomechanical and beam dynamics studies are presented as well. The paper concludes with a conceptual study on dipole mode detuning by means of length adjustment.
Highlights
In ion beam analysis, protons of a few MeV are used for material characterization, with the proton-induced x-ray emission (PIXE) [1] being the most widely used ion beam analysis technique
The final rf design is validated by means of beam dynamics simulations, where a distribution of macroparticles is tracked through the electromagnetic field while it is subject to Lorentz force and potentially space charge forces
The length is fixed by the beam dynamics design, and lower or higher order modes are detuned by means of dipole stabilization rods (DSR), among others, as it has been accomplished for the PIXE radio frequency quadrupole (RFQ)
Summary
Protons of a few MeV are used for material characterization, with the proton-induced x-ray emission (PIXE) [1] being the most widely used ion beam analysis technique. The PIXE RFQ is a four-vane type structure designed and constructed with the experience gained from the Linac RFQ [8,9] and the high-frequency RFQ for medical applications (HF RFQ) [5,10,11,12,13,14] It operates at a frequency of 749.48 MHz resulting in a small cavity with a cross section less than 14 cm wide [Figs. The rf design for the PIXE RFQ is initiated with a study on the 2D cross section, before 3D effects of the vane modulation are included. This paper first focuses on the rf design studies conducted for the PIXE RFQ cavity, its particular end shapes and dipole stabilization rods, tuners, pumping ports, pickup antennas, and the input power coupler. The effect of a detuned frequency on the beam dynamics is evaluated
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