An adjustable focusing system for a 2 MeV H- ion beam line based on permanent magnet quadrupoles

TL;DR

This paper presents a compact, adjustable focusing system for a 2 MeV H- ion beam line using permanent magnet quadrupoles, enabling precise beam control with high flexibility for ion beam applications.

Contribution

The paper introduces a novel, compact adjustable focusing system based on permanent magnet quadrupoles for a 2 MeV H- RFQ Linac, including design, construction, and testing.

Findings

Achieved a minimal beam spot size of 1.2 x 2.2 mm^2.

Demonstrated good agreement between measured and simulated magnetic fields.

Provided a flexible, high-performance beam focusing solution.

Abstract

A compact adjustable focusing system for a 2 MeV H- RFQ Linac is designed, constructed and tested based on four permanent magnet quadrupoles (PMQ). A PMQ model is realised using finite element simulations, providing an integrated field gradient of 2.35 T with a maximal field gradient of 57 T/m. A prototype is constructed and the magnetic field is measured, demonstrating good agreement with the simulation. Particle track simulations provide initial values for the quadrupole positions. Accordingly, four PMQs are constructed and assembled on the beam line, their positions are then tuned to obtain a minimal beam spot size of (1.2 x 2.2) mm^2 on target. This paper describes an adjustable PMQ beam line for an external ion beam. The novel compact design based on commercially available NdFeB magnets allows high flexibility for ion beam applications.