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The Design of a Permanent Magnet Quadrupole Lens Focusing System for An Alpha-Irradiator

H Arya*, Y Lai, A Chalise, Y Cao, M Jin, Y Chi, University of Texas at Arlington, Arlington, Texas


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: the cellular/subcellular response under controlled irradiation conditions is an important experimental technology to advance the fundamental understanding of radiobiology. However, the reliance of accelerators to produce high energetic ions (starting from several MeV/nucleon) limits the replication of beam focus and control infrastructures. In this work, we propose to build and optimize a focusing lens system to focus MeV alpha particles generated from Am-241 irradiation source with the purpose of developing an easy-to-adopt, compact and cost-effective controlled system for radiobiology experimental study.

Methods: an initial attempt, we chose to use the electromagnetic focusing lens made up of permanent magnets. The design and optimization was performed using the COMSOL Multiphysics software. Focusing strength, beam stability under various aberration conditions, commercial material availability as well as ease of manufacture were considered when performing the entire system design.

Results: quadrupole triplet lens was formed. The lens compromises of 12 cylindrical magnets assembled in an iron core with a total length of 244 mm. The magnets in the three quadruple sets have magnetization strengths of 1.18, 1.48 and 1.48 Tesla, respectively. The ratio for the diameter of magnets to aperture is 1.147. The lens produces a de-magnification of ~7.5 for an input 4.604 MeV alpha beam with 1 mm in diameter and 0.001 rad in angular divergence. The assumed angular divergence was achievable using a pair of cylindrical collimators of 1 mm in diameter and an interval of 1 m. Aberrations caused by the manufacturing, e.g., the dimensions and magnetization strength of the magnets were tested and a de-magnification of ~ 4.5-7.5 were obtained in the worst to best case scenarios.

Conclusion: demonstrated the achievability of the concept of forming focusing beams from natural radioactive source by the design and optimization of a magnetic quadrupole triplet for an alpha irradiator.

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Heavy Ions, Alpha-particles, Magnetic Fields


IM- Other (General): Magnetization (general)

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