Enhanced beam extraction system at the U-120M cyclotron

Abstract

Since its commissioning in 1977, the U-120M cyclotron was initially equipped with a single pair of harmonic coils aimed at optimizing beam quality at lower accelerating radii. In 2022, a significant upgrade introduced a second pair of harmonic coils, positioned at a radius of approximately 50 cm, aligning with the outermost beam orbit. This addition is essential for the efficient extraction of positively accelerated ions and serves as the basis for the newly developed extraction system, which, unlike the original fully electrostatic system, consists of electrostatic deflectors and magnetic channels. This paper describes the design and installation of new harmonic coils in the accelerator vacuum chamber and presents a new extraction system using precession and linear integer resonance methods. Basic properties of these two extraction methods are given and finally, an evaluation of their advantages and limitations concerning their possible use in the cyclotron and an estimation of the efficiency of the new extraction system is made.