Analysis of the injection and extraction systems for RIKEN Superconducting Ring Cyclotron

Abstract

The design of the injection and extraction systems for RIKEN Superconducting Ring Cyclotron (SRC) was changed in order to increase the energy gain per turn. The system was changed from one with three radio frequency cavities to one with four radio frequency cavities. The injection and extraction systems should be changed significantly according to this change. This analysis was performed aiming to optimize the layout and the specification of the injection and extraction elements. The SRC has a strong stray field originated from the sector magnets, and this magnetic field depends nonlinearly on the magnetic rigidities of the beams. Therefor, the trajectories of various beams are considerably different each other. In addition, the injection and extraction elements should be installed in a small space limited with the sector magnets, radio frequency cavities, and vacuum chambers. The required fields of the elements and the differences of trajectories in the elements were minimized in the analysis. In the calculation to trace the beam trajectories, electric or magnetic field of each element was superimposed on the field of the sector magnets. A layout of the injection and extraction elements and the trajectories of O-16 and U-238 beams are presented. Specifications of the injection and extraction elements are also presented.

理研超伝導リングサイクロトロン(SRC)の入射および取出系は、ターン当たりのエネルギー利得を増やすために、3個の高周波空洞から構成される系から4個の系へ変更された。これに伴ない、入射および取出系にかなりの変更が必要となった。本解析は、SRCの入射および取出部分のレイアウトと仕様を最適化することを目的に行った。SRCはセクタ磁石から発生する強い漂遊場を持ち、この磁場はビームの磁気剛性に非線形的に依存する。従って、種々のビームの軌道は互いにかなり異なってしまう。その上、入射および取出部分をセクタ磁石、高周波空洞、および真空チェンバで制限された狭い空間に設置しなければならない。本解析では、各部分の要求磁場と部分内の軌道差を最小にした。ビーム軌道を追跡する計算では、各部分の電場または磁場をセクタ磁石の電磁場に重ねた。入射および取出部分のレイアウトと、O-16およびU-238ビームの軌道を示し、入射部分と取出部分の仕様も示した。