EicC对撞光学设计

EicC是中国科学院近代物理研究所计划建造的中国电子-离子对撞机装置,该对撞机质心能位于20 GeV附近,是研究海夸克的最佳能量窗口,同时还可研究胶子和价夸克。EicC对撞粒子为高极化率质子和电子束团,质子环pRing采用八字环设计方案,可以更好地保持极化质子束团极化率,电子环eRing采用跑道形环设计方案,可以更好地利用隧道空间。该装置电子束流能量中心值为3.5 GeV,电子束RMS发射度为水平方向60 nm·rad,垂直方向60 nm·rad,对撞点b函数为水平方向0.4 m,垂直方向0.12 m;质子束流能量中心值20 GeV,质子束RMS发射度为水平方向300 nm·rad,垂直方向180 nm·rad,对撞点b函数为水平方向0.08 m,垂直方向0.04 m,设计亮度2×1033 cm–2s–1。EicC采用双对撞区非对称光学设计,通过对EicC不同色品补偿方案的研究,最终确定了弧区加短直线节共同补偿的色品补偿方案;通过研究对撞点处b函数以及对撞点间相移对动力学孔径的影响,最终得到pRing动力学孔径大于8 s(s为束团RMS尺寸)、eRing动力学孔径大于20 s,满足大于束团尺寸6 s的要求。

EicC Collider Lattice Design

Electron Ion Collider in China (EicC), a new plan proposed by Institute of Modern Physics, Chinese Academy of Science to upgrade the HIAF facility, is mainly designed for studying sea quark, gluon and valence quark. The Center Mass Energy of the EicC is near 20 GeV. In order to maintain polarizability of proton bunched beams, the pRing (proton Ring) is designed to have the octave shape layout, while the racetrack layout is adopted by the eRing (electron Ring) to make full use of the tunnel space. For pRing, the proton center energy is 20 GeV, the horizontal and vertical rms emittance is 300 and 180 nm·rad respectively, and the β function at collider point is 0.08 and 0.04 m in the horizontal and vertical plane. For eRing, the electron beam center energy is 3.5 GeV, the rms emittance in transversal plane is 60 nm·rad, and the β function at collider point is optimized to be 0.4 and 0.12 m in horizontal and vertical direction respectively. As a result, the designed luminosity can achieve 2×1033 cm–2s–1. Furthermore, the influence of chromaticity compensation scheme on the Dynamic Aperture (DA), including the compensation patterns, the beta function and the phase advance in the collision points, is also studied. Accordingly, chromaticity compensation scheme is finalized as compensating by arc and short straight sextupoles, the DA of the pRing (>8σ) and the eRing (>20σ) can meet the design requirement of the beam size larger than 6σ.