BEPCⅡ正电子源(英文)

BEPCⅡ Positron Source

BEPCⅡ是一粒子工厂型的正负电子对撞机,为北京正负电子对撞机(BEPC)的改造、升级工程．它对直 线注入器的基本要求是40mA,1．89GeV的正电子柬流,发射度1．6μm,能散度好于±0．5％,保证储存环的注入速 率≥50mA/min,实现TOP OFF注入方式．因为正电子流强与打靶电子束流功率成正比,采用一把新的10A电 子枪来提高打靶电流,采用新加速结构和65MW速调管SLAC5045把目前140MeV的打靶能量提高到240MeV． 正电子源本身也是一非常关键、极其复杂的系统,它包括正电子转换靶室、12kA“磁号”脉冲电源、7m长聚焦 节、大功率直流电源和支架等．目前,正电子产生加速器,从电子枪直到正电子源,已经安装到了BEPC直线加 速器隧道．本文将着重介绍正电子源系统的设计、加工和测试．

BEPC Ⅱ- an upgrade project of the Beijing Electron Positron Collider （BEPC） is a factory type of e^＋e^- collider. The fundamental requirements for its injector linac are the beam energy of 1.89GeV for on-energy injection and a 40mA positron beam current at the linac end with a low beam emittance of 1.6μm and a low energy spread of±0.5% so as to guarantee a higher injection rate （≥50mA/min） to the storage ring. Since the positron flux is proportional to the primary electron beam power on the target, we will increase the electron gun current from 4A to 10A by using a new electron gun system and increase the primary electron energy from 120MeV to 240MeV. The positron source itself is an extremely important system for producing more positrons, including a positron converter target chamber, a 12kA flux modulator, the 7m focusing module with DC power supplies and the support, The new positron production linac from the electron gun to the positron source has been installed into the tunnel. In what follows, we will emphasize the positron source design, manufacture and tests.