Design of injection and extraction delay-line kicker magnet for circular electron-positron collider
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摘要: 环形正负电子对撞机(CEPC)是一台周长100 km,最高能量为120 GeV的双环对撞机。为了满足不同能量粒子从增强器注入到对撞环,针对W和Z能量模式设计了对撞环离轴注入系统,用于实现束流的累积。为了提高注入效率,兼容不同注入能量,不同束流填充模式,同时尽可能减少注入过程中冲击磁铁对其它束团的扰动,要求对撞环离轴注入冲击磁铁系统是一个上升时间和下降时间小于200 ns,脉冲底宽调节范围为440~2420 ns的梯形波脉冲放电系统。和常见的集中参数型冲击磁铁相比,分布参数型冲击磁铁具有更优越的动态响应特性,适合产生一个前沿更加陡峭、波形更为理想的梯形波脉冲。根据CEPC的束流注入物理需求,完成了一台分布参数型冲击磁铁的物理设计和结构设计,并采用了PSpice和Opera程序进行模拟仿真。设计结果表明:冲击磁铁由26级LC单元结构叠装而成,磁铁总长为1018 mm,磁有效长度为942 mm;在[−20,20] mm磁铁孔径内,磁场强度为0.042 1 T,磁场均匀性优于±0.2%;冲击磁铁系统总上升时间(10%~90%)为193 ns,下降时间(90%~10%)为191 ns。理论分析、PSpice程序和Opera程序模拟均验证了磁铁设计方案的可行性。Abstract: Circular electron-positron collider (CEPC) is a double ring collider with a circumference of 100 km and a maximum energy of 120 GeV. To meet the needs of different energy particles injected from the booster to the collision ring, an off-axis injection system of the collision ring is designed for the W and Z energy modes to realize the accumulation of beam. To improve the injection efficiency, also be compatible with different injection energy, and different beam filling modes, and at the same time reduce the disturbance of other bucket by the kicker magnet during the injection process as much as possible, the off-axis injection kicker magnet system of the collision ring is required to be a trapezoidal wave pulse discharge system with a rise time and falling time of less than 200 ns and a pulse bottom width adjustment range of 440−2420 ns. Compared with the common lumped-inductance kicker magnet, the delay-line kicker magnet has better dynamic response characteristics and is suitable for producing a trapezoidal pulse with steeper front and more ideal waveform. In this paper, according to the physical requirements of beam injection of CEPC, the physical design and structure design of a delay-line kicker magnet are completed, and the PSpice and Opera programs are used for simulation. The design results show that the delay-line kicker magnet is composed of 26 LC units superimposed. The total length of the kicker magnet is 1018 mm, and the magnetic effective length is 942 mm. In [−20, 20] mm magnet aperture, the magnetic field strength is 0.042 1 T, the magnetic field uniformity is better than ±0.2%; the total rise time (10%−90%) of the kicker magnet system is 193 ns, and the fall time (90%−10%) is 191 ns. Theoretical analysis, PSpice program and Opera program simulation all verify the feasibility of the magnet design scheme.
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表 1 CEPC对撞环离轴注入冲击磁铁系统设计物理要求
Table 1. Physical requirements of CEPC off-axis injection kicker system
repetition
rate/Hzpulse
width/nsflat
top/nsrise (fall)
time/nskick
angle/mradintegral field
strength/(T·m)beam pipe
aperture1000 440~2420
(adjustable)0~1980
(adjustable)<220 0.1 0.04 75 mm×56 mm 表 2 镍锌铁氧体性能参数
Table 2. Performance parameters of Ni-Zn ferrite
initial
permeabilitysaturation flux
density/mTresidual flux
density/mTcoercive
force/(A· $ {\mathrm{m}}^{-1} $)density/
(g· $ {\mathrm{c}\mathrm{m}}^{-3} $)Curie
temperature/℃2100 330 130 9.5 5.27 130 表 3 典型的MOSFET和IGBT开关参数
Table 3. Typical MOSFET and IGBT switching parameters
type Vbr/V Td(on)/ns Tr/ns Td(off) /ns Tf/ns MOSFET 1700 65 20 48 18 IGBT 1200 10 60 530 30 -
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