可变高梯度永磁体四极杆（QUAPEVA）
Variable high gradient permanent magnet quadrupole (QUAPEVA)
摘要：
高梯度四极杆在激光等离子体加速器、对撞机、衍射极限光源等不同的应用中是必需的。永磁体四极提供比常规电磁体更高的场强度和紧凑性。提出了一种基于永磁体的四极（所谓的“QUAPEVA”）的原始设计，其由放置在中心的Halbach环组成，孔半径为6 mm，并且由能够提供210 T/m的梯度的四个永磁体圆柱体包围。QUAPEVAs的设计，包括磁模拟建模，和机械问题的报告。给出了七个不同长度系统的磁测量结果，并证实了理论预期。在改变梯度强度时，磁中心的变化为+/-10微米。三个QUAPEVA磁体的三重体用于聚焦由激光等离子体加速源产生的具有大能量扩展和高发散度的光束，用于自由电子激光演示。
英文摘要：
High gradient quadrupoles are necessary for different applications such as laser plasma acceleration, colliders, and diffraction limited light sources. Permanent magnet quadrupoles provide a higher field strength and compactness than conventional electro-magnets. An original design of permanent magnet based quadrupole (so-called "QUAPEVA"), composed of a Halbach ring placed in the center with a bore radius of 6 mm and surrounded by four permanent magnet cylinders capable of providing a gradient of 210 T/m, is presented. The design of the QUAPEVAs, including magnetic simulation modeling, and mechanical issues are reported. Magnetic measurements of seven systems of different lengths are presented and confirmed the theoretical expectations. The variation of the magnetic center while changing the gradient strength is +/- 10 micrometer. A triplet of three QUAPEVA magnets are used to focus a beam with large energy spread and high divergence that is generated by Laser Plasma Acceleration source for a free electron laser demonstration.
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