In this article, we design and construct gradient coils for a Halbach permanent-magnet array magnetic resonance (MR) scanner. The target field method, which is widely applied for the case of axial static magnetic fields, has been developed for a transverse static magnetic field as produced by a Halbach permanent-magnet array. Using this method, current densities for three gradient directions are obtained and subsequently verified using a commercial magneto-static solver. Stream functions are used to turn the surface current densities into wire patterns for constructing the gradient coils. The measured fields are in good agreement with simulations and their prescribed target fields. 3-D images have been acquired using the constructed gradient coils with a very low degree of geometric distortion.

中文翻译：

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基于 Halbach 的 MRI 系统的梯度线圈设计与实现

在本文中，我们为 Halbach 永磁阵列磁共振 (MR) 扫描仪设计和构建梯度线圈。靶场法广泛应用于轴向静磁场的情况，是针对由 Halbach 永磁体阵列产生的横向静磁场开发的。使用这种方法，可以获得三个梯度方向的电流密度，随后使用商业静磁求解器进行验证。流函数用于将表面电流密度转换为用于构建梯度线圈的线型。测量场与模拟及其规定的目标场非常吻合。已使用构造的梯度线圈获得了具有极低几何失真度的 3-D 图像。