A four-vane type Radio Frequency Quadrupole (RFQ) is very sensitive to geometrical errors since these may result into mixing of unwanted modes with the desired operating mode. This perturbs the voltage profile of the RFQ, which may deteriorate the beam dynamics, and increase the emittance growth and beam loss. In order to tune the RFQ for a desired voltage profile, a computer program based on transmission line model of RFQ is typically used. Although the theory of tuning program and its experimental validation has been discussed in earlier publications (Palmieri et al., 2010; Sanyasirao, 2014), here we discuss a methodology to perform the tuning of an RFQ in a simulation environment. This approach enables us to do an in-depth analysis of the tuning process, which is illustrated by performing the studies for an example case of the RFQ for the proposed Indian Facility for Spallation Research (IFSR), using the 3D Electro-Magnetic (EM) code CST-MWS. In these simulations, modelling of the vane-tip modulations of the RFQ has been performed in the code CST-MWS, for which a new procedure, using a macro, has been developed, which is presented here. We study perturbation in the voltage profile for two specific situations — first, due to vane-tip modulations, and second, due to misalignment errors. We correct the effect due to each of these perturbations in the simulation environment, using the tuning algorithm, and verify it using the 3D EM code. It has been shown in the paper that the same tuning algorithm with suitable modification can be used also for tuning of the end-cells of RFQ.

四叶片型射频四极杆（RFQ）对几何误差非常敏感，因为这些误差可能导致不必要的模式与所需的工作模式混合。这会扰乱RFQ的电压曲线，这可能会使光束动力学恶化，并增加发射率的增长和光束损耗。为了针对期望的电压轮廓调整RFQ，通常使用基于RFQ的传输线模型的计算机程序。尽管调谐程序的理论及其实验验证已在较早的出版物中进行了讨论（Palmieri等人，2010； Sanyasirao，2014），但此处我们讨论了一种在仿真环境中执行RFQ调谐的方法。这种方法使我们能够对调优过程进行深入分析，通过使用3D电磁（EM）代码CST-MWS对拟议的印度散裂研究设施（IFSR）的RFQ示例进行研究，可以说明这一点。在这些模拟中，已经在代码CST-MWS中对RFQ的叶尖调制进行了建模，为此开发了使用宏的新过程，在此处介绍。我们研究了两种特定情况下电压曲线的扰动-首先是由于叶尖调制引起的，其次是由于失准误差引起的。我们使用调整算法来校正由于仿真环境中的这些扰动而产生的影响，并使用3D EM代码进行验证。在论文中已经表明，具有适当修改的相同调谐算法也可以用于RFQ端单元的调谐。