Radio Frequency Quadrupoles (RFQs) are applied widely in proton accelerator facilities. The development of the high-frequency RFQs enables the construction of compact proton accelerator facilities, but faces with more tuning difficulties. The traditional tuning methods based on the theoretical characteristics of the RFQ cannot achieve good results with compact proton accelerators. The tuning method based on the response matrix and SVD method meets the problem of the solution being out of the range that tuners can reach.

This study aims to purpose a novel tuning method for efficient reduction of dipole components by a transform of the tuning method, so as to tune the compact RFQs better and limit the range of the solution.

Firstly, a tuning method based on the response matrix and the least squares method was designed and implemented. The solution was limited, and a different weight was assigned to the dipole components for diminution during the tuning progress. Then, the tuning method was experimentally tested in the simulation environment on the aluminum RFQ prototype for verification. Both tuning with single tuner and multiple tuners were tested in simulation.

Verification results show that high precision is achieved and the solution is within the expected range even without limitation. Experimental results of verification on the aluminum RFQ prototype show that the quadrupole and dipole component errors are 1.57% and 24.09%, respectively, in the initial state, but reduce to 1.39% and 2.33%, respectively, after five rounds of tuning.

The novel tuning method based on response matrix is verified by this study for its validity of limiting the range of the solution and reducing the dipole components efficiently, hence can be applied to RFQs operating at other frequencies as well. It can contribute to the development of compact proton accelerators and promote medical proton facilities in the future.