Study On The Low Energy High Current High Charge State RFQ

The radio frequency quadrupole(RFQ)accelerator is the most effective accelerator for accelerating the low energy high current continuous wave(CW)beam,but achieving the stable CW operation is a challenge for the high current ion accelerator.This dissertation studies the methods for the stable CW operation of the RFQ accelerator and systematically presents the development of a high current heavy ion CW RFQ accelerator.The CW RFQ accelerator is very suitable for accelerating the low energy high current beam,but there are challenges of stable CW operation.Focusing on the issues of the stable operation of CW RFQ,the following researches are carried out.In order to reduce the power consumption and power density of the cavity,through comparing various types of the RFQ accelerator cavity,the constant voltage four-vane cavity,which is suitable for the high current CW operation,is selected.To reduce the maximum surface field,the cavity structure is optimized.In order to realize the cavity electromagnetic mode stable,the frequency separation problem in the four vane cavity and the effect of the ? mode stabilizer loop on frequency separation are studied,and the admixture of the dipole field is reduced.Through low-power testing and tuning of the cavity,the frequency and field distribution of the cavity are optimezed.In order to maintain the frequency stability,study the resonant frequency sensitivities of the cooling water temperature,and the sensitivities are utilized to tune the cavity frequency.In order to ensure the stability of the cavity structure,the multi-physics of the cavity are analyzed.To reduce the cavity deformation and stress caused by changes of the water flow and temperature,the frequency tuning scheme and the cooling water flow temperature control scheme are proposed.In order to control the secondary electron yield effect in the cavity,the secondary electrons under the different power conditions in the cavity are studied.The study is to avoid the secondary electron yield effect when the power is needed for the beam commissioning;In order to achieve stable transmission of high frequency power supply and coupling,a solid state power amplifier and dual-port couplers for power coupling are employed.This dissertation is based on the above studies that contribute to the realization of CW RFQ stable operation.Combined with the requirements of LEAF,the LEAF RFQ accelerator has completed the entire process of the design and test,such as,highfrequency design,multiphysics analysis,study of the tuning method by changing the water temperatures,lowpower test,high power condtioning and beam acceleration experiments.The tests indicate that the LEAF RFQ accelerator meets the requirements of the stable CW operation and could provide the stable beam for the experimental terminals.