Impedance measurements of the extraction kicker system for the rapid cycling synchrotron of China Spallation Neutron Source

Abstract

The Rapid Cycling Synchrotron (RCS) of China Spallation Neutron Source (CSNS) includes eight modules of the ferrite kicker magnets with window-frame geometry. The fast extraction kicker system is one of the most important accelerator components, whose inner structure will be the main source of the impedance in the RCS. It is necessary to understand the kicker impedance before its installation into the tunnel. The conventional and improved wire methods are employed for the benchmarking impedance measurement results. The experimental result on the kicker's impedance is explained by comparison with the CST PARTICLE STUDIO simulation. The simulation and measurements confirm that the window-frame ferrite geometry and the end plate are the important structures causing the coupling impedance. It is proved in the measurements that the mismatching among the long cable, the termination and the power form network lead a serious oscillation sideband in the longitudinal and vertical impedance, which can be restricted by the ferrite absorb ring. The total impedance of the eight modules systems is determined by the scaling law from the measurement and the impedance measurement of the kicker system is summarized.

Upgrade the impedance model in RCS of CSNS

“…Conventional and improved wire methods were employed to measure the impedance as shown in Fig. 7, before its installation into the tunnel [13]. The small oscillation sideband of the longitudinal and vertical impedance is due to the mismatching between the kicker magnet and the pulse form network.…”

“…The RCS accelerates the beam up to 1. 6 GeV with a repetition rate of 25 Hz, aiming to provide a 100 kW output beam power with an intensity of 1.56 × 10 13 at an injection energy of 80 MeV. At present, the beam power has reached 140 kW with an intensity of 2.18 × 10 13 , 40 % more than the nominal power.…”

“…6 GeV with a repetition rate of 25 Hz, aiming to provide a 100 kW output beam power with an intensity of 1.56 × 10 13 at an injection energy of 80 MeV. At present, the beam power has reached 140 kW with an intensity of 2.18 × 10 13 , 40 % more than the nominal power. An impedance model has been provided in the Ref [3], and new vacuum components have been installed in the RCS to enhance beam power, such as the installation of a magnetic alloy cavity as the second harmonic cavity in summary 2022.…”

Design study for a 500 MeV proton synchrotron with CSNS linac as an injector

“…The simulation code based on AT [11] has also been developed in order to analyze a mechanism of realistic RFKO and to realize more precise control. The maximum spiral step is bigger than 4.5 mm.…”