Optimization of RF phase and beam loading distribution among RF stations in SuperKEKB

TL;DR

This paper presents a method to evaluate and optimize RF phase and beam loading distribution among RF stations in SuperKEKB to enhance beam stability and power efficiency at high beam currents.

Contribution

It introduces a novel method for assessing and adjusting beam loading among numerous RF stations using RF power measurements, improving operation in SuperKEKB.

Findings

Effective evaluation of beam loading balance achieved.

Optimized RF phase distribution enhances stability and efficiency.

Method applicable to large-scale RF systems like SuperKEKB.

Abstract

SuperKEKB is the e-/e+ collider which targets the world highest luminosity. In recent operation, SuperKEKB achieved a new world record of $4.71\times 10^{34} cm^{-2}s^{-1}$ for luminosity with the beam current of 1.4 A. In the future, the beam current will be increased further to aim at the design value of 3.6 A and much higher luminosity. The RF system consists of 38 cavities (30 klystron stations), which share the huge beam loading brought by high current beam with each other cavities. For beam stability and power efficiency, it is important to distribute the beam loading properly among RF cavities. It is equivalent to adjust the acceleration phase of each cavity. However, it is difficult to evaluate the acceleration phase using only the pickup signal. Therefore, we established a method to evaluate the beam loading balance among RF stations from the RF power measurement for each cavity, and to adjust the acceleration phase. This report introduces the method for evaluating and optimizing the beam loading (acceleration phase) among stations in SuperKEKB, which has a large number of RF stations, and its operation.