Study on transient beam loading compensation for China ADS proton linac injector II

TL;DR

This paper presents a novel transient beam loading compensation method using combined PI feedback and feedforward control, effectively reducing cavity field variation during pulsed beam operation in a proton linac for the China ADS project.

Contribution

The paper introduces a simple yet effective transient beam loading compensation technique combining PI feedback and feedforward control for proton linacs.

Findings

Superconducting cavity field variation was reduced to less than 1.7%.

The combined control method significantly improved gradient regulation during pulsed beam operation.

Experimental results validate the effectiveness of the proposed compensation approach.

Abstract

Significant transient beam loading effects were observed during beam commissioning tests of prototype II of the injector for the Accelerator Driven Sub-critical (ADS) system, which took place at the Institute of Modern Physics, Chinese Academy of Sciences, between October and December 2014. During these tests experiments were performed with CW operation of the cavities with pulsed beam current, and the system was configured to make use of a prototype digital low level radio frequency (LLRF) controller. The system was originally operated in pulsed mode with a simple PID feedback control algorithm, which was not able to maintain the desired gradient regulation during pulsed 10 mA beam operations. A unique simple transient beam loading compensation method which made use of a combination of PI feedback and feedforward control algorithm was implemented in order to significantly reduce the beam induced transient effect in the cavity gradients. The superconducting cavity field variation was reduced to less than 1.7% after turning on this control algorithm. The design and experimental results of this system are presented in this paper.