Proposed design and optimization of a higher harmonic cavity for ALS-U

H Feng; S De Santis; K Baptiste; W Huang; C Tang; D Li

doi:10.1063/1.5135955

Proposed design and optimization of a higher harmonic cavity for ALS-U

Rev Sci Instrum. 2020 Jan 1;91(1):014712. doi: 10.1063/1.5135955.

Authors

H Feng¹, S De Santis¹, K Baptiste¹, W Huang², C Tang², D Li¹

Affiliations

¹ Lawrence Berkeley National Lab, Berkeley, California 94720, USA.
² Department of Engineering Physics, Tsinghua University, Beijing 100084, China and Key Laboratory of Particle and Radiation Imaging (Tsinghua University), Ministry of Education, Beijing 100084, China.

PMID: 32012627
DOI: 10.1063/1.5135955

Abstract

Higher harmonic cavities (HHCs), also known as Landau cavities, have been proposed to increase the beam lifetime and Landau damping by lengthening the bunch and increasing the synchrotron tune spread. Here, we present an optimized 1.5 GHz normal conducting HHC design for the Advanced Light Source Upgrade project at Lawrence Berkeley National Lab with a superconducting-like geometry for lower R/Q. The optimization goal is to reach the required shunt impedance while maintaining a relatively high Q value of the cavities. A multi-objective genetic algorithm (MOGA)-based optimization process is applied to optimize the radio frequency (RF) design. This study serves as an example of how a genetic algorithm can be used to optimize RF cavities. Detailed exploration and characterization of the MOGA-based RF cavity optimization have been demonstrated from the aspects of minimizing the coupled bunch instabilities and analyzing the higher-order modes and the corresponding impedance of the HHC.