Coupled Bunch Instabilities Growth in the Fermilab Booster during Acceleration Cycle

TL;DR

This paper analyzes coupled bunch instabilities in Fermilab's Booster during acceleration, focusing on their growth, timing, and intensity dependence, to inform future mitigation strategies at higher beam intensities.

Contribution

It provides a detailed analysis of LCBI growth and timing during acceleration, including measurements at high intensities and insights for future mitigation.

Findings

Identification of mode origin timing during the cycle

Growth rates increase with beam intensity

Unexpected LCBI behaviors observed at high intensities

Abstract

Currently, Fermilab Booster accelerates ~4.5E12 protons per pulse (ppp) in 81 bunches from 400 MeV to 8 GeV at 15 Hz to provide beam to multiple HEP experiments and is being upgraded to handle higher beam intensity >6.7E12 ppp at a repetition rate of 20 Hz. In the current mode of operation, we control longitudinal coupled bunch instabilities (LCBI) using combination of passive and active dampers. The issues with LCBI are expected to worsen at higher beam intensities. Here, we would like to investigate at what time in the beam cycle a particular mode is going to originate and how much it contributes at a different time of the acceleration cycle using the collected wall current monitor data from injection to extraction. Also, measure growth rates as a function of beam intensity for some dominant modes. Finally, this paper presents results from the observed LCBI analysis for the highest available beam intensities, unexpected findings, and future plans to mitigate the LCBI at higher beam intensities