Bayesian optimization experiment for trajectory alignment at the low energy RHIC electron cooling system

Y Gao,J Morris,K A Brown,W Lin,S Seletskiy,G H Hoffstaetter,X Gu

doi:10.1103/physrevaccelbeams.25.014601

Abstract

The low energy RHIC electron cooling (LEReC) system is the world's first electron cooler utilizing radio frequency (rf) accelerated electron bunches, and a nonmagnetized electron beam. It is also the first electron cooler applied directly to colliding hadron beams. The unique approach to cooling makes beam dynamics in LEReC very different from the conventional electron coolers. Numerous LEReC parameters can affect the cooling rate. One of the most critical factors is the alignment of the electron and ion trajectories in the cooling section. In this work, we apply Bayesian optimization to check and if needed to optimize the trajectories' alignment. Experimental results are presented and it is demonstrated that machine learning (ML) methods can be applied to perform the control tasks effectively in the RHIC controls system.

Highlights

To increase the collision rate [1] at the Relativistic Heavy Ion Collider (RHIC), the Collider-Accelerator Department (C-AD) at Brookhaven National Laboratory (BNL) developed, commissioned and operated the Low Energy RHIC electron Cooler (LEReC) [2,3]
The beam-based calibration and alignment of the cooling section (CS) Beam Position Monitor (BPM) is performed to zero the BPMs offsets
The present target BPM positions for electrons are ðx 1⁄4 0; y 1⁄4 0Þ

Summary

Introduction

To increase the collision rate [1] at the Relativistic Heavy Ion Collider (RHIC), the Collider-Accelerator Department (C-AD) at Brookhaven National Laboratory (BNL) developed, commissioned and operated the Low Energy RHIC electron Cooler (LEReC) [2,3]. LEReC is the world’s first electron cooler where electron bunches are accelerated with an rf linac. The electrons are generated from the 400 keV photo-gun and accelerated to the designed energy of 1.6– 2 MeV (depending on the energy of the ions to be cooled) in the 704 MHz superconducting rf cavity. The electrons are delivered first to the cooling section (CS) in the “Yellow” RHIC ring and passing the 180 degree bend, to the CS in the “Blue” RHIC ring, cooling the ion bunches in both rings of the collider.

Objectives

Results

Conclusion