Design, development, and construction of the new beam stoppers for CERN's injector complex

TL;DR

This paper details the design, construction, and implementation of new beam stoppers at CERN's injector complex, upgraded to handle higher beam energies for improved safety and reliability.

Contribution

It introduces a new standardized design for beam stoppers capable of managing increased beam energies up to 92.5 kJ, addressing safety, maintainability, and operational requirements.

Findings

Successful installation of 28 new beam stoppers.

Enhanced safety and reliability for higher beam energies.

Positive operational feedback since LS2.

Abstract

Beam stoppers are installed in the transfer lines of the CERN accelerator complex; these components are used as part of the access safety system, which guarantees the safety of workers in the accelerators. They are designed to stop one or at most a few pulses of the beam, where "stop" means the partial or complete absorption of the primary beam in such a way that the remaining unabsorbed primary or secondary beam remains below a specified threshold, as defined by the needs of radiation protection. Prior to Long Shutdown 2 (LS2; 2018--2021), beam stoppers in the injector complex were dimensioned for beam-pulse energies between 9.0 and 30~kJ. The upgrade of the accelerator complex in the framework of the LHC Injectors Upgrade (LIU) project involves beam-pulse energies of up to 92.5~kJ, meaning that these beam stoppers are not able to fulfill the new functional specifications. To cope with the LIU beam parameters and fulfil requirements for safety, maintainability, efficiency, and reliability, a new generation of 28 beam stoppers has been designed, built, and installed. The aim of this paper is to demonstrate the requirements-driven design of these new beam stoppers, outlining the main requirements along with a description of the design and structural assessments. This document presents the implementation and integration of a standardized but adaptable design using a unique 564-mm-long stopper core with a CuCr1Zr absorber and an Inconel~718 diluter, taking into account radiological and infrastructure challenges. The installation process is also described, and the first operational feedback received since LS2 is presented.