Beam screen cryogenic control improvements for the LHC run 2

B Bradu,G Ferlin,E Rogez,A Tovar-Gonzalez,E Blanco-Viñuela

doi:10.1088/1757-899x/171/1/012128

Abstract

This paper presents the improvements made on the cryogenic control system for the LHC beam screens. The regulation objective is to maintain an acceptable temperature range around 20 K which simultaneously ensures a good LHC beam vacuum and limits cryogenic heat loads. In total, through the 27 km of the LHC machine, there are 485 regulation loops affected by beam disturbances. Due to the increase of the LHC performance during Run 2, standard PID controllers cannot keeps the temperature transients of the beam screens within desired limits. Several alternative control techniques have been studied and validated using dynamic simulation and then deployed on the LHC cryogenic control system in 2015. The main contribution is the addition of a feed-forward control in order to compensate the beam effects on the beam screen temperature based on the main beam parameters of the machine in real time.

Highlights

To maintain a good vacuum in the LHC (Large Hadron Collider) beam pipe and to limit heat loads to the 1.9 K pumping unit, it is necessary to keep a stable beam screen temperature around 20 K all the time, including beam injection and current ramping of superconducting magnets [1]
Results obtained during LHC Run 2 in 2015 This improved control scheme has been incrementally deployed in the 485 beam screen cooling loops along the LHC according to the machine operation and beam screen heat load observations
Concerning refrigeration power, the cycle is optimized as the average temperature respects the set-point of 20 K and as all the heating power is immediately cancelled at the injection due to the feed-forward action on the heater and it is restored without major overshoot at the beam dump

Summary

Introduction

To maintain a good vacuum in the LHC (Large Hadron Collider) beam pipe and to limit heat loads to the 1.9 K pumping unit, it is necessary to keep a stable beam screen temperature around 20 K all the time, including beam injection and current ramping of superconducting magnets [1]. The main contribution is the addition of a feed-forward control in order to compensate the beam effects on the beam screen temperature based on the main beam parameters of the machine in real time.

Results

Conclusion