Nonlinear Model Predictive Control for the Superfluid Helium Cryogenic Circuit of the Large Hadron Collider

Abstract-Superfluid helium is used in the cryogenic circuit that cools down and stabilizes temperature of more than 1600 high performance, main superconducting magnets of the Large Hadron Collider (LHC) -the new particle accelerator at European Organization for Nuclear Research (CERN). This paper presents a simulation study of the application of Nonlinear Model Predictive Control (NMPC) to the Superfluid Helium Cryogenic Circuit. First, the new first principles, distributed parameter model of the circuit to be used in online optimization is reviewed. Then stabilization of the superconducting magnets temperature using NMPC based on the model and Continuation/Generalized Minimum Residual (C/GMRES) algorithm is described. Finally the small computational cost of C/GMRES solution/approximation method and resulting real-time feasibility are highlighted

He II Heat Exchanger Test Unit for the LHC Inner Triplet

The Inner Triplet Heat Exchanger Test Unit (IT-HXTU) is a 30-m long thermal model designed at Fermilab, built in US industry, fully automated and tested at CERN as part of the US LHC program to develop the LHC Interaction Region quadrupole system. The cooling scheme of the IT-HXTU is based on heat exchange between stagnant pressurized He II in the magnet cold mass and saturated He II (two-phase) flowing in a heat exchanger located outside of and parallel to the cold mass. The purposes of this test are, among others, to validate the proposed cooling scheme and to define an optimal control strategy to be implemented in the future LHC accelerator. This paper discusses the results for the heat exchanger test runs and emphasizes the thermal and hydraulic behavior of He II for the inner triplet cooling scheme

Non-linear Model Predictive Control for cooling strings of superconducting magnets using superfluid helium

En cada uno de los ocho arcos del Gran Colisionador de Hadrones (LHC) de 27 km de circunferencia, largas cadenas de imánes superconductores de 2.5 km se enfrian con helio II superfluido a 1.9 K. La estabilización de la temperatura es un problema de control retador debido a complejas dinámicas no lineales de la temperatura de los imanes y la presencia de múltiples restricciones operativas. No-linealidades fuertes y tiempos muertos variables de la dinámica se originan en la conductividad de calor eficaz de superfluido dependiendo fuertemente de flujo de calor y pueden variar hasta tres órdenes de magnitud dentro de la gama de posibles condiciones operativas. Con el fin de mejorar la estabilización de la temperatura, se ha realiado una demostración con un Controlador Predictivo No-lineal económico (NMPC) con retroalimentación de salida que se presenta en esta tesis. El controlador se basa en un modelo numerico de primeros principios y de parámetros distribuidos, novedoso y complejo, para la dinámica de la temperatura en un subsector del LHC de 214 m de largo. El modelo se caracteriza por el muy bajo costo computacional de la simulación, necesario en control de procesos avanzado basado en optimización en tiempo real. Se presenta un análisis exhaustivo de los procesos físicos termo-hidráulicos que rigen la dinámica de temperatura, incluido la revisión de programas de I+D relacionados. El análisis explica las principales características de la dinámica de temperatura y ha sido el punto de partida para el desarrollo del modelo y la estrategia de control. También se describen las configuraciones experimentales utilizadas para identificar la dinámica y los parámetros del modelo de este sistema criogénico superfluido único. A través de la tesis, destaco los métodos prácticos utilizados para lograr la factibilidad de tiempo real del controlador, incluyendo: 1) aproximaciones, manejo de rigidez y ecuaciones algebraicas en el modelado y simulación, 2) la aplicación del estimador de estado híbrido Luenberger Observer - Mover Horizonte Estimación que permite el control de retroalimentación de salida a un costo muy bajo de computación, 3) parametrización de las trayectorias de variables optimizadas que reduce significamente el número de variables optimizados, 4) la aproximación del problema de optimización no-lineal original con restricciones de desigualdad usando uno con restricciones de desigualdad tipo caja que es mucho más fácil de resolver y 5) la aplicación de un solo paso de un método Quasi-Newton para el problema de optimización con restricciones tipo caja específico que se resuelve repetidamente en un controlador basado en la optimización. Se presentan dos configuraciones NMPC para la estabilización de la temperatura de los imanes sobre un sub-sector del LHC de 214 m de largo: 1) que manipula dos válvulas de control, probado experimentalmente en el LHC, y 2) que manipula las dos válvulas y 12 calentadores eléctricos, probado en simulaciones. Ambas configuraciones son factibles en tiempo real y presentan un excelente funcionamiento robusto en amplia gama de condiciones de operación, validando así tanto el modelo de parámetros distribuidos y el NMPC en linea con realimentación de salida basado en un modelo complejo de primeros principiosDepartamento de Ingeniería de Sistemas y Automátic

Comparison of different cryogenic control strategies via simulation applied to a superconducting magnet test bench at CERN

Industrial process controllers for cryogenic systems used in test facilities for superconducting magnets are typically PIDs, tuned by operational expertise according to users' requirements (covering cryogenic transients and associated thermo-mechanical constraints). In this paper, an alternative fully-automatic solution, equally based on PID controllers, is proposed. Following the comparison of the operational expertise and alternative fully-automatic approaches, a new process control configuration, based on an estimated multiple-input/multiple-output (MIMO) model is proposed. The new MIMO model-based approach fulfils the required operational constraints while improving performance compared to existing solutions. The analysis and design work is carried out using both theoretical and numerical tools and is validated on the case study of the High Field Magnet (HFM) cryogenic test bench running at the SM18 test facility located at CERN. The proposed solution have been validated by simulation using the CERN ECOSIMPRO software tools using the cryogenic library (CRYOLIB [1]) developed at CERN

HE-LHC: The High-Energy Large Hadron Collider: Future Circular Collider Conceptual Design Report Volume 4

Overview of the research program of LHC at high energies

HE-LHC: The High-Energy Large Hadron Collider – Future Circular Collider Conceptual Design Report Volume 4

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre-of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries

HE-LHC: The High-Energy Large Hadron Collider: Future Circular Collider Conceptual Design Report Volume 4

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre-of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries

HE-LHC: The High-Energy Large Hadron Collider: Future Circular Collider Conceptual Design Report Volume 4

Abstract: In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre-of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries

HE-LHC: The High-Energy Large Hadron Collider

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre-of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries