Optimal Modal Truncation

This paper revisits the modal truncation from an optimisation point of view. In particular, the concept of dominant poles is formulated with respect to different systems norms as the solution of the associated optimal modal truncation problem. The latter is reformulated as an equivalent convex integer or mixed-integer program. Numerical examples highlight the concept and optimisation approach

Etude d'un réseau cryogénique multi-clients pour SPIRAL2

The thesis works describe in this manuscript deal with the modelling and the control ofLINAC cryogenic process. The components of the LINAC cryogenic system (cryomodule,valves, pipes,...) are modeled as interconnectable objects. Those same objects are usedto model the SPIRAL2 cryogenic system. The model trueness is evaluated through comparisonbetween experimental and simulated data. Once the model prediction capabilityhas been validated, the models are used to synthetized control laws. More specifically, alinear quadratic command and an extended Kalman filter has been realized for the SPIRAL2cryomodule. Finally, a hierarchical control for a cryogenic refrigerator has beenstudied. A method is proposed for the control of multiple interconnected subsystemsregulated through PID, LQ and MPC controllers.Les travaux de thèse décrits dans ce manuscrit s’intéressent à la modélisation et lecontrôle de procédés cryogéniques associés à un LINAC supraconducteur. Les élémentsconstituants le système cryogénique du LINAC (cryomodules, vannes, tuyaux,...) sontmodélisés sous forme d’objets inter-connectables. Ces mêmes objets sont utilisés pourmodéliser le système cryogénique de l’accélérateur SPIRAL2. La justesse de ces modèlesest évaluée à travers des comparaisons entre simulations non-linéaires et mesures expérimentales.Une fois la capacité de prédiction des modèles validée, ces derniers sont utiliséspour synthétiser des lois de commande. Tout particulièrement, une commande linéairequadratique ainsi qu’un filtre de Kalman étendu ont été réalisés pour les cryomodulesde SPIRAL2. Enfin, la réalisation d’une commande hiérarchisée appliquée au cas d’unréfrigérateur cryogénique est étudiée. Une méthode est proposée pour le contrôle de plusieurssous-systèmes inter-connectés et régulés par des contrôleurs PID, LQ et MPC

Study of a multi-client cryogenic system for SPIRAL2

Les travaux de thèse décrits dans ce manuscrit s’intéressent à la modélisation et lecontrôle de procédés cryogéniques associés à un LINAC supraconducteur. Les élémentsconstituants le système cryogénique du LINAC (cryomodules, vannes, tuyaux,...) sontmodélisés sous forme d’objets inter-connectables. Ces mêmes objets sont utilisés pourmodéliser le système cryogénique de l’accélérateur SPIRAL2. La justesse de ces modèlesest évaluée à travers des comparaisons entre simulations non-linéaires et mesures expérimentales.Une fois la capacité de prédiction des modèles validée, ces derniers sont utiliséspour synthétiser des lois de commande. Tout particulièrement, une commande linéairequadratique ainsi qu’un filtre de Kalman étendu ont été réalisés pour les cryomodulesde SPIRAL2. Enfin, la réalisation d’une commande hiérarchisée appliquée au cas d’unréfrigérateur cryogénique est étudiée. Une méthode est proposée pour le contrôle de plusieurssous-systèmes inter-connectés et régulés par des contrôleurs PID, LQ et MPC.The thesis works describe in this manuscript deal with the modelling and the control ofLINAC cryogenic process. The components of the LINAC cryogenic system (cryomodule,valves, pipes,...) are modeled as interconnectable objects. Those same objects are usedto model the SPIRAL2 cryogenic system. The model trueness is evaluated through comparisonbetween experimental and simulated data. Once the model prediction capabilityhas been validated, the models are used to synthetized control laws. More specifically, alinear quadratic command and an extended Kalman filter has been realized for the SPIRAL2cryomodule. Finally, a hierarchical control for a cryogenic refrigerator has beenstudied. A method is proposed for the control of multiple interconnected subsystemsregulated through PID, LQ and MPC controllers

Cryogenic Tests of the SPIRAL2 LINAC Systems

International audienceTwo full cool-down of the SPIRAL2 superconducting LINAC have been performed in 2017 and 2018 respectively, followed by a total of around 5 months of tests at 4 K. Several cool-down strategies were tested, in order to minimize 100 K effect on the SC cavities. Helium bath regulations (level and pressure) have been tested and optimized. Effects of pressure instabilities and coupling with the cryogenic plant have also been observed. Cryogenic performances of each cryomodule have been measured. Low-level RF measurements were also performed on all cavities and showed unidentified modulations at frequencies around 5Hz. These turned out to be thermoacoustic oscillations (TAO) on the cryogenic lines, which generate important pressure instabilities. Several solutions to remove TAO and cure these instabilities have been tested and one has been successfully deployed

SPIRAL2 Cryogenic System Thermodynamic Behavior Prediction Through Dynamic Modeling

International audienceSPIRAL 2 (Caen, France) is a state of the art superconducting linear accelerator composed of 26 quarter wave accelerating cavities. Each cavity is plunged in a liquid helium bath at 4.4 K itself surrounded by a thermal shield at 70 K. In this paper, a dynamic model of the cryogenic systemof the LINAC is proposed. Thismodel simulates the dynamic behaviour of the 19 cryomodules and their respective valves box connected through the cryodistribution. Model accuracy is evaluated through a comparison between simulation and experimental data. Using the model we should be able to predict the behaviour of the cryogenic system for different beam operating conditions of the accelerator. The model also highlights the link between the cryogenic system and the cavity RF losses through a dynamic estimator of those RF losses in the cavity walls. The latter could be used as a rough estimator of the quality factor of a cavity

Snapshot Initialization: a New Method to Synchronize Dynamic Digital Twins Applied to Industrial Process

International audienceDigital twins are high-fidelity computational models vastly used to improve several industrial areas. In most applications, the digital twin requires synchronization to the real asset to properly represent the system. However, the expenses associated with theimplementation of current synchronization methodologies for modeling vast industrial systems render such endeavors impracticable. In this work, a methodology to synchronize large-scale industrial digital twins through a snapshot file initialization approach is proposed. The method consists on creating an extensive data-base of snapshots files that represents the full parametric space of the system of interest. Each snapshot is linked to a period of measurements, which enables tracking the state of the system. A research approach is then applied to find the best snapshot file to initialize the model, synchronizing it to the real system based on measurements from the real asset. The methodology is demonstrated on an industrial process to separate zirconium and hafnium. The results show that, even if the real measurements are not precise and noisy, the approach can estimate a snapshot file to initialize the model with a error under 15 %

Cryogenic thermo-acoustic oscillations highlight and study in the SPIRAL2 superconducting LINAC

Cryogenic thermoacoustic oscillations is an area of interest of several studies. For superconducting accelerators, it is an unwanted phenomena that we usually want to get rid off. The SPIRAL2 superconducting accelerator had distributed Taconis all over its cryostats. This paper spans the different steps from their first detection to their damping with a highlight on the methods and the instrumentation that has been used. The presented study also sets the ground for a real life experimental investigation of thermo-ascoustics in complex geometries such as superconducting LINACs. With modern Big data analysis and simulation tools, it also sets the ground for the developments of new data linked codes that fit these complex situations

Cryogenic thermo-acoustic oscillations highlight and study in the SPIRAL2 superconducting LINAC

Cryogenic thermoacoustic oscillations is an area of interest of several studies. For superconducting accelerators, it is an unwanted phenomena that we usually want to get rid off. The SPIRAL2 superconducting accelerator had distributed Taconis all over its cryostats. This paper spans the different steps from their first detection to their damping with a highlight on the methods and the instrumentation that has been used. The presented study also sets the ground for a real life experimental investigation of thermo-ascoustics in complex geometries such as superconducting LINACs. With modern Big data analysis and simulation tools, it also sets the ground for the developments of new data linked codes that fit these complex situations

First full cool down of the SPIRAL 2 superconducting LINAC

International audience• First full cool down of the SPIRAL 2 superconducting linear accelerator. • Cool down requirements methods and procedures as well as actual data. • Preparing the operation mode through experimental run. • New multidisciplinary challenges between cryogenic and RF for superconducting accelerator