The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) has established a particle physics program concerning precise measurements for the confirmation of Standard Model predictions, as well as research of new physics. The LHC confines high energy beams of charged hadrons and provides collisions between them at four interaction points, where the main experiments are installed: ATLAS, CMS, LHCb and ALICE. Muon detection is a useful tool to recognize interesting physics events over the high background rate produced at the LHC. For this reason, each experiment is equipped with a set of dedicated detectors, called Muon Systems. Muon Systems at the LHC experiments are very large apparatuses on the order of several thousand meters squared and are based on gaseous ionization detectors. A correct and stable mixture composition is at the basis of a safe long-term operation of these detectors. Throughout this thesis work, a gas analysis campaign has been carried out, using two different methods to monitor the stability and correctness of gas mixtures supplied to gaseous detectors in CMS, LHCb and ALICE experiments. The first solution is to use Gas Chromatography (GC), which is a laboratory technique used to separate and quantify the concentrations of different components in a given gas mixture. GC was combined with Mass Spectrometry (MS) to identify and study the accumulation of particular pollutants within the ALICE MTR detector, under different gas recirculation regimes. The second technique discussed in this thesis is the employment of basic gaseous detectors, namely Single Wire Proportional Counters (SWPCs), as an on-line gas monitoring tool. Two SWPCs have been assembled and characterized in laboratory, using a gas mixture consisting of 70% Ar and 30% CO2 and irradiated with a gamma 55Fe source. SWPCs have been employed as continuous gas monitoring tools, thanks to their extreme sensitivity to pollutants and changes in mixture composition, which allows a fast detection of sudden variations of the components concentrations.
Il Large Hadron Collider (LHC) del Centro Europero per la Ricerca Nucleare (CERN) ha istituito un programma di fisica delle particelle che riguarda misure precise per la conferma delle previsioni del modello standard e la ricerca di nuova fisica. L'LHC confina fasci di adroni carichi ad alta energia e fornisce collisioni tra di loro in quattro punti di interazione, dove sono installati gli esperimenti principali: ATLAS, CMS, LHCb e ALICE. Il rilevamento di muoni è uno strumento utile per riconoscere eventi fisici rilevanti nonostante l’elevato rumore di fondo prodotto all’LHC. Per questo motivo, ogni esperimento è dotato di una serie di rivelatori dedicati, chiamati Muon Systems. I Muon Systems sono apparati di grandi dimensioni dell'ordine di diverse migliaia di metri quadrati e si basano su rivelatori a ionizzazione a gas. Una composizione corretta e stabile della miscela è alla base del funzionamento sicuro a lungo termine di questi rivelatori. Durante tutto il lavoro di tesi è stata condotta una campagna di analisi di gas, utilizzando due diversi metodi per monitorare la stabilità e la correttezza delle miscele di gas fornite ai rivelatori negli esperimenti CMS, LHCb e ALICE. La prima soluzione consiste nell'utilizzare la gas cromatografia (GC), una tecnica di laboratorio utilizzata per separare e quantificare le concentrazioni dei diversi componenti in una data miscela. La GC è stato combinata con la spettrometria di massa (MS) per identificare e studiare l'accumulo di particolari inquinanti all'interno del rivelatore ALICE MTR, in diversi regimi di ricircolo dei gas. La seconda tecnica discussa in questa tesi è l'impiego di semplici rivelatori a gas, in particolare contatori proporzionali a filo singolo (Single Wire Proportional Counter, SWPC), come strumento di monitoraggio e analisi in tempo reale. Due SWPC sono stati assemblati e caratterizzati in laboratorio, utilizzando una miscela di gas composta da 70% Ar e 30% CO2 e irradiata con una sorgente gamma 55Fe. Gli SWPC sono stati utilizzati come strumenti di monitoraggio continuo dei gas, grazie alla loro estrema sensibilità agli inquinanti e alle variazioni nella composizione della miscela, che consentono un rapido rilevamento di variazioni improvvise delle concentrazioni dei diversi component presenti nella miscela.
Gas monitoring systems for LHC detectors
CANDREVA, GIULIO
2017/2018
Abstract
The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) has established a particle physics program concerning precise measurements for the confirmation of Standard Model predictions, as well as research of new physics. The LHC confines high energy beams of charged hadrons and provides collisions between them at four interaction points, where the main experiments are installed: ATLAS, CMS, LHCb and ALICE. Muon detection is a useful tool to recognize interesting physics events over the high background rate produced at the LHC. For this reason, each experiment is equipped with a set of dedicated detectors, called Muon Systems. Muon Systems at the LHC experiments are very large apparatuses on the order of several thousand meters squared and are based on gaseous ionization detectors. A correct and stable mixture composition is at the basis of a safe long-term operation of these detectors. Throughout this thesis work, a gas analysis campaign has been carried out, using two different methods to monitor the stability and correctness of gas mixtures supplied to gaseous detectors in CMS, LHCb and ALICE experiments. The first solution is to use Gas Chromatography (GC), which is a laboratory technique used to separate and quantify the concentrations of different components in a given gas mixture. GC was combined with Mass Spectrometry (MS) to identify and study the accumulation of particular pollutants within the ALICE MTR detector, under different gas recirculation regimes. The second technique discussed in this thesis is the employment of basic gaseous detectors, namely Single Wire Proportional Counters (SWPCs), as an on-line gas monitoring tool. Two SWPCs have been assembled and characterized in laboratory, using a gas mixture consisting of 70% Ar and 30% CO2 and irradiated with a gamma 55Fe source. SWPCs have been employed as continuous gas monitoring tools, thanks to their extreme sensitivity to pollutants and changes in mixture composition, which allows a fast detection of sudden variations of the components concentrations.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/141286