Dissertations / Theses on the topic 'Runaway Electron'

La crescita delle instabilità del plasma può causare un'improvvisa perdita di energia termica e magnetica. In questi eventi disruttivi, gli elettroni possono venire accelerati a energie relativistiche e ottenere una frazione significativa dell'energia immagazzinata nel campo magnetico del tokamak. A queste velocità, le collisioni Coulombiane con il plasma di background diventano trascurabili e l'accelerazione dei runaway electrons è limitata solamente da effetti relativistici e perdite radiative. Quando il confinamento viene perso, il fascio energetico di runaway electrons può collidere con le componenti all'interno della camera da vuoto causando gravi danni. Gli eventi non mitigati di runaway electrons possono forzare lunghi periodi di arresto della durata di diversi mesi per consentire le riparazioni. Evitare questi scenari estremi è fondamentale per il successo di tokamak come ITER. Durante le disruzioni, i runaway electrons possono essere accelerati fino a energie nell'ordine di diversi MeV. Uno dei meccanismi che limitano questa accelerazione è l'emissione di radiazione di bremsstrahlung, causata dall'interazione delle particelle relativistiche con il plasma di background. A causa dell’elevata energia di questi elettroni, lo spettro della radiazione bremsstrahlung si estende fino a diversi MeV, nell’ intervallo di energia dei raggi X duri. Questo lavoro illustra come si possa ricostruire lo spazio di velocità dei runaway electrons dall'emissione di bremsstrahlung misurata. Nella prima metà di questo lavoro vengono discussi lo sviluppo, la caratterizzazione e l'implementazione di nuovi spettrometri a raggi X duri ottimizzati per la misura di bremsstrahlung da runaway electrons. Un nuovo spettrometro HXR compatto, con capacità di conteggio superiori a 1 Mcps, è stato sviluppato per il sistema Gamma-Ray Imager del tokamak DIII-D. Questo rivelatore si basa su un cristallo scintillatore YAP: Ce accoppiato con un fotomoltiplicatore di silicio. L'energia del rivelatore ha un ampio intervallo dinamico superiore a 20 MeV e una risoluzione energetica di circa il 9% a 661,7 keV. Il design di questo dispositivo è stato guidato dai risultati sperimentali raccolti a DIII-D con un precedente prototipo, basato su un cristallo scintillatore LYSO: Ce accoppiato con un fotomoltiplicatore di silicio. In questa sezione della tesi viene inoltre presentato lo sviluppo del Runaway Electron GAmma-Ray Detection System (REGARDS). REGARDS è un nuovo spettrometro HXR portatile a progettato per la misurazione della bremsstrahlung dei runaway electrons. Il rivelatore è basato su un cristallo scintillatore LaBr3: Ce accoppiato a un tubo fotomoltiplicatore. Il sistema ha un ampio intervallo dinamica per la spettroscopia HXR con un limite in energia superiore superiore a 20 MeV e una risoluzione energetica di circa il 3% a 661,7 keV. Il guadagno del rivelatore HXR di REGARDS è monitorato da un sistema di controllo esterno. REGARDS è stato utilizzato presso i tokamaks AUG e COMPASS. Nella seconda metà di questa tesi viene discussa l'analisi degli esperimenti di runaway electrons eseguiti presso i tokamaks AUG e JET. Un modello completo dell'emissione di bremsstrahlung è stato creato utilizzando il codice GENESIS e la funzione di risposta degli spettrometri HXR è stata generata utilizzando MCNP. La regolarizzazione di Tikhonov viene utilizzata per ricostruire la funzione di distribuzione dell'energia dei runaway electrons dalle misurazioni. Le funzioni di distribuzione di energia dei runaway electrons ricostruite consentono una descrizione quantitativa del fascio durante la scarica. Le informazioni raccolte con queste tecniche sono cruciali per comprendere la formazione di runaway electrons, per validare i modelli da principi primi e per valutare l'efficacia di diverse tecniche di mitigazione degli runaway electrons come la massive gas injection, la shattered pellet injection e la resonant magnetic perturbation.
The growth of plasma instabilities can cause a sudden loss of thermal and magnetic energy. In this disruptive event, electrons can be accelerated to relativistic energies and gain a significant fraction of the energy stored in the tokamak magnetic field. At these velocities, Coulomb collisions with background plasma become negligible and the acceleration of the runaway electrons is only limited by relativistic effects and radiative losses. When the post-disruption magnetic field is lost, the energetic runaway electron beam can collide with the in-vessel plasma-facing components causing severe and localized damage. Unmitigated runaway electron events can hinder operation by forcing long shutdown periods of several months to allow repairs. The avoidance of these extreme scenarios is paramount to the success of large-scale tokamaks. The threat posed by runaway electrons is a primary focus of the fusion community. Extensive modelling and experimental campaigns are currently ongoing in most large and medium-scale tokamaks. During disruptions, runaway electrons can be accelerated up to energies in the order of several MeVs. One of the mechanisms that limit this acceleration is the emission of bremsstrahlung radiation caused by the interaction of the relativistic particles with the background plasma. Due to the extreme energy these electrons can reach, the bremsstrahlung radiation spectrum extends to several MeVs, in hard X-ray energy range. This work illustrates how information on the runaway electron velocity space can be extracted from the measured bremsstrahlung X-ray emission. In the first half of this work, the development, characterization and implementation of novel hard x-ray spectrometers optimized for runaway electron bremsstrahlung measurement are discussed. A new compact HXR spectrometer with high counting rate capabilities in excess of 1 MCps was developed for the array configuration of the tokamak DIII-D Gamma-Ray Imager system. This detector is based on a YAP:Ce scintillator crystal coupled with a silicon photomultiplier. The detector energy has a wide dynamic range in excess of 20 MeV and an energy resolution of approximately 9% at 661.7 keV. The design of this device was informed by the experimental results collected at DIII-D with a previous prototype based on a LYSO:Ce scintillator crystal coupled with a silicon photomultiplier. In this section, the development of the Runaway Electron GAmma-Ray Detection System (REGARDS) is also presented. REGARDS is a novel portable hard X-ray spectrometer designed for RE bremsstrahlung measurement. The detector is based on a LaBr3:Ce scintillator crystal coupled with a photomultiplier tube. The system has a wide dynamic range for HXR spectroscopy with an upper energy bound in excess of 20 MeV and an energy resolution of approximately 3% at 661.7 keV. REGARDS HXR detector gain is monitored by an external gain control system. REGARDS was deployed at the tokamaks AUG and COMPASS. In the second half of this thesis, analysis of the runaway electron experiments performed at the tokamaks AUG and JET is discussed. A full model of the bremsstrahlung emission is created using the GENESIS code and the HXR spectrometers response function is generated using MCNP. Tikhonov regularization is used to reconstruct the runaway energy distribution function from the measurements. The reconstructed runaway electron energy distribution functions allow for a quantitative description of the runaway electron beam throughout the discharge. The information collected with these techniques is crucial to understand runaway electron formation, to validate first-principle models and to evaluate the effectiveness of different runaway electron mitigation techniques such as massive gas injection (MGI), shattered pellet injection (SPI) and magnetic resonant perturbation (RMP).

La thèse étudie la dynamique des Electrons Découplés (DE) dans une disruption plasma déclenchée par injection massive de gaz dans le tokamak JET et simulée par le code JOREK. Cette investigation est permise par l’implémentation d’un module de suivi des particules tests relativistes dans JOREK. L’étude montre que les électrons peuvent ‘survivre’dans le chaos magnétique caractérisant la phase dite de ‘Disjonction Thermique’ (DT) de cette disruption (simulée) grâce à la reformation des surfaces magnétiques fermées. Deuxièmement, l’accélération des électrons causée par les champs électriques dus aux fluctuations magnétohydrodynamiques (MHD) pendant la DT est analysée. Cela montre que les électrons peuvent être accélérés par ces champs et devenir DE, après reconfinement, pendant la phase dite de ‘Disjonction de Courant’. Une étude préliminaire sur les dépendances entre le courant des DE et l’activité MHD dans les expériences de disruption du tokamak ASDEX Upgrade est également reportée
In view of better understanding Runaway Electron (RE) generation processes during tokamak disruptions, this work investigates test electron dynamics during a JET disruption simulated with the JOREK code. For this purpose, a JOREK module computing relativistic test particle orbits in the simulated fields has been developed and tested. The study shows that a significant fraction of pre-disruption thermal electrons remain confined in spite of the magnetic chaos characterizing the Thermal Quench (TQ) phase. This finding, which is related to the prompt reformation of closed flux surfaces after the TQ, supports the possibility of the so-called “hot tail” RE generation mechanism. In addition, it is found that electrons may be significantly accelerated during the TQ due to the presence of strong local electric field (E) fluctuations related to magnetohydrodynamic (MHD) activity. This phenomenon, which has virtually been ignored so far, may play an important role in RE generation. In connection to this modelling work, an experimental study on ASDEX Upgrade disruptions has been performed, suggesting that strong MHD activity reduces RE production

Lo studio degli ioni ed elettroni veloci è fondamentale per il successo della prossima generazione di tokamak di grande dimensione, come ITER, che mirano a dimostrare la possibilità di produrre energia attraverso la fusione termonucleare. Siano essi accelerati dal riscaldamento ausiliario o nati da reazioni di fusione, gli ioni possono raggiungere energie nell’ordine dei MeV. Questa energia viene poi trasmessa al plasma attraverso collisioni, aumentandone l’energia media e il rateo delle reazioni di fusione. È quindi cruciale migliorare il confinamento degli ioni veloci e sviluppare schemi di riscaldamento efficienti. Gli elettroni, invece, possono raggiungere velocità relativistiche se accelerati da campi elettrici induttivi generati durante disruzioni di plasma. Questi elettroni runaway rappresentano una minaccia per l'integrità strutturale dei tokamak di grandi dimensioni e necessitano di essere mitigati. Questa tesi tratta di metodi di deconvoluzione applicati alla ricostruzione della distribuzione delle particelle veloci a partire dall’emissione di radiazione nel range di energia del MeV. La deconvoluzione è stata declinata in due modi: unfolding della distribuzione di velocità degli elettroni runaway a partire dalla loro radiazione di bremsstrahlung, e tomografia della distribuzione di densità di ioni veloci o elettroni runaway a partire dalla misura dei loro profili di emissione fatta con linee di vista multiple. Questi algoritmi sono stati implementati in una libreria Python open source. Quattro algoritmi per l’unfolding sono stati implementati: singular value decomposition, maximum likelihood - expectation maximization, regolarizzazione di Tikhonov and di Poisson. La matrice di probabilità necessaria per svolgere queste inversioni è stata calcolata usando il codice GENESIS per stimare la probabilità di emettere fotoni di bremsstrahlung, e il codice MCNP per calcolare la funzione di risposta del detector. Queste funzioni di risposta sono state calcolate per tutte le diagnostiche hard X-ray installate nei tokamak Joint European Torus ed ASDEX Upgrade. I quattro metodi sono stati comparati su spettri sintetici e sperimentali, questi ultimi misurati ad ASDEX Upgrade. Maximum likelihood - expectation maximization si è dimostrato il più accurato sia nella ricostruzione della distribuzione in energia degli elettroni runaway, sia nel calcolo della loro energia media e massima. È stata inoltre studiato l’effetto del taglio a basse energie applicato ai dati sperimentali e il numero minimo di conteggi nello spettro necessario per svolgere una ricostruzione. In vista di una futura ricostruzione in 2D della distribuzione delle velocità degli elettroni runaway, sono state calcolate le matrici di probabilità come funzioni dell’energia e del pitch degli elettroni per tutte le diagnostiche hard X-ray installate a JET. I risultati sono presentati col formalismo delle weight-function, che permette di studiare la sensitività del detector a elettroni con energia e pitch differenti. Le matrici riportate mostrano un picco di sensitività per particelle aventi pitch-angolo uguale all’angolo racchiuso tra linea di vista del detector e il campo magnetico.
Fast particles, both electrons and ions, play an important role for the success of the next generation of large tokamak devices, such as ITER, that will prove the feasibility of magnetically confined thermonuclear fusion as an energy source. Ions accelerated by external heating or born in fusion reactions can reach energies in the MeV range. Their primary role is to sustain the plasma temperature and the fusion reaction rate, thus lots of efforts have been put into the development of efficient heating schemes and in the improvement of their confinement. On the other hand, during fast terminations of plasma pulses on tokamaks, electrons can accelerate to relativistic velocities, entering the runaway regime. Runaway electrons have enough energy to seriously damage the plasma facing components of large tokamaks, thus mitigation techniques are under study in view of ITER operations. This thesis focuses on the implementation of deconvolution techniques for the reconstruction of the fast particles distributions from their emission in the MeV energy range. The problem was approached from two different perspectives: the unfolding of the runaway electrons velocity-space distribution from spectroscopic measurements of their bremsstrahlung emission, and the tomographic reconstruction of the density distribution of both fast ions and runaway electrons from the integrated measurement of their emission performed with multiple lines of sight. These algorithms were implemented in an open source Python library. Four deconvolution algorithms were implemented for the unfolding of runaway electrons energy distribution: singular value decomposition, maximum likelihood - expectation maximization, Tikhonov regularization and Poissonian regularization. The transfer matrix necessary for this inversion was calculated using the GENESIS code for estimating the probability of bremsstrahlung emission and the MCNP code for computing the detector response function. The detector response function was calculated for all the hard X-rays diagnostics systems installed at the Joint European Torus and ASDEX Upgrade tokamaks. The performance of the four methods wes then compared over both synthetic and experimental spectra, the latter being measured at ASDEX Upgrade. Maximum likelihood - expectation maximization was found to be the most accurate in the reconstruction of both the runaway electrons energy distribution and their average and maximum energies. The robustness of the four methods against experimental limitations, such as low-energy cut and low statistics, was also investigated. In the path towards the generalization of these unfolding algorithms to the reconstruction of the runaway electrons 2D velocity-space distribution, the transfer matrices in energy and pitch were calculated for all the hard X-ray diagnostics installed at JET. The weight-function formalism was adopted, which allows studying the sensitivity of the detectors to different energy and pitch regions. The matrices showed a sensitivity peak in the pitch axis which is determined by the angle between the line of sight and the magnetic field. Finally, the gamma camera upgrade installed at the Joint European Torus, with its 10 by 9 lines of sight that observe a poloidal section of the tokamak from two perpendicular projections, allows reconstructing the spatial distribution of fast particles. A tomographic algorithm that makes use of smoothing along the magnetic field lines was implemented. This tomography was first applied to recent three-ion radio frequency heating experiments in D-3He mixed plasmas, during which the gamma camera was able to detect the 16.4 MeV γ-rays from 3He(D,γ)5Li reactions. The spatial distribution of the α-particles born in 3He(D,p)4He reactions was reconstructed and the results were used to validate TRANSP simulations. The tomographic algorithm was also applied to the reconstruction of the runaway electrons spatial profiles during plasma disruptions.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1986.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 208-212.
by Eric Hans Esarey.
Ph.D.

Dans les tokamaks, Sous l'application champ de électrique, les électrons sont accélérés et en même temps, ils subissent une force de friction due aux collisions avec les autres particules du plasma. Cependant, une fraction de la population totale d'électrons peuvent surmonter la force de friction et atteindre une vitesse proche de la vitesse lumière. Ces électrons relativistes sont découplés du plasma et sont appelés électrons runaway (ER). Ils peuvent apparaître lors des différentes phases d'une décharge de plasma. Par exemple, dans la phase de démarrage ou alors pendant les disruptions, au cours desquelles une fraction importante du courant plasma peut être convertie en ER ayant une énergie pouvant atteindre quelques dizaines de MeV. Les ER créés pendant la phase de perturbation peuvent causer des dommages aux premiers composants murs si un dépôt localisé de forte puissance se produit. ITER étant un tokamak de grande taille et un projet coûteux, la génération d'ER n'est pas souhaitable. La viabilité de la machine nécessite que les ER soient détectés en temps réel. La thèse fournit une étude détaillée dans cette direction pour le développement des deux principaux diagnostics sur ITER impliqués dans les mesures de paramètres pour les ER, à savoir, le moniteur de rayons X durs qui détecte le rayonnement de bremsstrahlung et les caméras visibles et infrarouges qui détectent le rayonnement synchrotron. Une solution de conception unique a été proposée pour le moniteur HXRM et est développée ici et optimisée. Pour les caméras, une modélisation des signaux est effectuée pour la première fois. Pour ce faire, un code de calcul a été développé et validé sur différents tokamaks
In tokamaks, under the application of the electric field, a small fraction of the total electrons population can overcome collisional drag force and attain high velocity close to the speed of light. These relativistic electrons are called Runaway-Electrons (REs). The REs can occur during different phases of a plasma discharge. REs created during the disruptions phase can form a high energetic RE-beam that poses a risk to damage the first wall components if localized high power deposition takes place. ITER being a large size tokamak and an expensive project, generation of REs is not desirable during any phases of a plasma discharge. Detection of these REs and measurements of its parameters are important for the tokamak operation. Hence, RE diagnostics have to be in place to aid the commissioning of the disruption mitigation system and also for the post-event analysis to improve the reliability of RE avoidance. The present thesis gives a detailed study in this direction for the development of the two principal ITER Diagnostics involved in RE parameter measurements, namely the Hard X-Ray Monitor (HXRM) that detects bremsstrahlung radiation and the Visible and Infrared Cameras that detect synchrotron radiation. A unique design solution has been given for the HXRM and is developed, R&D tests were performed and optimized in line with this understanding. For the cameras, it is predicted for the first time which images and signal intensity can be expected. To achieve this, a simple but comprehensive code has been developed and validated on tokamaks that can predict RE parameters and corresponding diagnostic signals which may have further uses also in the context of RE avoidance

Les sprites sont de gigantesques phénomènes lumineux qui sont produits entre 40 et 90 km d’altitude généralement par des éclairs nuage-sol positifs. Les sprites sont des phénomènes très brefs (durée de quelques millisecondes) qui appartiennent à la famille des TLEs (évènements lumineux transitoires) et qui sont composés de structures filamentaires nommées streamers. Les streamers sont des filaments de plasma, qui se propagent à des vitesses allant jusqu’à ∼10⁷ m/s et qui possèdent des champs électriques très forts souvent proches de 150 kV/cm (champs réduit à la pression atmosphérique). Lors de ce travail, on a développé un modèle fluide de plasma qui simule les décharges streamers couplées avec un modèle simulant les émissions optiques afin d’étudier la physique des streamers, des TLEs et plus particulièrement des sprites dans le cadre de la mission spatiale TARANIS. Cette mission a pour objectif d’étudier le système Atmosphère-Ionosphère-Magnétosphère, et observera les TLEs et leurs émissions associées: électromagnétiques, optiques, et probablement radiations énergétiques depuis le nadir. Dans cette thèse, on propose d’étudier certains problèmes liés aux streamers et aux sprites qui sont cruciaux pour préparer la mission TARANIS. Plus particulièrement nous abordons certains mécanismes de production de radiations énergétiques par les streamers récemment proposés dans la littérature et nous développons une méthode qui permet de déterminer l’altitude, la vitesse et le champ électrique des streamers des sprites, à partir d’une analyse spectroscopique de leurs émissions optiques. Nos résultats renforceront donc le retour scientifique des futures missions spatiales observant les TLE depuis le nadir et particulièrement TARANIS
Sprites are large optical phenomena usually produced between 40 and 90 km altitude generally by positive cloud-to-ground lightning (+CG). These are short lifetime phenomena (duration of few milliseconds) that belong to the family of transient luminous events (TLEs) and composed of complex filamentary structures called streamers. Streamers are non-thermal plasma filament, highly collisional, propagating with velocities up to 10⁷ m/s, and characterized with high electric fields at their heads often close to 150 kV/cm when scaled to ground level air. In this work, we have developed a streamer plasma fluid model coupled with an optical emission model to investigate the physics of streamers and sprites in the framework of the TARANIS space mission. TARANIS will observe TLEs from a nadir-viewing geometry along with their related emissions (electromagnetic and particles). In this dissertation, we investigate some mechanisms of emission of energetic radiation from streamers recently proposed in the literature and we present an original spectroscopic method to determine sprite streamers altitudes, velocities, and electric fields through their optical emissions. This method is especially useful for increasing the scientific return of space missions that have adopted nadir-based observation strategies

The oldest and also most used type of secondary cells is lead-acid accumulator. Basic functional principle stayed same as in foundation time, only operation parameters are still improving (for example one of the most important is lifetime). Significant technical problem is temperature of lead-acid battery and her influence on functionality and running reactions. Master thesis is focused on this section, when is necessary to evaluate new pieces of knowledge in development. The work deals with description existing types of accumulators, further deals with theory of temperature balance and in the end by measured datas and theirs analyzing.

Cette thèse porte sur la modélisation du rayonnement de raies émis par les plasmas de fusion magnétique pour faire des applications au diagnostic. Une attention particulière est apportée aux électrons découplés (« runaway »), qui sont attendus avec une proportion significative dans ITER. Dans le premier chapitre, nous donnons une introduction générale sur la fusion magnétique et sur les machines tokamak, ainsi que sur les disruptions ; ces dernières sont engendrées par des instabilités et elles peuvent conduire à la formation de faisceaux d’électrons runaway très énergétiques. Dans le deuxième chapitre, le formalisme utilisé dans les modèles d'élargissement de raies spectrales est présenté, à partir d’outils de mécanique quantique et de physique statistique. Des calculs numériques de raies de Balmer sont également effectués dans le cadre d’une application aux diagnostics synthétiques. Dans le troisième chapitre, nous discutons de la physique relative aux ondes de Langmuir, notamment, l’amortissement Landau et son processus inverse, l’instabilité faisceau-plasma. Ce processus engendre un champ électrique oscillant, dont l’amplitude peut être évaluée à l’aide de la théorie quasi-linéaire. Nous présentons cette théorie ainsi qu’une généralisation aux régimes fortement non linéaires dans lesquels les ondes de Langmuir sont couplées aux ondes sonores et électromagnétiques. Enfin, dans le quatrième chapitre, nous appliquons le formalisme pour différentes densités de faisceau dans des conditions de plasma de bord de tokamak et nous examinons la faisabilité d’un diagnostic spectroscopique des électrons runaway
This thesis focuses on the modeling of the atomic line radiation emitted by magnetic fusion plasmas for diagnostic purposes. An improvement of the accuracy of diagnostics is proposed, in order to have a better characterization of runaway electrons in the context of ITER preparation. In the first chapter, we discuss about fusion reaction, about how it is produced in tokamak machines, and we discuss about the disruptions, which are a consequence of instabilities. They are one cause of runaway electrons. In the second chapter, the formalism used in spectral line broadening models is introduced based on quantum mechanics and statistical physics. Numerical calculations are also presented. They are done for applications to synthetic diagnostics in tokamak divertor plasma conditions. Hydrogen Balmer lines with a moderate principal quantum number are considered. In the third chapter, we discuss the physics underlying Langmuir waves. This includes the Landau damping process and its inverse counterpart, the plasma-beam instability mechanism. It is possible to calculate the magnitude of the electric field which is created by a beam of electrons using the quasilinear theory. We present this theory and we present a generalization to strongly nonlinear regimes for which the Langmuir waves are coupled with the ion sound and electromagnetic waves. Finally, we discuss this model and, next, apply the formalism for different beam densities in tokamak edge plasmas and we examine the possibility for making a diagnostic of runaway electrons based on atomic spectroscopy in the fourth chapter

Performance degradation of lithium-ion batteries (LIBs) from in-service abuse was analyzed using novel dynamic abuse tests and sensor-based in-situ monitoring of battery state of health (SOH). The relation between dynamic impact and structure changes of LiCoO₂ (LCO) electrode was analyzed through a nano-impact test directly applied to the electrode and Raman imaging. After the electrode structure damage induced by the dynamic loading was analyzed, the performance of the LIBs with the abused electrodes was evaluated to establish the relation between the number of impact cycles and LIB performance degradation. The mechanism of impact related LIB capacity decrease was analyzed, and the capacity change can be predicted based on the impact abuse history using this approach. In order to provide more detailed information on the battery performance degradation caused by the in-service dynamic loads, a dynamic aging testing platform was designed to simulate in-service vibration and impact experienced by the LIBs. Based on the lessons learned, a sensor network was constructed to provide a comprehensive in-situ evaluation of the SOH of commercial batteries. Mechanisms of LIB capacity fade, temperature increase, and cell deformation from cycling in representative dynamic environments were analyzed and correlated with theoretical predictions. Difference between the aging of a battery pack and that of a single cell was also investigated, which presented the influence of current imbalance on the SOH decay of battery packs. SEM imaging, Raman imaging, and electrochemical impedance spectroscopy (EIS) analysis were also applied to support the sensor network measurements.

Indiana University-Purdue University Indianapolis (IUPUI)
Lithium-ion batteries are widely used for portable electronics due to high energy density, mature processing technology and reduced cost. However, their applications are somewhat limited by safety concerns. The lithium-ion battery users will take risks in burn or explosion which results from some internal components failure. So, a practical method is required urgently to find out the failures in early time. In this thesis, a new method based on temperature difference between internal point and surface (TDIS) of the battery is developed to detect the thermal failure especially the thermal runaway in early time. A lumped simple thermal model of a lithium-ion battery is developed based on TDIS. Heat transfer coefficients and heat capacity are determined from simultaneous measurements of the surface temperature and the internal temperature in cyclic constant current charging/discharging test. A look-up table of heating power in lithium ion battery is developed based on the lumped model and cyclic charging/discharging experimental results in normal operating condition. A failure detector is also built based on TDIS and reference heating power curve from the look-up table to detect aberrant heating power and bad parameters in transfer function of the lumped model. The TDIS method and TDIS detector is validated to be effective in thermal runaway detection in a thermal runway experiment. In the validation of thermal runway test, the system can find the abnormal heat generation before thermal runaway happens by detecting both abnormal heating power generation and parameter change in transfer function of thermal model of lithium ion batteries. The result of validation is compatible with the expectation of detector design. A simple and applicable detector is developed for lithium ion battery catastrophic failure detection.