Thèses sur le sujet « Electric dipole spin resonance »
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El, Homsy Victor. « Apprivoiser le bruit pour les qubits de spin d'électrons en CMOS ». Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALY007.
Texte intégralWhile being a bit more than a century old, quantum physics have become technological. The most ubiquitous instance of the use of quantum physics is the transistor, as the building block of modern computing devices. Progress in nanoscale fabrication has fostered an exponential increase of transistor density In microelectronics circuits. Once in the nanometer range, unavoidable quantum effects tamper further miniaturization. Alternative transistor designs are being developed to mitigate this showstopper. The complementary metal-oxide-semiconductor (CMOS) fully-depleted silicon-on-insulator (FD-SOI) platform is one of them.In parallel to these developments, quantum physics spawned a new generation of technological innovation, thanks to the ability to control matter at the single particle level. Isolating elementary particles in a quiet environment gives access to their superposition and entanglement properties. Using these to process information would realize the quantum computing paradigm shift, where classically intractable problems are promised to come at reach. Many candidates are racing for the best implementation of a quantum bit (or “qubit”) and all of them are facing the challenge to up-scale their architecture from a few lab qubits to an industrial processor. Among them, electrons trapped in silicon structures offer promising prospects thanks to their reduced exposure to magnetic nuclei and spin-orbit interaction, and to the possibility to purify away non-zero nuclear spins. Moreover, the expected compatibility of silicon structures with microelectronics know-how gives hopes for scalability. In this thesis, we study single electrons trapped in gate-defined quantum dots formed in CMOS FD-SOI transistors. We investigate on how to improve their use as qubits, focusing on experimental noise aspects.First, we demonstrate coherent manipulation of a single CMOS electron spin with electrically driven spin resonance. A micromagnet is patterned directly on top of the CMOS chip, creating an inhomogeneous magnetic field. Driving the electron motion inside this gradient with the available electric gates makes it feel an effective oscillating magnetic field, and enables single qubit operations, with a relatively low 1 MHz Rabi frequency and short 500 ns dephasing time. This limited performance is attributed to a finite number of two-level fluctuators and smaller quantum dot sizes compared to other silicon architectures. The shape of the Rabi decay and the sub-µs dephasing time are characteristic of hyperfine interaction with spinful nuclei. However, dynamically decoupling the electron spin from this frequency range showed state-of-the-art coherence times and performance limited by charge noise, in accordance with simple charge sensor measurements at low frequencies. These results point towards the relevance of isotopic purification to avoid hyperfine-induced dephasing in CMOS FD-SOI devices.After focusing on qubit control, a second part of this thesis deals with readout noise. The objective was to demonstrate the use of a traveling-wave parametric amplifier (TWPA) in the amplification chain of radio-frequency readout of CMOS devices. Patterning inductors on the CMOS chip reduced the parasitic capacitance of our resonators and enabled to perform lumped-element reflectometry in the 3-4 GHz range, closer to usual TWPA operating regimes. Even when being pumped far from its gap, the TWPA shows nominal figures of merit, and a resilience to magnetic fields typical for spin qubit experiments. Its high -100dBm compression point, wide and tunable 2 GHz bandwidth and quantum-limited added noise enabled to get more than 10dB signal-to-noise ratio improvement on interdot charge transitions in our devices, and to multiplex interdot readout in a 6-gate device. This compatibility between a large bandwidth superconducting amplifier and multi-gate CMOS FD-SOI quantum devices is promising towards CMOS electron spin qubit experiments at larger scale
Farrington, Benjamin Joseph. « A tale of two spins : electron spin centre assemblies with N@C60 for use in QIP ». Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:7f280123-41af-4d96-bf34-04094aaba1dd.
Texte intégralDal, Farra Maria Giulia. « The Photoexcited Triplet State as a Spin Probe for Distance Determination in Pulse EPR Dipolar Spectroscopy ». Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3426695.
Texte intégralIl ruolo di molte macromolecole di interesse biologico come ad esempio proteine ed acidi nucleici, dipende dalla loro struttura tridimensionale e da movimenti di domini dell’ordine di pochi nanometri. La spettroscopia paramagnetica elettronica (EPR) ed in particolare le tecniche di spettroscopia impulsata dipolare (PDS) costituiscono lo strumento ideale per studiare sistemi di quest’ordine di grandezza. Tuttavia, per poter utilizzare tecniche PDS nella caratterizzazione di bio-macromolecole, queste devono contenere centri paramagnetici come ad esempio ioni o cluster metallici, oppure centri radicalici. Nel caso in cui il sistema sia diamagnetico è necessario quindi inserire delle sonde paramagnetiche o sostituire eventuali metalli diamagnetici con altri metalli EPR-attivi. I radicali nitrossidi sono le sonde di spin più comunemente impiegate nella spettroscopia dipolare, soprattutto per studi in proteina in cui, per introdurre di tali sonde, è possibile seguire un protocollo di mutagenesi sito-specifica seguita da spin labeling diretto alle cisteine. L’inserimento di sonde di spin tuttavia può causare forti modifiche strutturali alla macromolecola o addirittura interferire con il suo corretto folding. Per questo motivo, quando possibile si tenta di sfruttare centri paramagnetici che siano naturalmente presenti in proteina. Sono stati infatti effettuati diversi studi di spettroscopia dipolare in metallo-proteine sfruttando la transizione ¢mS Æ §1/2 del gruppo prostetico contenente il centro metallico. L’utilizzo di tali gruppi prostetici non causa alcuna alterazione strutturale alla molecola, inoltre, diversamente da molte sonde endogene, questi sono strettamente ancorati all’intorno proteico e forniscono quindi informazioni strutturali più accurate. La porfirina in stato di tripletto fotoeccitato è stata di recente introdotta tra la collezione di sonde di spin utilizzabili nelle tecniche PDS. Nel loro stato fondamentale le porfirine sono diamagnetiche e pertanto EPR silenti, ma in seguito a fotoeccitazione laser possono popolare tramite inter-system crossing lo stato di tripletto eccitato a più bassa energia, divetando in tal modo EPR-attive. Il popolamento tramite inter-system crossing fa si che la popolazione dei sottolivelli di tripletto devii dalla distribuzione di Boltzmann, aumentando enormemente l’intensità del segnale EPR di tale specie che vengono per questo motivo definite "polarizzate". Inoltre derivati porfirinici sono presenti in numerosi sistemi naturali, come ad esempio le emoproteine o le proteine conivolte in processi fotosintetici, e ciò li rende particolarmente interessanti per l’utilizzo in spettroscopia dipolare in quanto possono essere sfruttati come sonde endogene. Il labeling ortogonale, basato sull’impiego di sonde di spin spettroscopicalmente distinte che possono essere eccitate selettivamente durante un esperimento EPR, rappresenta un approccio particolarmente vantaggioso nelle tecniche PDS. Gli stati di tripletto fotoeccitato hanno un valore aggiunto come sonde ortogonali perchè aggiungono alla selezione spettrale il fatto di essere sonde foto-indotte. Questa caratteristica fa si che sia possibile misurare distanze intarmolecolari tripletto-nitrossido, applicando la fotoeccitazione laser, e distanze ntermolecolari nitrossido-nitrossido spegnedo invece la fotoeccitazione. Mentre la fattibilità di esperimenti di spettroscopia dipolare applicati a stati di tripletto fotoeccitati era già stata dimostrata precedentemente a questo lavoro di tesi [Di Valentin, M.; Albertini, M.; Zurlo, E.; Gobbo, M. and Carbonera, D. J. Am. Chem. Soc., 2014, 136, 6582 -6585], mancavano completemente indagini in grado di stabilire l’affidabilità e l’accuratezza del nuovo sistema di labeling e un inquadramento teorico in grado di escrivere il comportamento di tali sistemi polarizzati ad alto spin durante l’esperimento PDS. Il lavoro alla base della presente tesi è consistito nella completa caratterizzazione spettroscopica e teorica di questi sistemi di spin. Per verificare l’affidabilità del nuovo approccio, le sonde di tripletto sono state testate con diverse tecniche PDS, e sono stati inoltre utilizzati vari cromofori per la foto-generazione del centro paramagnetico, effettuando l’analisi sia su sistemi modello che in proteina. Lo studio è stato completato con un esaustivo trattamento teorico dei sistemi tripletto-radicale in spettroscopia dipolare. La precisione e l’accuratezza del metodo sono state verificate misurando le tracce dipolari di un righello spettroscopico costituito da una serie di perptidi in ®-elica di lunghezza crescente, ognuno marcato con un cromoforo porfirinico e un radicale nitrossido. L’ottima correlazione trovata tra le distanze ottenute analizzando le tracce sperimentali e i dati strutturali derivanti dai calcoli ha permesso di dimostrare l’affidabilità delle sonde di tripletto nelle tecniche PDS. Attualmente sono disponibili diverse sequenze PDS che sfruttano diversi meccanismi per indurre l’oscillazione dipolare nelle tracce sperimentali. Molte di queste sequenze sono state quindi testate sulla sonda di tripletto in modo da verificarne le prestazioni con le diverse tecniche. La disponibilità di molteplici sequenze PDS e il loro buon funzionamento su sistemi fotoindotti permette di selezionare, a seconda dei casi, lo schema di impulsi che garantisce le migliori prestazioni in termini di rapporto segnale-rumore e ciò dimostra la versitilità delle sonde di tripletto. La nuova metodologia è stata estesa anche a studi in proteina utilizzando come sistemi modello la Peridinin-Chlorophyill a-Protein, appartenente alla classe delle proteine fotosintetiche, e neuroglobina umana, facente parte della famiglia dellle globine. In Peridinin-Chlorophyill a-Protein è stata misurata l’interazione dipolare tra uno dei carotenoidi presenti nel sito attivo e un nitrossido inserito tramite spin labeling, permettendo non solo l’individuazione del pigmento coinvolto nel meccanismo di fotoprotezione, ma espendendo anche l’applicabilità dell’esperimento a cromofori diversi dai derivati porfirinici. Nella neuroglobina umana invece la zinco-sostituzione dell’eme ha permesso di popolare lo stato di tripletto nel gruppo endogeno e dimostrando che la tecnica dipolare fotoindotta può essere utilizzata anche nello studio strutturale di proteine (macromolecole) apparteneneti alla classe delle emoproteine. Infine è stata effettuata anche un’esaustiva caratterizzazione teorica delle sonde di tripletto basata sul formalismo della matrice densità. E’ stata ricavata l’espressione che descrive la modulazione delle tracce dipolari in sistemi tripletto-radicale, che è risultata essere analoga a quella ottenuta per sistemi di due radicali interagenti. Successivamente è stato implementato un programma per il calcolo numerico di tracce dipolari che ha permesso una descrizione quantitativa diversi sistemi tripletto-radicale.
Bolton, David Robert. « Circuits and systems for CW and pulsed high-field electron spin resonance ». Thesis, University of St Andrews, 2006. http://hdl.handle.net/10023/7104.
Texte intégralSWANSON, DALE DORSETT. « ELECTROCHEMICAL AND SPECTROSCOPIC STUDIES OF THIOETHER COORDINATION COMPLEXES (CYCLIC VOLTAMMETRY, OCTAHEDRAL LOW-SPIN METALS, BLUE COPPER PROTEINS, ELECTRON PARAMAGNETIC RESONANCE) ». Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188102.
Texte intégralHsu, Fang-Chi. « Electric field effect in "metallic" polymers ». Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1127229727.
Texte intégralTitle from first page of PDF file. Document formatted into pages; contains xxi, 177 p.; also includes graphics (some col.). Includes bibliographical references (p. 167-177). Available online via OhioLINK's ETD Center
Rosenthal, Marcel Verfasser], Jörg [Akademischer Betreuer] [Pretz, A. [Akademischer Betreuer] Lehrach et Kurt [Akademischer Betreuer] Aulenbacher. « Experimental benchmarking of spin tracking algorithms for electric dipole moment searches at the cooler synchrotron COSY / Marcel Rosenthal ; Jörg Pretz, A. Lehrach, Kurt Aulenbacher ». Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1130352447/34.
Texte intégralRosenthal, Marcel Stephan [Verfasser], Jörg [Akademischer Betreuer] Pretz, A. [Akademischer Betreuer] Lehrach et Kurt [Akademischer Betreuer] Aulenbacher. « Experimental benchmarking of spin tracking algorithms for electric dipole moment searches at the cooler synchrotron COSY / Marcel Rosenthal ; Jörg Pretz, A. Lehrach, Kurt Aulenbacher ». Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1130352447/34.
Texte intégralZechlau, Thorsten Sven [Verfasser], Peter [Akademischer Betreuer] [Gutachter] Fierlinger et Winfried [Gutachter] Petry. « Ultra-Cold Neutron Transport and Spin Manipulation System for the Measurement of the Neutron Electric Dipole Moment / Thorsten Sven Zechlau ; Gutachter : Peter Fierlinger, Winfried Petry ; Betreuer : Peter Fierlinger ». München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/1120013925/34.
Texte intégralSouza, Jean Carlo 1993. « Estudos de ressonância de spin eletrônico (RSE) em isolantes topológicos dopados com terras-rara ». [s.n.], 2017. http://repositorio.unicamp.br/jspui/handle/REPOSIP/326704.
Texte intégralDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
Made available in DSpace on 2018-09-02T11:57:27Z (GMT). No. of bitstreams: 1 Souza_JeanCarlo_M.pdf: 4438731 bytes, checksum: aaba7a375b2b45b638619e944111c41b (MD5) Previous issue date: 2017
Resumo: A ideia de topologia na Física da Matéria da Condensada, apesar de ter surgido com o efeito Hall quântico inteiro, só voltou a ser explorada recentemente na busca de novas fases da matéria depois do surgimento dos Isolantes Topológicos (ITs) 2D. Após a previsão teórica, e a descoberta experimental, foi proposto que esta nova fase poderia ser generalizada para sistemas 3D, em que o volume do material seria isolante com estados metálicos de superfície que possuiriam canais de spin polarizados. Apesar de diversos experimentos e o surgimento de outras fases topológicas da matéria subsequentes, ainda há dúvidas sobre a natureza dos ITs 3D. Os efeitos topológicos mais claros ainda não foram observados de forma inequívoca e reprodutível experimentalmente e ainda seria de extrema valia encontrar técnicas experimentais que possam complementar os mais discutidos experimentos de ARPES. Nesta dissertação foram estudadas duas famílias distintas de materiais propostas como possíveis ITs 3D: os binários Bi2Se3 e Sb2Te3 e o half-Heusler YPdBi. Utilizando a técnica de auto-fluxo e a fusão estequiométrica, os sistemas foram sintetizados dopados com os terras-rara Gd3+, Nd3+ e Er3+ para realizar estudos de ressonância de spin eletrônico (RSE) e do papel dos efeitos de campo cristalino (CEF) - no caso do half-Heusler. Para o ternário YPdBi foram feitos dois estudos. Na família dos half-Heuslers, a ordem topológica surge da relação entre o acoplamento spin-órbita e a hibridização, que está ligada com a mudança do parâmetro de rede, então os efeitos de CEF poderiam estar refletindo a transição entre a trivialidade e a não-trivialidade. A partir das medidas de susceptibilidade magnética em função da temperatura das amostras dopadas com Nd3+ e Er3+ combinadas com os estudos de RSE, foi possível extrair os parâmetros de campo cristalino (CFP) de quarta e sexta ordem. Comparando esses dados com resultados anteriores para o material, supostamente, não-trivial YPtBi, observou-se uma mudança sistemática no sinal dos CFP. Resultados prévios para as amostras de YPtBi dopadas com Nd3+ mostram uma evolução não usual para uma forma de linha difusiva com a potência de micro-onda. Neste trabalho também foi realizado um estudo da forma de linha em função da potência. Apenas a ressonância do Nd3+ para os monocristais de 10% de Nd em YPdBi mostrou uma forma de linha difusiva que evolui com a potência da micro-onda. No caso dos binários Bi2Se3 e Sb2Te3, o objetivo era otimizar a rampa de tratamento térmico para obter monocristais melhores que poderiam permitir a observação de um espectro totalmente resolvido do Gd3+. Após mudanças no crescimento dos monocristais, o espectro totalmente resolvido foi obtido para as amostras de Bi2Se3. No caso do Sb2Te3 apenas uma linha central com a estrutura fina colapsada foi observada. Acompanhando o deslocamento g e a evolução da largura de linha dH da RSE do Gd3+ com a temperatura, o comportamento negativo do deslocamento g para toda a faixa de temperatura indica que elétrons do tipo p são os grandes responsáveis pela formação da superfície de Fermi residual destes sistemas. Um aumento no coeficiente angular de dH em função da temperatura, a taxa Korringa b, foi observado em baixas temperaturas, logo diferentes concentrações de Gd3+ foram utilizadas para estudar este comportamento. Novamente observou-se um comportamento anômalo em baixas temperaturas, o que poderia estar relacionado com a evolução dos CFP com a temperatura. Todos esses resultados foram discutidos levando-se em conta a possibilidade de existência de topologia não-trivial na estrutura eletrônica desses materiais, com foco particular na relação da interação spin-órbita e os efeitos de campo cristalino com a manifestação da topologia não trivial nesses sistemas
Abstract: The idea of topological systems in Condensed Matter Physics, although already explored in the Quantum Hall Effect, has recently become a topic of intense scientific investigation. In particular, great efforts have been dedicated to the search for new quantum phases since the proposal of the Topological Insulators (TIs) in 2D. After the theoretical prediction and the experimental discovery of the TIs in the 2D case, the existence of the Quantum Hall Spin Effect in 3D, 3D TIs, was proposed, where an insulator bulk and metallic surface states with spin polarized channels could be experimentally realized. Although many experiments have been performed, and some groups claimed the direct observation of such new topological phases, there is still a lot of controversy about the nature of the 3D TIs and about the actual microscopic origin of the metallic states on the surface of the studied materials. Other signatures of the topological phases have not been unambiguously and repeatedly measured yet and there is an obvious lack of a supplementary lab technique to be compared to the most used technique to probe these states, which is ARPES. In this work we have studied two different classes of 3D TIs: the binaries Bi2Se3 and Sb2Te3 and the half-Heusler YPdBi. We have been able to grow single crystals of these materials pure and rare-earth doped with Gd3+, Nd3+ and Er3+ using the self-flux technique and the stoichiometric melting. The aim was to use these crystals to study Electron Spin Resonance (ESR) as a potential probe to investigate the existence of the metallic surface states and to explore the possible of the crystalline electrical field (CEF) effects on the formation of the non-trivial electronic structure of these materials. Regarding the YPdBi, our ESR and magnetization studies have revealed that, in the half-Heusler family, the topological order emerges from the interplay between spin-orbit coupling and the hybridization, which is connected with the changes on the lattice parameter. Thus, the CEF effects could reflect the transition from trivial to nontrivial topology. From the magnetic susceptibility data as a function of temperature from the Nd3+ and Er3+ doped samples combined with the ESR studies, it was possible to extract the fourth and sixth order crystal field parameters (CFP). Comparing our data with the previous results from YPtBi, which is a putative non-trivial material, a systematic change in the sign of the CFP was observed. Previous results with the YPtBi Nd-doped samples show an unusual evolution of the Nd3+ ESR line to a diusive-like line shape as a function of the microwave power. In this work we have performed a similar study of the Nd3+ ESR line shape as a function of the microwave power. Only for the single crystal of 10% Nd in YPdBi resonance shows a diffusive-like line shape that evolves with the microwave power. In the case of the binaries Bi2Se3 e Sb2Te3, the aim of this work was to optimize the heat treatment used in previous works of our group to obtain better single crystals that could allow the observation of the full resolved spectra from Gd3+. After many changes in the single crystal growth method, we were able to observe fully resolved Gd3+ ESR spectra in the Bi2Se3 samples. Regarding the Sb2Te3 single crystals, only a single Gd3+ Dysonian ESR line was observed. Following the Gd3+ ESR dg and dH as a function of temperature, the observed negative behavior of dg, in the whole temperature range studied, indicates that p-type electrons are the main source for the formation of the small the Fermi surface of these materials. An increase of the angular coefficient of dH as a function of temperature, the Korringa rate b, at low temperatures was observed and different concentrations of Gd3+ were required to investigate this anomaly. Again this anomalous behavior at low temperatures was observed for the all Gd-doped samples, which could be related to an evolution of CFP with temperature. We discuss our results taking into account the existence of non-trivial topological states in our samples and the role of spin-orbit and CEF effects might have in the formation of such states
Mestrado
Física
Mestre em Física
132653/2015-0
CNPQ
CAPES
FAPESP
Mahmoud, Salman. « Étude théorique des molécules diatomiques BN, SiN et LaH, structure électronique et spectroscopie ». Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20080/document.
Texte intégralIn the present work a theoretical investigation of the lowest molecular states of BN, SiN and LaH molecule, in the representation 2s+1Λ(+/-), has been performed via complete active space self-consistent field method (CASSCF) followed by multireference single and double configuration interaction method (MRSDCI). The Davidson correction noted as (MRSDCI+Q) was then invoked in order to account for unlinked quadruple clusters. The entire CASSCF configuration space was used as a reference in the MRCI calculation which has been performed via the computational chemistry program MOLPRO and by taking advantage of the graphical user interface Gabedit. Forty-two singlet, triplet, and quintet lowest electronic states in the 2s+1Λ(+/-) representation below 95000 cm-1 have been investigated of the molecule BN. While twenty-eight electronic states in the representation2s+1Λ(+/-)up to 70000 cm-1 of the SiN molecule have been investigated.On the other hand the Twenty four low-lying electronic states of LaH in the representation 2s+1Λ(+/-) below 35000 cm-1 have been studied by two different methods and by taking into consideration the spin orbit effect of the molecule LaH we give in the energy splitting of the eight electronic states. The potential energy curves (PECs) together with the harmonic frequency ωe, the equilibrium internuclear distance re, the rotational constants Be and the electronic energy with respect to the ground state Te have been calculated for the considered electronic states of BN, SiN and LaH molecule respectively. Using the canonical functions approach, the eigenvalues Ev, the rotational constants Bv ,the centrifugal distortion constants Dv and the abscissas of the turning points Rmin and Rmax have been calculated for electronic states up to the vibrational level v =51 for LaH molecule.Eighteen and Nine electronic states have been investigated here for the first time for the molecules of BN and SiN respectively, while for LaH, news results are performed for twenty three electronic states of LaH molecule and the spin-orbit effect of LaH molecule is given here for the first time. A comparison with experimental and theoretical data for most of the calculated constants demonstrated a very good accuracy. Finally, we expect that the results of our work should invoke further experimental investigations for these molecules. Our results have been published in Canadian journal of chemistry, Journal of Quantitative Spectroscopy and Radiative Transfer and we have two other papers in preparation to submit
Bouillaud, Thomas. « Le champ magnétique interne de l'expérience n2EDM pour sonder la symétrie CP : calcul du champ magique et maîtrise des non-uniformités ». Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALY065.
Texte intégralElectric Dipole Moments (EDMs) in spin 1/2 particles such as the neutron are highlysensitive probes for Charge-Parity (CP) violation Beyond the Standard Model (BSM),one of the requirements needed to fully explain the Baryon Asymmetry of the Uni-verse (BAU). The n2EDM experiment, currently in the commissioning phase at thePaul Scherrer Institute in Switzerland, constitutes a leading effort to search for theneutron EDM. It relies on the principle of submitting spin-polarized Ultra-Cold Neu-trons (UCNs) to parallel electric and magnetic fields and measuring their precessionfrequency. This experiment hopes to achieve a record sensitivity ∆dn ≤ 10−27 e cm,a goal which can only be reached by tackling statistical and systematical uncertain-ties affecting the measurement. The work we present here contributes to the controlof systematic errors generated by non-uniform magnetic fields, through the calcula-tion of a systematic effect and the precise characterization of the internal magneticenvironment.The first part of this thesis motivates and introduces the n2EDM experiment,particularly the theme of magnetic field uniformity. We begin with a review of thetheoretical grounds on which EDM experiments stand, which are prompted by cos-mological observations that CP-violating interactions must exist in nature, and bythe inability of the Standard Model (SM) of particle physics to provide enough ofthese. We then present the n2EDM experiment, which relies at its core on the Ram-sey method of separated rotating magnetic fields to determine the spin-precessionfrequency of UCNs. We finally give the stringent uniformity requirements that theinternal magnetic environment of n2EDM must satisfy, and justify the existence ofnon-uniform contributions by studying the symmetries of the generated field.The second part focuses on the so-called false EDM, a dire systematic effect inn2EDM arising from the unfortunate combination of a relativistic motional field andrandom non-uniformities. We first propose a new frequency-domain derivation ofthe false EDM via the Wiener-Khinchin theorem, before expanding on a recent ap-proach to cancel this effect by tuning the coil-generated field to a “magic value”.We conclude through our alternative calculation of the magic field, and its extensionto dipole-like magnetic contaminations, that it is possible to suppress the total falseEDM by at least one order of magnitude by setting the magnetic field to a value of10.5 μT.The third part relies on magnetic field mapping to estimate and correct non-uniformities responsible for undesirable effects such as the false EDM. After es-tablishing the accuracy of the mapping apparatus and taming unruly residual fieldpatterns, we show through an analysis of the mapping data that the n2EDM mag-netic environment fully satisfies the experiment’s statistical and systematical re-quirements. We finally propose and apply a field optimization strategy to suppressresidual non-uniformities even further. The optimized field generates a negligiblefalse EDM and boasts an unprecedented level of uniformity, with a root mean squaredeviation on the vertical field component σ(Bz) = 35 pT over the neutron’s preces-sion volume
PEREIRA, CLOTILDE C. « Desenvolvimento de membranas aniônicas obtidas por enxertia via irradiação para aplicação em células a combustível alcalinas ». reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27979.
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As membranas de troca aniônica são uma alternativa promissora para o desenvolvimento de eletrólitos mais eficientes para células a combustível alcalinas. Em geral, as membranas de troca aniônica são ionômeros capazes de conduzir íons hidroxila devido aos grupos quaternário de amônio e têm como característica elevado pH equivalente. Com o objetivo de desenvolver membranas aniônicas química e termicamente estáveis, com satisfatória condutividade iônica para aplicação em células a combustível alcalinas, as membranas aniônicas foram sintetizadas a partir de polímeros base de polietileno de baixa densidade (LDPE), polietileno de ultra alto peso molecular (PEUHMW), poli(etileno-co-tetrafluoroetileno) (PETFE) e poli(tetrafluoroetilleno-co-hexafluoroetileno) (PFEP) previamente irradiados nas fontes de radiação gama de 60Co ou com feixe de elétrons, para enxertia do monômero de estireno e funcionalizados com trimetilamina para incorporação dos grupos quaternário de amônio. As membranas resultantes foram caracterizadas por espectroscopia de ressonância paramagnética eletrônica (EPR), espectroscopia Raman, termogravimetria (TG), espectroscopia de impedância eletroquímica (EIS), além da determinação do grau de enxertia, capacidade de absorção de água por gravimetria e capacidade de troca iônica, por titulação. As membranas sintetizadas com os polímeros LDPE e UHMWPE pré-irradiados a 70 kGy com feixe de elétrons e armazenadas a baixa temperatura (-70 °C) por até 10 meses, mostraram resultados de condutividade iônica, quando na forma (OH-), de 29 mS.cm-1 e 14 mS.cm-1 a 65 °C, respectivamente. Os filmes de PFEP irradiados no processo simultâneo mostram níveis de enxertia insuficientes para a síntese de membranas aniônicas, necessitando maiores estudos para aperfeiçoar os processos de irradiação e enxertia. As membranas baseadas em PETFE, pré-irradiadas a 70 kGy com feixe de elétrons e armazenadas a baixa temperatura (-70 °C) por até 10 meses, mostraram maior condutividade iônica, quando na forma hidroxila (OH-), com valores de condutividade iônica entre 90 mS.cm-1 e 165 mS.cm-1 na faixa de temperatura entre 30 e 60 °C. Estes resultados mostraram que membranas de LDPE, UHMWPE e PETFE são eletrólitos promissores para a aplicação em células a combustível alcalinas.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
Silva, Marcos Antonio da. « Estudo de compostos LiMePO4 (Me=Mg, Co, Ni) através de Ressonância Magnética Nuclear ». Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-13032014-112117/.
Texte intégralThis work reports a 7Li and 31P nuclear magnetic resonance study in the Li1-3xMgFexPO4 phases between 150 and 410 K. This study, complementary to those made using Mössbauer and magnetic neutron diffraction experiments, confirms that the Fe3+ ions enter as in the lattice, and that they enter substituting Li ions. The behavior of the 7Li e 31P nuclear magnetic resonance spectra, together with ionic conductivity measurements, show that no Li mobility occurs in temperature range studied even with the addition of the Fe impurity.
Chiu, Zhi-Hsung, et 邱志宣. « Electric-dipole-induced spin resonance in mesoscopic system ». Thesis, 2008. http://ndltd.ncl.edu.tw/handle/fm9xvn.
Texte intégral國立交通大學
電子物理系所
96
This thesis seeks after the manifestation of the electric-dipole-induced spin resonance (EDSR) in mesoscopics transport through a Rashba-type quantum channel. The EDSR con‾guration involves a static ‾eld along the channel and an ac electric ‾eld in parallel with the magnetic ‾eld. Within a time dependent perturbation that induces first sideband, we study the spin fipping in the transmitted wavefunctions. For the case when the incident energy falls within the Zeeman gap, and the sideband energies (ε±ω) outside of it, both the upper and lower sideband involves intraband (interband) transition which is nonspin (spin) fipping. Our major fnding is that the spin fipping component exhibits resonance characteristics when the sideband energy coincides with either the Zeeman gap edges or the subband bottom, when the density of state is large. Furthermore, the spin density oscillates in space according to the interference between the spin fipping and non-spin fipping comments. Additional beating features in the spin density spatial pro‾le is found to result from the interference between the spin density oscillations due to (ε+ω)and (ε-ω) sidebands. Our calculation has incorporated the effects of evanescent modes. We have performed a detail analyze on the evanescent modes. The longitudinal wavevector kx is found to be complex rather then pure imaginary.
Zheng, Wangzhi. « Experiments of Search for Neutron Electric Dipole Moment and Spin-Dependent Short-Range Force ». Diss., 2012. http://hdl.handle.net/10161/5493.
Texte intégralIt is of great importance to identify new sources of discrete symmetry violations because it can explain the baryon number asymmetry of our universe and also test the validity of various models beyond the standard model. Neutron Electric Dipole Moment (nEDM) and short-range force are such candidates for the new sources of P&T violations. A new generation nEDM experiment was proposed in USA in 2002, aiming at improving the current nEDM upperlimit by two orders of magnitude. Polarized
A Monte-Carlo simulation is used to simulate the entire
We also built an apparatus to demonstrate that the
During this SQUID test, two interesting phenomena were discovered. One is the pressure dependence of the T1 of the polarized
In addition to the nEDM experiment, polarized
Dissertation
Ihn, Yong-Sup. « Experiment to measure the electron electric dipole moment using laser cooled Cs atoms ». 2013. http://hdl.handle.net/2152/21325.
Texte intégraltext