Miniature biplanar coils for alkali-metal-vapor magnetometry

Atomic spin sensors offer precision measurements using compact, microfabricated packages, placing them in a competitive position for both market and research applications. Performance of these sensors such as dynamic range may be enhanced through magnetic field control. In this work, we discuss the design of miniature coils for three-dimensional, localized field control by direct placement around the sensor, as a flexible and compact alternative to global approaches used previously. Coils are designed on biplanar surfaces using a stream-function approach and then fabricated using standard printed-circuit techniques. Application to a laboratory-scale optically pumped magnetometer of sensitivity $\sim$20 fT/Hz$^{1/2}$ is shown. We also demonstrate the performance of a coil set measuring $7 \times 17 \times 17$ mm$^3$ that is optimized specifically for magnetoencephalography, where multiple sensors are operated in proximity to one another. Characterization of the field profile using $^{87}$Rb free-induction spectroscopy and other techniques show $>$96% field homogeneity over the target volume of a MEMS vapor cell and a compact stray field contour of $\sim$1% at 20 mm from the center of the cell

Optically detected nuclear magnetic resonance above and far below earth's magnetic field: spin dynamics and relaxation in unconventional regimes

(English) This thesis describes theoretical background, simulations, experimental apparatus and measurements of nuclear spin dynamics via optically pumped magnetometers in unconventional magnetic field regimes. It is divided into four parts: Magnetometry, Nuclear Magnetic Resonance Spectroscopy, Nuclear Relaxation Dispersion, and Nuclear Spin Control, each looking at different aspects of this topic. The magnetometry section describes how through integration of techniques from DC spin-exchange relaxation-free and rf magnetometers, a widely tunable magnetometer is developed that offers a nearly flat response from DC up to few kHz with a sensitivity of less than 20 fT √Hz. Within this range, it surpasses the capabilities of inductive detection methods and eliminates the necessity for cryogenic temperatures that are required for superconducting quantum interference devices (SQUIDs). The subsequent part employs the magnetometer for conducting nuclear magnetic resonance spectroscopy experiments involving coupled nuclear spin systems. A comprehensive analysis is undertaken to ascertain the optimal magnetic field that yields the most precise determination of the J-coupling constant. It is shown that for some systems the ultra-low field regime offers advantages compared to the zero- and high-field regime. A key factor in choosing the optimal field is the nuclear spin relaxation’s strong field dependency, explored in the thesis’s third part. This section thoroughly examines this subject in the unconventional ultra-low field range, discussing long-lived coherences and the impact of long correlations in molecular dynamics. The thesis experimentally investigates this by adapting the established fast-field cycling method to ultra-low fields and combining it with optical detection. The thesis’ s final part focuses on enhancing nuclear spin dynamics manipulation through advanced methods that ensure selective, efficient, accurate, and fault-tolerant spin control. Ultra-low fields possess unique attributes, making even basic techniques like spin-selective resonant pulses challenging to implement. To address this, novel concepts were devised, enabling effective spin control in the ultra-low field range, rivaling or surpassing high-field counterparts. The efficiency of these improved pulse sequences is demonstrated in dynamical decoupling, polarimetry, and spectral filtering experiments.(Català) Aquesta tesi doctoral descriu la teoria, simulacions, aparell experimental i mesuraments de dinàmiques de espín nuclear per mitjà de magnetòmetres de bombeig òptic en règims magnètics no convencionals. Aquesta tesi està dividida en quatre parts: magnetometria, espectroscòpia de ressonància magnètica nuclear, dispersió relaxació nuclear i control de espín nuclear. La secció de magnetometria descriu com, mitjançant la integració de les tècniques d’intercanvi de espín DC lliure de relaxació i magnetòmetres RF, s’ha desenvolupat un magnetòmetre àmpliament ajustable que ofereix una resposta gairebé plana des de DC fins a uns pocs kHz amb una sensibilitat de menys de 20 fT √Hz. En aquest rang, sobrepassa les capacitats de mètodes de detecció inductiva i elimina la necessitat de temperatures criogèniques necessàries en aparells superconductors d'interferència quàntica o SQUIDs (per les sigles en anglès). A la següent part s'empra el magnetòmetre per realitzar experiments d'espectroscòpia de ressonància magnètica nuclear en sistemes amb espines nuclears acoblats. Es fa una anàlisi exhaustiva per trobar el camp magnètic que dóna la determinació més precisa de la constant J d'acoblament. Es demostra que alguns sistemes en règim de camps ultra baixos ofereixen avantatges quan es comparen amb els camps a zero y alt règim. Un factor clau per triar el camp magnètic és la forta dependència de la relaxació de l'espín nuclear amb el camp. Aquesta dependència s'explora a la tercera part d'aquesta tesi al rang no convencional de camps ultra baixos, amb una discussió sobre coherències persistents de llarga vida i l'impacte de correlacions esteses a les dinàmiques moleculars. Aquest estudi es realitza experimentalment adaptant el mètode establert de rotació ràpida de camp (fast field cycling) a camps ultra baixos i combinant-ho amb detecció òptica. La part final d'aquesta tesi s'enfoca a millorar la manipulació de les dinàmiques d'espín nuclear mitjançant mètodes avançats que asseguren un control de l'espín selectiu, eficient, exacte i a prova d'errors. Els camps ultra baixos tenen atributs únics que fan que fins i tot les tècniques bàsiques com els polsos ressonants selectius d'espín siguin difícils d'implementar. Per resoldre això, s'han desenvolupat nous conceptes que permeten el control efectiu de l'espín en el rang de camps ultra baixos similars o fins i tot millors que les contraparts de camps alts. L'eficàcia d'aquestes seqüències de polsos millorades es demostra amb experiments de desacoblament dinàmic, polarimetria i filtratge espectral.DOCTORAT EN FOTÒNICA (Pla 2013

Miniature Biplanar Coils for Alkali-Metal-Vapor Magnetometry

| openaire: EC/H2020/820393/EU//macQsimal | openaire: EC/H2020/766402/EU//ZULF | openaire: EC/H2020/754510/EU//PROBIST Funding Information: The work was funded by: the European Union Horizon 2020 research and innovation programme under project macQsimal (Grant Agreement No. 820393); the Horizon H2020 Marie Skłodowska-Curie Actions projects ITN ZULF-NMR (Grant Agreement No. 766402) and PROBIST (Grant Agreement No. 754510); the Spanish MINECO project OCARINA (the PGC2018-097056-B-I00 project funded by MCIN/AEI/10.13039/501100011033/FEDER, “A way to make Europe”); the Severo Ochoa program (Grant No. SEV-2015-0522); the Generalitat de Catalunya through the CERCA program; the Agència de Gestió d’Ajuts Universitaris i de Recerca under Grant No. 2017-SGR-1354; the Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya, cofunded by the European Union Regional Development Fund within the ERDF Operational Program of Catalunya (project QuantumCat, ref. 001-P-001644); the Fundació Privada Cellex; and the Fundació Mir-Puig. M.C.D.T. acknowledges financial support through the Junior Leader Postdoctoral Fellowship Programme from the “La Caixa” Banking Foundation (project LCF/BQ/PI19/11690021). We also thank Jacques Haesler, Sylvain Karlen, and Thomas Overstolz of the Centre Suisse d’Electronique et de Microtechnique SA (CSEM) in Neuchâtel (Switzerland) for supplying the MEMS vapor cells. Publisher Copyright: © 2022 American Physical Society.Atomic spin sensors offer precision measurements using compact microfabricated packages, placing them in a competitive position for both market and research applications. The performance of these sensors, such as the dynamic range, may be enhanced through magnetic field control. In this work, we discuss the design of miniature coils for three-dimensional localized field control by direct placement around the sensor, as a flexible and compact alternative to global approaches used previously. Coils are designed on biplanar surfaces using a stream-function approach and then fabricated using standard printed-circuit techniques. Application to a laboratory-scale optically pumped magnetometer of sensitivity approximately 20fT/Hz is shown. We also demonstrate the performance of a coil set measuring 7×17×17mm3 that is optimized specifically for magnetoencephalography, where multiple sensors are operated in close proximity to one another. Characterization of the field profile using 87Rb free-induction spectroscopy andother techniques show >96% field homogeneity over the target volume of a MEMS vapor cell and a compact stray-field contour of approximately 1% at 20 mm from the center of the cell.Peer reviewe

Real-Time Polarimetry of Hyperpolarized ¹³C Nuclear Spins Using an Atomic Magnetometer

We introduce a method for nondestructive quantification of nuclear spin polarization, of relevance to hyperpolarized spin tracers widely used in magnetic resonance from spectroscopy to in vivo imaging. In a bias field of around 30 nT we use a high-sensitivity miniaturized 87Rb-vapor magnetometer to measure the field generated by the sample, as it is driven by a windowed dynamical decoupling pulse sequence that both maximizes the nuclear spin lifetime and modulates the polarization for easy detection. We demonstrate the procedure applied to a 0.08 M hyperpolarized [1–13C]-pyruvate solution produced by dissolution dynamic nuclear polarization, measuring polarization repeatedly during natural decay at Earth’s field. Application to real-time and continuous quality monitoring of hyperpolarized substances is discussed

Magnetometer-detected Nuclear Magnetic Resonance of Photochemically Hyperpolarized Molecules

Photochemically induced dynamic nuclear polarization (photo-CIDNP) enables nuclear spin ordering by irradiating samples with light. Polarized spins are conventionally detected via high-field chemical shift-resolved NMR (above 0.1 T), however, of particular importance are CIDNP processes occurring at relatively low fields (<50 mT). In this paper, we demonstrate in situ low-field photo-CIDNP measurements using shielded fast-field-cycling NMR combined with audio-frequency detection of Larmor precession via atomic magnetometers. A model system is used comprising tetraphenyl porphyrin as a photosensitizer, and 1,4-benzoquinone as a quencher. For solutions comprising sub-mM concentrations of the photosensitizer and mM concentrations of the quencher, hyperpolarized 1H magnetization is detected by pulse-acquire NMR spectroscopy at 170 nT and 2 μT fields. The observed NMR linewidths are about 5 times narrower than normally anticipated in high-field NMR and are systematically affected by light irradiation during the acquisition period, reflecting a reduction of the transverse relaxation time constant, T_{2}*. Magnetometer-detected photo-CIDNP spectroscopy enables straightforward observation of spin-chemistry processes in the ambient field range of a few nT to tens of mT and may help resolve open questions regarding the nature of avian magneto sensing