Comprehensive analysis on the magnetic field error of a K–Rb–21Ne comagnetometer with low-frequency bias magnetic field sensitivity

The spin-exchange relaxation-free comagnetometer (SERFC) is of important research value compared to existing high-precision gyroscopes because of its extremely high theoretical limit sensitivity and long-term stability, in which one significant limiting factor is the magnetic field error. First, the relationship between the magnetic field gradient and the nuclear spin relaxation mechanism is introduced into the frequency response and steady-state response models of SERFC. Then, a novel method for suppression of the low-frequency magnetic field error based on the modified bias magnetic field sensitivity model is proposed. Finally, the effectiveness of the proposed suppression methods is demonstrated by optimizing the cell temperature, pump light power, and compensation magnetic field gradient to increase the suppression factor by 72.19%, 20.24%, and 69.86%, and the corresponding bias instability increased by 55.41%, 20.84%, and 27.63%, respectively. This study contributes to improving the long-term zero bias stability of the SERFC

Novel Magnetic-Sensing Modalities with Nitrogen-Vacancy Centers in Diamond

In modern-day quantum metrology, quantum sensors are widely employed to detect weak magnetic fields or nanoscale signals. Quantum devices, exploiting quantum coherence, are inevitably connected to physical constants and can achieve accuracy, repeatability, and precision approaching fundamental limits. As a result, these sensors have shown utility in a wide range of research domains spanning both science and technology. A rapidly emerging quantum sensing platform employs atomic-scale defects in crystals. In particular, magnetometry using nitrogen-vacancy (NV) color centers in diamond has garnered increasing interest. NV systems possess a combination of remarkable properties, optical addressability, long coherence times, and biocompatibility. Sensors based on NV centers excel in spatial resolution and magnetic sensitivity. These diamond-based sensors promise comparable combination of high spatial resolution and magnetic sensitivity without cryogenic operation. The above properties of NV magnetometers promise increasingly integrated quantum measurement technology, as a result, they have been extensively developed with various protocols and find use in numerous applications spanning materials characterization, nuclear magnetic resonance (NMR), condensed matter physics, paleomagnetism, neuroscience and living systems biology, and industrial vector magnetometry. In this chapter, NV centers are explored for magnetic sensing in a number of contexts. In general, we introduce novel regimes for magnetic-field probes with NV ensembles. Specifically, NV centers are developed for sensitive magnetometers for applications where microwaves (MWs) are prohibitively invasive and operations need to be carried out under zero ambient magnetic field. The primary goal of our discussion is to improve the utility of these NV center-based magnetometers

STUDIES OF MAGNETICALLY INDUCED FARADAY ROTATION BY POLARIZED HELIUM-3 ATOMS

Gyromagnetic Faraday rotation offers a new method to probe limits on properties of simple spin systems such as the possible magnetic moment of asymmetric dark matter or as a polarization monitor for polarized targets. Theoretical calculations predict the expected rotations of linearly polarized light due to the magnetization of spin-1/2 particles are close to or beyond the limit of what can currently be measured experimentally (10−9 rad). So far, this effect has not been verified. Nuclear spin polarized 3He provides an ideal test system due to its simple structure and ability to achieve high nuclear spin polarization via spin-exchange optical pumping (SEOP). To maximize the expected signal from 3He, a SEOP system is built with a modern narrowband pumping laser and a 3He target designed to use with a multipass cavity. Additionally, a sensitive triple modulation apparatus for polarimetry is utilized and further developed to detect Faraday rotations on the order of nanoradians. This works presents the results of the measurement of the magnetic Faraday effect

NASA Tech Briefs, January 2008

Topics covered include: Induction Charge Detector with Multiple Sensing Stages; Generic Helicopter-Based Testbed for Surface Terrain Imaging Sensors; Robot Electronics Architecture; Optimized Geometry for Superconducting Sensing Coils; Sensing a Changing Chemical Mixture Using an Electronic Nose; Inertial Orientation Trackers with Drift Compensation; Microstrip Yagi Antenna with Dual Aperture-Coupled Feed; Patterned Ferroelectric Films for Tunable Microwave Devices; Micron-Accurate Laser Fresnel-Diffraction Ranging System; Efficient G(sup 4)FET-Based Logic Circuits; Web-Enabled Optoelectronic Particle-Fallout Monitor; SiO2/TiO2 Composite for Removing Hg from Combustion Exhaust; Lightweight Tanks for Storing Liquefied Natural Gas; Hybrid Wound Filaments for Greater Resistance to Impacts; Making High-Tensile-Strength Amalgam Components; Bonding by Hydroxide-Catalyzed Hydration and Dehydration; Balanced Flow Meters without Moving Parts; Deflection-Compensating Beam for Use inside a Cylinder; Four-Point-Latching Microactuator; Curved Piezoelectric Actuators for Stretching Optical Fibers; Tunable Optical Assembly with Vibration Dampening; Passive Porous Treatment for Reducing Flap Side-Edge Noise; Cylindrical Piezoelectric Fiber Composite Actuators; Patterning of Indium Tin Oxide Films; Gimballed Shoulders for Friction Stir Welding; Improved Thermal Modulator for Gas Chromatography; Nuclear-Spin Gyroscope Based on an Atomic Co-Magnetometer; Utilizing Ion-Mobility Data to Estimate Molecular Masses; Optical Displacement Sensor for Sub-Hertz Applications; Polarization/Spatial Combining of Laser-Diode Pump Beams; Spatial Combining of Laser-Diode Beams for Pumping an NPRO; Algorithm Optimally Orders Forward-Chaining Inference Rules; Project Integration Architecture; High Power Amplifier and Power Supply; Estimating Mixing Heights Using Microwave Temperature Profiler; and Multiple-Cone Sunshade for a Spaceborne Telescope

Optical Magnetometry Using Multiphoton Transitions

Optical magnetometry plays a critical role in low-energy precision measurements and numerous other applications. In particular, permanent electric dipole moment (EDM) searches impose strict requirements on magnetic field sensitivity of the underlying atomic or molecular species. Other magnetometer properties -- such as chemical reactivity, dielectric strength, and interaction cross-sections with other species -- also impose limitations on experimental conditions. Here, we explore a novel approach to optical magnetometry, using multiphoton transitions of diamagnetic atoms to detect Larmor precession of polarized nuclei. Resonant probes are possible at moderate ultraviolet wavelengths, and hyperfine structure couples spin precession to fluorescence transitions with negligible backgrounds; paramagnetic rotation due to intensity-dependent dispersion may also be detectable. Nuclear spins and nonlinear optical excitation introduce new degrees of freedom, and evade limitations arising from rapid electronic decoherence. This dissertation reports progress towards two-photon optical magnetometry using ytterbium, rubidium, and xenon. We characterize the influence of probe polarization and magnetic fields on fluorescence spectra, for one- and two-photon continuous-wave (cw) excitation of ytterbium. Resolved hyperfine and isotope structure allow us to use spin-zero isotopes for diagnostics and normalization, and we develop analysis for overlapping two-photon resonances. We also report measurements of two-photon excitation in ytterbium and rubidium using picosecond laser pulses, and in xenon using a cw laser. Although hyperfine structure is unresolved, the rubidium measurements are sensitive to probe field polarization. Fluorescence spectra from two-photon excitation of ytterbium with femtosecond pulses show modulation when the repetition rate changes. Although techniques for polarizing noble gas nuclei are mature, existing cell designs are incompatible with two-photon magnetometry. We describe development of silicate-assisted hydroxide-catalysis bonding for both aluminosilicate EDM cells with silicon electrodes, and sapphire-windowed cells that transmit ultraviolet excitation light. Progress in measuring the 129Xe nuclear EDM is discussed. Absolute referencing of the picosecond laser to potassium transitions is proposed for two-photon spectroscopy of ytterbium and xenon, and a compatible frequency-tripling method is outlined to produce excitation light for xenon. Novel possibilities including spatial resolution and multiphoton optical pumping of nuclear spins are considered.PHDPhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135807/1/sdegen_1.pd

Optimisation of xenon-rich stopped-flow spin-exchange optical pumping for functional lung imaging

Spin-exchange optical pumping (SEOP) is a hyperpolarisation method used in the hyperpolarisation of noble gases and can enhance nuclear spin polarisation by five orders of magnitude. Hyperpolarised (HP) 129-Xe has many properties that make it ideally suited to clinical lung imaging, but since its first demonstration in animals in 1994 and humans in 1996, translation to the clinic has been hampered by challenges associated with scaling up production. Within this thesis, construction and demonstration of a clinical-scale stopped-flow hyperpolariser is described, the design of which is based on the record holding XeUS and XeNA polarisers developed previously by our consortium, which had aimed to address the issue of production scale-up. Modifications enhancing the ease of operation and utility in-clinic are presented, as are modifications that reduce the capital cost of such a system. These include a re-design of the gas manifold and the development of a low-cost low-field NMR spectrometer which achieved an SNR of 125 at a cost of ~$300, a 13-fold improvement in cost/SNR compared with the existing spectrometer at a saving of ~$19,000. In continuous-flow 129-Xe polarisers there has long been a discrepancy in the polarisation achieved and that predicted by the standard model of SEOP which was shown recently to be due to the presence of rubidium clusters. Here, the standard model is applied to- and validated for the first time against the stopped-flow regime. The validated model is used to explore parameter space to identify the most effective ways to increase production yield in future stopped-flow polarisers. Stopped-flow SEOP in the xenon-rich regime presents unique thermal management problems due to the absence of gas flow and abundance of poorly thermally conductive, Rb spin destroying Xe. Raman spectroscopy is used to spatially examine in-cell thermal behaviour under steady-state and turbulent 'rubidium runaway' conditions as a function of temperature and Xe density and the beneficial impact of adding thermally conductive helium to the standard N2-Xe gas mix is demonstrated. Hybrid Rb-Cs-Xe SEOP is demonstrated for the first time and examined using in-situ NMR and Raman spectroscopies. High polarisations of ~50% were obtained. Finally, progress on the HP-Xe clinical trial is presented to illustrate the impact of the 4-fold increase in SNR that will come with the installation of the new N-XeUS stopped-flow polariser

Optimisation of xenon-rich stopped-flow spin-exchange optical pumping for functional lung imaging

Spin-exchange optical pumping (SEOP) is a hyperpolarisation method used in the hyperpolarisation of noble gases and can enhance nuclear spin polarisation by five orders of magnitude. Hyperpolarised (HP) 129-Xe has many properties that make it ideally suited to clinical lung imaging, but since its first demonstration in animals in 1994 and humans in 1996, translation to the clinic has been hampered by challenges associated with scaling up production. Within this thesis, construction and demonstration of a clinical-scale stopped-flow hyperpolariser is described, the design of which is based on the record holding XeUS and XeNA polarisers developed previously by our consortium, which had aimed to address the issue of production scale-up. Modifications enhancing the ease of operation and utility in-clinic are presented, as are modifications that reduce the capital cost of such a system. These include a re-design of the gas manifold and the development of a low-cost low-field NMR spectrometer which achieved an SNR of 125 at a cost of ~$300, a 13-fold improvement in cost/SNR compared with the existing spectrometer at a saving of ~$19,000. In continuous-flow 129-Xe polarisers there has long been a discrepancy in the polarisation achieved and that predicted by the standard model of SEOP which was shown recently to be due to the presence of rubidium clusters. Here, the standard model is applied to- and validated for the first time against the stopped-flow regime. The validated model is used to explore parameter space to identify the most effective ways to increase production yield in future stopped-flow polarisers. Stopped-flow SEOP in the xenon-rich regime presents unique thermal management problems due to the absence of gas flow and abundance of poorly thermally conductive, Rb spin destroying Xe. Raman spectroscopy is used to spatially examine in-cell thermal behaviour under steady-state and turbulent 'rubidium runaway' conditions as a function of temperature and Xe density and the beneficial impact of adding thermally conductive helium to the standard N2-Xe gas mix is demonstrated. Hybrid Rb-Cs-Xe SEOP is demonstrated for the first time and examined using in-situ NMR and Raman spectroscopies. High polarisations of ~50% were obtained. Finally, progress on the HP-Xe clinical trial is presented to illustrate the impact of the 4-fold increase in SNR that will come with the installation of the new N-XeUS stopped-flow polariser

Spinor Bose-Einstein comagnetometer and interhyperfine interactions in 87Rb

In this work we demonstrate the first realization of a comagnetormeter in the ultracold regime. In comparison to regular magnetometers, which are designed to maximize their magnetic field sensitivity, a comagnetometer uses paired magnetometers in a differential configuration to cancel the effects of the magnetic field and resolve weak dynamics that differently affect its constituents. Here, we implement a omagnetometer within the f=1 and f=2 ground state hyperfine manifolds of a Rb87 spinor Bose-Einstein condensate (SBEC). The hyperfine manifolds feature nearly opposite gyromagnetic ratios and thus the sum of their precession angles is only weakly coupled to external magnetic fields, while being highly sensitive to any effect that rotates both manifolds in the same way. A fundamental limitation of the comagnetometer is f=2--> f=1 hyperfine relaxing collisions, where the liberated kinetic energy expels colliding atoms from the optical trap. These collisions are state-dependent and can be avoided by preserving the f=2 spin state in a stretched configuration. We show how this can be achieved at low magnetic fields, where the spin-dependent contact interaction is the dominant energy contribution and stabilizes the spin orientation of the SBEC. Under these conditions, the comagnetometer coherence time can be extended to ~1 s and the observed common magnetic field suppression is 44.0(8)dB. The technique is applied to precision measurement of the interhyperfine interaction in 87Rb. The uncertainty in the obtained interhyperfine scattering lengths is reduced by more than a factor three with respect to previously reported values. We also present preliminary studies on phase-resolved parametric amplification within a SBEC comagnetometer. In this case, the f=2 manifold undergoes parametric amplification, while the f=1 manifold keeps track of the rotating reference frame induced by the applied external magnetic field. We describe technical improvements to the experimental system in two areas: magnetic control and manipulation, and optical trapping and probing. The first group of improvements includes the implementation of radiofrequency (rf) and microwave (mw) driving and the development of a real-time rf source. The second group of improvements includes a pulsed optical trapping technique, a digital implementation of the laser locking scheme, and a hyperfine-selective Faraday probing method.Aquesta tesi demostra el primer comagnetòmetre implementat en un sistema d’àtoms ultrafreds. Els magnetòmetres són altament sensibles a canvis en el camp magnètic. Els comagnetòmetres, en canvi, utilitzen magnetòmetres aparellats diferencialment per a cancel·lar la dependència del camp magnètic extern i discernir camps o interaccions que afecten de forma diferent als seus constituents. En aquest treball, s’implementa un comagnetòmetre mitjançant una superposició coherent dels estats hiperfins f=1 i f=2 d’un condensat spinorial de Bose-Einstein de Rb87. Aquests estats tenen fraccions giromagnètiques gairebé oposades, de manera que la suma dels seus angles de precessió no depèn del camp magnètic però es veu doblement afectada per interaccions que roten els dos estats en la mateixa direcció. Col·lisions de relaxació hiperfina f=2 --> f=1 limiten el temps de coherència del comagnetòmetre. En concret, els àtoms que hi participen són expulsats de la trampa òptica degut a l’energia cinètica alliberada en la col·lisió. Aquest tipus de col·lisió depenen de l’estat de spin i es cancel·len per a estats que maximitzen el spin a f =2. En aquesta tesis demostrem la cancel·lació de col·lisions de relaxació hiperfina a camps magnètics baixos, on la interacció de spin és la contribució energètica dominant i estabilitza l’estat a f = 2. Sota aquestes condicions, el temps de coherència del comagnetòmetre s’estén fins a ~1 s i el soroll de camp magnètic es veu atenuat per 44.0(8) dB. El comagnetòmetre s’ha usat per caracteritzar la interacció hiperfina en àtoms de Rb87. En comparació a estudis experimentals anteriors, s’ha aconseguit reduir en un factor tres la incertesa en les longituds de dispersió entre estats hiperfins. També presentem experiments preliminars d’amplificació paramètrica amb resolució de phase, on l’amplificació paramètrica té lloc a f=2 i les rotacions magnètiques del sistema de referència són mesurades de forma simultània a f=1. Els avenços tècnics es divideixen en millores del control i de la manipulació magnètica, així com en millores del confinament i de la detecció òptica. Els primers inclouen els sistemes de manipulació atòmica mitjançant radiofreqüència i microones, com també el desenvolupament d’una font de radiofreqüència amb control en temps real. Els segons inclouen una tècnica de confinament polsat, la digitalització del sistema d’estabilització làser i la detecció òptica d’ambdós estats hiperfins.Postprint (published version