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We propose to develop an optically pumped magnetometer (OPM) that implements spin squeezing to achieve better than standard quantum limit (SQL) performance while operating in mission relevant environments. This performance enhancement would allow us to increase the useable bandwidth by a factor > 2 while maintaining world class magnetic sensitivity, an order of magnitude better than commercially available options.
We are developing a polarized 3He target for use in high luminosity electron scattering experiments within the high magnetic field environment of Jefferson Lab's CLAS12 spectrometer. By combining recent advancements in metastability exchange optical pumping (MEOP) of 3He with cryogenic, double-cell target methods as used for the MIT-Bates 88-02 experiment, a target with polarization and gas density comparable to traditional, low-field polarized 3He targets can be reached within high magnetic field environments. We have begun polarizing sealed 3He cells at fields up to 5 T at Jefferson Lab, and are preparing for our first tests exploring polarization performance versus magnetic field and gas pressure in a single cell before we move to the construction of a full, cryogenic, double-cell prototype target. A key focus of our research is the determination of polarization relaxation under the irradiation of an ionizing particle beam within high magnetic fields.
Polarized 3He nuclear targets are invaluable surrogates for polarized neutron targets in spin-dependent scattering studies of the structure of matter. Traditional polarized 3He targets have seen steady improvements and active use over the last three decades, however they have been limited to operation in low magnetic fields. This has precluded their use in spectrometers that utilize high-magnetic-field tracking systems, such as Jefferson Lab's CLAS12 spectrometer. Developments in high-magnetic-field metastability exchange optical pumping of 3He, recently incorporated into the design of a polarized 3He ion source for RHIC and the EIC, could enable a new, polarized 3He fixed target to operate within high fields. Combining high-field techniques with the double-cell cryogenic target design used for the MIT-Bates 88-02 experiment, polarization and target density comparable to traditional polarized 3He targets could be reached while within a high magnetic field environment. We discuss the conceptual design for such a target, show our progress in this target's development, and outline plans for in-beams tests in Jefferson Lab's Hall B.
The use of spin polarized fuel could increase the deuterium-tritium (D-T) fusion cross section by a factor of 1.5 and, owing to alpha heating, increase the fusion power by an even larger factor. Issues associated with the use of polarized fuel in a reactor are identified. Theoretically, nuclei remain polarized in a hot fusion plasma. The similarity between the Lorentz force law and the Bloch equations suggests polarization can be preserved despite the rich electromagnetic spectrum present in a magnetic fusion device. The most important depolarization mechanisms can be tested in existing devices. The use of polarized deuterium and 3 He in an experiment avoids the complexities of handling tritium, while encompassing the same nuclear reaction spin-physics, making it a useful proxy to study issues associated with full D-T implementation. 3 He fuel with 65% polarization can be prepared by permeating optically-pumped 3 He into a shell pellet. Dynamically polarized 7 Li-D pellets can achieve 70% vector polarization for the deuterium. Cryogenically-frozen pellets can be injected into fusion facilities by special injectors that minimize depolarizing field gradients. Alternatively, polarized nuclei could be injected as a neutral beam. Once injected, the lifetime of the polarized fuel is monitored through measurements of escaping charged fusion products. Multiple experimental scenarios to measure the polarization lifetime in the DIII-D tokamak and other magnetic-confinement facilities are discussed, followed by outstanding issues that warrant further study.
Ultrafast time-resolved extreme ultraviolet (EUV) reflectivity measurements of optically pumped amorphous carbon (a-C) have been performed with the FERMI free electron laser (FEL). This work extends the energy range used in previous reflectivity studies and adds polarization dependence. The EUV probe is known to be sensitive to lattice dynamics, since in this range the reflectivity is essentially unaffected by the photo-excited surface plasma. The exploitation of both s- and p-polarized EUV radiation permits variation of the penetration depth of the probe; a significant increase in the characteristic time is observed upon increasing the probing depth (1 vs. 5 ps) due to hydrodynamic expansion and consequent destruction of the excited region, implying that there is only a short window during which the probed region is in the isochoric regime. A weak wavelength dependence of the reflectivity is found, consistent with previous measurements and implying a maximum electronic temperature of 0.8 eV ± 0.4.
We report on an ultrafast nonequilibrium phase transition with a strikingly long-lived martensitic anomaly driven by above-threshold single-cycle terahertz pulses with a peak field of more than 1 MV/cm. A nonthermal, terahertz-induced depletion of low-frequency conductivity in Nb 3 Sn indicates increased gap splitting of high-energy 12 bands by removal of their degeneracies, which induces the martensitic phase above their equilibrium transition temperature. In contrast, optical pumping leads to a Γ 12 gap thermal melting. Such light-induced nonequilibrium martensitic phase exhibits a substantially enhanced critical temperature up to ~100 K, i.e., more than twice the equilibrium temperature, and can be stabilized beyond technologically relevant, nanosecond time scales. Together with first-principle simulations, we identify a compelling terahertz tuning mechanism of structural order via Γ 12 phonons to achieve the ultrafast phase transition to a metastable electronic state out of equilibrium at high temperatures far exceeding those for equilibrium states.
Vigorous research efforts during the past several decades have successfully closed the “terahertz gap” between microwaves and infrared light, offering new and increasingly efficient ways to produce, detect, and manipulate radiation fields in the terahertz (THz) frequency range. In our laboratory, THz time-domain spectroscopy (THz-TDS) and optical-pump THz-probe (OPTP) experiments have been routinely utilized as ultrafast spectroscopy tools to investigate a variety of emerging quantum materials and metamaterials. The ultrafast THz pulses are produced by femtosecond laser excitation of photoconductive antennas, semiconductor surfaces (InAs), and nonlinear crystals (ZnTe, GaSe, and LiNbO 3 ). Photoconductive antennas and nonlinear crystals also allow for the coherent detection of these pulses in the time domain, with amplitude and phase spectra obtained in the frequency domain via fast Fourier transform. Although such solid-state schemes are highly desirable in many aspects and thus also commonly utilized in many research laboratories and industrial applications, they typically suffer from limited bandwidths due to the absorption and frequency dispersion induced primarily by phonon resonances, limiting THz applications such as spectroscopy of emerging materials, imaging and detection, and biomedical characterization.
The magnetic fields of the solar system’s planets provide valuable insights into their interiors and can have dramatic consequences for the evolution of their atmospheres and interaction with the solar wind. However, we have little direct knowledge of magnetic fields in exoplanets. Here we present a method for detecting magnetic fields in the atmospheres of close-in exoplanets based on spectropolarimetric transit observations at the wavelength of the helium line at 1083 nm. This methodology has been successfully applied for exploring magnetic fields in solar coronal filaments. Strong absorption signatures (transit depths on the order of a few percent) in the 1083 nm line have recently been observed for several close-in exoplanets. We show that in the conditions in these escaping atmospheres, metastable helium atoms should be optically pumped by the starlight and, for field strengths more than a few × 10 -4 G, should align with the magnetic field. This results in linearly polarized absorption at 1083 nm that traces the field direction (the Hanle effect), which we explore by both analytic computation and the HAZEL numerical code. The linear polarization $\sqrt{{Q}^{2}+{U}^{2}}/I$ ranges from ~10 -3 in optimistic cases down to a few × 10 -5 for particularly unfavorable cases, with very weak dependence on field strength. The line-of-sight component of the field results in a slight circular polarization (the Zeeman effect), also reaching $V/I\sim \mathrm{few}\times {10}^{-5}({B}_{\parallel }/10\,{\rm{G}})$. We discuss the detectability of these signals with current (SPIRou) and future (Extremely Large Telescope) high-resolution infrared spectropolarimeters, and we briefly comment on possible sources of astrophysical contamination.
We are developing a polarized 3He target concept for use in high luminosity electron scattering experiments in the high magnetic field environment of Jefferson Lab's CLAS12 spectrometer. By combining recent advancements in metastability exchange optical pumping of 3He with cryogenic, double-cell target methods such as those used for the MIT-Bates 88-02 experiment, a target with polarization and gas density comparable to traditional, low-field polarized 3He targets can be reached within high magnetic fields. We have established a new 3He pumping system at JLab, and are preparing for our first tests exploring polarization performance versus magnetic field and gas pressure in a single cell before we move to the construction of a full, cryogenic, double-cell prototype target.
Driven magnetometer accurately measures the components of a low strength magnetic field in each of three mutually perpendicular directions. To accomplish this, it employs the principle of magnetic resonance in optically pumped rubidium vapor.
Eigenvalues for electron configurations of rare earth ions in yttrium-aluminum garnet by optically pumped lasers
Space radiation effects on gallium arsenide laser diodes and optically pumped lasers
Nuclear g factor ratio to electronic g factor in ground electronic state of free Rb 85 and Rb 87 using optical pumping
Rare earth iron garnets were used in experiments to determine the feasibility of optically pumping a magnetic material to effect the switching process. It was found that rare earth garnets are limited by an absorption edge, only terbium and dysprosium offer a possibility of pumping at energies below the conduction band edge.
Orientation of diamagnetic ground state Pb 207 atoms with nonzero orbital angular momentum by means of optical pumping and determination of nuclear moment
Population inversion in Cs133 ground state hyperfine levels, using CW GaAs laser at 77 K for optical pumping
The stability of Rb-87 optically pumped masers and Rb gas cells is examined. Descriptions are given of the technical procedures used in construction and the changes made to solve the problems encountered in the electronics of the systems.
The lifetimes and fine structure of He(-) were studied using time-of-flight techniques and quenching by a static axial magnetic field. Using level-crossing spectroscopy the hyperfine constants A and B and the lifetime of the 3 2P3/2 state of Li-7 were measured. Polarization of the Ru 7S level was created as a first step in determining the hyperfine structure of the alkali excited S state. The parametric interaction between light and microwaves in optically pumped Rb-87 vapor were investigated. Measurements and analyses of transitions in formaldehyde and its isotopic species and in the lowest two excited vibrational states of H2CO were also made, as well as of transitions in furan, pyrrole, formic acid, and cyanoacetylene. The Hanle effect was studied in the NO molecule, and RF oscillators were developed with flat, wideband output to observe excited state hyperfine transitions at zero field. Data was generated on the time-dependent behavior of photon echoes in ruby. Stimulated Raman scattering was studied in atomic Tl vapor. A Q switched, temperature-tuned ruby laser was developed which operates between 6934 and 6938 A. The frequency shift due to resonant interaction between identical radiating atoms was calculated.