Physics and Astronomy › Atomic and Molecular Physics, and Optics

Atomic and Subatomic Physics Research

Description

This cluster of papers focuses on advances in atomic magnetometry techniques, including the use of atomic magnetometers for magnetic resonance imaging with hyperpolarized gases, measurement of neutron lifetime, exploration of quantum states, and applications in magnetoencephalography and lung function imaging. The research also covers topics such as optical pumping, spin-exchange relaxation, and microfabricated devices for atomic sensing.

Keywords

Atomic Magnetometer; Magnetic Resonance Imaging; Hyperpolarized Gases; Neutron Lifetime Measurement; Quantum States; Magnetoencephalography; Lung Function Imaging; Optical Pumping; Spin-Exchange Relaxation; Microfabricated Devices

The representation of Fermi particles by two-component Pauli spinors satisfying a second order differential equation and the suggestion that in $\ensuremath{\beta}$ decay these spinors act without gradient couplings leads to … The representation of Fermi particles by two-component Pauli spinors satisfying a second order differential equation and the suggestion that in $\ensuremath{\beta}$ decay these spinors act without gradient couplings leads to an essentially unique weak four-fermion coupling. It is equivalent to equal amounts of vector and axial vector coupling with two-component neutrinos and conservation of leptons. (The relative sign is not determined theoretically.) It is taken to be "universal"; the lifetime of the $\ensuremath{\mu}$ agrees to within the experimental errors of 2%. The vector part of the coupling is, by analogy with electric charge, assumed to be not renormalized by virtual mesons. This requires, for example, that pions are also "charged" in the sense that there is a direct interaction in which, say, a ${\ensuremath{\pi}}^{0}$ goes to ${\ensuremath{\pi}}^{\ensuremath{-}}$ and an electron goes to a neutrino. The weak decays of strange particles will result qualitatively if the universality is extended to include a coupling involving a $\ensuremath{\Lambda}$ or $\ensuremath{\Sigma}$ fermion. Parity is then not conserved even for those decays like $K\ensuremath{\rightarrow}2\ensuremath{\pi} or 3\ensuremath{\pi}$ which involve no neutrinos. The theory is at variance with the measured angular correlation of electron and neutrino in ${\mathrm{He}}^{6}$, and with the fact that fewer than ${10}^{\ensuremath{-}4}$ pion decay into electron and neutrino.
The first two terms in a frequency expansion of the photon scattering amplitude are considered in the case where the scatterer is a particle of spin \textonehalf{}. It is shown … The first two terms in a frequency expansion of the photon scattering amplitude are considered in the case where the scatterer is a particle of spin \textonehalf{}. It is shown that an exact calculation in quantum field theory gives results identical with those obtained by classical methods or else by use of the Dirac equation with an anomalous Pauli moment. The results depend only on the charge, mass, and magnetic moment of the scatterer. In the case of the proton, the second term, arising from scattering by the magnetic moment, appears to be negligible in comparison with effects due to Thomson and Rayleigh scattering.
Current theories of the large cross sections of slow neutrons are contradicted by frequent absence of strong scattering in good absorbers as well as the existence of resonance bands. These … Current theories of the large cross sections of slow neutrons are contradicted by frequent absence of strong scattering in good absorbers as well as the existence of resonance bands. These facts can be accounted for by supposing that in addition to the usual effect there exist transitions to virtual excitation states of the nucleus in which not only the captured neutron but, in addition to this, one of the particles of the original nucleus is in an excited state. Radiation damping due to the emission of $\ensuremath{\gamma}$-rays broadens the resonance and reduces scattering in comparison with absorption by a large factor. Interaction with the nucleus is most probable through the $s$ part of the incident wave. The higher the resonance region, the smaller will be the absorption. For a resonance region at 50 volts the cross section at resonance may be as high as ${10}^{\ensuremath{-}19}$ ${\mathrm{cm}}^{2}$ and 0.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}20}$ ${\mathrm{cm}}^{2}$ at thermal energy. The estimated probability of having a nuclear level in the low energy region is sufficiently high to make the explanation reasonable. Temperature effects and absorption of filtered radiation point to the existence of bands which fit in with the present theory.
Fabrication techniques usually applied to microelectromechanical systems (MEMS) are used to reduce the size and operating power of the core physics assembly of an atomic clock. With a volume of … Fabrication techniques usually applied to microelectromechanical systems (MEMS) are used to reduce the size and operating power of the core physics assembly of an atomic clock. With a volume of 9.5mm3, a fractional frequency instability of 2.5×10−10 at 1s of integration, and dissipating less than 75mW of power, the device has the potential to bring atomically precise timing to hand-held, battery-operated devices. In addition, the design and fabrication process allows for wafer-level assembly of the structures, enabling low-cost mass-production of thousands of identical units with the same process sequence, and easy integration with other electronics.
Baz' and Rybachenko have proposed the use of the Larmor precession as a clock to measure the time it takes a particle to traverse a barrier. An applied magnetic field … Baz' and Rybachenko have proposed the use of the Larmor precession as a clock to measure the time it takes a particle to traverse a barrier. An applied magnetic field is confined to the barrier. The spin of the incident particles is polarized perpendicular to this field. The extent of the Larmor precession occurring during transmission is used as a measurement of the time spent traversing the barrier. However, the particles tunneling through an opaque barrier also acquire a spin component parallel to the field since particles with spin parallel to the field have a higher transmission probability than particles with spin antiparallel to the field. Similar effects are actually used to polarize electrons and neutrons. An interpretation of this experiment compares the results with an approach which determines the traversal time by studying transmission of particles through a time-modulated barrier. This leads to three characteristic times describing the interaction of particles with a barrier. A dwell time measures the average time interval during which a particle interacts with the barrier whether it is reflected or transmitted at the end of its stay, a traversal time measures the time interval during which a particle interacts with the barrier if it is finally transmitted, and a reflection time measures the interaction time of a reflected particle.
We have built a high-speed velocimeter that has proven to be compact, simple to operate, and fairly inexpensive. This diagnostic is assembled using off-the-shelf components developed for the telecommunications industry. … We have built a high-speed velocimeter that has proven to be compact, simple to operate, and fairly inexpensive. This diagnostic is assembled using off-the-shelf components developed for the telecommunications industry. The main components are fiber lasers, high-bandwidth high-sample-rate digitizers, and fiber optic circulators. The laser is a 2W cw fiber laser operating at 1550nm. The digitizers have 8GHz bandwidth and can digitize four channels simultaneously at 20GS∕s. The maximum velocity of this system is ∼5000m∕s and is limited by the bandwidth of the electrical components. For most applications, the recorded beat frequency is analyzed using Fourier transform methods, which determine the time response of the final velocity time history. Using the Fourier transform method of analysis allows multiple velocities to be observed simultaneously. We have obtained high-quality data on many experiments such as explosively driven surfaces and gas gun assemblies.
We squeeze unconditionally the collective spin of a dilute ensemble of laser-cooled rubidium-87 atoms using their interaction with a driven optical resonator. The shape and size of the resulting spin … We squeeze unconditionally the collective spin of a dilute ensemble of laser-cooled rubidium-87 atoms using their interaction with a driven optical resonator. The shape and size of the resulting spin uncertainty region are well described by a simple analytical model [M.H.S., I.D.L., V.V., arXiv:0911.3936] through two orders of magnitude in the effective interaction strength, without free parameters. We deterministically generate states with up to 5.6(6) dB of metrologically relevant spin squeezing on the canonical rubidium-87 hyperfine clock transition.
The Arthurs and Dalgarno space-fixed (SF) axes formulation of the quantum theory of atom-diatom scattering is compared with the body-fixed (BF) axes formulation of Curtiss using consistent notation to facilitate … The Arthurs and Dalgarno space-fixed (SF) axes formulation of the quantum theory of atom-diatom scattering is compared with the body-fixed (BF) axes formulation of Curtiss using consistent notation to facilitate the comparison. While equivalent, the two theories are not always equally convenient. When rotation is treated in a sudden approximation, the BF formulation has a tremendous conceptual and computational advantage: It allows an infinite-order sudden approximation, independent of the form of the potential energy, which should be very helpful in vibrationally inelastic and reactive scattering problems. Also, a rapid procedure for calculating WKB phase shifts is presented.
Received 1 January 1911DOI:https://doi.org/10.1103/PhysRevSeriesI.32.492Š1911 American Physical Society Received 1 January 1911DOI:https://doi.org/10.1103/PhysRevSeriesI.32.492Š1911 American Physical Society
Spin-exchange optical pumping of mixtures of alkali-metal vapors and noble gases can be used to efficiently polarize the nuclei of the noble-gas atoms. Liters of noble gases at standard temperature … Spin-exchange optical pumping of mixtures of alkali-metal vapors and noble gases can be used to efficiently polarize the nuclei of the noble-gas atoms. Liters of noble gases at standard temperature and pressure and with nuclear spin polarizations of several tens of percent are now used in many applications. The authors describe the basic phenomena that govern the spin-exchange process and review the physics of angular momentum transfer and loss in optical pumping and spin-exchange collisions.
A new magneto-optical trap is demonstrated which confines atoms predominantly in a ``dark'' hyperfine level, that does not interact with the trapping light. This leads to much higher atomic densities … A new magneto-optical trap is demonstrated which confines atoms predominantly in a ``dark'' hyperfine level, that does not interact with the trapping light. This leads to much higher atomic densities as repulsive forces between atoms due to rescattered radiation are reduced and trap loss due to excited-state collisions is diminished. In such a trap, more than ${10}^{10}$ sodium atoms have been confined to densities approaching ${10}^{12}$ atoms ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$.
The nonadiabatic transitions which a system with angular momentum $J$ makes in a magnetic field which is rotating about an axis inclined with respect to the field are calculated. It … The nonadiabatic transitions which a system with angular momentum $J$ makes in a magnetic field which is rotating about an axis inclined with respect to the field are calculated. It is shown that the effects depend on the sign of the magnetic moment of the system. We therefore have an absolute method for measuring the sign and magnitude of the moment of any system. Applications to the magnetic moment of the neutron, the rotational moment of molecules, and the nuclear moment of atoms with no extra-nuclear angular momentum are discussed.
A new method is developed for integrating coupled differential equations arising in bound state and scattering problems in quantum mechanics. The wavefunctions are easily constructed in piecewise analytic form, to … A new method is developed for integrating coupled differential equations arising in bound state and scattering problems in quantum mechanics. The wavefunctions are easily constructed in piecewise analytic form, to any prescribed accuracy.
We have used a neutron interferometer to observe the quantum-mechanical phase shift of neutrons caused by their interaction with Earth's gravitational field.Received 14 April 1975DOI:https://doi.org/10.1103/PhysRevLett.34.1472Š1975 American Physical Society We have used a neutron interferometer to observe the quantum-mechanical phase shift of neutrons caused by their interaction with Earth's gravitational field.Received 14 April 1975DOI:https://doi.org/10.1103/PhysRevLett.34.1472Š1975 American Physical Society
Zener has suggested a type of interaction between the spins of magnetic ions which he named "double exchange." This occurs indirectly by means of spin coupling to mobile electrons which … Zener has suggested a type of interaction between the spins of magnetic ions which he named "double exchange." This occurs indirectly by means of spin coupling to mobile electrons which travel from one ion to the next. We have calculated this interaction for a pair of ions with general spin $S$ and with general transfer integral, $b$, and internal exchange integral $J$.One result is that while the states of large total spin have both the highest and lowest energies, their average energy is the same as for the states of low total spin. This should be applicable in the high-temperature expansion of the susceptibility, and if it is, indicates that the high-temperature Curie-Weiss constant $\ensuremath{\theta}$ should be zero, and $\frac{1}{\ensuremath{\chi}}$ vs $T$ a curved line. This is surprising in view of the fact that the manganites, in which double exchange has been presumed to be the interaction mechanism, obey a fairly good Curie-Weiss law.The results can be approximated rather well by a simple semiclassical model in which the spins of the ion cores are treated classically. This model is capable of rather easy extension to the problem of the whole crystal, but the resulting mathematical problem is not easily solved except in special circumstances, e.g., periodic disturbances (spin waves).
The measurements of the hyperfine structure of free, naturally occurring, alkali atoms are reviewed. The experimental methods are discussed, as are the relationships between hyperfine structure data and other atomic … The measurements of the hyperfine structure of free, naturally occurring, alkali atoms are reviewed. The experimental methods are discussed, as are the relationships between hyperfine structure data and other atomic constants.
Alkali-metal magnetometers compete with SQUID detectors as the most sensitive magnetic field sensors. Their sensitivity is limited by relaxation due to spin-exchange collisions. We demonstrate a K magnetometer in which … Alkali-metal magnetometers compete with SQUID detectors as the most sensitive magnetic field sensors. Their sensitivity is limited by relaxation due to spin-exchange collisions. We demonstrate a K magnetometer in which spin-exchange relaxation is completely eliminated by operating at high K density and low magnetic field. Direct measurements of the signal-to-noise ratio give a magnetometer sensitivity of $10\text{ }\mathrm{f}\mathrm{T}\text{ }\mathrm{H}{\mathrm{z}}^{\mathrm{\ensuremath{-}}\mathrm{1}\mathrm{/}\mathrm{2}}$, limited by magnetic noise produced by Johnson currents in the magnetic shields. We extend a previous theoretical analysis of spin exchange in low magnetic fields to arbitrary spin polarizations and estimate the shot-noise limit of the magnetometer to be $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}\text{ }\mathrm{T}\text{ }\mathrm{H}{\mathrm{z}}^{\mathrm{\ensuremath{-}}\mathrm{1}\mathrm{/}\mathrm{2}}$.
Momentum-transfer cross sections for electrons in He, Ar, Kr, and Xe are obtained from a comparison of theoretical and experimental values of the drift velocities and of the ratio of … Momentum-transfer cross sections for electrons in He, Ar, Kr, and Xe are obtained from a comparison of theoretical and experimental values of the drift velocities and of the ratio of the diffusion coefficient to the mobility coefficient for electrons in these gases. The theoretical transport coefficients are obtained by calculating accurate electron-energy distribution functions for energies below excitation using an assumed energy-dependent momentum-transfer cross section. The resulting theoretical values are compared with the available experimental data and adjustments made in the assumed cross sections until good agreement is obtained. The final momentum cross sections for helium is 5.0\ifmmode\pm\else\textpm\fi{}0.1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{2}$ for an electron energy of 5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}3}$ eV and rises to 6.6\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{2}$ for energies near 1 eV. The cross sections obtained for Ar, Kr, and Xe decrease from 6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}16}$, 2.6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}15}$, and ${10}^{\ensuremath{-}14}$ ${\mathrm{cm}}^{2}$, respectively, at 0.01 eV to minimum values of 1.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$ at 0.3 eV for Ar, 5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$ at 0.65 eV for Kr, and 1.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{2}$ at 0.6 eV for Xe. The agreement of the very-low-energy results with the effective-range theory of electron scattering is good.
Experiments on slow neutrons, and theoretical considerations of Bohr have shown that heavy nuclei possess an enormous number of energy levels which are very closely spaced if the nucleus is … Experiments on slow neutrons, and theoretical considerations of Bohr have shown that heavy nuclei possess an enormous number of energy levels which are very closely spaced if the nucleus is highly excited. A crude method is suggested for calculating the spacing between these levels. The method is statistical: The individual nuclear particles are supposed to move in a simple potential hole, and the energy of the complete nucleus is supposed to be the sum of the energies of the individual particles. A critical discussion of these assumptions is given in section 5. The problem then reduces itself to the calculation of the "entropy" of a Fermi gas containing a given number of particles $A$ and having a given excitation energy $Q$ above the zero point energy of the Fermi gas (cf. section 2 and 3). This calculation gives the total number of levels of the complete nucleus in a given energy interval irrespective of the angular momentum, which will, for most of the levels, be very large. For the theory of neutron capture, it is necessary to calculate the density of nuclear levels with a given angular momentum $I$ (section 4). The spacing of nuclear levels is found to depend on the product of the mass number $A$ and the excitation energy $Q$ of the nucleus, and to be roughly given by ${\ensuremath{\Delta}=\frac{4.1\ifmmode\cdot\else\textperiodcentered\fi{}{10}^{6}{x}^{4}{e}^{\ensuremath{-}x}}{(2I+1)} \mathrm{volts}}{x,=\frac{{(\mathrm{AQ})}^{\frac{1}{2}}}{2.20},}$ $Q$ being expressed in MV and $I$ being the nuclear spin. For the capture of slow neutrons by nuclei of medium weight ($A$ around 100), $\ensuremath{\Delta}$ is of the order 50 to 500 volts. The spacing between adjacent levels decreases rapidly with increasing atomic weight. For given atomic weight, the spacing of the nuclear levels responsible for neutron capture is wider if the capture leads to the formation of a radioactive nucleus than if a stable nucleus is formed. This explains the experimental fact that only moderately large cross sections are found for the capture of thermal neutrons leading to radioactive nuclei while the very largest cross sections are all connected with the formation of stable nuclei. The dependence of the spacing on various factors is discussed (section 6); the results seem to be in qualitative agreement with experiment.
Received 10 November 1931DOI:https://doi.org/10.1103/PhysRev.38.2082.2Š1931 American Physical Society Received 10 November 1931DOI:https://doi.org/10.1103/PhysRev.38.2082.2Š1931 American Physical Society
A measurement using a one-electron quantum cyclotron gives the electron magnetic moment in Bohr magnetons, g/2 = 1.001 159 652 180 73 (28) [0.28 ppt], with an uncertainty 2.7 and … A measurement using a one-electron quantum cyclotron gives the electron magnetic moment in Bohr magnetons, g/2 = 1.001 159 652 180 73 (28) [0.28 ppt], with an uncertainty 2.7 and 15 times smaller than for previous measurements in 2006 and 1987. The electron is used as a magnetometer to allow lineshape statistics to accumulate, and its spontaneous emission rate determines the correction for its interaction with a cylindrical trap cavity. The new measurement and QED theory determine the fine structure constant, with alpha^{-1} = 137.035 999 084 (51) [0.37 ppb], and an uncertainty 20 times smaller than for any independent determination of alpha.
The reliability of biomagnetic measurements is traditionally challenged by external interference signals, movement artifacts, and comparison problems caused by different positions of the subjects or different sensor configurations. The Signal … The reliability of biomagnetic measurements is traditionally challenged by external interference signals, movement artifacts, and comparison problems caused by different positions of the subjects or different sensor configurations. The Signal Space Separation method (SSS) idealizes magnetic multichannel signals by transforming them into device-independent idealized channels representing the measured data in uncorrelated form. The transformation has separate components for the biomagnetic and external interference signals, and thus, the biomagnetic signals can be reconstructed simply by leaving out the contribution of the external interference. The foundation of SSS is a basis spanning all multichannel signals of magnetic origin. It is based on Maxwell's equations and the geometry of the sensor array only, with the assumption that the sensors are located in a current free volume. SSS is demonstrated to provide suppression of external interference signals, standardization of different positions of the subject, standardization of different sensor configurations, compensation for distortions caused by movement of the subject (even a subject containing magnetic impurities), suppression of sporadic sensor artifacts, a tool for fine calibration of the device, extraction of biomagnetic DC fields, and an aid for realizing an active compensation system. Thus, SSS removes many limitations of traditional biomagnetic measurements.
An experimental search for an electric dipole moment (EDM) of the neutron has been carried out at the Institut Laue-Langevin, Grenoble. Spurious signals from magnetic-field fluctuations were reduced to insignificance … An experimental search for an electric dipole moment (EDM) of the neutron has been carried out at the Institut Laue-Langevin, Grenoble. Spurious signals from magnetic-field fluctuations were reduced to insignificance by the use of a cohabiting atomic-mercury magnetometer. Systematic uncertainties, including geometric-phase-induced false EDMs, have been carefully studied. The results may be interpreted as an upper limit on the neutron EDM of $|{d}_{n}|<2.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}26}e\text{ }\text{ }\mathrm{cm}$ (90% C.L.).
It is pointed out that the usual principle of invariance under isotopic spin rotation is not consistant with the concept of localized fields. The possibility is explored of having invariance … It is pointed out that the usual principle of invariance under isotopic spin rotation is not consistant with the concept of localized fields. The possibility is explored of having invariance under local isotopic spin rotations. This leads to formulating a principle of isotopic gauge invariance and the existence of a b field which has the same relation to the isotopic spin that the electromagnetic field has to the electric charge. The b field satisfies nonlinear differential equations. The quanta of the b field are particles with spin unity, isotopic spin unity, and electric charge $\ifmmode\pm\else\textpm\fi{}e$ or zero.
Laboratory optical atomic clocks achieve remarkable accuracy (now counted to 18 digits or more), opening possibilities for exploring fundamental physics and enabling new measurements.However, their size and the use of … Laboratory optical atomic clocks achieve remarkable accuracy (now counted to 18 digits or more), opening possibilities for exploring fundamental physics and enabling new measurements.However, their size and the use of bulk components prevent them from being more widely adopted in applications that require precision timing.By leveraging silicon-chip photonics for integration and to reduce component size and complexity, we demonstrate a compact optical-clock architecture.Here a semiconductor laser is stabilized to an optical transition in a microfabricated rubidium vapor cell, and a pair of interlocked Kerr-microresonator frequency combs provide fully coherent optical division of the clock laser to generate an electronic 22 GHz clock signal with a fractional frequency instability of one part in 10 13 .These results demonstrate key concepts of how to use silicon-chip devices in future portable and ultraprecise optical clocks.
We present the result of an experiment to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields … We present the result of an experiment to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ultracold neutrons (UCN). Our measurement stands in the long history of EDM experiments probing physics violating time reversal invariance. The salient features of this experiment were the use of a Hg-199 co-magnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic field changes. The statistical analysis was performed on blinded datasets by two separate groups while the estimation of systematic effects profited from an unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is $d_{\rm n} = (0.0\pm1.1_{\rm stat}\pm0.2_{\rm sys})\times10^{-26}e\,{\rm cm}$.
Optical pumping of ground-state and metastable atoms and ions is reviewed. We present a critical survey of the literature on pumping mechanisms, light propagation, relaxation mechanisms, spin exchange, and experimental … Optical pumping of ground-state and metastable atoms and ions is reviewed. We present a critical survey of the literature on pumping mechanisms, light propagation, relaxation mechanisms, spin exchange, and experimental details on the various atomic species which have been successfully pumped.
Detecting photon echoes from superconducting Higgs modes is challenging due to the necessity of preserving and retrieving phase coherence encoded in multiple Higgs and quasiparticle (QP) excitations. Here, we demonstrate … Detecting photon echoes from superconducting Higgs modes is challenging due to the necessity of preserving and retrieving phase coherence encoded in multiple Higgs and quasiparticle (QP) excitations. Here, we demonstrate the emergence of a Higgs echo in niobium superconductors. This approach disentangles unique quantum pathways involving the Higgs mode and QP excitations. Using Higgs echo spectroscopy, we also uncover unconventional echo formation caused by inhomogeneous broadening and "soft" QP bands, which dynamically evolve under terahertz (THz) driving. Specifically, THz pulse pairs modulate the superconducting gap, imprinting coherence and forming a temporal "Higgs grating." This grating produces echoes with distinctive characteristics: (i) echo rephasing spectral peaks at superconducting gap frequencies, (ii) asymmetric echo formation delays unlike those observed in atoms or semiconductors, and (iii) negative-time echo signals stemming from Higgs-QP anharmonic interactions. Combined with advanced time-frequency analysis, these findings distinguish Higgs from QP responses and clarify their intricate interactions in THz-driven superconductivity.
Lei Cong , Wei Ji , Pavel Fadeev +7 more | Reviews of Modern Physics
The Light-only Liquid Xenon experiment (LoLX) employs a small-scale detector equipped with 96 Hamamatsu VUV4 silicon photomultipliers (SiPMs) submerged in 5 kg of liquid xenon (LXe) to perform characterization measurements … The Light-only Liquid Xenon experiment (LoLX) employs a small-scale detector equipped with 96 Hamamatsu VUV4 silicon photomultipliers (SiPMs) submerged in 5 kg of liquid xenon (LXe) to perform characterization measurements of light production, transport and detection in xenon. In this work, we perform a novel measurement of the "external cross-talk" (ExCT) of SiPMs, where photons produced in the avalanche escape the device and produce correlated signals on other SiPMs. SiPMs are the photodetector technology of choice for next generation rare-event search experiments; understanding the sources and effects of correlated noise in SiPMs is critical for producing accurate estimates of detector performance and sensitivity projections. We measure the probability to observe ExCT through timing correlation of detected photons in low-light conditions within LoLX. Measurements of SiPM ExCT are detector dependent; thus the ExCT process is simulated and modelled using the Geant4 framework. Utilizing simulations, we determine the average transport and detection efficiency for ExCT photons within LoLX, a necessary input to extract the true ExCT probability and detector independent photon emission intensity. For an applied overvoltage of 4 V and 5 V, we measure a mean number of photons emitted into LXe per avalanche of 0.5-0.2+0.3 and 0.6-0.2+0.3, respectively. Using an optical model to describe photon transmission through the SiPM surface, this corresponds to an estimated photon yield inside the bulk silicon of 20-9+11 and 25-9+12 photons per avalanche. The relative increase in intensity of SiPM ExCT emission between 4 and 5 V is consistent with expectation for the linear increase of gain with respect to overvoltage.
Abstract We present the design and performance of a four-phased radiofrequency (RF) carpet system for ion transport between 200–600 mbar, significantly higher than previously demonstrated RF carpet applications. The RF … Abstract We present the design and performance of a four-phased radiofrequency (RF) carpet system for ion transport between 200–600 mbar, significantly higher than previously demonstrated RF carpet applications. The RF carpet, designed with a 160 $$\upmu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> m pitch, is applied to the lateral collection of ions in xenon at pressures up to 600 mbar. We demonstrate transport efficiency of caesium ions across varying pressures, and compare with microscopic simulations made in the SIMION package. The novel use of an N-phased RF carpet can achieve ion levitation and controlled lateral motion in a denser environment than is typical for RF ion transport in gases. This feature makes such carpets strong candidates for ion transport to single ion sensors envisaged for future neutrinoless double-beta decay experiments in xenon gas.
In recent years, new technologies have been developed to study epilepsy, in particular optically pumped magnetometers. In this editorial, I review some recent work on on-scalp magnetoencephalography in epilepsy and … In recent years, new technologies have been developed to study epilepsy, in particular optically pumped magnetometers. In this editorial, I review some recent work on on-scalp magnetoencephalography in epilepsy and ponder the question: is it science fiction or reality? I specifically develop two aspects of my point of view on advances and challenges in brain investigation, one from the researcher’s side and one from the clinician’s.
Abstract Objective: The reliability of biomagnetic measurements is improved by data processing techniques like the signal space separation (SSS) method, which transforms multichannel signals into device-independent channels with separate components … Abstract Objective: The reliability of biomagnetic measurements is improved by data processing techniques like the signal space separation (SSS) method, which transforms multichannel signals into device-independent channels with separate components for internal biomagnetic and external interference signals based on sensor geometry. Newer on-scalp sensors, such as optically-pumped magnetometers (OPM), have recently been deployed in MEG systems, bringing a need for refined SSS variants to capture the potentially improved spatial resolution provided by the on-scalp sensors. Standard single-origin SSS may fail to capture the full brain-space when the sensors are on scalp. In this paper, we propose potential solutions to this problem including novel multi-origin SSS (mSSS). With multiple optimized origins and radii used together, the basis can span the brain-space without encroaching on the sensor space. Other adaptations to SSS include vector spheroidal harmonics, which create signal space expansions using ellipsoidal geometry to model the brain-space. This adaptation is further modified to combine an interior spheroidal with exterior single-SSS. &amp;#xD;Approach: Focusing on two-origin mSSS, the spheroidal constructions and the single-origin SSS are investigated with simulated data from an internal current dipole source coupled with an external interference signal with geometry from the 432-channel Kernel Flux OPM system, the 306-channel MEGIN/Elekta Neuromag SQUID system, and the 192-Channel Triaxial QuSpin OPM system. Finally, each variant is used to process collected data including auditory evoked data measured at the University of Washington with the Kernel Flux OPM system, previously recorded empty-room data collected in a lightly-shielded magnetically shielded room (MSR) with 192-channel third generation triaxial QuSpin Zero Field Magnetometers, and publicly available single-subject audiovisual data collected with an 86-Channel dual-axis QuSpin OPM system at the University College London (UCL). &amp;#xD;Main Results: The mSSS method has comparable or better stability to the SSS method in all sensor geometries and reconstructs interior simulated signals while successfully suppressing exterior interference, and performs better in simulated cases with variably placed on-scalp MEG systems. Additionally, results with Kernel and QuSpin data show the mSSS basis provides a lower noise floor than other SSS variants and had the best performance with on-scalp systems, even with low-channel-count OPM systems.&amp;#xD;Significance: With on-scalp MEG systems becoming more widely available, the MEG community needs updated data analysis techniques. mSSS is a straightforward and robust modification to the SSS method which functions for novel on-scalp sensor systems without needing drastic modification to the underlying mathematical method. &amp;#xD;
Abstract Magnetomyography (MMG) can be used as a contactless modality to study the neuromuscular system. On the one hand, being contactless is a practical advantage as there is no need … Abstract Magnetomyography (MMG) can be used as a contactless modality to study the neuromuscular system. On the one hand, being contactless is a practical advantage as there is no need to prepare skin or attach electrodes as in electromyography (EMG). On the other hand, it is also a disadvantage because the magnetic field decays with increasing distance. However, the effect of sensor-to-source distance in MMG has not been systematically studied. Comparative in vivo and in silico experiments of the effect of sensor-to-source distance were performed. In vivo, muscle activity was recorded using simultaneous surface EMG and one triaxial optically pumped magnetometer (OPM). For the simulations, an established multiscale muscle model was used to predict how distance affects the signal-to-noise ratio (SNR) and the signal’s spectral content. Given an environmental noise level of 0.5–1 pT root-mean-square (RMS) from 10 to 350 Hz, it was impossible to robustly detect muscle activity of one finger flexor muscle beyond a distance of two centimeters using OPM technology. In silico experiments showed a high SNR between 8 and 29 for MMG at 0.5 cm distance. Increasing the distance increases the MMG’s median frequency content. The simulations uncovered that this is due to the effect of noise. For distances greater than two centimeters, measuring MMG of voluntary contractions in medium-sized muscles with current OPM technology and conventional magnetic shielding cannot be recommended.
We present a review of the current experimental and theoretical understanding of electron transport in noble liquids. Special attention is given to recent measurements that coincide with the development of … We present a review of the current experimental and theoretical understanding of electron transport in noble liquids. Special attention is given to recent measurements that coincide with the development of time projection chambers using liquid xenon and argon as detector media. To enable transparent benchmarking of simulations and to facilitate the comparison between early studies and modern time projection chamber data, we introduce a new open-access database of electron mobility and diffusion measurements. In particular, we emphasize the transition to large-scale detector designs which incorporate extended drift distances alongside improved purity control and field uniformity. On the theoretical side, we contrast empirical transport models with ab initio approaches, highlighting our recent efforts to incorporate low-energy, liquid-specific scattering phenomena, including coherent scattering, polarization screening, and bulk potential modifications. While elastic transport has seen substantial theoretical progress, inelastic processes in liquids, including ionization, exciton formation and interband transitions, remain poorly understood due to the lack of experimental cross sections and validated models. We also discuss the applications and challenges of modeling scintillation, doped and mixture-liquid targets, and gas–liquid interface behavior, all of which are critical for the design and optimization of next-generation detectors.
This manuscript presents integrated field, petrographic, microstructural, and thermodynamic modeling results documenting the high-pressure channelization of H2 and the rheological impact of its reactivity with carbonate (dolomite and calcite)-rich rocks … This manuscript presents integrated field, petrographic, microstructural, and thermodynamic modeling results documenting the high-pressure channelization of H2 and the rheological impact of its reactivity with carbonate (dolomite and calcite)-rich rocks along a serpentinite-hosted shear zone from Alpine Corsica (France). Microstructures within the carbonates attest to the occurrence of a deformation continuum, evolving from initial brittle fracturing to strain localization by viscous deformation. Raman spectra of fluid inclusions within the carbonates reveal the circulation of H2 and CH4 at all stages of the microstructural evolution, the latter interpreted to be the result of H2-carbonate interactions. Thermodynamic models suggest that carbonate phase stability at pressure-temperature conditions representative of a subduction setting is modified by the presence of H2, with dolomite being progressively replaced by calcite + graphite + magnetite with increasing H2 in the system. An initial phase of overpressure created by H2-rich fluids led to the brecciation of dolomite, creating a fine-grained aggregate, which facilitated a switch to a semi-brittle mode of deformation and created high-permeability pathways for subsequent phases of H2 infiltration. Subsequent phases of infiltration of H2 were accompanied by transformation of dolomite to calcite, the degree of transformation dependent upon the efficiency of H2 percolation. Calcite, being rheologically weaker than dolomite at these temperatures, underwent viscous flow in domains of extensive dolomite reduction, whereas adjacent dolomite-rich domains contain minimal imprints of extensive plastic deformation. Our results demonstrate extensive fossilized H2-carbonate reactivity and show that the infiltration of H2-rich fluids strongly affects the rheology of carbonates by inducing reactivity and phase transitions.
Abstract Implementing multifunctional characteristics in a metallo‐supramolecular system with reversible stimuli‐induced response is a significant challenge. In this study, a simple, readily available macrocyclic Nd(III) complex [Nd L (CF 3 … Abstract Implementing multifunctional characteristics in a metallo‐supramolecular system with reversible stimuli‐induced response is a significant challenge. In this study, a simple, readily available macrocyclic Nd(III) complex [Nd L (CF 3 SO 3 ) 3 ] ( 1 ) exhibits tunable emission from the lanthanide center, which can be modulated by temperature and pressure. Within phase α at 1.5 GPa the onset of negative linear compressibility (NLC) along axis a takes place. At 3.0 GPa, single‐crystal X‐ray diffraction reveals the CF 3 SO 3 − ion ordering, inducing a non‐centrosymmetric phase β with modified material properties. Phase α shows strong pressure‐induced absorption and emission changes, suitable for precise, temperature‐independent luminescent manometry, with an emission line shift of Δ λ /Δ p = 2.85 nm GPa −1 in the NIR range. The designed optical sensor also enables remote temperature monitoring (15–460 K) through a pressure‐independent band intensity ratio of Nd(III) Stark components. Finally, field‐induced slow relaxation of magnetization is observed and analyzed using both standard fitting procedures and alternative approach that accounts for the influence of local vibration modes. This unique coexistence of these behaviors mark a significant step toward creating multifunctional supramolecular platforms, easily extendable to other systems with tunable properties.
Blood oxygen level-dependent functional magnetic resonance imaging (fMRI) is a widely used, non-invasive method to assess brain hemodynamics. Resting-state fMRI (rsfMRI) estimates functional connectivity (FC) by measuring correlations between the … Blood oxygen level-dependent functional magnetic resonance imaging (fMRI) is a widely used, non-invasive method to assess brain hemodynamics. Resting-state fMRI (rsfMRI) estimates functional connectivity (FC) by measuring correlations between the time courses of different brain regions. However, the reliability of rsfMRI FC is fundamentally compromised by statistical artifacts arising from signal cyclicity, autocorrelation, and preprocessing-induced distortions. We discuss how standard rsfMRI preprocessing -particularly the widely used band-pass filters such as 0.009-0.08 Hz and 0.01-0.10 Hz- introduce biases that increase correlation estimates between independent time series. Additionally, filtering without appropriate downsampling further distorts correlation coefficients, inflating statistical significance and increasing the risk of false positives. Under these conditions, commonly used multiple comparison corrections fail to fully control Type I errors, with up to 50-60% of detected correlations in white noise signals remaining significant after correction depending on the sampling rate, filter and duration. To mitigate these biases, we recommend adjusting sampling rates to align with the analyzed frequency band and employing surrogate data methods that better account for the statistical properties of rsfMRI signals and reduce autocorrelation-driven false positives. Additionally, we show that structured brain states-such as epilepsy and anesthesia-induced burst suppression-impose low-frequency neural activity that further amplifies these biases, distorting FC estimates. These findings indicate that accepted rsfMRI preprocessing pipelines systematically amplify spurious correlations and call for an improved statistical framework. This framework must explicitly account for autocorrelation, cyclicity, and multiple comparison biases, while excluding or correcting for structured neural activity that further distorts connectivity estimates.
Abstract X‐ray imaging and detection technologies based on scintillators are extensively utilized in both medical diagnosis and industrial nondestructive inspection. However, traditional rigid planar scintillation screens are susceptible to vignetting … Abstract X‐ray imaging and detection technologies based on scintillators are extensively utilized in both medical diagnosis and industrial nondestructive inspection. However, traditional rigid planar scintillation screens are susceptible to vignetting and distortion problems because of the inhomogeneity of X‐ray dose distribution. Flexible scintillation screens based on highly efficient metal‐based halides can effectively solve the above‐mentioned problems. In this work, a series of novel 0D Mn(II)‐based halides ((C 5 H 5 N) 2 MnBr 4 , (C 7 H 10 N) 2 MnBr 4 , (C 8 H 12 N) 2 MnBr 4 and (C 9 H 14 N) 2 MnBr 4 ) are designed and synthesized with small‐sized pyridine derivatives. Increasing the Mn–Mn distances through an alkyl chain modification strategy can effectively suppress the nonradiative transition and enhance exciton utilization, and thus their photoluminescence quantum yields (PLQYs) are significantly enhanced from 58.76% to 99.64%. (C 9 H 14 N) 2 MnBr 4 crystals with the highest PLQYs demonstrate superior X‐ray scintillation properties with a high relative light yield of 57739 photons MeV −1 , which is 2.6 times higher than the commercial scintillators (LuAG: Ce). Moreover, the flexible scintillation screen composed of (C 9 H 14 N) 2 MnBr 4 and thermoplastic polyurethane achieves a high resolution of 17.8 lp mm −1 and is successfully applied for nonplanar objects to reduce image distortion. This work not only provides a strategy for improving PLQYs of Mn(II)‐based halides but also demonstrates their practical applications for X‐ray imaging of non‐planar objects.
Compact cesium beam clocks are widely utilized in various applications. In contemporary commercial cesium clocks, two primary approaches are employed: the magnetically selected state scheme and the optical pumping scheme. … Compact cesium beam clocks are widely utilized in various applications. In contemporary commercial cesium clocks, two primary approaches are employed: the magnetically selected state scheme and the optical pumping scheme. Here, we propose a magneto-optically pumped cesium beam clock with a frequency stability of 2.3×10−12τ−1/2. In this scheme, the pumping light and state selection magnet are both used for the preparation of atomic states. In the magnetic field of the state selection magnet, the relationship between pumping efficiency and laser frequency, laser power, and laser position has been investigated. Eventually, we find a position that allows the laser to resonate with cyclic transition line |F=3⟩−|F′=2⟩ to pump almost all of the atoms |F=3⟩ to state |F=4⟩. Therefore, we can pump and detect atoms without the use of an AOM. This approach not only combines the advantage of low atomic velocity from the magnetically selected state scheme and the high atomic utilization efficiency from the optical pumping scheme but also simplifies the scheme of optically pumped cesium beam clock. In addition, this physical system can also facilitate the investigation of the shift in cesium atomic energy levels under strong magnetic fields.
We demonstrate coherent manipulation of the nuclear degrees of freedom of ultracold ground-state strontium-87 atoms, thus providing a toolkit for fully exploiting the corresponding large Hilbert space as a quantum … We demonstrate coherent manipulation of the nuclear degrees of freedom of ultracold ground-state strontium-87 atoms, thus providing a toolkit for fully exploiting the corresponding large Hilbert space as a quantum resource and for quantum simulation experiments with <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mrow><a:mrow><a:mi mathvariant="fraktur">s</a:mi></a:mrow><a:mi mathvariant="normal">u</a:mi></a:mrow></a:mrow><a:mo stretchy="false">(</a:mo><a:mi>N</a:mi><a:mo stretchy="false">)</a:mo></a:math>-symmetric matter. By controlling the resonance conditions of Raman transitions with a tensor light shift, we can perform rotations within a restricted Hilbert space of two isolated spin states among the <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mn>2</g:mn><g:mi>F</g:mi><g:mo>+</g:mo><g:mn>1</g:mn><g:mo>=</g:mo><g:mn>10</g:mn></g:math> possible states. These manipulations correspond to engineering unitary operations derived from generators of the <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mrow><i:mrow><i:mrow><i:mi mathvariant="fraktur">s</i:mi></i:mrow><i:mi mathvariant="normal">u</i:mi></i:mrow></i:mrow><i:mo stretchy="false">(</i:mo><i:mi>N</i:mi><i:mo stretchy="false">)</i:mo></i:math> algebra beyond what can be done by simple spin precession. We present Ramsey interferometers involving an isolated pair of Zeeman states with no measurable decoherence after 3 s. We also demonstrate that one can harness the large spin degrees of freedom as a qudit resource by implementing two interferometer schemes over four states. The first scheme senses in parallel multiple external fields acting on the atoms, and the second scheme simultaneously measures multiple observables of a collective atomic state—including noncommuting ones. Engineering unitary transformations of the large spin driven by other generators than the usual spin-<o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mi>F</o:mi></o:math> representation of the <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mrow><q:mrow><q:mrow><q:mi mathvariant="fraktur">s</q:mi></q:mrow><q:mi mathvariant="normal">u</q:mi></q:mrow></q:mrow><q:mo stretchy="false">(</q:mo><q:mn>2</q:mn><q:mo stretchy="false">)</q:mo></q:math> group offers new possibilities from the point of view of quantum metrology and quantum many-body physics, notably for the quantum simulation of large-spin <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"><w:mrow><w:mrow><w:mrow><w:mi mathvariant="fraktur">s</w:mi></w:mrow><w:mi mathvariant="normal">u</w:mi></w:mrow></w:mrow><w:mo stretchy="false">(</w:mo><w:mi>N</w:mi><w:mo stretchy="false">)</w:mo></w:math>-symmetric quantum magnetism with fermionic alkaline-earth atoms. Published by the American Physical Society 2025
NULL AUTHOR_ID | Physical review. D/Physical review. D.
Hyperinflation in chronic obstructive pulmonary disease (COPD) patients worsens on exertion/exercise when breathing frequency increases. Fast breathing, paced at 40 breaths per minute using a metronome (metronome-paced tachypnea, MPT), induces … Hyperinflation in chronic obstructive pulmonary disease (COPD) patients worsens on exertion/exercise when breathing frequency increases. Fast breathing, paced at 40 breaths per minute using a metronome (metronome-paced tachypnea, MPT), induces dynamic hyperinflation (DH) and can be performed during MRI. MPT in combination with phase-resolved functional lung (PREFUL) MRI can be used to assess stress-driven ventilation dynamics globally and regionally. A 90 s time series of one coronal slice centered to the trachea was acquired for PREFUL MRI during 60 s of resting tidal breathing (RTB) and 30 s of MPT at 40 breaths per minute in COPD patients and healthy volunteers. MPT detected DH in 12 out of 15 COPD patients and in 1 out of 15 healthy controls. During MPT, the global fractional ventilation decreased by 20% in healthy subjects (p = 0.01) and by 48% in COPD patients (p < 0.001). The end-expiratory lung area remained stable in healthy subjects and increased significantly by 7% in COPD patients over the course of MPT (p = 0.004). Younger, healthy volunteers adapted to increase breathing frequency by reducing tidal volume (global fractional ventilation), while older healthy volunteers showed less tidal volume reduction (p = 0.036). The MPT-induced change of regional ventilation homogeneity (flow volume loop cross-correlation, FVL-CCMPT/RTB) increased with age in healthy volunteers (p = 0.039) likely due to the development of compensatory dystelectasis in younger volunteers leading to reduced homogeneity during MPT. In the future, the MPT test during MR imaging may be used for COPD treatment analysis and disease monitoring.
Cu(I)‐based metal halides have gained significant interests as scintillators. However, their X‐ray luminescence efficiency is mainly determined by the competition between radiative organic ligands and nonradiative metal cluster‐centered charge transfer. … Cu(I)‐based metal halides have gained significant interests as scintillators. However, their X‐ray luminescence efficiency is mainly determined by the competition between radiative organic ligands and nonradiative metal cluster‐centered charge transfer. How to regulate their charge transfer pathways to enhance radiative emission is intractable challenge. Here, guided by coordination dynamics, we present a solvent mediation strategy to modulate coordination environments and intramolecular charge transfer of organic cuprous halides to achieve vibrant emissions. Mechanistic studies reveal that the coordinated clusters can efficiently absorb radiation ionization to generate electron‐hole pairs and transferred to ligands for enhanced luminescence. Conversely, ligand‐free structures exhibit an absence of organic‐ligand‐related excited states upon excitation, leading to luminescence quenching. Due to optimized metal‐to‐ligand charge transfer dynamics, 5 times enhancement of emission efficiency was achieved with a peak photoluminescence quantum yield (PLQY) of 82.14%. Correspondingly, radioluminescence was significantly improved to 2.22 and 10 times greater than that of (Lu,Y)2SiO5:Ce (LYSO) and C6H18N2Cu2Br4 with a high light yield of 73881 photons/MeV (C12H28N4Cu2I2) and excellent photochemical stability. A high X‐ray imaging resolution of 9.7 lp/mm was also demonstrated by the soft C12H28N4Cu2I2 screen even with the thickness of 30 μm. Our study provides a solvent‐mediated ligand engineering of copper halide cluster scintillators.
Cu(I)‐based metal halides have gained significant interests as scintillators. However, their X‐ray luminescence efficiency is mainly determined by the competition between radiative organic ligands and nonradiative metal cluster‐centered charge transfer. … Cu(I)‐based metal halides have gained significant interests as scintillators. However, their X‐ray luminescence efficiency is mainly determined by the competition between radiative organic ligands and nonradiative metal cluster‐centered charge transfer. How to regulate their charge transfer pathways to enhance radiative emission is intractable challenge. Here, guided by coordination dynamics, we present a solvent mediation strategy to modulate coordination environments and intramolecular charge transfer of organic cuprous halides to achieve vibrant emissions. Mechanistic studies reveal that the coordinated clusters can efficiently absorb radiation ionization to generate electron‐hole pairs and transferred to ligands for enhanced luminescence. Conversely, ligand‐free structures exhibit an absence of organic‐ligand‐related excited states upon excitation, leading to luminescence quenching. Due to optimized metal‐to‐ligand charge transfer dynamics, 5 times enhancement of emission efficiency was achieved with a peak photoluminescence quantum yield (PLQY) of 82.14%. Correspondingly, radioluminescence was significantly improved to 2.22 and 10 times greater than that of (Lu,Y)2SiO5:Ce (LYSO) and C6H18N2Cu2Br4 with a high light yield of 73881 photons/MeV (C12H28N4Cu2I2) and excellent photochemical stability. A high X‐ray imaging resolution of 9.7 lp/mm was also demonstrated by the soft C12H28N4Cu2I2 screen even with the thickness of 30 μm. Our study provides a solvent‐mediated ligand engineering of copper halide cluster scintillators.
In polarization experiments at storage rings, one of the challenges is to maintain the spin-resonance condition of a radio-frequency spin rotator with the spin precessions of the orbiting particles. Time-dependent … In polarization experiments at storage rings, one of the challenges is to maintain the spin-resonance condition of a radio-frequency spin rotator with the spin precessions of the orbiting particles. Time-dependent variations of the magnetic fields of ring elements lead to unwanted variations of the spin-precession frequency. We report here on a solution to this problem by shielding (or masking) one of the bunches stored in the ring from the high-frequency fields of the spin rotator, so that the masked pilot bunch acts as a comagnetometer for the other signal bunch, tracking fluctuations in the ring on a time scale of about one second. While the new method was developed primarily for searches of electric dipole moments of charged particles, it may have far-reaching implications for future spin physics facilities, such as the EIC and NICA. Published by the American Physical Society 2025
Hans‐Ulrich Kauczor | American Journal of Roentgenology