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S. K. Lamoreaux

Publications and source records attributed to S. K. Lamoreaux.

At least 55 records · Page 3Linked to original sources
arXiv2008

Magnetic susceptibility and magnetization fluctuation measurements of mixed Gadolinium-Yttrium Iron Garnets

We study the magnetic properties of Gadolinium-Yttrium Iron Garnet ($\text{Gd}_{x}\text{Y}_{3-x}\text{Fe}_5\text{0}_{12}$, $x=3,1.8$) ferrite ceramics. The complex initial permeability is measured in the temperature range 2 K to 295 K at frequency of 1 kHz, and in the frequency range 100 Hz to 200 MHz at temperatures 4 K, 77 K, and 295 K. The magnetic viscosity-induced imaginary part of the permeability is observed at low frequencies. Measurements of the magnetization noise are made at 4 K. Using the fluctuation-dissipation theorem, we find that the observed magnetization fluctuations are consistent with our measurements of the low-frequency imaginary part of permeability. We discuss some implications for proposed precision measurements as well as other possible applications.

cond-mat.mtrl-sci↗
arXiv2008

Quantum cryptography with polarization, phase and time encoding

We develop and present a quantum cryptography concept in which phase determinations are made from the time that a photon is detected, as opposed to where the photon is detected, and hence is a non-interferometric process. The phase-encoded quantum information is contained in temporal and polarization superpositions of single photon states, forming a complex qudit of Hilbert dimension D equal to or greater than 4. Based on this, we have developed a new quantum key distribution protocol that allows the generation of secret key in the presence of higher noise than is possible with other protocols.

quant-ph↗
arXiv2007

Investigation of the Gravitational Potential Dependence of the Fine-Structure Constant Using Atomic Dysprosium

Radio-frequency E1 transitions between nearly degenerate, opposite parity levels of atomic dysprosium were monitored over an eight month period to search for a variation in the fine-structure constant. During this time period, data were taken at different points in the gravitational potential of the Sun. The data are fitted to the variation in the gravitational potential yielding a value of $(-8.7 \pm 6.6) \times 10^{-6}$ for the fit parameter $k_α$. This value gives the current best laboratory limit. In addition, our value of $k_α$ combined with other experimental constraints is used to extract the first limits on k_e and k_q. These coefficients characterize the variation of m_e/m_p and m_q/m_p in a changing gravitational potential, where m_e, m_p, and m_q are electron, proton, and quark masses. The results are $k_e = (4.9 \pm 3.9) \times 10^{-5}$ and $k_q = (6.6 \pm 5.2) \times 10^{-5}$.

physics.atom-ph↗
arXiv2007

Time-variability of alpha from realistic models of Oklo reactors

We reanalyze Oklo $^{149}$Sm data using realistic models of the natural nuclear reactors. Disagreements among recent Oklo determinations of the time evolution of $α$, the electromagnetic fine structure constant, are shown to be due to different reactor models, which led to different neutron spectra used in the calculations. We use known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Two Oklo reactors, RZ2 and RZ10, were modeled with MCNP. The resulting neutron spectra were used to calculate the change in the $^{149}$Sm effective neutron capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. We independently deduce ancient $^{149}$Sm effective cross sections, and use these values to set limits on the time-variation of $α$. Our study resolves a contradictory situation with previous Oklo $α$-results. Our suggested $2 σ$ bound on a possible time variation of $α$ over two billion years is stringent: $ -0.24 \times 10^{-7} \le \frac{Δα}α \le 0.11 \times 10^{-7}$, but model dependent in that it assumes only $α$ has varied over time.

nucl-ex↗
arXiv2007

Dressed Spin of Helium-3

We report a measurement of dressed-spin effects of polarized 3He atoms from a cold atomic source traversing a region of constant magnetic field B0 and a transverse oscillatory dressing field Bd cos(omega * t). The observed effects are compared with a numerical simulation using the Bloch equation as well as a calculation based on the dressed-atom formalism. An application of the dressed spin of 3He for a proposed neutron electric dipole moment measurement is also discussed.

nucl-ex↗
arXiv2006

Limit on the Temporal Variation of the Fine-Structure Constant Using Atomic Dysprosium

Over a period of eight months, we have monitored transition frequencies between nearly degenerate, opposite-parity levels in two isotopes of atomic dysprosium (Dy). These transition frequencies are highly sensitive to temporal variation of the fine-structure constant ($α$) due to relativistic corrections of large and opposite sign for the opposite-parity levels. In this unique system, in contrast to atomic-clock comparisons, the difference of the electronic energies of the opposite-parity levels can be monitored directly utilizing a radio-frequency (rf) electric-dipole transition between them. Our measurements show that the frequency variation of the 3.1-MHz transition in $^{163}$Dy and the 235-MHz transition in $^{162}$Dy are 9.0$\pm$6.7 Hz/yr and -0.6$\pm$6.5 Hz/yr, respectively. These results provide a value for the rate of fractional variation of $α$ of $(-2.7\pm2.6)\times 10^{-15}$ yr$^{-1}$ (1 $σ$) without any assumptions on the constancy of other fundamental constants, indicating absence of significant variation at the present level of sensitivity.

physics.atom-ph↗
arXiv2006

Linear electric field frequency shift (important for next generation electric dipole moment searches) induced in confined gases by a magnetic field gradient

The search for particle electric dipole moments (edm) represents a most promising way to search for physics beyond the standard model. A number of groups are planning a new generation of experiments using stored gases of various kinds. In order to achieve the target sensitivities it will be necessary to deal with the systematic error resulting from the interaction of the well-known $\overrightarrow{v}\times \overrightarrow{E}$ field with magnetic field gradients (often referred to as the geometric phase effect (Commins, ED; Am. J. Phys. \QTR{bf}{59}, 1077 (1991), Pendlebury, JM \QTR{em}{et al;} Phys. Rev. \QTR{bf}{A70}, 032102 (2004)). This interaction produces a frequency shift linear in the electric field, mimicking an edm. In this work we introduce an analytic form for the velocity auto-correlation function which determines the velocity-position correlation function which in turn determines the behavior of the frequency shift (Lamoreaux, SK and Golub, R; Phys. Rev \QTR{bf}{A71}, 032104 (2005)) and show how it depends on the operating conditions of the experiment. We also discuss some additional issues.

nucl-ex↗
arXiv2006

High Voltage Test Apparatus for a Neutron EDM Experiment and Lower Limit on the Dielectric Strength of Liquid Helium at Large Volumes

A new search for a permanent electric dipole moment (EDM) of the neutron is underway using ultracold neutrons produced and held in a bath of superfluid helium. Attaining the target sensitivity requires maintaining an electric field of several tens of kilovolts per centimeter across the experimental cell, which is nominally 7.5 cm wide and will contain about 4 liters of superfluid. The electrical properties of liquid helium are expected to be sufficient to meet the design goals, but little is known about these properties for volumes and electrode spacings appropriate to the EDM experiment. Furthermore, direct application of the necessary voltages from an external source to the experimental test cell is impractical. An apparatus to amplify voltages in the liquid helium environment and to test the electrical properties of the liquid for large volumes and electrode spacings has been constructed. The device consists of a large-area parallel plate capacitor immersed in a 200 liter liquid helium dewar. Preliminary results show the breakdown strength of normal state liquid helium is at least 90 kV/cm at these volumes, at the helium vapor pressure corresponding to 4.38 K. These fields hold for more than 11 hours with leakage currents less than 170 pA (about 20% of the maximum tolerable in the EDM experiment). The system is also found to be robust against anticipated radiation backgrounds. Preliminary results for superfluid show that fields of at least 30 kV/cm can be sustained at the volumes required for the EDM experiment, about 60% of the design goal. These results are likely limited by the low pressure that must be maintained above the superfluid bath.

physics.ins-det↗
arXiv2005

Detailed discussion of a linear electric field frequency shift (important for next generation) electric dipole moment searches) induced in confined gases by a magnetic field gradient: Implications for electric dipole moment experiments (II)

The search for particle electric dipole moments represents a most promising way to search for physics beyond the standard model. A number of groups are planning a new generation of experiments using stored gases of various kinds. In order to achieve the target sensitivities it will be necessary to deal with the systematic error resulting from the interaction of the well-known E x v field with magnetic field gradients (often referred to as the geometric phase effect [9,10]). This interaction produces a frequency shift linear in the electric field, mimicking an edm. In this work we introduce an analytic model for the correlation function which determines the behavior of the frequency shift [11], and show in detail how it depends on the operating conditions of the experiment. We also propose a method to directly measure ths correlation function under the exact conditions of a given experiment.

nucl-ex↗
arXiv2005

On the sensitivity of condensed-matter P- and T-violation experiments

Experiments searching for parity- and time-reversal-invariance-violating effects that rely on measuring magnetization of a condensed-matter sample induced by application of an electric field are considered. A limit on statistical sensitivity arises due to random fluctuations of the spins in the sample. The scaling of this limit with the number of spins and their relaxation time is derived. Application to an experiment searching for nuclear Schiff moment in a ferroelectric is discussed.

cond-mat.other↗
arXiv2005

Measurement of the electron electric dipole moment using GdIG

A new method for the detection of the electron edm using a solid is described. The method involves the measurement of a voltage induced across the solid by the alignment of the samples magnetic dipoles in an applied magnetic field, H. A first application of the method to GdIG has resulted in a limit on the electron edm of 5E-24 e-cm, which is a factor of 40 below the limit obtained from the only previous solid-state edm experiment. The result is limited by the imperfect discrimination of an unexpectedly large voltage that is even upon the reversal of the sample magnetization.

physics.atom-ph↗
arXiv2005

Collisional perturbation of radio-frequency E1 transitions in an atomic beam of dysprosium

We have studied collisional perturbations of radio-frequency (rf) electric-dipole (E1) transitions between the nearly degenerate opposite-parity levels in atomic dysprosium (Dy) in the presence of 10 to 80 $μ$Torr of H$_\text{2}$, N$_\text{2}$, He, Ar, Ne, Kr, and Xe. Collisional broadening and shift of the resonance, as well as the attenuation of the signal amplitude are observed to be proportional to the foreign-gas density with the exception of H$_2$ and Ne, for which no shifts were observed. Corresponding rates and cross sections are presented. In addition, rates and cross sections for O$_2$ are extracted from measurements using air as foreign gas. The primary motivation for this study is the need for accurate determination of the shift rates, which are needed in a laboratory search for the temporal variation of the fine-structure constant [A. T. Nguyen, D. Budker, S. K. Lamoreaux, and J. R. Torgerson, Phys. Rev. A \textbf{69}, 22105 (2004)].

physics.atom-ph↗
arXiv2005

Detailed Discussion of a linear electric field frequency shift induced in confined gases by a magnetic field gradient: Implications for neutron electric dipole moment experiments

The search for particle electric dipole moments (edm) is one of the best places to look for physics beyond the standard model because the size of time reversal violation predicted by the standard model is incompatible with present ideas concerning the creation of the Baryon-Antibaryon asymmetry. As the sensitivity of these edm searches increases more subtle systematic effects become important. We develop a general analytical approach to describe a systematic effect recently observed in an electric dipole moment experiment using stored particles \cite{JMP}. Our approach is based on the relationship between the systematic frequency shift and the velocity autocorrelation function of the resonating particles. Our results, when applied to well-known limiting forms of the correlation function, are in good agreement with both the limiting cases studied in recent work that employed a numerical/heuristic analysis. Our general approach explains some of the surprising results observed in that work and displays the rich behavior of the shift for intermediate frequencies, which has not been previously studied.

nucl-ex↗
arXiv2004

Optical Velocimetry

This work considers current potential uses of laser Doppler velocimetry. A discussion of other optical velocimetry techniques is presented and compared with their practical application to modern shock physics diagnostics, such as VISAR.

physics.optics↗
arXiv2004

Thermal noise limitations to force measurements with torsion pendulums: Applications to the measurement of the Casimir force and its thermal correction

A general analysis of thermal noise in torsion pendulums is presented. The specific case where the torsion angle is kept fixed by electronic feedback is analyzed. This analysis is applied to a recent experiment that employed a torsion pendulum to measure the Casimir force. The ultimate limit to the distance at which the Casimir force can be measured to high accuracy is discussed, and in particular the prospects for measuring the thermal correction are elaborated upon.

quant-ph↗
arXiv2004

Kerr effect in liquid helium at temperatures below the superfluid transition

The electro-optical Kerr effect induced by a slowly-varying applied electric field in liquid helium at temperatures below the $λ$-point is investigated. The Kerr constant of liquid helium is measured to be $(1.43\pm 0.02^{(stat)} \pm 0.04^{(sys)})\times 10^{-20}$ (cm/V)$^2$ at $T=1.5$ K. Within the experimental uncertainty, the Kerr constant is independent of temperature in the range $T=1.5$ K to 2.17 K, which implies that the Kerr constant of the superfluid component of liquid helium is the same as that of normal liquid helium. Our result also indicates that pair and higher correlations of He atoms in the liquid phase account for about 23% of the measured Kerr constant. Liquid nitrogen was used to test the experimental set-up, the result for the liquid nitrogen Kerr constant is $(4.38\pm 0.15)\times 10^{-18} $(cm/V)$^2$. The knowledge of the Kerr constant in these media allows the Kerr effect to be used as a non-contact technique for measuring the magnitude and mapping out the distribution of electric fields inside these cryogenic insulants.

physics.optics↗