Comparison of discharge lamp and laser pumped cesium magnetometers

We have performed a comparison of laser (LsOPM) and lamp (LpOPM) pumped cesium vapor magnetometers. Although the LsOPM operated 50% above its shot-noise limit we found an intrinsic sensitivity of 15 fT/√Hz and 25 fT/√Hz for the LsOPM and the LpOPM, respectively. Two modes of operation, viz. the phase-stabilized and the self-oscillating modes, were investigated and found to yield a similar performance. We have compared the performance of the LsOPM and the LpOPM directly by simultaneous measurements of field fluctuations of a 2-μT magnetic field inside a multilayer magnetic shield and have used one of the magnetometers for an active field stabilization. In the stabilized mode we found a gradient instability of 25 fT within an integration time of 100 s, which represents an upper limit of the long-term stability of the magnetometers. Our research is motivated by the need for an improved control of magnetic fields and gradients in a planned neutron electric dipole experimen

Ultimate parameters of an all-optical MX resonance in Cs in ultra-weak magnetic field

We present the results of studying the parameters of the magnetic MX resonance in an all-optical sensor built according to the two-beam Bell-Bloom scheme in nonzero ultra-weak magnetic fields in which the effects of spin-exchange broadening suppression are partially manifested. We report on the features of the resonance under these conditions. We also optimize the resonance parameters to achieve maximum sensitivity in magnetoencephalographic sensors. We demonstrate an improvement in the ultimate achievable sensitivity of an all-optical MX sensor by a factor of four or more, which in our experiment corresponds to a decrease from 13 to 3 fT/Hz1/2 in a volume of 0.13 cm3. We also report the effect of incomplete suppression of spin-exchange broadening under conditions of strong transverse modulated optical pumping, and propose a semi-empirical model to describe it

Optically driven spin-alignment precession

The effect of optically driven spin precession discovered in the late 50s by W. Bell and A. Bloom is widely used nowadays as a basis for numerous experiments in fundamental physics and for diverse applications. In this paper, we consider a much less popular version of the light-induced spin precession that does not imply coherent precession of the spin-system magnetization and is excited by the linearly (rather than circularly) polarized light. The pump-probe measurements performed on D2 line of cesium vapor have shown that magnitude of the signal of the optically driven spin-alignment precession, in vacuum cells (with no buffer gas) is close to that of the classical spin-orientation precession. In the presence of buffer gas, however, the signal of spin-alignment precession appears to be strongly suppressed. The discovered effect is ascribed to spin mixing of excited states of cesium atoms in the cycle of optical pumping.Comment: 7 pages, 4 figure

An Improved Neutron Electric Dipole Moment Experiment

A new measurement of the neutron EDM, using Ramsey's method of separated oscillatory fields, is in preparation at the new high intensity source of ultra-cold neutrons (UCN) at the Paul Scherrer Institute, Villigen, Switzerland (PSI). The existence of a non-zero nEDM would violate both parity and time reversal symmetry and, given the CPT theorem, might lead to a discovery of new CP violating mechanisms. Already the current upper limit for the nEDM (|d_n|<2.9E-26 e.cm) constrains some extensions of the Standard Model. The new experiment aims at a two orders of magnitude reduction of the experimental uncertainty, to be achieved mainly by (1) the higher UCN flux provided by the new PSI source, (2) better magnetic field control with improved magnetometry and (3) a double chamber configuration with opposite electric field directions. The first stage of the experiment will use an upgrade of the RAL/Sussex/ILL group's apparatus (which has produced the current best result) moved from Institut Laue-Langevin to PSI. The final accuracy will be achieved in a further step with a new spectrometer, presently in the design phase.Comment: Flavor Physics & CP Violation Conference, Taipei, 200

Testing isotropy of the universe using the Ramsey resonance technique on ultracold neutron spins

Physics at the Planck scale could be revealed by looking for tiny violations of fundamental symmetries in low energy experiments. In 2008, a sensitive test of the isotropy of the Universe using has been performed with stored ultracold neutrons (UCN), this is the first clock-comparison experiment performed with free neutrons. During several days we monitored the Larmor frequency of neutron spins in a weak magnetic field using the Ramsey resonance technique. An non-zero cosmic axial field, violating rotational symmetry, would induce a daily variation of the precession frequency. Our null result constitutes one of the most stringent tests of Lorentz invariance to date.Comment: proceedings of the PNCMI2010 conferenc

Three-component variometer based on a scalar potassium sensor

Abstract A new variometer is developed comprising a fast-response scalar optically pumped potassium magnetometer inside a rotating magnetic field created by a two-dimensional coil system mounted on a quartz frame. The variometer measures three components of the Earth&apos;s field: the total field intensity and two transverse components. The theoretically predicted accuracy of the field component measurement is not worse than 0.1 nT. The noise-limited sensitivity measured in a quiet magnetic field has been proved to be not worse than 25 pT rms at 0.2 s and 30 pT rms at 1 min; comparison with a proton vector magnetometer and a fluxgate magnetometer shows 1.5 nT p-t-p daily deviation

λ8\frac{\lambda}{8}-period optical potentials

A Raman configuration of counterpropagating traveling wave fields, one of which is $lin\bot lin$ polarized and the other $lin\Vert lin$ polarized, is shown to lead to optical potentials having $\frac{\lambda}{8}$ periodicity. Such optical potentials may be used to construct optical lattices having $\frac{\lambda}{8}$ periodicity. Using numerical diagonalization, we obtain the optical potentials for $^{\text{85}}$Rb atoms.Comment: 3 pages, 2 figure

Optically pumped Cs magnetometers enabling a high-sensitivity search for the neutron electric dipole moment

An array of 16 laser-pumped scalar Cs magnetometers was part of the neutron electric dipole moment (nEDM) experiment taking data at the Paul Scherrer Institute in 2015 and 2016. It was deployed to measure the gradients of the experiment's magnetic field and to monitor their temporal evolution. The originality of the array lies in its compact design, in which a single near-infrared diode laser drives all magnetometers that are located in a high-vacuum chamber, with a selection of the sensors mounted on a high-voltage electrode. We describe details of the Cs sensors' construction and modes of operation, emphasizing the accuracy and sensitivity of the magnetic-field readout. We present two applications of the magnetometer array directly beneficial to the nEDM experiment: (i) the implementation of a strategy to correct for the drift of the vertical magnetic-field gradient and (ii) a procedure to homogenize the magnetic field. The first reduces the uncertainty of the nEDM result. The second enables transverse neutron spin relaxation times exceeding 1500 s, improving the statistical sensitivity of the nEDM experiment by about 35% and effectively increasing the rate of nEDM data taking by a factor of 1.8