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The response of a SERF atomic magnetometer to a repetitive short-pulsed pump was investigated. Quantum sub-resonances at a repetition rate of $1/n$ of the Larmor frequency of the magnetic field inside the shield are experimentally observed and theoretically explained. This is a type of synchronization phenomenon. Investigations in single alkali atoms cells as well as mixed alkali atoms of K and Rb are presented. In the later, one species is pumped while the probe is on the other specie polarized by spin exchange. The effect of spin destruction, spin exchange and collisions are studied in order to account for the width of the resonances. Quantum calculations of a three levels $\Lambda$ model for this phenomenon exhibit a dip at the resonance frequency in the absorption spectrum for both cases of pulsed and CW pump modes and an evidence for EIT., Comment: 14 pages, 11 figures

This article presents a method to determine the magnetic field distribution within the vapor cell of a spin-exchange relaxation-free (SERF) atomic magnetometer with a sensitivity of the order of 10 femtoTesla and a bandwidth of DC to 100 Hz, in the presence of an uncompensated ambient magnetic field of up to several nanoTesla. The method is based on the analysis of the atomic polarization in a multichannel pump–probe configuration, in which a spatially selective optical pumping enables to probe specific layers of the atomic vapor contained in a gas-buffered cell. An SERF magnetometer is inherently sensitive to one component of the magnetic field, orthogonal to the pump and probe laser beams. The sensor’s performance can be drastically degraded by the other uncompensated components of the magnetic field. Typically, SERF magnetometry requires very good magnetic shielding and active compensation of residual magnetic field to properly function; this is commonly achieved by applying a complex design of Helmholtz coils in a sophisticated compensation procedure. The method suggested in this article eliminates the influence of non-uniform residual magnetic fields on the accuracy of measurements without precise compensation of the interfering field components. This procedure is used to simplify the measurements of magnetic field distribution in a large vapor cell with required accuracy. This is critically important for precise multichannel magnetic field mapping used for localization of the magnetic dipole-field source.

The factorial design technique is implemented to achieve greater accuracy in the determination of magnetic field distribution within a single cell of spin-exchange relaxation-free atomic magnetometer. Three-dimensional magnetic field distribution within a single vapor cell can be found by consecutively pumping, layer by layer, all the cell volumes perpendicular to the probe laser beam, detected by a photodiode array. Thus each element of the array collects information about the magnetic field in the small volume (voxel) which forms when the corresponding part of the probe beam and optically pumped layer cross. One of the most effective ways to enhance measurement accuracy is repeated pumping of the layers and averaging the measured results. However, the measurement time is multiplied several times due to the repeated scanning of the cell volume. The suggested technique enables increased measurement accuracy of each voxel while preserving the number of measurements. Magnetic field distribution is determined by the illumination of the cell layers one by one or simultaneously, according to a special algorithm, with subsequent multifactorial analysis of the obtained results.

We show that a single-cell spin-exchange relaxation-free (SERF) atomic magnetometer can be used for 3-D field measurements. The 3-D operation is achieved by optically pumping the magnetometer cell in successive layers perpendicular to the laser probe beam and by collecting the signals with a photodiode array. The vapor cell is thus divided into voxels acting as local atomic magnetometers. Each voxel's contribution to the probe linear polarization rotation is proportional to the convolution of the local polarization and the magnetic field. The layers are pumped in sequence without waiting for the atomic polarization in the previously pumped layer to relax to zero, consequently, reducing the total measurement time. The photodiode signals are the sum of accumulated linear polarization rotation caused by all the layers. These signals are processed by a deconvolution algorithm that extracts the information originating from each individual voxel. Our theoretical analysis and experimental results show that the time of a single-layer pumping can be reduced below the atomic-cell relaxation time constant, with almost no loss of precision.

A Stark effect diagnostic yields measurements of the electric field distribution of Langmuir waves, P(E), in beam–plasma turbulence. When the destabilizing beam abruptly cuts off, the form of P(E)∝ exp(−E2) discovered earlier persists, with amplitude decaying exponentially in a microsecond. Strong fields last much longer than other time scales in strong turbulence theory. Exponential decay disagrees with recent power law scalings deduced from cascade theory. A possible explanation envisions Langmuir energy persisting at long wavelengths, slowly coalescing around nucleation density wells left by previous, ‘‘burnt‐out’’ solitons.

Ionization probability in three color excitation of uranium atoms depends on the photon flux which drives the transition to an autoionizing level. For a proper choice of the flux ratio, the ionization probability is insensitive of the actual fluxes over a considerable range. Thus, the laser intensities used may be lowered by a factor of about 3 as compared to values predicted on the basis of cross-sections of the individual transitions. A quantum-mechanical model, based on a detailed calculation of population dynamics of the levels in the ionization scheme, predicts the ionization probability as a function of the three-laser intensities. Ionization saturation measurements provide parameters for the model. The theoretical predictions were partially consistent with the experimental results. Ionization probabilities as high as 93% are achievable.

Using a Stark-effect diagnostic, we have explored a new regime of relativistic beam-plasma turbulence, 〈${\mathrm{E}}^{2}$〉g${\mathrm{nT}}_{\mathrm{e}}$. Measurements of E and of the plasma frequency used nonperturbing optical techniques during the electron-beam pulse. Fields up to 150 kV/cm display an exponential spectrum, exp(-${\mathrm{E}}^{2}$/${\mathrm{E}}_{0}^{2}$) with ${\mathrm{E}}_{0}$=85 kV/cm. This spectrum does not resemble that given by strong-turbulence theory, and involves stronger fields than are dealt with in current theory. '