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Register a new userHigh-precision control of static magnetic field magnitude, orientation, and gradient using optically pumped vapour cell magnetometry
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An integrated system of hardware and software allowing precise definition of arbitrarily oriented magnetic fields up to |B| = 1 {mu}T within a five-layer mumetal shield is described. The system is calibrated with reference to magnetic resonance observed between Zeeman states of the 6S$_{1/2}$ F = 4 $^{133}$Cs ground state. Magnetic field definition over the full 4{pi} solid angle is demonstrated, with one-sigma tolerances in magnitude, orientation and gradient of {delta}|B| = 0.94 nT, {delta}{theta} = 5.9 mrad and {delta}$ abla$ B = 13.0 pT/mm, respectively. This field control is used to empirically map Mx magnetometer signal amplitude as a function of the static field (B0) orientation.
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We investigate a search for the oscillating current induced by axion dark matter in an external magnetic field using optically pumped magnetometers (OPMs). This experiment is based upon the LC circuit axion detection concept of Sikivie, Sullivan, and Tanner. The modification of Maxwells equations caused by the axion-photon coupling results in a minute oscillating magnetic field at the frequency equal to the axion mass in the presence of magnetic field. This induced magnetic field could be searched for using an LC circuit amplifier with an OPM, the most sensitive cryogen-free magnetic-field sensor, in a room temperature experiment, avoiding the need for a complicated and expensive cryogenic system. We discuss how an existing magnetic resonance imaging (MRI) experiment can be modified to search for axions in a previously unexplored part of the parameter space. Our existing detection setup, optimized for MRI, is already sensitive to an axion-photon coupling of $10^{-7}$ GeV$^{-1}$ for an axion mass near $3times10^{-10}$ eV. While this is ruled out by limits from astrophysics and solar axion searches, we show that realistic modifications, and optimization of the experiment for axion detection, can set a new limit on the axion-photon coupling up to three orders of magnitude beyond the current best limit, for axion masses between $10^{-11}$ eV and $10^{-7}$ eV.ion masses between $10^{-11}$ eV and $10^{-7}$ eV.
Optically detected magnetic resonance of nitrogen vacancy centers in diamond offers novel routes to both DC and AC magnetometry in diamond anvil cells under high pressures ($>3$ GPa). However, a serious challenge to realizing experiments has been the insertion of microwave radiation in to the sample space without screening by the gasket material. We utilize designer anvils with lithographically-deposited metallic microchannels on the diamond culet as a microwave antenna. We detected the spin resonance of an ensemble of microdiamonds under pressure, and measure the pressure dependence of the zero field splitting parameters. These experiments enable the possibility for all-optical magnetic resonance experiments on sub-$mu$L sample volumes at high pressures.
The magnetic-field stability of a mass spectrometer plays a crucial role in precision mass measurements. In the case of mass determination of short-lived nuclides with a Penning trap, major causes of instabilities are temperature fluctuations in the vicinity of the trap and pressure fluctuations in the liquid helium cryostat of the superconducting magnet. Thus systems for the temperature and pressure stabilization of the Penning trap mass spectrometer ISOLTRAP at the ISOLDE facility at CERN have been installed. A reduction of the fluctuations by at least one order of magnitude downto dT=+/-5mK and dp=+/-50mtorr has been achieved, which corresponds to a relative frequency change of 2.7x10^{-9} and 1.5x10^{-10}, respectively. With this stabilization the frequency determination with the Penning trap only shows a linear temporal drift over several hours on the 10 ppb level due to the finite resistance of the superconducting magnet coils.
We present a design and characterization of optically transparent electrodes suitable for atomic and molecular physics experiments where high optical access is required. The electrodes can be operated in air at standard atmospheric pressure and do not suffer electrical breakdown even for electric fields far exceeding the dielectric breakdown of air. This is achieved by putting an ITO coated dielectric substrate inside a stack of dielectric substrates, which prevents ion avalanche resulting from Townsend discharge. With this design, we observe no arcing for fields of up to 120 kV/cm. Using these plates, we directly verify the production of electric fields up to 18~kV/cm inside a quartz vacuum cell by a spectroscopic measurement of the dc Stark shift of the $5^2S_{1/2} rightarrow 5^2P_{3/2}$ transition for a cloud of laser cooled Rubidium atoms. We also report on the shielding of the electric field and residual electric fields that persist within the vacuum cell once the electrodes are discharged. In addition, we discuss observed atom loss that results from the motion of free charges within the vacuum. The observed asymmetry of these phenomena on the bias of the electrodes suggests that field emission of electrons within the vacuum is primarily responsible for these effects and may indicate a way of mitigating them.
We demonstrate an optically pumped $^{87}$Rb magnetometer in a microfabricated vapor cell based on a zero-field dispersive resonance generated by optical modulation of the $^{87}$Rb ground state energy levels. The magnetometer is operated in the spin-exchange relaxation-free regime where high magnetic field sensitivities can be achieved. This device can be useful in applications requiring array-based magnetometers where radio frequency magnetic fields can induce cross-talk among adjacent sensors or affect the source of the magnetic field being measured.
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