A Miniature Permanent Magnet Assembly with Localized and Uniform Field with an Application to Optical Pumping of Helium

Atomic state preparation can benefit from a compact and uniform magnetic field source. Simulations and experimental measurements have been used to design, build, and test such a source as shown by optical pumping of atomic Helium. This source is a 9.5 mm (3/8") OD x 6.7 mm (1/4") ID x 9.5 mm (3/8") long, NdFeB-N42 assembly of 1.6 mm (1/16") thick customized annular magnets. It has octopole decay with a residual dipole far field from imperfect dipole cancelations. It has greater than 50% clear aperture with uniform and collimated magnetic field consistent with the prediction of several models. Octopole roll-off localizes the field minimizing the need for shielding in applications. The device is applied to a high precision 3,4He laser spectroscopy experiment using σ+ or σ- optical pumping currently resulting in a measured 99.3% preparation efficiency and in accordance with a rate-equation model.

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A Miniature Permanent Magnet Assembly with Localized and Uniform Field with an Application to Optical Pumping of Helium

Applied Sciences ◽

10.3390/app11198886 ◽

2021 ◽

Vol 11 (19) ◽

pp. 8886

Author(s):

Garnet Cameron ◽

Jonathan Cuevas ◽

Jeffrey Pound ◽

David Shiner

Keyword(s):

Magnetic Field ◽

Optical Pumping ◽

Equation Model ◽

Atomic State ◽

Uniform Field ◽

Field Source ◽

Design Build ◽

Spectroscopy Experiment ◽

Field Decay ◽

Atomic Helium

Atomic state preparation can benefit from a compact and uniform magnetic field source. Simulations and experimental measurements have been used to design, build, and test such a source and then apply it to the optical pumping of atomic helium. This source is a 9.5 mm (3/8″) OD × 6.7 mm (1/4″) ID × 9.5 mm (3/8″) long, NdFeB-N42 assembly of 1.6 mm (1/16″) thick customized annular magnets. It has octupole decay with a residual dipole far field from imperfect dipole cancelations. Fast B-field decay localizes the field, minimizing the need for shielding in applications. It has a greater than 50% clear aperture with a uniform and collimated magnetic field consistent with the prediction of several models. The device is applied to a high precision 3,4He laser spectroscopy experiment using σ+ or σ− optical pumping currently resulting in a measured 99.3% preparation efficiency and in accordance with a rate equation model.

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Cylindrically symmetric waves in the magnetohydrodynamic approximation

Journal of Plasma Physics ◽

10.1017/s0022377800007182 ◽

1972 ◽

Vol 8 (3) ◽

pp. 331-340 ◽

Cited By ~ 1

Author(s):

M. L. Woolley

Keyword(s):

Magnetic Field ◽

Uniform Magnetic Field ◽

Equations Of Motion ◽

Continuous Group ◽

Uniform Field ◽

Cylindrically Symmetric ◽

Sonic Waves ◽

Parametric Description ◽

Full Solution ◽

The Magnetic Field

The equations of motion of an ideally conducting medium, in the magnetohydrodynamic approximation, are solved exactly under the hypotheses that (i) one component of the magnetic field is constant everywhere, (ii) the magnetic and hydrodynamic pressures are in equilibrium, and (iii) the solution is invariant under a continuous group of transformations which preserves the symmetry of the uniform magnetic field. It is seen that the invariants of the group of transformations form the basis for a parametric description of the full solution that describes the propagation of cylindrically symmetric magneto-sonic waves in the direction of the uniform field. A number of general features of the motion are deduced, and an integral expression is given for the amplitude of the component of velocity, perpendicular to the uniform magnetic field, which undergoes potential well oscillations.

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Research on MRF Shear Stress Measurement Method under Non-Uniform Magnetic

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.620.347 ◽

2014 ◽

Vol 620 ◽

pp. 347-350

Author(s):

Shao Qing Ren ◽

Chun Fu Gao ◽

Peng Huang ◽

Xin Sheng He ◽

Hong Yun Wang ◽

...

Keyword(s):

Magnetic Field ◽

Field Theory ◽

Shear Stress ◽

Uniform Magnetic Field ◽

Fluid Shear Stress ◽

Large Deviation ◽

Stress Measurement ◽

Uniform Field ◽

Application Process ◽

Magneto Rheological

Magnetorheological fluid as an important branch of the emerging intelligent material, its excellent characteristics make it widely used in electrical system and mechanical system. Common MRF system environment is limited to a uniform magnetic field, the practical application process to the vast of magneto rheological characteristics devices has shown the phenomenon, which does not match the uniform magnetic field theory, the reason is that the actual work environment is the non-uniform magnetic [1-2]. To study the characteristics of MRF shear stress in a non-uniform magnetic field, this paper established a non-uniform field magneto-rheological fluid shear stress measurement device. Comparing the experimental shear stress curves with the uniform magnetic field measured shear stress curves, we found that the non-uniform magnetic field strength of the environmental equivalent shear stress values compared with the uniform magnetic field data have large deviation, this indicates that the existing uniform magnetic field theory is not well to explain non-uniform magnetic field shear properties of MRF, we need to build the introduction of non-uniform magnetic field theory.

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Fluid flow generated by switching a magnetic field on or off

Journal of Fluid Mechanics ◽

10.1017/s0022112073000674 ◽

1973 ◽

Vol 61 (2) ◽

pp. 209-217 ◽

Cited By ~ 1

Author(s):

Alfred Sneyd

Keyword(s):

Magnetic Field ◽

Reynolds Number ◽

Uniform Magnetic Field ◽

Magnetic Reynolds Number ◽

Simple Expression ◽

Conducting Fluid ◽

Uniform Field ◽

Vorticity Distribution ◽

Magnetic Prandtl Number ◽

Initial Vorticity

A uniform magnetic field is switched on at time t = 0 outside a body of conducting fluid. It is assumed that the field strength increases in time in proportion to 1 -e−αt, where α is a constant of the circuit generating the field. Under the assumption of small magnetic Reynolds number and small magnetic Prandtl number the equations governing the diffusion of the field into the fluid are derived and a simple expression is given for the initial vorticity distribution produced in the fluid. The situation in which an initially uniform field is switched off is also considered. It is shown that, for sufficiently symmetrically shaped bodies of fluid, the vorticity generated by the switching-on of the field is the same as that generated by the switching-off. The particular case of an infinitely long circular cylinder of conducting fluid is considered in detail and an explicit expression is derived for the vorticity distribution.

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