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

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.

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

2021 ◽  
Author(s):  
Garnet Cameron ◽  
Jonathan Cuevas ◽  
Jeffrey Pound Jr. ◽  
David Shiner
Keyword(s):  
Magnetic Field ◽  
Uniform Magnetic Field ◽  
Optical Pumping ◽  
Equation Model ◽  
Atomic State ◽  
Uniform Field ◽  
Field Source ◽  
Design Build ◽  
Spectroscopy Experiment ◽  
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 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.

scholarly journals A New View on Young Pulsars in Supernova Remnants: Slow, Radio-quiet & X-ray Bright

2000 ◽  
Vol 177 ◽  
pp. 699-702 ◽  
Author(s):  
E. V. Gotthelf ◽  
G. Vasisht
Keyword(s):  
Magnetic Field ◽  
Neutron Stars ◽  
Supernova Remnants ◽  
Simple Explanation ◽  
Crab Pulsar ◽  
Radio Pulsars ◽  
Substantial Fraction ◽  
Subsequent Evolution ◽  
X Ray ◽  
Field Decay

AbstractWe propose a simple explanation for the apparent dearth of radio pulsars associated with young supernova remnants (SNRs). Recent X-ray observations of young remnants have revealed slowly rotating (P∼ 10s) central pulsars with pulsed emission above 2 keV, lacking in detectable radio emission. Some of these objects apparently have enormous magnetic fields, evolving in a manner distinct from the Crab pulsar. We argue that these X-ray pulsars can account for a substantial fraction of the long sought after neutron stars in SNRs and that Crab-like pulsars are perhaps the rarer, but more highly visible example of these stellar embers. Magnetic field decay likely accounts for their high X-ray luminosity, which cannot be explained as rotational energy loss, as for the Crab-like pulsars. We suggest that the natal magnetic field strength of these objects control their subsequent evolution. There are currently almost a dozen slow X-ray pulsars associated with young SNRs. Remarkably, these objects, taken together, represent at least half of the confirmed pulsars in supernova remnants. This being the case, these pulsars must be the progenitors of a vast population of previously unrecognized neutron stars.

scholarly journals Magnetoactive elastomers for magnetically tunable vibrating sensor systems

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Tatiana I. Becker ◽  
Yuriy L. Raikher ◽  
Oleg V. Stolbov ◽  
Valter Böhm ◽  
Klaus Zimmermann
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Smart Materials ◽  
Excitation Frequency ◽  
Experimental Studies ◽  
Uniform Field ◽  
Sensor Systems ◽  
Ongoing Research ◽  
Amplification Ratio ◽  
Field Distortion

Abstract Magnetoactive elastomers (MAEs) are a special type of smart materials consisting of an elastic matrix with embedded microsized particles that are made of ferromagnetic materials with high or low coercivity. Due to their composition, such elastomers possess unique magnetic field-dependent material properties. The present paper compiles the results of investigations on MAEs towards an approach of their potential application as vibrating sensor elements with adaptable sensitivity. Starting with the model-based and experimental studies of the free vibrational behavior displayed by cantilevers made of MAEs, it is shown that the first bending eigenfrequency of the cantilevers depends strongly on the strength of an applied uniform magnetic field. The investigations of the forced vibration response of MAE beams subjected to in-plane kinematic excitation confirm the possibility of active magnetic control of the amplitude-frequency characteristics. With change of the uniform field strength, the MAE beam reveals different steady-state responses for the same excitation, and the resonance may occur at various ranges of the excitation frequency. Nonlinear dependencies of the amplification ratio on the excitation frequency are obtained for different magnitudes of the applied field. Furthermore, it is shown that the steady-state vibrations of MAE beams can be detected based on the magnetic field distortion. The field difference, which is measured simultaneously on the sides of a vibrating MAE beam, provides a signal with the same frequency as the excitation and an amplitude proportional to the amplitude of resulting vibrations. The presented prototype of the MAE-based vibrating unit with the field-controlled “configuration” can be implemented for realization of acceleration sensor systems with adaptable sensitivity. The ongoing research on MAEs is oriented to the use of other geometrical forms along with beams, e.g. two-dimensional structures such as membranes.

scholarly journals Evidence for Heating of Neutron Stars by Magnetic-Field Decay

2007 ◽  
Vol 98 (7) ◽  
Author(s):  
José A. Pons ◽  
Bennett Link ◽  
Juan A. Miralles ◽  
Ulrich Geppert
Keyword(s):  
Magnetic Field ◽  
Neutron Stars ◽  
Field Decay

scholarly journals Mutual influence of magnetic field decay and thermal evolution of rotational neutron stars

2012 ◽  
Vol 8 (S291) ◽  
pp. 586-588
Author(s):  
Xia Zhou ◽  
Miao Kang ◽  
Na Wang
Keyword(s):  
Magnetic Field ◽  
Neutron Stars ◽  
Mutual Influence ◽  
Thermal Evolution ◽  
Chemical Heating ◽  
Field Decay ◽  
The Magnetic Field

AbstractThe effect of magnetic field decay on the chemical heating and thermal evolution of neutron stars is discussed. Our main goal is to study how chemical heating mechanisms and thermal evolution are changed by field decay and how magnetic field decay is modified by the thermal evolution. We show that the effect of chemical heating is suppressed by the star spin-down through decaying magnetic field at a later stage; magnetic field decay is delayed significantly relative to stars cooling without heating mechanisms; compared to typical chemical heating, the decay of the magnetic field can even cause the temperature to turn down at a later stage.

Full treatment of the proton radiography technique for laser-driven capacitor-coil targets

2021 ◽  
Author(s):  
Xiaoxia Yuan ◽  
Cangtao Zhou ◽  
Hua Zhang ◽  
Jiayong Zhong ◽  
Bo Han ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Fields ◽  
Small Angle ◽  
Primary Source ◽  
Numerical Calculations ◽  
Stopping Power ◽  
Magnetic Field Generation ◽  
Proton Radiography ◽  
Field Source ◽  
Comprehensive Study

Abstract Ultrafast proton radiography has been frequently used for direct measurement of the electromagnetic fields around laser-driven capacitor-coil targets. The goal is to accurately infer the coil currents and their magnetic field generation for a robust magnetic field source that can lead to many applications. The technique often involves numerical calculations for synthetic proton images to reproduce experimental measurements. While electromagnetic fields are the primary source for proton deflections around the capacitor coils, stopping power and small angle deflection can also contribute to the observed experimental features. Here we present a comprehensive study of the proton radiography technique including all sources of proton deflections as a function of coil shapes, current magnitudes, and proton energies. Good agreements were achieved between experimental data and numerical calculations that include both the stopping power and small angle deflections, particularly when the induced coil currents were small.

scholarly journals Remote manipulation of magnetic nanoparticles using magnetic field gradient to promote cancer cell death

2018 ◽  
Author(s):  
Mahendran Subramanian ◽  
Arkadiusz Miaskowski ◽  
Stuart Iain Jenkins ◽  
Jenson Lim ◽  
Jon Dobson
Keyword(s):  
Magnetic Field ◽  
Magnetic Nanoparticles ◽  
Field Gradient ◽  
Biomedical Applications ◽  
Magnetic Field Gradient ◽  
Field Source ◽  
Remote Manipulation ◽  
Cancer Cell Death ◽  
The Magnetic Field

AbstractThe manipulation of magnetic nanoparticles (MNPs) using an external magnetic field, has been demonstrated to be useful in various biomedical applications. Some techniques have evolved utilizing this non-invasive external stimulus but the scientific community widely adopts few, and there is an excellent potential for more novel methods. The primary focus of this study is on understanding the manipulation of MNPs by a time-varying static magnetic field and how this can be used, at different frequencies and displacement, to manipulate cellular function. Here we explore, using numerical modeling, the physical mechanism which underlies this kind of manipulation, and we discuss potential improvements which would enhance such manipulation with its use in biomedical applications, i.e., increasing the MNP response by improving the field parameters. From our observations and other related studies, we infer that such manipulation depends mostly on the magnetic field gradient, the magnetic susceptibility and size of the MNPs, the magnet array oscillating frequency, the viscosity of the medium surrounding MNPs, and the distance between the magnetic field source and the MNPs. Additionally, we demonstrate cytotoxicity in neuroblastoma (SH-SY5Y) and hepatocellular carcinoma (HepG2) cells in vitro. This was induced by incubation with MNPs, followed by exposure to a magnetic field gradient, physically oscillating at various frequencies and displacement amplitudes. Even though this technique reliably produces MNP endocytosis and/or cytotoxicity, a better biophysical understanding is required to develop the mechanism used for this precision manipulation of MNPs, in vitro.

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