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The Design of Hollow Square Copper Wires for Strong Magnetic Field in Ultra-cold Atoms

Fan Ha

Published Jan 1, 2015• 0 citations
OpenAlex

Abstract

A pair of coils were made by hollow square copper wires with a rectangular transversal surface,which can be used to realize the trap for ultra-cold atoms and control of interaction among atoms by Feshbach resonance.We experimentally measured the magnetic field strength created by coils in Helmholtz and anti-Helmholtz configuration,and payed spcial attention to the factors such as spacing between two coils which influences the spatial distribution of magnetic field strength.At the same time,we calculated numerically the magnetic field strength in anti-Helmholtz configuration and presented the optimal value such as spacing when the uniformity of magnetic field strength was the best.With compari the measured and the simulated data,it is well-paralized with each other.Simultaneously working power of coils was calculated,as well as water speed and pressure for cooling coils.

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Investigation of the benefits and disadvantages of using double-pair anti-Helmholtz coils in BEC-producing MOT setups and optimizing their design

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This work has investigated the Magneto-Optical Trap (MOT) system used to produce Bose-Einstein Condensate (BEC). A primary challenge addressed in this study concerns the geometric limitations of traditional single-pair anti-Helmholtz coil configurations, where the magnetic field peaks occur outside the accessible inter-coil region. To overcome this limitation, we have explored the use of double-pair anti-Helmholtz coil configurations that create well-shaped magnetic field potentials centered at the experimentally accessible $z=0$ location. This investigation encompasses the three sequential processes of atom cooling: cooling in a linear external magnetic field through Doppler cooling, cooling in a well-shaped magnetic field through trapping, and evaporative cooling of atoms to achieve sub-microkelvin temperatures. Through theoretical analysis and numerical simulation, we have determined optimal geometric parameters for the coil configuration and operational parameters including laser detuning, saturation intensity, and initial atom populations for ${}^{87}\text{Rb}$ BEC production. The results indicate that with the optimized configuration, the system can achieve final temperatures of approximately $T_f \sim 60\,\mathrm{nK}$ and produce condensate populations of $\sim 10^5$ atoms with a mean density of $n_0 = 4.9 \times 10^{15}\,\mathrm{m}^{-3}$, providing systematic design guidance for experimental BEC systems

physics.atom-phCross-listedarXiv:2512.23874•Dec 31, 2025•0 citations
A pair of coils were made by hollow square copper wires with a rectangular transversal surface,which can be used to realize the trap for ultra-cold atoms and control of interaction among atoms by Feshbach resonance.We experimentally measured the magnetic field strength created by coils in Helmholtz and anti-Helmholtz configuration,and payed spcial attention to the factors such as spacing between two coils which influences the spatial distribution of magnetic field strength.At the same time,we calculated numerically the magnetic field strength in anti-Helmholtz configuration and presented the optimal value such as spacing when the uniformity of magnetic field strength was the best.With compari the measured and the simulated data,it is well-paralized with each other.Simultaneously working power of coils was calculated,as well as water speed and pressure for cooling coils.
We have constructed in our laboratory two rectangular shaped current carrying coils in accordance with the parameters used in our design so that they can be put in use in the Two Dimensional Magneto Optical Trap (2D-MOT)to obtain very high value of Optical Depth(OD). The dimensions of the coils are 8cm x 10cm. When put in anti-Helmholtz configuration as required in a 2D-MOT, these coils generate magnetic field such that it becomes zero along a line bisecting the space between the two coils. The magnetic field gradient near the zero magnetic field line is measured to be 3.33 Gauss/cm when the current passing through the coils is 3.5A. We have also made measurements at other values of current and found, as expected, this gradient increases with current. These results match nicely with the estimated values and hence a significant step forward towards the experimental realization of the design proposed by us.
Abstract Strong-field-seeking states are the lowest-energy configurations for paramagnetic molecules in the magnetic field. Molecules in strong-field-seeking states cannot be trapped in a magnetostatic field because a magnetostatic maximum in free space is not allowed. In this paper, we propose an AC magnetic trap composed of two pairs of Helmholtz coils. The spatial magnetic field distribution is numerically calculated and the time-sequential control is depicted. We investigate the influence of the switching frequency and the electric current in the coils on the performance of our trap. Variations of the location and phase-space distribution during a whole switching cycle are simulated. Finally, we study the impact of time during which the field is switched off on the number of captured molecules in a switching cycle.
We describe the design, construction and performance of three realizations of a high-field superconducting magnetic trap for neutral atoms and molecules. Each of these traps utilizes a pair of coaxial coils in the anti-Helmholtz geometry and achieves depths greater than 4 T, allowing it to capture magnetic atoms and molecules cooled in a cryogenic buffer gas. Achieving this depth requires that the repulsive force between the coils (which can exceed 30 metric tons) be contained. We also describe additional features of the traps, including the elimination of trapped fluxes from the coils and the integration of the coils into a cryogenic vacuum environment suitable for producing cold atoms and molecules.
Abstract Atom chips provide flexible technologies for implementing modern concepts in quantum optics, quantum measurement, and quantum information processing. Atom chips are miniature devices that confine, control and manipulate cold atoms using electric, magnetic, and light fields. Due to the shrinkage of scale, arbitrary magnetic traps can be generated from current sources outside the chip’s vacuum compartment, in contrast to a traditional setup. This makes it easy to change trap configurations in an experiment that involves rapid prototyping of quantum states and quantum trajectory designs in free space. In this work, we show relevant parameters needed for transferring a cold atom cloud at the recoil limit from a magneto-optical trap (MOT) to an area close to the atom chip. To create a movable magnetic potential for this transfer, we used the MOT coils and an additional pair of coils in an anti-Helmholtz configuration. The properties of the movable potential were obtained by performing the Computer Simulation Tool (CST EM Studio suite®). Furthermore, an appropriate magnetic trap on a chip is developed, based on the simulation from COMSOL Multiphysics. We used a magnetic field gradient of around 20 G/cm to transport the cold atom with a distance over 20 mm with a temperature gain below 100 micro-Kelvin. The simulation results are based on an atom chip with a size of 2×2 cm2 and a copper wire thickness of 2 mm. The atom chip consists of Z, U and I-shaped wires that generate a quadrupole magnetic field. The resulting field minimum can be made at least 7 mm away from the chip surface.
This work has investigated the Magneto-Optical Trap (MOT) system used to produce Bose-Einstein Condensate (BEC). A primary challenge addressed in this study concerns the geometric limitations of traditional single-pair anti-Helmholtz coil configurations, where the magnetic field peaks occur outside the accessible inter-coil region. To overcome this limitation, we have explored the use of double-pair anti-Helmholtz coil configurations that create well-shaped magnetic field potentials centered at the experimentally accessible z=0z=0z=0 location. This investigation encompasses the three sequential processes of atom cooling: cooling in a linear external magnetic field through Doppler cooling, cooling in a well-shaped magnetic field through trapping, and evaporative cooling of atoms to achieve sub-microkelvin temperatures. Through theoretical analysis and numerical simulation, we have determined optimal geometric parameters for the coil configuration and operational parameters including laser detuning, saturation intensity, and initial atom populations for 87Rb{}^{87}\text{Rb}87Rb BEC production. The results indicate that with the optimized configuration, the system can achieve final temperatures of approximately Tf∼60 nKT_f \sim 60\,\mathrm{nK}Tf​∼60nK and produce condensate populations of ∼105\sim 10^5∼105 atoms with a mean density of n0=4.9×1015 m−3n_0 = 4.9 \times 10^{15}\,\mathrm{m}^{-3}n0​=4.9×1015m−3, providing systematic design guidance for experimental BEC systems