Abstract
We present an electromagnet combining a large number of windings in a constrained volume with efficient cooling. It is based on bulk copper where a small pitch spiral is cut out and impregnated with epoxy, forming an ensemble which is then machined at will to maximize the use of the available volume. Water cooling is achieved in parallel by direct contact between coolant and the copper windings. A pair of such coils produces magnetic fields suitable for exploiting the broad Feshbach resonance of ^66Li at 832.2\,832.2G. It offers a compact and cost-effective alternative solution for quantum gas experiments.
Highlights
Homogeneous magnetic fields of the order of a thousand Gauss are at the core of quantum gas experiments, from laser cooling and trapping [1] to the use of Feshbach resonances controlling the inter-atomic interactions [2]
More compact systems of magnetic traps use in-vacuum electromagnets [9,10,11], or atom chips [12, 13], but those are not adapted to experiments requiring large homogeneous fields
We present electromagnets optimizing space occupation, offering very large shape flexibility while allowing to reach the high fields required for the use of Feshbach resonances in 6Li [17]
Summary
Homogeneous magnetic fields of the order of a thousand Gauss are at the core of quantum gas experiments, from laser cooling and trapping [1] to the use of Feshbach resonances controlling the inter-atomic interactions [2]. As experimental apparatus become more and more complex, with more laser beams or high-aperture imaging systems to accommodate, space occupation as well as heat management constraints become more and more acute, calling for optimized and flexible electromagnet designs. The common ground of these electromagnet concepts is the improvement over the widely used design based on wound copper wire (see for example [14]) This solution is privileged due to its robustness, and the use of hollow wire allows for water cooling with good contact between copper and the coolant. Several circuits of coolant fluid are needed to limit temperature inhomogeneities in the coil Another drawback is the lack of flexibility and poor space occupation efficiency: hollow copper wires are typically several millimeters wide, restricting the number of windings in a given volume. We present the detailed fabrication procedure of the ensemble, as well as performance in terms of magnetic fields and heat management, demonstrating the suitability of this approach for quantum gas experiments
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