Magnetic trap design for precision antihydrogen gravity measurement in ALPHA-g at CERN

ALPHA first measured the gravitational mass of antihydrogen atoms in a magnetic minimum trap in 2013, limiting anomalous gravity-like forces coupled to the antiatoms to \textless 75 times the ordinary gravity. A new apparatus is being designed to tighten the limit to much better than order unity. It entails a \textasciitilde 2 meter long magnetic trap with a vertical long axis to enhance gravity signal. The trap magnets are designed to ensure magnetic up-down asymmetry \textgreater 1e-5 T in the central region. This field control is achieved by carefully considering the effect of winding errors, the inter-connections between current loops, the location of current leads, shape of slices, as well as the detailed characteristics of superconducting wires.