Annular cooling fluid passage for magnets

A magnet having an annular coolant fluid passage is generally described. Various examples provide a magnet including a first magnet and a second magnet disposed around an ion beam coupler with an aperture there through. The first and second magnets each including a metal core having a cavity therein, one or more conductive wire wraps disposed around the metal core, and an annular core element configured to be inserted into the cavity, wherein an annular coolant fluid passage is formed between the cavity and the annular core element. Furthermore, the annular core element may have a first diameter and a middle section having a second diameter, the second diameter being less than the first diameter. Other embodiments are disclosed and claimed.