Magnets
Last steps for poloidal field coil #5
20 Apr 2020
In a spacious manufacturing facility on site, Europe's first production poloidal field coil has been transferred to the final assembly station. Contractors used a 400-tonne gantry crane to lift the coil on 11 April.
From the start of coil winding activities in September 2017, to the resin impregnation of the fully formed coil last month, the realization of poloidal field coil #5 (PF5) has been a meticulous, stage-by-stage process. It is now just one step from completion, as the coil has been moved to the final workstation for cleaning, testing (dimensional and electrical), covering and clamping.
Nearly 12 kilometres of niobium-titanium (NbTi) conductor have gone into the winding of PF5, which is formed from eight individually impregnated double pancakes. The pancakes were stacked, joined electrically, and wrapped in ground insulation (glass/kapton tape) in preparation for vacuum pressure impregnation—a process that confers rigidity to the final winding pack and insulates the coil electrically.
Impregnation took place in March. First, all air was pumped out of the mould that had been built around the winding pack. Then the mould was heated (90 °C for 96 hours) to dry the coil insulation and then cooled (to 50 °C). Over a period of 60 hours, approximately 3,000 litres of resin were injected under pressure, and the resin was allowed to "gel." Finally, the resin was "cured" for 60 hours.
On 11 April, the 280-tonne PF5 winding pack was gently lifted by gantry crane and transferred to the last production station of the facility—final assembly. After the mould is removed and final covers and clamps are attached, the final weight of the coil will be 342 tonnes.
Read a full report on the Fusion for Energy website.