Development of a 7 T NbTi solenoidal magnet with 72 mm aperture

•A close-packed coil with a 72 mm aperture is developed.•The can generate a 7.35 T central magnetic field at an operation current of 176 a with no coil quench.•The maximum loadline of the coil is proved to be 98.96%.•The VPI method is applicable to the close-packed coils (tcoil ≤ 28 mm) wound from the formvar-insulated NbTi wire.