TJ-II:Coil system

The core coil pack consists of three coils: the circular core (CC), the helix 1 (HX1), and the helix 2 (HX2).

The TJ-II coil system is listed in the table below. All coils are directly cooled by water flowing trough longitudinal holes in the conductors. All coils have a reinforced structure to avoid mechanical deformations.

Coil	Number	Size (m)	Turns
Circular (CC)	1	R = 1.5	24
Helical (HX)	1	R = 1.5 swing = 0.07	24
Toroidal (TF)	28	r = 0.425	8
Toroidal (TF)	4	r = 0.475	9
Vertical (VF)	2	R = 2.25	16
Compensation (OH)	2	R = 0.78	20
Compensation (OH)	2	R = 2.29	1
Radial (R)	2	R = 0.74	7
Radial (R)	2	R = 2.24	5

The main helical field is produced by the CC, HX, and TF coils. The vertical field coils (VF) allow positioning the magnetic axis. The ohmic coils (OH) can generate a loop voltage of 0.1 V, intended to cancel spurious toroidal currents. The radial coils (R) produce a trimming radial field of up to 100 G, intended to compensate stray fields.