A. Matsuoka et al., VACUUM PROPERTY IMPROVEMENT OF A L=1 HELIOTRON TORSATRON DEVICE BY HIGHER HARMONIC MODULATION ON A HELICAL-COIL/, Journal of the Physical Society of Japan, 63(1), 1994, pp. 121-126
A winding law of a helical coil with higher harmonic modulation can pr
oduce a deep magnetic well because of a suitable Vertical field format
ion. The sin (n phi) modulation (n = 1, 2, 3, 4) on a L = 1 helical co
il makes magnetic surfaces resembling those of L = n helical coil at t
heta = 0. Also it increases a magnetic ripple and rotational transform
on a magnetic axis.