Observation of oscillatory radial electric field relaxation in a helical plasma by Alonso, J, Sanchez, E, Calvo, I, Velasco, J, Perfilov, S, Chmyga, A, Eliseev, L, Krupnik, L, Estrada, T, Kleiber, R, McCarthy, K, Melnikov, A, Monreal, P, Parra Diaz, F, Zhezhera, A, TJ-II Team