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We discuss the oscillation and the radiation of a superconducting dot in a nonuniform magnetic .eld produced by a Helmholtz coil. Two oscillation modes (parallel mode and antiparallel mode) exist, depending on which direction the currents °ow in the two coils of the Helmholtz coil. Our calculations are as follows: (i) There is a characteristic diameter-to-height ratio of Helmholtz coil for which a maximum frequency can be produced. The ratios are 0.76 and 0.82 for the parallel mode and the antiparallel mode, respectively. (ii) Flux trapped in a superconducting dot promoted a nonlinear oscillation. In other words, as the trapped °ux increases, the antiparallel-mode frequency increases for a certain radius-to-height ratio of a Helmholtz coil. Even though the frictional force is not present, an energy loss still exists due to radiation. We show that the oscillations in both modes stop as time approaches in.nity. As time increases, the oscillation amplitude decreases in an inverse-root form for the parallel-mode oscillation and exponentially for the antiparallel-mode oscillation. The half-lives of the amplitudes have been calculated as 2:0 £ 1031 years for the parallel-mode oscillation and 2:1 £ 1031 years for the antiparallel-mode oscillation.