Using a tilted electric field (TEF) soft-landing collector, one of the authors has achieved an efficiency improvement of a TWT from 11.8 percent to 43.0 percent. However, the TEF collector requires a uniform magnetic field covering the entire collector space, and hence, a heavy magnet or electromagnet, which is far from practical in high-power tubes. This paper proposes the periodic magnetic field (PMF) soft-landing collector, which is a periodic field version of the TEF collector. It requires much lighter magnets than a TEF collector does. The principle, design theory, preliminary low-perveance experiment, and a relevant computer simulation are presented. Finally experiments with a medium-power UHF TWT equipped with a PMF collector are described.