In this paper, the application of simultaneous wireless information and power transfer (SWIPT) to non-orthogonal multiple access (NOMA) is investigated. A new cooperative SWIPT NOMA protocol is proposed in which near NOMA users which are close to the source act as energy harvesting relays to help far NOMA users. By assuming that all users are spatially randomly located in the network, new analytical expressions for outage probability are derived both for the near and far users, in order to characterize the performance of the proposed protocol. The diversity of both the near and far users is analyzed to demonstrate that the use of SWIPT will not jeopardize the diversity order compared to the conventional NOMA. Numerical results are also provided to verify the accuracy of the developed analytical results.