Conway, Z.A. Barcikowski, A. Cherry, G.L. Fischer, R.L. Gerbick, S.M. Hopper, C.S. Kedzie, M. Kelly, M.P. Kim, S.H. MacDonald, S.W.T. Mustapha, B. Ostroumov, P.N. Reid, T. JACoW Geneva, Switzerland 978-3-95450-178-6 10.18429/JACoW-SRF2015-WEBA05 English 973-975 WEBA05 cavity niobium accelerating-gradient cryomodule vacuum Contribution to a conference proceedings 2015 2015-12 http://dx.doi.org/10.18429/JACoW-SRF2015-WEBA05 http://srf2015.vrws.de/papers/weba05.pdf We have designed, fabricated and tested two new half-wave resonators following the successful development of a series of niobium superconducting quarter-wave cavities. The half-wave resonators are optimized for β = 0.11 ions, operate at 162.5 MHz and are intended to provide up to 2 MV effective voltage for particles with the optimal velocity. Testing of the first two half-wave resonators is complete with both reaching accelerating voltages greater than 3.5 MV with low-field residual resistances of 1.7 and 2.3 nΩ respectively. The intention of this paper is to provide insight into how Argonne achieves low-residual resistances and high surface fields in low-beta cavities by describing the cavity design, fabrication, processing and testing.