The neutron scattering community has endorsed the need for a high‐power (1 to 5 MW) accelerator‐driven source of neutrons for materials research. Properly configured, the accelerator could produce very short (sub‐microsecond) bursts of cold neutrons, said time structure offering advantages over the continuous flux from a reactor for a large class of experiments. The recent cancellation of the ANS reactor project has increased the urgency to develop a comprehensive strategy based on the best technological scenarios. Studies to date have built on the experience from ISIS (the 160 kW source in the UK), and call for a high‐current (approx. 100 mA peak) H− source‐linac combination injecting into one or more accumulator rings in which beam may be further accelerated. The 1 to 5 GeV proton beam is extracted in a single turn and brought to the target‐moderator stations. The high current, high duty‐factor, high brightness and high reliability required of the ion source present a very large challenge to the ion sou...