[en] This paper examines the performance of another possibility for accumulating beam - an isochronous ring - because it can also be used to accumulate a large current, but with this type of ring stacking and extraction occur before instabilities have time to build up. Another feature is that bunch structure is preserved during stacking, and thus rebunching can be avoided. We will look at the use of an isochronous ring for a demonstration high temperature experiment which has been proposed as a means for developing and proving the accelerator technology, but with a more modest investment than required for the fusion driver, then examine the possible extrapolation of this concept to a demonstration driver