Abstract
We describe a very compact dilution refrigerator with base temperature below 3 mK and the potential for a large circulation rate. The heat exchangers, of sintered silver "Grenoble" type, are straight and very simple to make. The exchangers are stacked vertically in a hexagonal array with alternate "up" and "down" flow paths for economy of space. Such a configuration alone presents difficulties in initial filling and also gives rise to instabilities during running. A simple "short-circuit" can be used to cure all these problems. The resultant machine is easily filled and runs without instabilities. The design allows high power dilution refrigerators to be used in dewars of much smaller diameter than is customary now, with heat exchangers which can be readily made in any laboratory.