Abstract We introduce a mini 3 He refrigerator, operating at ∼300 mK starting from 4.2 K without pumping on the main 4 He bath. The innovative idea is that the present one is suitable for a very fast operation; for its use, it is sufficient a storage 4 He Dewar. In this way we drastically reduce the time required to cool it down, because there is no need for a classic cryostat. This prototype is particularly aimed for all those operations in which it is necessary to test a large number of samples that do not require long duration measurements at low temperature.