Efficient 4He cryostats for storage Dewars

We have designed 4He cryostats which can be inserted into storage Dewars. These cryostats have the advantages of extremely low (and recoverable) helium consumption, fast cool-down and warm-up times, excellent temperature range and stability, and they supply a low electrical noise and low vibration environment for electrical and thermal measurements. Design and construction details of one such cryostat are presented. We further present specific heat data on crystalline boron to demonstrate the performance of one of these cryostats in a particularly sensitive experiment.