Title: High-power closed-cycle $^4$He cryostat with top-loading sample exchange,
Abstract: We report on the development of a versatile cryogen-free laboratory cryostat
based upon a commercial pulse tube cryocooler. It provides enough cooling power
for continuous recondensation of circulating $^4$He gas at a condensation
pressure of approximately 250~mbar. Moreover, the cryostat allows for exchange
of different cryostat-inserts as well as fast and easy "wet" top-loading of
samples directly into the 1 K pot with a turn-over time of less than 75~min.
Starting from room temperature and using a $^4$He cryostat-insert, a base
temperature of 1.0~K is reached within approximately seven hours and a cooling
power of 250~mW is established at 1.24~K.