Cryogen Free closed-cycle systems are an option, if liquid Helium is hardly available or Helium consumption is critical. Closed-cycle sytems are either available with Gifford-MacMahon type cryocoolers, Pulse Tube cryocooloers (from different manufactures) or Stirling type cooler from Sunpower, Inc.
Stirling type cryocoolers can be used down to 40 K and are easy to install and maintain. Pulse Tube cryocoolers represent the lastest technology in cryogen free cooling. As there are no moving parts inside the cooler they are an excellent choice for low vibration setups. Pulse Tube cryocoolers are available in different power classes up to 1.5 W @ 4 K. Samples can either be in vacuum or in exchange gas. If vibration is not a problem, CryoVac can also integrate GM-type cryocoolers in optical setups.