LHe bath cryostats (Dewar flasks) are made from DURAN borosilicate glass 3.3 in compliance with DIN/ISO 3585 and have been designed for the use of liquid helium. Glass cryostats must be designed so that they can be re-evacuated, as DURAN borosilicate glass 3.3 is not helium-tight. The standard vacuum connection used is an NW25 glass flange with clamp and O-ring, which makes it possible to establish the connection to the vacuum pump using small flange components made from metal. Upon request, a vacuum glass tap or a glued-on metal flange can be delivered as a pump flange.
The helium cryostats are only made to order. Changes as to the dimensions, connections or volumes can usually be made at no extra charge. The LHe cryostats listed in the table correspond to the most common dimensions and volumes. The standard LHe cryostats come with opposing viewing strips. The cryostats can also be delivered with one viewing strip or fully silvered.