  Liquid Helium is used widely, from hospitals to characterization of materials
at low temperatures. Many experiments at low temperatures require liquid
Helium, particularly when vibration isolation precludes the use of cryocoolers
and when one needs to cool heavy equipment such as superconducting coils. Here
we describe methods to simplify the operations required to use liquid Helium by
eliminating the use of high pressure bottles, avoiding blockage and improving
heating and cooling rates. First we show a simple and very low cost method to
transfer liquid Helium from a transport container into a cryostat that uses a
manual pump having pumping and pressurizing ports, giving a liquid Helium
transfer rate of about 100 liters an hour. Second, we describe a closed cycle
circuit of Helium gas cooled in an external liquid nitrogen bath that allows
precooling a cryogenic experiment without inserting liquid nitrogen into the
cryostat, eliminating problems associated to the presence of nitrogen around
superconducting magnets. And third, we show a sliding seal assembly and an
inner vacuum chamber design that allows inserting large experiments into liquid
Helium.
