Ten layers of aluminum foil separated by glass-fibre tissue were used to super insulate and heat loses from the
shield was further reduced. The three temperature control loops were operated under computer control using an a.c. resistance bridge, channel scanner, and programmable power supplies. For operation below ambient temperature, the apparatus was immersed in a Dewar vessel filled with ethanol which is cooled down thanks to a Julabo system programming the temperature to be 253 K when the working temperature is 273 K and 283 K when it is 325 K. In this way is easy to assure the correct behavior of controllers which are designed only to heat