3 December, 1996

We worked alot today with Paul Sullivan who is a cryogenic technician here at the pole. HIs responsibilities include providing crogenic gases and equipment for the researchers. Many of the researchers here use liquid nitrogen and liquid helium in their instruments. These are used in the detectors of the instruments since these devices are trying to detect small amounts of incoming radiation of various

types: radio waves, gamma rays,infrared waves, etc. If the detectors are warm it would be more difficult for them to sense these incoming energies, and so they are kept very cold by using cryogenic gases.

The most common gases that I have seen in use so far are Helium and Nitrogen. The gases are stored in large containers and then moved

into other containers for use that are called dewars. There are several very large dewars here at the South Pole. The gases also behave differently here because of the low temperatures. The temperatures may be so cold that some gases, such as propane, are below their vapor pressure, which means that when you open the valve on the tank, no gas changes to vapor. Instead it either has to be warmed up first or pumped out with another gas such as nitrogen. Propane is used to for heating in some of the buildings. Helium

is also used for balloon launches We spent the day pumping out

the dewar on the detector part of the instrument and refilling

it with nitrogen. The dewar is pumped out using a vacuum pump

to establish a good vacuum inside and then it is filled with nitrogen. We will allow the dewar to sit here overnight to

determine if it is leaking or not.