Saturday, February 21, 2009

Gas Analyzer

The Thermal and Evolved Gas Analyzer (TEGA) is a scientific instrument aboard the Phoenix spacecraft. TEGA's design is based on experience gained from the failed Mars Polar Lander. Soil samples taken from the Martian surface by the robot arm are eventually delivered to the TEGA, where they are heated in an oven to about 1,000ÂșC. This heat causes the volatile compounds to be given off as gases which are sent to a mass spectrometer for analysis. This spectrometer is adjusted to measure particularly the isotope ratios for hydrogen, oxygen, carbon, nitrogen, and heavier gases. Detection values as low as 10 parts per billion. The Phoenix TEGA has 8 ovens, which are enough for 8 samples.

A residual gas analyzer (RGA) is a small and usually rugged mass spectrometer, typically designed for process control and contamination monitoring in the semiconductor industry. Utilizing quadrupole technology, there exists two implementations, utilizing either an open ion source (OIS) or a closed ion source (CIS). RGAs may be found in high vacuum applications such as research chambers, surface science setups, accelerators, scanning microscopes, etc. RGAs are used in most cases to monitor the quality of the vacuum and easily detect minute traces of impurities in the low-pressure gas environment. These impurities can be measured down to 10 − 14 Torr levels, possessing sub-ppm detectability in the absence of background interferences.

RGAs would also be used as sensitive in-situ, helium leak detectors. With vacuum systems pumped down to lower than 10 - 5Torr—checking of the integrity of the vacuum seals and the quality of the vacuum—air leaks, virtual leaks and other contaminants at low levels may be detected before a process is initiated.