TRD Gas System


A complication of the Transition Radiation Detector (TRD) is the need for this special Xe:CO2 mixture. The mixture must be carefully regulated (80% xenon, accurate to better than 1%), free of contamination (less than 1 part per million of fluorocarbons or oxygen, for example), it mustn't leak out, and the pressure must be monitored carefully.

To keep the detector stocked with good gas, AMS has a gas-mixing system; an extra 100 lbs of Xe and 5 of CO2, stored in lightweight bottles, will accompany the TRD into space. A network of valves and pressure sensors can whip up fresh Xe:CO2 80:20, at a rate of 7 liters per day, and introduce it to the 300 liter detector volume. Within the TRD, the gas is kept going around and around in a circuit to keep it uniform, and there are pumps, valves, and CO2 analyzers to monitor it.

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