Argon purification studies and a novel liquid argon re-circulation system

Future giant liquid argon (LAr) time projection chambers (TPCs) require a purity of better than 0.1 parts per billion (ppb) to allow the ionised electrons to drift without significant capture by any electronegative impurities. We present a comprehensive study of the effects of electronegative impuri...

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Bibliographic Details
Published in:Journal of instrumentation 2011-08, Vol.6 (8), p.1-22
Main Authors: Mavrokoridis, K, Calland, R G, Coleman, J, Lightfoot, P K, McCauley, N, McCormick, K J, Touramanis, C
Format: Article
Language:English
Subjects:
Argon
Cartridges
Electronegativity
Impurities
Liquids
Purification
Purity
Scintillation
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Summary:Future giant liquid argon (LAr) time projection chambers (TPCs) require a purity of better than 0.1 parts per billion (ppb) to allow the ionised electrons to drift without significant capture by any electronegative impurities. We present a comprehensive study of the effects of electronegative impurity on gaseous and liquid argon scintillation light, an analysis of the efficiency of various purification chemicals, as well as the Liverpool LAr setup, which utilises a novel re-circulation purification system. Of the impurities tested - Air, O sub(2), H sub(2)O, N sub(2) and CO sub(2) in the range of between 0.01 ppm to 1000 ppm - H sub(2)O was found to have the most profound effect on gaseous argon scintillation light, and N sub(2) was found to have the least. Additionally, a correlation between the slow component decay time and the total energy deposited with 0.01 ppm - 100 ppm O sub(2) contamination levels in liquid argon has been established. The superiority of molecular sieves over anhydrous complexes at absorbing Ar gas, N sub(2) gas and H sub(2)O vapour has been quantified using BET isotherm analysis. The efficiency of Cu and P sub(2)O sub(5) at removing O sub(2) and H sub(2)O impurities from 1 bar N6 argon gas at both room temperature and -130 degree C was investigated and found to be high. A novel, highly scalable LAr re-circulation system has been developed. The complete system, consisting of a motorised bellows pump operating in liquid and a purification cartridge, were designed and built in-house. The system was operated successfully over many days and achieved a re-circulation rate of 27 litres/hour and high purity.
ISSN:1748-0221
1748-0221
DOI:10.1088/1748-0221/6/08/P08003