Speaker
Dr
Henning Back
(Princeton University)
Description
The cosmogenic $^39$Ar concentration in atmospheric argon is 8.1x10$^{-16}$, which amounts to 1Bq of $^39$Ar decays in a kg of atmospheric argon. This decay rate can limit the size of liquid argon dark matter detectors due to pile-up. The cosmic ray shielding by the earth means that argon from deep underground should not contain $^39$Ar. CO$_2$ wells in Southwestern Colorado have been found to contain approximately 500ppm of argon as a contamination in the CO$_2$. We have developed an extensive system of processes to extract the low radioactivity underground argon (UAr) from the CO$_2$ and purify it for use in the Darkside 50 experiment. Through chromatography, our plant in Colorado extracts an UAr/He/N$_2$ mixture from the CO$_2$, which, to date, has produced more than 170 kg of UAr. At Fermilab we have developed cryogenic plants that: separate helium at high pressure, remove residual organic contamination (CO$_2$, C$_4$H$_10$, C$_5$H$_12$, etc.), and finally purify the argon from the nitrogen through cryogenic distillation. We are also trapping residual argon in our waste streams to maximize UAr retention. In this talk I will discuss each of these plants and their performance, as well as the status of UAr purification.
Primary author
Dr
Henning Back
(Princeton University)
Co-authors
Prof.
Andrew Alton
(Augustana College)
Mr
Augusto Goretti
(Princeton University)
Dr
Ben Loer
(FNAL)
Mr
Cary Kendziora
(Fermilab)
Prof.
Cristiano Galbiati
(Princeton University)
David Montanari
(Fermilab)
Mr
Federico Gabriele
(LNGS)
Prof.
Frank Calaprice
(Princeton University)
Mr
Michele Montuschi
(LNGS)
Mr
Pablo Mosteiro
(Princeton University)
Mr
Paolo Cavalcante
(LNGS)
Stephen Pordes
(Fermilab)