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Liquid Argon

20 May 2024

LARA Test Stand

Development of LARA

The UCL LARA test stand (Liquid Argon Research Area) is one of only a handful of working liquid argon chambers in the UK. It is constantly being improved upon so that UCL can contribute to both liquid argon detector R&D, as well as to provide a testing facility for our contributions to experiments such as SBND and WA105 (ProtoDUNE Double-Phase).


Liquefaction of argon inside LARA

At LARA's core is a 30l stainless steel chamber which is first evacuated to high vacuum, and using ordinary liquid argon as a coolant, it is then filled with pure gas argon which then liquefies in the chamber to fill it with liquid argon. The large picture below shows the LARA test stand with a vacuum pump on the left, and a dewar containing the inner LAr chamber on the right. The top consists of a piping system with which the gas argon can further be purified via a number of filtering systems if desired.

The LARA chamber has been used and tested a number of times now and liquefaction has successfully been achieved, testing equipment such as SiPMs, temperature and level meters, and also a PMT with TPB as a wavelength shifter to shift the very-UV 128nm light in liquid argon to higher wavelengths to be detectable by the optical detectors. The left image above shows the LARA chamber, and the "blue" image shows the inside of the LARA chamber approximately half filled with liquid argon during one of the tests. Importantly, the chamber has also been used to leak test a cold high voltage feedthrough for Dark Matter experiments. We have also used the LARA test stand to leak and stress test the SBND high voltage feedthrough prototypes and to test the WA105 purity monitor prototype. For questions about LARA please contact Dr Anastasia Freshville.