This week DarkSide had a meeting with the INFN Review Committee with fruitful discussions and good feedback. I presented the results of the first run of the UAr testbed for the DS-20k detector Mock-up in the UAr Cryogenics breakout session. We used our spare time to open the cryostat and to install the new heat exchanger geometry. After performing a couple of other upgrades and maintenance on the setup, we are on track to restart operations beginning of February!

Liquid argon is running through the veins of our UAr cryogenics test stand! The cryostat is fully filled and we commence the testing of the cooling control system and the system efficiency.

For the DS-20k Mockup TPC I am responsible for the design of the capacitive short level meters, the liquid level control and a cryogenic camera. The first parts are already finished. Thanks to the team of the Mechanical Workshop of the Physics Department of the University of Zurich for the incredible machining job! In the pictures we see the bubbler/boiler unit and parts of the level meters for the liquid level control.

The run has started today and we are currently acquiring valuable data with gas argon at room temperature to characterise the compressor performance and the flow resistance of the recirculation circuit. Thanks to everybody involved – the reassembly of the system at LNGS after the transport from CERN was a huge amount of work and the start of the run is an important landmark.

This week we have installed the nitrogen phase separator on the cryogenics system test bed in Hall C at LNGS. This is the last major piece of the setup. The run can start soon!

Last week we have started to unbox, place and assemble the Underground Argon (UAr) Cryogenic System for DarkSide-20k (DS-20k) underground at the Laboratori Nazionali del Gran Sasso (LNGS), Italy, which was shipped from CERN end of last year after its successful benchmarking. All heavy items are in place and connected, and interfaces with the lab have been identified. We will continue the testing of the cryo-system at LNGS, in particular with a modified heat exchanger geometry for argon boil-off, before the system will be used for a mechanical mockup test of DS-20k.

Today is the last day of data acquisition of a one-month measurement campaign at CERN building 182. We monitored the longterm stability of the light yield of a large-scale PEN-ESR wavelength shifter reflector cage. This is a collaborative project of members of the DarkSide, LEGEND, DUNE and DEAP collaborations from AstroCeNT Warsaw, the University of Zurich, the Technical University Munich, the University of Edinburgh, from Nikhef Amsterdam and the University of Hawai’i at Mānoa.

This week I finally performed the measurement of the condensation rate of GAr in a tube heat exchanger immersed in LAr at various differential pressures. This test helps us to dimension the size and define the geometry of the heat exchanger for DS-20k, needed to boil of energy-efficiently 1000 slpm for recirculation. I measured the heat transfer coefficient for LAr-GAr cooling and phase change, and for LAr-LAr cooling.

This is my first self-made feedthrough, potted with epoxy and it is leak-tight! It is for the signal cables of a PT-100 temperature probe of the LAr-GAr heat transfer test setup from my previous post.

These are the gas components for a setup to test the liquefaction rate of pressurised argon gas when cooled by liquid argon at atmospheric pressure in an open tube heat exchanger. The gas components sit on top of an open Dewar flask, the heat exchanger will be immersed in the liquid below. Not bad for a one-day job with components I found in the lab and a little bit of DIY work, no?

The goal of the test is to determine the optimal geometry and the required exchange surface for the heat exchanger in the DS-20k cryostat. This heat exchanger will be necessary to boil off argon gas on the return site at a high rate for gas purification, and to liquefy the purified gas on the supply site.