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.
This week we had a Collaboration Meeting at GSSI in L’Aquila, Italy. I presented the progress on the cryogenics test within the Mockup programme and gave an update on the UAr Working Group activities.
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!
In the week of 12–16 June, the collaboration came together for a general meeting and progress review at LNGS. I had the opportunity to present the measurement prospects with the Mockup detector which will soon start operations, and I could engage in fruitful discussions on cryogenics-related aspects. It was also inspiring to see the exciting progress on the installation of the warm structure of the cryostat underground.
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.
New paper on the arXiv! In arXiv:2303.13963 my former group at UZH presents first electron drift measurements in liquid xenon with a 53 cm purity monitor in Xenoscope, a vertical DARWIN demonstrator. We present drift speed and diffusion measurements from a several-months run at 25–75 V/cm drift field. The highest electron lifetime reached was (664±23) µs. It also contains a description and the commissioning performance of the liquid recovery system BoX which was part of my PhD work. In the next phase, the purity monitor will be replaced by a 2.6 m TPC, built to directly demonstrate a drift over the full DARWIN height.
Edit 21 August 2023: The article is now published: Eur. Phys. J. C 83 717 (2023).
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.
The DarkSide collaboration met between 15th and 18th November at GSSI in L’Aquila, Italy, for a general meeting. We had many productive discussions and it was great to see everyone again.
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.
