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.
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.
The utility model for the levelling system developed for Xenoscope at UZH is now visible online under the file number DE 20 2021 101 412 U1. This mechanism allows for a precise, almost force-free horizontal fine-adjustment of high mass assemblies. I developed it during my PhD with input by my colleague Frédéric Girard. In depth searches by both the German Patent and Trade Mark Office, and the Swiss Federal Institute of Intellectual Property indicate its novelty.
Edit 1 October 2022: The pending Swiss patent is now also published: CH718439 A2
My PhD thesis will be awarded with a distinction by the Faculty of Science of UZH! I will receive the certificate during the PhD graduation ceremony on September 30.
