Abstract
The Cosmics Leaving OUtdoor Droplets (CLOUD) experiment at the European Organization for Nuclear Research (CERN) is investigating the nucleation and growth of aerosol particles under atmospheric conditions and their activation into cloud droplets. The experiment comprises an ultraclean 26 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> chamber and its associated systems (the CLOUD facility) together with a suite of around 50 advanced instruments attached to the chamber via sampling probes to analyze its contents. The set of instruments changes for each experimental campaign according to the scientific goals. The central function of the CLOUD DAQ (data acquisition) system is to combine the data from these autonomous and inhomogeneous instruments into a single, integrated CLOUD experiment database. The DAQ system needs to be highly adaptable to allow a fast setup over a single installation week at the start of each campaign when the instruments are brought to CERN and installed at the CLOUD chamber. Each campaign requires high flexibility and fast response to changes in instrument configuration or experimental parameters. The experiments require online monitoring of the physical and chemical measurements with delays of only a few seconds. In addition, the raw data, the monitoring databases, and the processed data must be archived and provided to the international collaboration for both real-time and later analyses. We will describe the various components of the CLOUD DAQ and computing infrastructure, together with the reasons for the chosen solutions.
Highlights
T HE Cosmics Leaving OUtdoor Droplets (CLOUD) experiment at the European Organization for NuclearResearch (CERN) studies the formation and growth of aerosolManuscript received June 14, 2020; accepted August 24, 2020
We have described a novel DAQ system for the CLOUD experiment at CERN, which combines the data from a diverse set of autonomous instruments into a single integrated experiment
The DAQ system can be rapidly established over a short period of around five days at the start of each measurement campaign when the instruments are brought to the CLOUD chamber
Summary
T HE Cosmics Leaving OUtdoor Droplets (CLOUD) experiment at the European Organization for Nuclear. Such controlled measurements are performed during campaigns, occurring once or twice a year with an approximate duration of three months, during which data are collected 24 h/day and seven days per week During these measurement periods, researchers from collaborating institutes operate their instruments at the CLOUD chamber, to obtain a comprehensive understanding of the processes involved. As the campaign proceeds, flexibility, fast response, and immediate interpretation of the data are key to choosing the optimum operating conditions for the experiments This makes quasi-real-time online monitoring of the experimental data mandatory. The raw and processed data from each campaign must be stored and made available to the collaboration This includes the data from both the instruments and the CLOUD facility systems (gas, illumination, thermal, chamber mixing fans, high voltage, and beam counters).
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