Temperature uniformity in the CERN CLOUD chamber

The CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at CERN is studying the nucleation and growth of aerosol particles under atmospheric conditions, and their activation into cloud droplets. A key feature of the CLOU
The CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at CERN is studying the nucleation and growth of aerosol particles under atmospheric conditions, and their activation into cloud droplets. A key feature of the CLOUD experiment is precise control of the experimental parameters. Temperature uniformity and stability in the chamber are important since many of the processes under study are sensitive to temperature and also to contaminants that can be released from the stainless steel walls by upward temperature fluctuations. The air enclosed within the 3 m CLOUD chamber is equipped with several arrays (strings) of high precision, fast-response thermometers to measure its temperature. Here we present a study of the air temperature uniformity inside the CLOUD chamber under various experimental conditions. Measurements were performed under calibration conditions and run conditions, which are distinguished by the flow rate of fresh air and trace gases entering the chamber: 20 l/min and up to 210 l/min, respectively. During steady-state calibration runs between −70 °C and +20 °C, the air temperature uniformity is better than +/−0.06 °C in the radial direction and +/−0.1 °C in the vertical direction. Larger non-uniformities are present during experimental runs, depending on the temperature control of the make-up air and trace gases (since some trace gases require elevated temperatures until injection into the chamber). The temperature stability is a few times 0.01 °C over periods of several hours during either calibration or steady-state run conditions. During rapid adiabatic expansions to activate cloud droplets and ice particles, the chamber walls are up to 10 °C warmer than the enclosed air. This results in larger non-uniformities while the air returns to its equilibrium temperature with time constant of about 200 s.
show moreshow less

Download full text files

Export metadata

  • Export Bibtex
  • Export RIS
Metadaten
Author:Antonio Dias, Sebastian Ehrhart, Alexander L. Vogel, Christina Williamson, Joao Almeida, Jasper Kirkby, Serge Mathot, Samuel Mumford, Antti Onnela
URN:urn:nbn:de:hebis:30:3-450221
DOI:http://dx.doi.org/10.5194/amt-2017-114
ISSN:1867-8610
Parent Title (English):Atmospheric measurement techniques discussions
Publisher:Copernicus
Place of publication:Katlenburg-Lindau
Document Type:Article
Language:English
Year of Completion:2017
Date of first Publication:2017/05/16
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2017/12/12
Volume:10
Pagenumber:29
First Page:1
Last Page:29
Note:
© Author(s) 2017. CC-BY 3.0 License
HeBIS PPN:427808278
Institutes:Geowissenschaften
Dewey Decimal Classification:550 Geowissenschaften
Sammlungen:Universitätspublikationen
Licence (German):License LogoCreative Commons - Namensnennung 3.0

$Rev: 11761 $