The use of Oxygen in gas mixtures for drift chambers is highly discouraged because Oxygen, being strongly electronegative, is generally believed to lead, even in very small quantities, to extremely reduced drift electron survival probability, thus preventing the detector's operation.The drift chamber of the MEG II experiment at PSI has been operating for several years with a gas mixture that mainly contains He:Isobutane in relative proportions of 90:10% by molar concentration, in addition to 1.5% Isopropanol and 0.5% Oxygen. Oxygen and Isopropanol are essential for the proper functioning of the chamber. The electron attachment in the mixture used has proven negligible for the proper operation of the chamber and agrees well with the Garfield++ simulation after correctly accounting for the three-body attachment simulation.
@article{arxiv.2511.07082,
title = {The Use of O2 in Gas Mixtures for Drift Chambers},
author = {A. M. Baldini and L. Bianco and H. Benmansour and G. Cavoto and F. Cei and M. Chiappini and A. Corvaglia and M. Francesconi and E. Gabbrielli and L. Galli and G. Gallucci and F. Grancagnolo and E. G. Grandoni and M. Grassi and F. Leonetti and D. Nicolo' and M. Panareo and D. Pasciuto and A. Papa and F. Renga and S. Scarpellini and A. Venturini and C. Voena},
journal= {arXiv preprint arXiv:2511.07082},
year = {2026}
}
Comments
19+1 pages, 15 figures, prepared for submission to JINST