Average pulse height as a function of drift time for pionsand electrons (with and without radiator). The time axis is shown with an arbitrary offset of\SI{0.3}{\micro\second}. The measurements were performed at the CERN PS with prototype read-out chambers that were smaller in overall size (active area \SI{25}{\centi\meter} $\times$ \SI{32}{\centi\meter}) but otherwise similar in construction to that of the final detector. Figure taken from .