We investigate the gas gain behaviour of a triple-GEM configuration in gas
mixtures of argon, krypton and xenon with ten and thirty percent of carbon
dioxide at pressures between 1 and 3 bar. Since the signal widths affect the
dead time behaviour of the detector we present signal length measurements to
evaluate the use of the triple-GEM in time-resolved X-ray imaging.Comment: 19 pages, 21 figures, revised version, accepted for publication in
Nucl. Instr. and Meth.