We report the calibration of a gaseous Time Projection
Chamber based on Micromegas charge readout modules with cosmic ray
muons, utilizing their penetrating power and relatively uniform
energy deposition per unit length. Muon events were selected
through track reconstruction to characterize detector performances,
such as the drift velocity, electron lifetime, detector gain, and
electric field distortion. The evolution of detector performances
over a 50-day data-taking cycle was measured with the muon
calibration method. For instance, the drift velocity degraded from
3.40 ± 0.07 cm/μs to 3.06 ± 0.06 cm/μs
without gas purification, and then recovered with gas purification.
A 137Cs calibration source was also placed inside the
detector as a reference for muon calibrations.