Characterization of Ar/N2 gaseous mixtures for MPGD-based detectors

We report a spectroscopic study of primary scintillation of Ar/$N_{2}$ mixtures obtained under X-ray irradiation, for different concentrations of $N_{2}$ (0%-100%) and pressures (1-5 bar). Special care was taken with respect to Nitric Oxide (NO) contamination in the chamber, which was found to produce strong scintillation at the ppm level, in accordance with previous works. Scintillation of $N_{2}$ was determined to be independent of the existence of NO.
We show the good performance of $N_{2}$, in comparison to $CF_{4}$, as VUV-quencher and wavelength shifter, where the highest scintillation yield was measured in the range of 0.5% - 10% of $N_{2}$ concentration.