Pressure dependence of secondary NIR scintillation

The variation with the charge gain of the total number of photons emitted per electron, in the visible and NIR regions (0.4 < λ < 1 μm), in Ar/CF₄ mixtures, is investigated for CF₄ concentrations below 15%. Measurements are performed in a uniform field configuration and results are presented for charge gains below 100, under X-ray excitation. The spectral distribution of the emitted light in Ar/CF₄ mixtures is also analyzed. The pressure dependence (1-5 atm) of the secondary light output, in the visible and near infrared regions (NIR) is studied as a function of the reduced electric field E/P for pure argon and argon-tetrafluoromethane mixtures. Above charge multiplication threshold, the number of NIR photons decreases with increasing pressure.