Charge and light gain measurements in argon-nitrogen mixtures using a gas scintillation proportional counter

Gaseous scintillation detection and amplification in variable pressure scanning electron microscopy

“…62 The first continuum is dominant over the second continuum at high values of E / p, and the second continuum dominates at low E / p. Many PMTs used in GPSC have their peak response in the near UV ͑300− 380 nm͒ to short vis range. 59,60 The intensity of the second positive band has been found to ͑i͒ increase with increasing admixture partial pressure up to concentrations of Ϸ0.1% and then decrease with increasing admixture concentration and ͑ii͒ increase with decreasing p at constant admixture concentration. 46,56,60,63,64 The presence of a small concentration ͑Ϸ0.1% -4 % ͒ of N 2 in an atomic gas, such as Ar, quenches the continuum emissions, described above, and gives rise to corresponding emission lines between 300 and 420 nm that are referred to as the second positive band.…”

“…For example, if a swarm electron excites a gas molecule above a particular resonance level the difference between the energy imparted to the molecule by the electron and the resonance level will emit continuous radiation. 25,44,58 The detection of ionizing radiation using gaseous proportional scintillation detectors is normally performed ͑i͒ using noble gases due to their strong emission characteristics 45,60 and ͑ii͒ at reduced electric fields ͑E / p͒ less than the threshold for ionization/charge multiplication in order to reduce statistical fluctuations in photon detection, improving energy resolution and signal-to-noise ratios. 40,41,53 Although gaseous scintillation and radiative recombination mechanisms produce line spectra and continuous radiation in the UV, 54-56 vis, 56,57 and IR ͑Refs.…”

“…In GPSC detection it has been found, for a nonvarying collection efficiency, that the total light produced in the gas through scintillation mechanisms is independent of p; however, the ratio of the intensities of the first and second continua varies. 46,56,60,63,64 The presence of a small concentration ͑Ϸ0.1% -4 % ͒ of N 2 in an atomic gas, such as Ar, quenches the continuum emissions, described above, and gives rise to corresponding emission lines between 300 and 420 nm that are referred to as the second positive band. 59 Therefore, in order to efficiently detect scintillation photons generated in GPSC it is often desirable to convert the strong VUV emissions, such as those described above, to vis wavelengths using an appropriate wavelength shifting quenching gas such as N 2 .…”

“…Furthermore, wavelength filtering of the primary and secondary scintillations produced in the gas, using optical bandpass filters, quenching or wavelength shifting gases, 46,60,63,81 or convolution techniques, can also be employed in order to eliminate unwanted skirt, PE, BSE, SE II , SE III , and SE IV signals ͑see Refs. For example, scintillation can be generated in the gas at electron energies below the ionization potential of the gas due to the existence of various resonance lines in this energy region.…”