Systematic uncertainties in accelerator oscillation neutrinoexperiments arise from nuclear models describing neutrino-nucleusinteractions. To mitigate these uncertainties, we can studyneutrino-nuclei interactions with detectors possessing enhancedhadron detection capabilities at energies below the nuclear Fermilevel. Gaseous detectors not only lower the particle detectionthreshold but also enable the investigation of nuclear effects onvarious nuclei by allowing for changes in the gas composition. Thisapproach provides valuable insights into the modelling ofneutrino-nucleus interactions and significantly reduces associateduncertainties. Here, we discuss the design and first operation of agaseous argon time projection chamber optically read. The detectoroperates at atmospheric pressure and features a single stage ofelectron amplification based on a thick GEM. Here, photons areproduced with wavelengths in the vacuum ultraviolet regime. In anoptical detector, the primary constraint is the light yield. Thisstudy explores the possibility of increasing the light by applying alow electric field downstream of the ThGEM. In this region, calledthe electroluminescence gap, electrons propagate and excite theargon atoms, leading to the subsequent emission of photons. Thisprocess occurs without any further electron amplification, and it isdemonstrated that the total light yield increases up to three timesby applying moderate electric fields of the order of3 kV/cm. Finally, an indirect method is discussed for determiningthe photon yield/charge gain of a ThGEM, giving a value of18.3 photons detected per secondary electron.