Characterization of THGEM coupled to submillimetric induction gaps in Ne/CH4 and Ar/CH4 mixtures

The coupling of a THGEM to an induction region having a thickness below 1 mm allows the application of intense induction electric fields, resulting in a more efficient extraction of the avalanche electrons into the anode electrode and the extension of the charge avalanche amplification into the induction region. In the present work, we investigate the performance of such configuration, operating in Ne-5% CH4 and Ar-20% CH4 mixtures, in terms of gain characteristics and energy resolution for 5.9 keV X-rays. Gains above 105 can be achieved in both mixtures without jeopardizing the energy resolution for induction gaps of 0.8 and 0.5 mm, while applying lower biasing voltages to the THGEM. We have demonstrated that it is possible to implement gas electron multiplier configurations having an effective reduction of its thickness and that high gains can be achieved in Ar-based mixtures having CH4 concentrations as high as 20%. Ar based mixtures present higher ionization yields and lower electron diffusion coefficients, when compared to Ne-based ones.