  The next generation of gaseous photon detectors is requested to overcome the
limitations of the available technology, in terms of resolution and robustness.
The quest for a novel photocathode, sensitive in the far vacuum ultra violet
wavelength range and more robust than present ones, motivated an R&D programme
to explore nanodiamond based photoconverters, which represent the most
promising alternative to cesium iodine. A procedure for producing the novel
photocathodes has been defined and applied on THGEMs samples. Systematic
measurements of the photo emission in different Ar/CH4 and Ar/CO2 gas mixtures
with various types of nanodiamond powders have been performed. A comparative
study of the response of THGEMs before and after coating demonstrated their
full compatibility with the novel photocathodes.
