Electroformed metal mesh THz-filters for selecting harmonics of NovoFEL radiation

In this report we present the results of experimental development and investigation of high-pass THz-filters for selecting higher radiation harmonics of Novosibirsk terahertz FEL. The filters are based on free standing nonresonant electroformed Ni-meshes a few tens microns thick with hexagonally packed round openings. The results of FT-characterization are being compared with results of electrodynamic simulations and direct measurements in high-power experiments at NovoFEL.