The obtained data (Table 1, 2) show that, irrespective of the substrate bias value, the lattice parameter of niobium layers reached on copper samples does not differ from the lattice parameter of bulk niobium, whereas for the layers obtained on sapphire it is bigger by roughly 0.001 nm. This indicates some stress within the layer. RRR values of layers deposited on sapphire varied from ca. 30 to 50 for layer thickness value ranging from 0.7 to 3 m. These values remain stable for the normal to substrate surface rotated by 300 to the arc plasma propagation direction. At the rotation angle of 750-900 RRR drops to below 20. SEM studies have shown that for such high rotation angles numerous surface irregularities (extrusions of dimensions of ca. 100 nm) are present in the surface layer which may result in an increased field emission in the RF field. A new planar arc stand with a “T-type” microdroplets filter has been installed in 2006, equipped with a plasma beam magnetic scanning system at its exit. An ion current of nearly 500 mA has been reached upstream of the scanning system at an arc current of 130 A. This corresponds to an average ion density of 7-8 mA/cm2 across a 0.71 dm2 substrate holder. The density of niobium micro-droplets (of radius bigger than 200 nm) has been reduced by using the filter, down to below 400/mm2 on most of the substrate holder surface. Two circular, 95 mm in diam. copper samples have been Nb-coated in 2006 using the “T-filter” and tested for Q value in Cornell University using a perturbation method. The quality factor values were 108 and 2108, respectively, at a Q-value for the empty cavity equal 3.8108.Another …