Continued study on photoelectron and secondary electron yields of tin and NEG (Ti-Zr-V) coatings at the KEKB positron ring

The photoelectron and secondary electron yields of a TiN coating and a NEG (Ti-Zr-V) coating on copper have been studied so far by using the KEK B-Factory (KEKB) positron ring. Recently, test chambers with these coatings were installed at a straight section of the ring, where the irradiated photon density was considerably smaller than that at an arc section in the previous experiments. The number of electrons around beams in the NEG-coated and the TiN-coated chambers were clearly smaller as compared to those of the uncoated copper chamber by the factors of 2-3 and 3-1, respectively. The evaluated maximum SEY (delta_max) for the TiN coating and the NEG coating and the copper were in the ranges of 0.8-1.0, 1.0-1.15, and 1.1-1.25, respectively. As an application of the simulation, delta_max values and the effective photoelectron yield including the geometrical effect were also estimated for copper chambers with one or two antechambers.