Preparation and test of caesium samples

The present document describes the status of the overall chain of collaborations among several institutes under development for the optimisation of usage of caesium in sources of negative hydrogen/deuterium ions. The report presents the preparation of caesium-coated molybdenum samples and the analysis of two samples. Deposition of a few samples in 2016 has permitted to improve the sample holder design, which now accepts a 16 x 16 mm2 flat target; the rest of the deposition was previously described [1]. Moreover a simple vacuum envelope was assembled to transport the finished samples to analyzing instruments. In other words, distributed preparation and analysis was shown feasible, and in perspective several deposition methods can be tested and calibrated against each other. The experience gained with our first oven shows easily tuneable and stable temperature, but heating times in the order of tens of minutes, for the large mass of copper shells used to keep cesium pipe isothermal; the upgrades to LNL design of pellet oven (whose first principle was described in a previous report) and its construction are also briefly reported. The results of XPS analyses of two samples show that the detected amount of caesium is related to temperature and evaporation time; the surface is found to be oxidised, probably during the sample handling. Impurities, like fluorine, are also found, probably related to pumping oils.