UHV system for clean hydrogenation experiments of thin film metal hydrides. Two types of experiments can be performed separately: 1. The measurement of resistivity versus the hydrogen pressure and temperature. 2. Recording of the optical transmission with spatial resolution as a function of hydrogen pressure and temperature. Hydrogen pressures from approximately 1 microbar to 1 bar, temperatures RT to 300-350 degrees C. Sample size 10x10 mmˆ2.