Active 3rd harmonic RF system for ALBA

ALBA is a 3rd generation synchrotron light source located in Barcelona, Spain. The circumference is 268.8 meters and electrons are stored at 3 GeV. In the framework of the upgrade towards the 4th generation light source ALBA II, an active 3rd harmonic RF system at 1.5 GHz is foreseen to increase the Touschek lifetime component. The system will be installed and available for operation in the current machine, which will allow to gather experience before the upgrade. Four normal conducting HOM damped harmonic cavities will be placed in the storage ring, each of it including a complete WR650 waveguide system with circulator and load, a 20 kW high power SSPA amplifier and a Low Level RF control system. We are presenting in this contribution the complete design of the active harmonic RF system for ALBA and the expected performance during operation.