Transverse damper and stability diagram

We describe a proof-of-principle test to measure Landau damping in a hadron ring using a destabilizing transverse feedback acting as a controllable source of beam coupling impedance. The test was performed at the Large Hadron Collider and stability diagrams for a range of its Landau octupole strengths have been measured for its injection energy of 450 GeV. In the future, the procedure could become an accurate way of measuring stability diagrams throughout the machine cycle.