Design of a real-time two-color interferometer for MAST Upgrade

摘要： A single chord two-color CO2/HeNe (10.6/0.633 μm) heterodyne laser interferometer has been designed to measure the line integral electron density along the mid-plane of the MAST Upgrade tokamak, with a typical error of 1 × 1018 m?3 (～2? phase error) at 4 MHz temporal resolution. To ensure this diagnostic system can be restored from any failures without stopping MAST Upgrade operations, it has been located outside of the machine area. The ?nal design and initial testing of this system, including details of the optics, vibration isolation, and a novel phase detection scheme are discussed in this paper.