Enhancement of JET’s mirror-link near-ultraviolet to near-infrared divertor spectroscopy system.

Since 1994, JET has had a mirror-link spectroscopy system with a poloidal view of 150 mm of the outer divertor split into three ranges: near-ultraviolet (near-UV) (∼ 300–450 nm), visible (450–750 nm), and near-infrared (near-IR) (750–1200 nm). The system consists of three Czerny–Turner/charge coupled device (CCD) pairs: 1 m focal length for the near-UV, 0.75 m focal length for the visible, and 0.5 m focal length for the near-IR. All were aligned along the same optical path to the divertor. As part of the JET ITER-like wall enhancements, the diagnostic system will be upgraded in five areas: (1) frame rate, (2) quantum efficiency (QE), (3) radial coverage, (4) optical throughput, and (5) for the near-UV, spectral resolution and survey capability. New CCDs for the near-UV and visible will have increased QE and allow three times frame rate. The near-UV will benefit from a 0.75 m imaging spectrometer with three gratings. The optics have been redesigned to allow ∼ 360 mm view and greater than two times throughput. This paper will look at the design and implementation as well as the new diagnostic capabilities of the system.