Prototyping of a tunable filterscope based on acousto-optic filters for tokamak plasma spectroscopy

We present the spectral characterization of a prototype filterscope leveraging an acousto-optic tunable filter (AOTF) operating in the wavelength range 400-650 nm. Using vibrational modes to selectively deflect a wavelength of light, AOTFs provide fast arbitrary wavelength interrogation without moving parts. The instrumental function of the system is determined through wavelength sweeps across line emission from Ne, Hg, and Xe using commercial spectral lamps, finding a FWHW~1-2 nm across the wavelength range. Full range sweeps are then used to perform a wavelength calibration as a function of the vibration frequency applied to the AOTF. A lambertian absolutely calibrated source is used for photometric calibration and to determine the diffraction efficiency. The commissioned prototype can be deployed on the DIII-D tokamak to demonstrate dynamic measurements of deuterium and impurity line emissions from the plasma edge.