Speaker
Mr
Jongin Wang
(NUPLEX, Seoul National University)
Description
A single channel of 94 GHz heterodyne interferometer system for measurement of the electron density [1] was successfully developed for Versatile Experiment Spherical Torus (VEST) at Seoul National University. The interferometer system has been upgraded to a multi-chord heterodyne interferometer system for the profile of electron density. The Gaussian probe beam from a horn antenna is expanded into a uniformly distributed beam by using a pair of Powell lenses [2]. The expanded beam is guided through 9 holes and collimating lenses, located vertically with the same interval of 75 mm, generating 9 channels of Gaussian beams. Each collimated beam is splitted and focused to generate minimum beam waist near the center of plasma utilizing the plano-convex lens. The beam is reflected at a concave mirror mounted on the center stack of VEST. After passing through the plasma, the reflected beam at the beam splitter is focused onto the multi-chord detector array. The probe beam and 97.2 GHz LO is mixed to produce Intermediate Frequency (IF) signal at 3.2 GHz, and the IF signal is further down-converted to 80 MHz through a frequency down-conversion circuit. Optimization of the lengths between the optical components and beam waists along the beam path is achieved by the Gaussian optics and the optical design code, CODE V [3]. Experimentally optimized lengths between the optical components of this system will be discussed with the simulated ones. The first results from the upgraded interferometer system will be presented as well.
[1] D. H. Choi *et al.*, *Design of interferometer system on Versatile Experiment Spherical Torus (VEST) at Seoul National University*, 2012 *JINST* 7 C01107.
[2] Y. B Nam *et al.*, *Compact ECEI system with in-vessel reflective optics for WEST*, *Rev. Sci. Instrum.* 87 (2016) 11E130.
[3] CODE V is an optical design software of Synopsys Inc., https://optics.synopsys.com/codev
Primary author
Mr
Jongin Wang
(NUPLEX, Seoul National University)
Co-authors
Mr
Dongjae Lee
(UNIST)
Prof.
Hyeon K. Park
(UNIST)
Mr
JongGab Jo
(Seoul National University)
Prof.
Yong-Seok Hwang
(Seoul National University)
