@misc{oai:repo.qst.go.jp:00076951,
 author = {Akiyama, T. and Van Zeeland, M.A. and Carlstrom, T.N. and Boivin, R.L. and Brunner, K.J. and Knauer, J. and Yasuhara, R. and Tanaka, K. and Liu, H.Q. and Zhou, Y. and Oyama, Naoyuki and Sirinelli, A. and Urabe, K. and Shirai, N. and Oyama, Naoyuki},
 month = {Sep},
 note = {Dispersion interferometers (DI) measure a phase shift caused by difference of the phase velocities in a medium (dispersion) between the fundamental and the second harmonic of laser light, a straightforward application of which is the measurement of electron density in a plasma. Common to all implementations, the DI probe beam is a mixture of above two wavelengths, both of which are interfered at the shorter wavelength after traversing the diagnosed medium and a frequency doubling crystal. Unlike conventional interferometers, DIs are insensitive to path length changes by mechanical vibrations. This advantage arises because the two wavelengths propagate along the same path and, in the final doubling process, fully cancel the vibration induced phase shift. While vibration compensation can also be achieved with two separate lasers in a so-called “two-color vibration compensated” system, additional advantages of the DI include the lack of a reference leg, a single laser source with common noise between the two colors and intrinsic co-linearity of the two colors. Hence the DI is able to obtain high density resolution with simple hardware and small alignment effort.

After application to Gas-Dynamic Trap (GDT), the density resolution of DIs has been improved further on various toroidal devices (TEXTOR, LHD, HL-2A, W7-X) in the last decade. This is mainly due to introductions of various phase modulation techniques and phase extraction methods. Extension of the bandwidth for electron-density-fluctuation measurements up to the MHz-range was demonstrated on DIII-D. Design and bench tests of DI systems have been implemented for EAST as well as future large devices including JT-60SA and ITER.

This talk will review recent progress of the DI by above diagnostic techniques, as well as applications to low-temperature plasmas, where the DI also offers an excellent opportunity for low-noise electron-density measurements., Laser Aided Plasma Diagnostics 2019},
 title = {Recent Progress on dispersion interferometers for nuclear fusion and low-temperature plasmas},
 year = {2019}
}