Ultrashort-pulse reflectometer on LHD

Abstract

We have applied an ultrashort-pulse reflectometer to large helical device plasmas for density profile measurement. The frequency range of the impulse is up-converted into the R band, which corresponds to the cutoff frequency of edge plasma region in the ordinary mode. The reflected wave from plasma is received and directly recorded by a sampling scope. This system can be controlled and monitored from remote site (Kyushu University) by using ultrawideband science information network (super-SINET) that ideal bandwidth reaches up to 1 Gbps. As a result of the measurement, we have confirmed reflection wave from the plasma when the plasma density reaches steady state during the measurement.

Architecture of Realized Millimeter‐Wave Diagnostic Systems

“…The delay time t r (ω i ) as function of frequency then allows for the reconstruction of the electron density profile through an Abel-inversion [28,29]. After reflection, the 15 GHz wide band is downconverted to 3-18 GHz.…”

“…29 Setup allowing for the overall calibration of an ECE radiometric system. A movable mirror inside the vacuum vessel can be brought into a position that, instead of the plasma, a hot/cold calibration arrangement can be viewed.…”

Multichannel ultrashort pulsed radar reflectometer on LHD

“…[1][2][3][4][5][6] Because an ultrashort pulse has broadband frequency components in Fourier space, one ultrashort pulse can take the place of a broadband microwave source. For example when we use a 10 ps full width at half maximum ͑FWHM͒ impulse, the usable frequency component is up to 100 GHz.…”

Reconstruction of Edge Density Profiles Using Ultrashort-Pulse Reflectometry in LHD

“…(2). The schematics of the USPR system employed on the Large Helical Device (LHD) have been shown elsewhere [5]. An impulse generator (Picosecond Labs, model 4015C) is utilized as a source.…”