Multi-channel analog lock-in system for real-time motional Stark effect measurements

Wi, H. M.; Ko, Jinseok; Chung, Jae-Hoon

doi:10.1016/j.fusengdes.2020.111664

Cited by 3 publications

(1 citation statement)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several research activities are underway to improve the MSE instrumentation and thereby the measurement reliability both in-house and via international collaborations. These include the real-time MSE measurements associated with the feedback control of the safety factor and current density profiles [24], the spectral MSE analysis technique directly related with the ITER MSE diagnostic system development [25], the in situ polarized background measurement and correction using the polychrometer technique [26], the systematic evaluation of the effect of multiple ion-source neutral beam injections on the MSE measurements [27], and finally the R & D activities to seek for a second MSE view for the measurement of the intrinsic radial electric field in tokamak plasmas.…”

Section: Jinst 17 C01065mentioning

confidence: 99%

Overview and recent progress of KSTAR diagnostics

et al. 2022

View full text Add to dashboard Cite

The 14th experimental campaign from the Korea Superconducting Tokamak Advanced Research (KSTAR) device has passed since the first experimental campaign was carried out in 2008. The basic diagnostic systems such as magnetic diagnostics, interferometer, inspection illuminator, visible spectrometer, ECE radiometer have been used for the first plasma experiment in KSTAR. Currently more than 50 diagnostic systems have been continuously installed including improved basic diagnostics and advanced imaging diagnostics in KSTAR. A recent progress and future plan of diagnostics for KSTAR are briefly discussed.

show abstract

Section: Jinst 17 C01065mentioning

confidence: 99%

Overview and recent progress of KSTAR diagnostics

et al. 2022

View full text Add to dashboard Cite

show abstract

Application of motional Stark effect in situ background correction to a superconducting tokamak

Scott

Levinton

et al. 2021

Review of Scientific Instruments

View full text Add to dashboard Cite

A polychrometer-type motional Stark effect (MSE) diagnostic technique, originally developed for the Alcator C-Mod tokamak, has been extended and applied to the Korea Superconducting Advanced Tokamak Research (KSTAR) device, the long-pulse superconducting tokamak, for the first time. It demonstrates a successful in situ subtraction of the polarized reflections off the vacuum vessel wall, sometimes up to half the total signal in some sightlines. To avoid the secondary neutral beam emission that may contaminate conventional beam-into-gas calibrations, a new approach, where the beam-into-gas measurements are made at various torus pressures with fixed vacuum fields, has been devised, which is possible with the stable superconducting coil systems of KSTAR. The validity of this new calibration scheme has been checked via plasma jog experiments. The experimental evidence of the polarized background light and the necessity of its correction in the MSE measurements made in KSTAR are presented as well.

show abstract

Feedback lock-in: A versatile multi-terminal measurement system for electrical transport devices

Barnard

Mikheev

Finney

et al. 2023

Review of Scientific Instruments

View full text Add to dashboard Cite

We present the design and implementation of a measurement system that enables parallel drive and detection of small currents and voltages at numerous electrical contacts to a multi-terminal electrical device. This system, which we term a feedback lock-in, combines digital control-loop feedback with software-defined lock-in measurements to dynamically source currents and measure small, pre-amplified potentials. The effective input impedance of each current/voltage probe can be set via software, permitting any given contact to behave as an open-circuit voltage lead or as a virtually grounded current source/sink. This enables programmatic switching of measurement configurations and permits measurement of currents at multiple drain contacts without the use of current preamplifiers. Our 32-channel implementation relies on commercially available digital input/output boards, home-built voltage preamplifiers, and custom open-source software. With our feedback lock-in, we demonstrate differential measurement sensitivity comparable to a widely used commercially available lock-in amplifier and perform efficient multi-terminal electrical transport measurements on twisted bilayer graphene and SrTiO3 quantum point contacts. The feedback lock-in also enables a new style of measurement using multiple current probes, which we demonstrate on a ballistic graphene device.

show abstract

Multi-channel analog lock-in system for real-time motional Stark effect measurements

Cited by 3 publications

References 26 publications

Overview and recent progress of KSTAR diagnostics

Overview and recent progress of KSTAR diagnostics

Application of motional Stark effect in situ background correction to a superconducting tokamak

Feedback lock-in: A versatile multi-terminal measurement system for electrical transport devices

Contact Info

Product

Resources

About