APS Logo

Recent Thomson scattering (TS) upgrades at LTX-ꞵ and a novel TS diagnostic concept with high-channel count and high-repetition rate

POSTER

Abstract

Thomson scattering (TS) measurements in the Lithium Tokamak Experiment-ꞵ (LTX-ꞵ) have demonstrated a low-recycling regime with a hot, low-density, low-collisionality edge, flat electron temperature profiles with little ∇T, as well as high energy confinement relative to scaling laws (without operating in H-mode). We present new data from the LTX-ꞵ TS system that has been upgraded to improve the understanding of this promising regime. The core "TVTS" system uses a high-throughput spectrometer and an intensified (ICCD) camera to measure 11 views covering from near the magnetic axis to the outer edge. Previously, 9 additional views covered 75% of the high-field side (HFS) and were instrumented with 5 polychromators. Those 9 fibers have now been moved with a new lens viewing the outer edge and scrape-off layer with better sensitivity and resolution than the core TVTS. A new HFS-TS fiber bundle has been procured with 10 views covering the entire HFS (2 per polychromator using split delay fibers), also with a new lens and location. Both new views are better matched in spot size, scattering angle, and throughput to the laser and polychromators, and have better viewing dumps. In addition, this poster presents a novel concept for a TS diagnostic to make 16 (or significantly more) separate, high-sensitivity, high-speed (>MHz) TS measurements on one instrument using a two-dimensional avalanche photodiode array (APDCAM) coupled to a high-throughput spectrometer.

Publication: M. Kaur, et al., "Upgrades to the Thomson scattering diagnostic on the Lithium Tokamak eXperiment-beta (LTX-ꞵ)" SOFE, IEEE Transactions on Plasma Science, submitted<br>D.P. Boyle, "A novel, high-channel-count, high-sensitivity, high-speed Thomson scattering diagnostic based on a 2-D avalanche photodiode array", Review of Scientific Instruments, submitted

Presenters

  • Dennis P Boyle

    Princeton Plasma Physics Laboratory (PPPL)

Authors

  • Dennis P Boyle

    Princeton Plasma Physics Laboratory (PPPL)

  • Manjit Kaur

    Princeton Plasma Physics Laboratory (PPPL)

  • Drew B Elliott

    Oak Ridge National Laboratory

  • Shigeyuki Kubota

    University of California, Los Angeles

  • Mate Lampert

    Princeton Plasma Physics Laboratory (PPPL)

  • Benoit Paul LeBlanc

    Princeton Plasma Physics Laboratory (PPPL)

  • Anurag Maan

    Princeton Plasma Physics Laboratory (PPPL)

  • Richard Majeski

    Princeton Plasma Physics Laboratory, Princeton Plasma Physics Laboratory (PPPL)

  • Enrique Merino

    Princeton Plasma Physics Laboratory