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Title: A poloidal high-k scattering system for NSTX-U

Journal Article · · Journal of Instrumentation
 [1];  [1];  [1];  [1];  [2];  [3];  [3];  [1]
  1. Univ. of California, Davis, CA (United States)
  2. Bridge12 Technologies, Framingham, MA (United States)
  3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
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A previous 5-channel tangential high-k scattering system is being replaced by an 8-channel, poloidal high-k scattering system on the National Spherical Torus eXperiment Upgrade (NSTX-U) device located in Princeton, NJ, USA. The 693 GHz poloidal scattering system replaces a 280 GHz tangential scattering system to study high-k electron density fluctuations on NSTX-U, thereby considerably enhancing planned turbulence physics studies by providing a measurement of the kθ-spectrum of both electron temperature gradient (ETG) and ion temperature gradient (ITG) modes. Two approaches to generating the 693 GHz probe beam are under development: an optically-pumped far-infrared (FIR) laser that generates ~50 mW, and a compact gyrotron that can potentially generate in excess of 5 W. Large aperture optics collect radiation scattered from density fluctuations in the plasma core at 8 simultaneous scattering angles ranging from 2 to 15° corresponding to poloidal wavenumbers that extend to >40 cm-1. Finally, steerable launch optics coupled with receiver optics mounted on a 5-axis receiver carriage allow the scattering volume to be placed radially from r/a = 0.3 out to the pedestal region (r/a ~ 0.99) and translated horizontally as needed to satisfy wavenumber matching.

Research Organization:
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States); University of California, Davis, CA (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
FG02-99ER54518; AC02-09CH11466; SC0018731
OSTI ID:
1886891
Journal Information:
Journal of Instrumentation, Journal Name: Journal of Instrumentation Journal Issue: 1 Vol. 17; ISSN 1748-0221
Publisher:
Institute of Physics (IOP)Copyright Statement
Country of Publication:
United States
Language:
English

References (8)

Low-Power Testing of Losses in Millimeter-Wave Transmission Lines for High-Power Applications journal August 2008
On the history of far-infrared (FIR) gas lasers: Thirty-five years of research and application journal June 1999
A collective scattering system for measuring electron gyroscale fluctuations on the National Spherical Torus Experiment journal December 2008
Far-infrared tangential interferometer/polarimeter design and installation for NSTX-U journal August 2016
The high- k poloidal scattering system for NSTX-U journal October 2018
Electron-scale turbulence spectra and plasma thermal transport responding to continuous E × B shear ramp-up in a spherical tokamak journal July 2013
Recent progress in understanding electron thermal transport in NSTX journal March 2017
Spectral Characteristics of a 140-GHz Long-Pulsed Gyrotron journal June 2007

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