Filter Polychromators


Eight-Channel Polychromator

For over 25 years, General Atomics has been making Thomson scattering measurements of high temperature plasmas. With the development of repetitively pulsing Nd:YAG lasers and avalanche photodiode detectors (APDs), Thomson scattering measurements have evolved from single point, single time measurements to multipoint, high repetition (over 100 Hz) measurements.

A contributor to the success of these measurements is the development of a high performance, compact polychromator that is easy to align and maintain. These polychromators have excellent stray light rejection and independent channel response; required features for precise light measurements in noisy environments. Forty-four polychromators are used on the Thomson scattering diagnostic for the DIII-D tokamak producing spatial profiles of the plasma electron density (0.05 ne(1020/m3) 5) and temperature (0.02 Te(keV) 20) at rates as high as 160 Hz. Although these polychromators have been optimized for Thomson scattering measurements with Nd:YAG lasers, General Atomics has the design tools and experience to optimize for other lasers and/or other applications using alternative interference filters and detectors.

APPLICATIONS

FEATURES

  • High Transmission
  • Compact
  • Up To 8 Wavelength Channels
  • Silicon Avalanche Photodiode Detectors
  • Advanced Detector Electronics
  • Temperature Stabilized
  • Fiber Optically Coupled
  • High Stray Light Rejection
  • Easy and Stable Alignment
  • Flexible Filter Arrangement

PROVEN PERFORMANCE

  • 44 units built, installed, operated on DIII-D at General Atomics

  • 32 fabricated for University of Wisconsin for MST , Pegasus and HSX .

  • 10 fabricated for SSPX at LLNL

  • 8 fabricated for Alcator C-Mod at MIT