Bragg Reflection Notch Filters

It’s vital to suppress power leakage at electron cyclotron heating frequencies that could damage sensitive plasma diagnostic detection equipment. General Atomics has provided notch filters to help suppress this leakage.

GA notch filters consist of multiple thin disks in series in corrugated waveguide. The notch depth is proportional to the number of the disks, while the bandwidth of the notch is proportional to the product of the disk dielectric constant and disk thickness. The narrowest notch filters use thin plastic sheets, while wider notch filters use fused quartz disks.

110 GHz notch filter in 63.5 mm corrugated waveguide. Plastic sheets are separated by thin sections of corrugated waveguide, which keep the sheets flat.

110 GHz notch filter in 63.5 mm corrugated waveguide. Plastic sheets are separated by thin sections of corrugated waveguide, which keep the sheets flat.

Bragg reflection notch filters with plastic sheets typically have the following characteristics:

  • > 30 dB attenuation over 1% bandwidth or
  • > 40 dB attenuation over 2% bandwidth
  • ~ 1 dB attenuation away from the notches
  • harmonics are also rejected
GA has supplied these filters with fundamental notch frequencies at 82.6 GHz, 84 GHz, and 110 GHz.

GA also supplies notch filters in fundamental rectangular waveguide.

Contact

Ray O’Neill, GA-ITER Program
oneill@fusion.gat.com
(858) 900-5214

John Doane, GA-MFE Technologies
doane@fusion.gat.com
(301) 362-9097