Hybrid transmission line for ECRH in the helically symmetric experiment

J. W. Radder, K. M. Likin, F. S.B. Anderson, D. T. Anderson

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


The HSX oversized, mode-converting ECRH transmission line has been upgraded to a hybrid system to increase launched microwave power and reduce electrical arcing. Filtering of high-order, spurious modes ensures efficient coupling to a Gaussian beam for optimal electron heating. A Vlasov mode converter and two phase-correcting ellipsoidal mirrors convert the TE02 gyrotron output mode to a symmetric, linearly polarized, microwave beam. A swappable twist reflector plate rotates beam polarization for 2nd-harmonic X-mode or fundamental O-mode ECRH. Long distances are traversed by coupling the beam to a dual-mode (TE11∈+∈TM11), smooth, circular cross-section waveguide. This system has been successfully tested without arcing for 50 ms pulses and over 100 kW of launched power. Analysis of the microwave beam for 50 kW, 2 ms microwave pulses reveals agreement with predicted beam shapes at two beam locations. The new system has also demonstrated increased plasma stored energy for ECRH plasmas with equal launched power.

Original languageEnglish (US)
Pages (from-to)360-372
Number of pages13
JournalInternational Journal of Infrared and Millimeter Waves
Issue number4
StatePublished - Apr 2008
Externally publishedYes


  • Electron cyclotron heating
  • Microwave transmission lines
  • Quasioptics
  • Stellarators


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