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Miller MC, Hanson JD, Hartwell GJ, et al. Design and implementation of a multichannel millimeter wave interferometer for the Compact Toroidal Hybrid experiment. Rev Sci Instrum. 2012;83(10):10E332doi: 10.1063/1.4732056.
Miller, M. C., Hanson, J. D., Hartwell, G. J., Knowlton, S. F., Maurer, D. A., & Stevenson, B. A. (2012). Design and implementation of a multichannel millimeter wave interferometer for the Compact Toroidal Hybrid experiment. The Review of scientific instruments, 83(10), 10E332. https://doi.org/10.1063/1.4732056
Miller, M C, et al. "Design and implementation of a multichannel millimeter wave interferometer for the Compact Toroidal Hybrid experiment." The Review of scientific instruments vol. 83,10 (2012): 10E332. doi: https://doi.org/10.1063/1.4732056
Miller MC, Hanson JD, Hartwell GJ, Knowlton SF, Maurer DA, Stevenson BA. Design and implementation of a multichannel millimeter wave interferometer for the Compact Toroidal Hybrid experiment. Rev Sci Instrum. 2012 Oct;83(10):10E332. doi: 10.1063/1.4732056. PMID: 23126990.
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Rev Sci Instrum. 2012 Oct;83(10):10E332. doi: 10.1063/1.4732056.

Design and implementation of a multichannel millimeter wave interferometer for the Compact Toroidal Hybrid experiment.

The Review of scientific instruments

M C Miller, J D Hanson, G J Hartwell, S F Knowlton, D A Maurer, B A Stevenson

Affiliations

  1. Physics Department, Auburn University, Auburn, Alabama 36849, USA. [email protected]

PMID: 23126990 DOI: 10.1063/1.4732056

Abstract

A three-channel 1 mm wave interferometer has been designed, assembled, and installed on the Compact Toroidal Hybrid torsatron (CTH). The interferometer design makes novel use of a subharmonic mixer for detection, which simplifies alignment. It employs a single electronically tunable source that is repetitively chirped using a sawtooth waveform of frequency up to 1 MHz. The 15.25 GHz drive oscillator is multiplied in two stages to 122 GHz before a final doubler stage brings it to 244 GHz. Local oscillator (LO) power at 122 GHz is directed through waveguide to the LO input of the subharmonic mixer of each viewing chord, simplifying alignment. Phase detection is performed by directly digitizing the amplified mixer outputs at 50 MHz and processing them with a software algorithm. Initial measurements made with the central chord of the new interferometer agree with those from the existing 4 mm system at low densities. The 1 mm system performs well in current-driven discharges reaching densities over 10(19) m(-3), whereas the lower frequency interferometer is found to be less reliable due to loss of fringes. This is a critical improvement for experiments studying the onset, avoidance, and vacuum magnetic transform dependence of disruptions in the CTH device.

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