Microwave probe diagnostic for the lower hybrid multijunction antenna on TdeV
- Centre canadien de fusion magnetique, Varennes, Quebec J3X 1S1 (Canada)
On the TdeV tokamak a microwave probe diagnostic enables direct measurement of the electromagnetic fields in ten reduced waveguides of the lower hybrid current drive multijunction antenna. In each instrumented reduced waveguide, the local field is measured at two different locations by probes through coupling holes located in the narrow wall of the waveguides. The amplitude and phase of the signals are measured with a multichannel heterodyne circuit and are used to calculate the incident and reflected fields at the antenna mouth. The probes are under vacuum and they are bakeable up to the maximum operating temperature of the antenna ({ital T}=350{degree}C). They are calibrated at room temperature but the evolution of their characteristic with temperature is taken into account in the data analysis. Typical accuracies of the field measurements at the grill mouth are: {plus_minus}9{percent} for the amplitude and {plus_minus}6{degree} for the phase. The probe diagnostic has been operating reliably for the last two years and the probes do not appear to perturb the operation of the antenna nor to reduce its power handling capability. Comparisons of the probe measurements with calculations from the multijunction antenna modeling code SWAN show that the code is accurate for low rf power densities at the antenna mouth. {copyright} {ital 1997 American Institute of Physics.}
- OSTI ID:
- 450586
- Journal Information:
- Review of Scientific Instruments, Vol. 68, Issue 2; Other Information: PBD: Feb 1997
- Country of Publication:
- United States
- Language:
- English
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