ALMA front-end beam efficiency evaluation. A.M. Baryshev NOVA/SRON/RuG. Outline. band 9 optics measurement system (example) Band 9 efficiency analysis NA FEIC data for band 9 and band 7 Q/A. The beam pattern measurement Set-Up. Typical near field measurements. Amplitude. Phase.
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ALMA front-end beam efficiency evaluation
The beam pattern measurement Set-Up
80% typical aperture efficiency
No central blockage
X and y axes are beam
offsets in degrees
Red – Pol 0
Green Pol 1
Blue secondary mirror
-19dB peak, -18dB total power
Red = -10dB
4 dB contour
Lambda/4 compensation off
Lambda/4 compensation needs to be looked at
Probe model: OEWG WR22: 33.00-50.00 GHz ?
Aperture efficiency 63.3%, Phase center X, Y, Z: 1.32, -0.83, 289 (mm) (0,-0.94) Deg
Aperture efficiency 65.1%, Phase center X, Y, Z: 1.32, -0.87, 292 (mm) (0, -1.40) Deg
Aperture Efficiency 42.9, Phase center X,Y,Z -- 2.22, 5.92, 103.84 (mm)