FEIC beam scanning meeting -- 26 Aug 2008

Details:

  • Date/Time: 9:30 AM EDT = 13:30UT on 26 Aug 2008
  • Attendees: Josh, Antonio, Geoff (NTC); Fred and Todd (CV), Darrel (TU), Richard (JAO), Bernard (IRAM), Andrey (SRON)

Agenda and Minutes

Todd's notes

  • Confirm the status of beam measurement setup at NA-FEIC
    • Andrey brought a small tapered horn on his visit, because an OEW is difficult to make. He had measured it in a microwave chamber and found good cross-pol performance.
    • The correction due this feed is small -- only a few tenths of a percent in terms of derived efficiencies
    • After determining best experimental method (unidirectional scans), the data obtained were of sufficient quality to confirm that the cartridge meets specification.
      • ACTION ITEM: Andrey will come up with criteria for phase drift and S/N required for a "good" scan.
    • OEWs are being acquired for NA-FEIC for all bands. Bernard noted that an oversized OEW should not be used.
  • Discuss aperture efficiency differences between NSI data and other methods
    • See Richard's Comparison_103.pdf
    • Andrey noted that NSI uses wrong algorithm for standing wave averaging.
    • There was general agreement that we want to process the raw data ourselves.
      • ACTION ITEM: Josh will find out if we can get the raw data out of the NSI software.
    • Andrey recommends that we increased padding of data before FFT until the change in resulting efficiency value is < 0.2%.
    • There was general agreement that 1% accuracy in measured efficiencies was a good value.
    • Richard: I think using X,Y,Z offsets to determine beam squint is fine, with the alternative being Bernard's approach in the farfield. Andrey and Richard fit for minimum phase error. Bernard tried that, but if there are several turns of phase across the aperture, then the algorithm gets lost. In the farfield, you can simply find the peak or barycenter. Richard: But you must define the procedure.

-- ToddHunter - 28 Aug 2008

Topic attachments
I Attachment Action Size Date Who Comment
minutesEXT minutes manage 4 K 2008-09-09 - 00:14 ToddHunter  
This topic: ALMA > WebHome > FrontEndIntegrationCenter > FEICBeamScanningResults > FEICBeamScanningMeeting2008aug26
Topic revision: 2009-04-17, ToddHunter
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