Summary plots of all roof-based maps
A gigantic file illustrating all the beam maps taken 8/1-8/2, in
chronological order. Data has been demodulated but not cleaned. It
starts off looking bad, but gets better towards the end...read it
like a story. A tour of the plots:
- P. 1-2: Beam slices in vertical and horizontal directions.
Central pixel, Gunn at 100 GHz with vertical polarization and
open-ended rectangular waveguide. Note that horizontal profile is
clean, but vertical profile is hardly Gaussian.
- P. 3: Long raster scan of central pixel. Same Gunn setup as
above. Once again, the X profile is clean, while the Y profile
isn't.
- P. 4: Fast raster scan of central pixel with same Gunn setup but
more attenuation. Hardly any signal visible.
- P. 5: Fast raster of central pixel. Gunn at 100 GHz with
horizontal polarization, medium power level. Note that with
the change of polarization, the X and Y profiles have swapped. The
bolometer responses also appear to have swapped. Thinking that this
was a source problem, we...
- P. 6: ...added a horn onto the end of the rectangular waveguide,
and repeated the fast raster of central pixel (Gunn at 100 GHz,
horizontal polarization). Not much change though.
- P. 7: Another source change -- removed the horn and replaced it
with a rectangular-to-circular transition. Gunn is still at 100
GHz, horizontal polarization. Still no change in the bizarre beam
shape.
- P. 8-11: Decided to give up on "fixing" the beam shape; stuck
with the rectangular/circular transition piece for the rest of data
taking. Varied power levels and Gunn polarization orientation.
- P. 12: Changed Gunn frequency to 106 GHz.
- P 13-14: Mapped off-axis pixel with Faraday rotator (A3, FR
100-2). Gunn at 100 GHz, both polarization orientations. We
have a clean beam! (Central beam was possibly vignetted by
surrounding horns? Height difference due to FRs being
present/absent -- see this picture of
the focal plane for run 4. Or maybe fuzzy focus problems?)
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CP beam maps: Gunn at 100 GHz, horizontal pol.
Just some beam maps at varying power levels (same as p. 7-9 in above
plots, but with some low pass filtering). With the polarization
oriented horizontally, the X scans pass through the crappy looking
part of the beam. Didn't analyze this data any further.
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CP beam maps: 100 GHz, vertical
pol, medium power and also high power
Same as above, but with vertical polarization orientation so that
the X scans look decent. Gaussian fits done on the X slices closest
to the center of the Y axis; sigma values listed on the plots. For
reference, Zemax says the central beam is supposed to have a sigma
of about 43 cm at a distance of 60 m. Timestream plots are also
shown (on a log scale)...do we see hints of sidelobes?
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CP beam maps: 106 GHz, vertical pol
A sanity check to see if beam shapes vary with frequency (of a
monochromatic source). Beam shape qualitatively looks the same.
One of the gaussian fits didn't work out so well (for CP-f)...but
the fit for CP-b looks good, and the beam width matches the 100 GHz
results.
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A3 beam maps: 100 GHz, horizontal
pol and also vertical pol
Beam maps for an off-axis pixel with a Faraday rotator (FR off for
these maps). Gunn at 100 GHz, both polarization orientations. The
beam wasn't terribly well centered with respect to the XY stage (it
was 7am, so sue us), but the shape was nice enough to do a 2D
gaussian fit. A rundown of sigmas (sigma-x and sigma-y,
respectively):
- A3-b, horizontal pol: 52 cm / 53 cm
- A3-f, horizontal pol: 47 cm / 47 cm
- A3-b, vertical pol: 50 cm / 50 cm
- A3-f, vertical pol: 51 cm / 52 cm
- Average: 50 cm (compare 43 cm predicted for CP = 16% difference)
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