The Advanced ACTPol 27/39 GHz Array
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Advanced ACTPol (AdvACT) will observe the temperature and polarization of the cosmic microwave background (CMB) at multiple frequencies and high resolution to place improved constraints on inflation, dark matter, and dark energy. Foregrounds from synchrotron and dust radiation are a source of contamination that must be characterized and removed across a wide range of frequencies. AdvACT will thus observe at five frequency bands from 27 to 230 GHz. We discuss the design of the pixels and feedhorns for the 27/39 GHz multichroic array for AdvACT, which will target the synchrotron radiation that dominates at these frequencies. To gain 35% in mapping speed in the 39 GHz band where the foreground signals are faintest, the pixel number was increased through reducing the pixel diameter to \(1.08\lambda \) at the lowest frequency, which represents a 22% decrease in size compared to our previously most tightly packed pixels.
KeywordsCosmic microwave background Advanced ACTPol Atacama Cosmology Telescope Synchrotron Foregrounds Multichroic pixel Detector design Polarization-sensitive detector Transition-edge sensor
This work was supported by the US National Science Foundation through Award 1440226. The development of multichroic detectors and lenses was supported by NASA Grants NNX13AE56G and NNX14AB58G. The work of BJK was supported by NASA Space Technology Research Fellowship award.
- 4.B.J. Koopman et al., J. Low Temp. Phys. (2018). https://doi.org/10.1007/s10909-018-1957-5