1. A LEKID-based CMB instrument design for large-scale observations in Greenland
- Author
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Araujo, D. C., Ade, P. A. R., Bond, J. R., Bradford, K. J., Chapman, D., Che, G., Day, P. K., Didier, J., Doyle, S., Eriksen, H. K., Flanigan, D., Groppi, C. E., Hillbrand, S. N., Johnson, B. R., Jones, G., Limon, M., Miller, A. D., Mauskopf, P., McCarrick, H., Mroczkowski, T., Reichborn-Kjennerud, B., Smiley, B., Sobrin, J., Wehus, I. K., and Zmuidzinas, J.
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Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
We present the results of a feasibility study, which examined deployment of a ground-based millimeter-wave polarimeter, tailored for observing the cosmic microwave background (CMB), to Isi Station in Greenland. The instrument for this study is based on lumped-element kinetic inductance detectors (LEKIDs) and an F/2.4 catoptric, crossed-Dragone telescope with a 500 mm aperture. The telescope is mounted inside the receiver and cooled to $<\,4$ K by a closed-cycle $^4$He refrigerator to reduce background loading on the detectors. Linearly polarized signals from the sky are modulated with a metal-mesh half-wave plate that is rotated at the aperture stop of the telescope with a hollow-shaft motor based on a superconducting magnetic bearing. The modular detector array design includes at least 2300 LEKIDs, and it can be configured for spectral bands centered on 150~GHz or greater. Our study considered configurations for observing in spectral bands centered on 150, 210 and 267~GHz. The entire polarimeter is mounted on a commercial precision rotary air bearing, which allows fast azimuth scan speeds with negligible vibration and mechanical wear over time. A slip ring provides power to the instrument, enabling circular scans (360 degrees of continuous rotation). This mount, when combined with sky rotation and the latitude of the observation site, produces a hypotrochoid scan pattern, which yields excellent cross-linking and enables 34\% of the sky to be observed using a range of constant elevation scans. This scan pattern and sky coverage combined with the beam size (15~arcmin at 150~GHz) makes the instrument sensitive to $5 < \ell < 1000$ in the angular power spectra.
- Published
- 2014
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