SWIPE multi-mode pixel assembly design and beam pattern measurements at cryogenic temperature

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Columbro F., Madonia P. G., Lamagna L., Battistelli E. S., Coppolecchia A., de Bernardis P., Gualtieri R., Masi S., Paiella A., Piacentini F., Presta G., Biasotti M., D'alessandro Giuseppe, Gatti F., Mele L., Siri B.
ISSN: 0022-2291

In this paper, we present beam pattern tests performed on the SWIPE multi-mode bolometric detector pixel assembly. A 20-mm-aperture horn is coupled to a large detector absorber (10 mm diameter) with a TES sensor located on the side. The pixel assembly has been tested at the bolometer base temperature of 340 mK, inside a custom cryogenic test bed, looking at a Gunn oscillator (128 GHz) located in the far field. We developed a custom cryogenic neoprene absorber, in addition to the stack of standard metal meshes low-pass filters, to reduce the background on the detector at a level similar to the one expected in flight, allowing to measure the main beam of the pixel assembly. The measured FWHM is 21°, slightly narrower than the expected one (24°), due to vignetting produced by the filters stack.

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