Article

Antenna-coupled TES bolometer arrays for BICEP2/Keck and SPIDER.

School of Physics and Astronomy, Cardiff University, CF24 3AA, Cardiff, UK
Proc SPIE 09/2010; DOI: 10.1117/12.857914
Source: arXiv

ABSTRACT BICEP2/Keck and SPIDER are cosmic microwave background (CMB) polarimeters targeting the B-mode polar-ization induced by primordial gravitational waves from inflation. They will be using planar arrays of polarization sensitive antenna-coupled TES bolometers, operating at frequencies between 90 GHz and 220 GHz. At 150 GHz each array consists of 64 polarimeters and four of these arrays are assembled together to make a focal plane, for a total of 256 dual-polarization elements (512 TES sensors). The detector arrays are integrated with a time-domain SQUID multiplexer developed at NIST and read out using the multi-channel electronics (MCE) developed at the University of British Columbia. Following our progress in improving detector parameters uniformity across the arrays and fabrication yield, our main effort has focused on improving detector arrays optical and noise performances, in order to produce science grade focal planes achieving target sensitivities. We report on changes in detector design implemented to optimize such performances and following focal plane arrays characterization. BICEP2 has deployed a first 150 GHz science grade focal plane to the South Pole in December 2009.

Download full-text

Full-text

Available from: Angiola Orlando, Jul 09, 2015
2 Followers
 · 
258 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report on the preliminary detector performance of the Bicep2 mm-wave polarimeter, deployed in 2009 to the South Pole. Bicep2 is currently imaging the polarization of the cosmic microwave background at 150 GHz using an array of 512 antenna-coupled superconducting bolometers. The antennas, band-defining filters and transition edge sensor (TES) bolometers are photolithographically fabricated on 4 silicon tiles. Each tile consists of an 8×8 grid of ~7 mm spatial pixels, for a total of 256 detector pairs. A patial pixel contains 2 sets of orthogonal antenna slots summed in-phase, with each set coupled to a TES by a filtered microstrip. The detectors are read out using time-domain multiplexed SQUIDs. The detector pair of each spatial pixel is differenced to measure polarization. We report on the performance of the Bicep2 detectors in the field, including the focal plane yield, detector and multiplexer optimization, detector noise and stability, and a preliminary estimate of the improvement in mapping speed compared to Bicep1.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2010; 7741:77411H. DOI:10.1117/12.857861
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Bicep2 deployed to the South Pole during the 2009-2010 austral summer, and is now mapping the polarization of the cosmic microwave background (CMB), searching for evidence of inflationary cosmology. Bicep2 belongs to a new class of telescopes including the Keck Array (ground-based) and Spider (balloon-borne) that follow on Bicep’s strategy of employing small, cold, on-axis refracting optics. This common design provides key advantages ideal for targeting the polarization signature from inflation, including: (i) A large field of view, allowing substantial light collecting power despite the small aperture, while still resolving the degree-scale polarization of the CMB; (ii) liquid helium-cooled optics and cold stop, allowing for low, stable instrument loading; (iii) the ability to rotate the entire telescope about the boresight; (iv) a baffled primary aperture, reducing sidelobe pickup; and (v) the ability to characterize the far field optical performance of the telescope using ground-based sources. We describe the last of these advantages in detail, including our efforts to measure the main beam shape, beam-match between orthogonally-polarized pairs, polarization efficiency and response angle, sidelobe pickup, and ghost imaging. We do so with ground-based polarized microwave sources mounted in the far field as well as with astronomical calibrators. Ultimately, Bicep2’s sensitivity to CMB polarization from inflation will rely on precise calibration of these beam features.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2010; 7741:77410V. DOI:10.1117/12.857868
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Next generation cosmic microwave background (CMB) polarization anisotropy measurements will feature focal plane arrays with more than 600 millimeter-wave detectors. We make use of high-resolution photolithography and wafer-scale etch tools to build planar arrays of corrugated platelet feeds in silicon with highly symmetric beams, low cross-polarization and low side lobes. A compact Au-plated corrugated Si feed designed for 150 GHz operation exhibited performance equivalent to that of electroformed feeds: ~-0.2 dB insertion loss, <-20 dB return loss from 120 GHz to 170 GHz, <-25 dB side lobes and <-23 dB cross-polarization. We are currently fabricating a 50 mm diameter array with 84 horns consisting of 33 Si platelets as a prototype for the SPTpol and ACTpol telescopes. Our fabrication facilities permit arrays up to 150 mm in diameter.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2010; DOI:10.1117/12.857701