We present a thermal kinetic inductance detector array design for CMB polarization observation at 90/150 GHz bands. A horn-coupled planar ortho-mode transducer is used for a broadband linear polarization separation. The frequency separation is done using a fast roll-off lumped-element diplexer. Thermal kinetic inductance detectors with Al is used as the detector. The array has more than 450 optical pixels with more than 1800 detectors. The array design and preliminary measurement results will be discussed.
For cosmic microwave background (CMB) telescopes, high-density polyethylene (HDPE) is widely used as reimaging lens material on account of its extremely low loss and excellent mechanical properties. The impedance mismatch between free space and lens can cause non-negligible reflection loss and low image quality. An anti-reflection (AR) coating is essential to reduce such effect. Single or multiple layers porous polytetrafluoroethylene (PTFE) membranes are glued to the HDPE lens surface as AR coatings in many previous CMB experiments. However, it is difficult to get a uniform bonding across a curvature surface for a large-aperture CMB telescope. Due to the mismatch of the thermal expansion of the lens and AR coating materials, the AR coatings have delamination or separation problem during cryogenic cycling. Simulated dielectric AR (SDAR) coatings based on the theory of meta-surface are suitable for low frequency and large aperture CMB telescopes. The effective refractive index of SDAR coating is tunable by cutting holes or grooves into the lens material to form sub-wavelength structure. The SDAR coating is made directly from lens bulk material, which can naturally solve the thermal expansion mismatch problem. In this paper, we present the SDAR coating prototype machined on a 30 mm thick HDPE plate. The measurement results show that the SDAR coating can effectively eliminate standing waves with the performance improvement about -10 dB to -20 dB. And the transmittance exceeds 98% in the 30 GHz to 50 GHz band, which is about 10% higher than that without AR coating.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.