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.
Future far-infrared (FIR) astronomy missions will need large detector arrays with high sensitivity. Low noise detectors with a noise equivalent power (NEP) of 3×10−19 to 1×10−20 W/Hz1/2 for space-based continuum observations are needed, to be photon noise limited. Transition edge sensor (TES) as a type of sensitive low-temperature superconducting detector, has significant advantages in the measurement of broad band electromagnetic radiation, from millimeter waves to X-ray and gamma-rays. We propose a design of low noise TESs for FIR applications, with the NEP of lower than 3×10−19 W/Hz1/2. The key component on TES bolometer island is aluminum-manganese (AlMn) superconducting film, which has been proved that its critical temperature can be adjusted over a wide range by baking after the film deposition. We optimize the NEP of AlMn TESs by reducing the critical temperature to around 60 mK and designing the thermally isolating legs to reduce the thermal conductance effectively. The pixel design will be used as foundation in our future TES array designs and will benefit high-sensitive detector development.
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.
The Hard X-ray Modulation Telescope (HXMT or also dubbed as Insight-HXMT) is China’s first astronomical satellite. It was launched on 15th June 2017 in JiuQuan, China and is currently in service smoothly. It was designed to perform pointing, scanning and gamma-ray burst (GRB) observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed. Here we introduce the mission and its progresses in aspects of payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and preliminary results.
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