- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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GroundBIRD: Observation of CMB Polarization with a Rapid Scanning and MKIDs
摘要： Cosmic microwave background (CMB) radiation is an afterglow from the Big Bang. CMB contains rich information about the early stage of the universe. In particular, odd-parity patterns (B-mode) in the CMB polarization on a large angular scale would provide an evidence of the cosmic in?ation. The aim of the GroundBIRD experiment is to observe the B-mode on large angular scales from the ground. One of the most novel characteristics of the telescope used for this experiment is its rapid rotational scanning technique. In addition, the telescope uses cold optics and microwave kinetic inductance detectors. We have developed a telescope mount with a three-axis rotation mechanism (azimuth, elevation, and boresight) and measured the vibration at the focal plane stage at 20 RPM scan rotation rate. We also performed focal plane detector tests on this mount. The tests con?rmed the expected response from the geomagnetism associated with the mount rotation. We have also developed a design for the magnetic shields and a detector array on a 3-in wafer. The preparations to begin the observations at the Teide Observatory in the Canary Islands in 2018 are proceeding smoothly.
关键词： Cosmic microwave background,Polarization,Microwave kinetic inductance detector
更新于2025-09-23 15:23:52
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Design and Characterisation of Titanium Nitride Subarrays of Kinetic Inductance Detectors for Passive Terahertz Imaging
摘要： We report on the investigation of titanium nitride (TiN) thin films deposited via atomic layer deposition (ALD) for microwave kinetic inductance detectors (MKID). Using our in-house ALD process, we have grown a sequence of TiN thin films (thickness 15, 30, 60 nm). The films have been characterised in terms of superconducting transition temperature Tc, sheet resistance Rs and microstructure. We have fabricated test resonator structures and characterised them at a temperature of 300 mK. At 350 GHz, we report an optical noise equivalent power NEPopt ≈ 2.3 × 10?15 W/√Hz, which is promising for passive terahertz imaging applications.
关键词： Titanium nitride,ALD,Kinetic inductance detector
更新于2025-09-23 15:22:29
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Optical Response of Lumped-Element Kinetic-Inductance Detector Arrays
摘要： We present an analysis of the optical response of lumped-element kinetic-inductance detector arrays, based on the NIKA2 1 mm array. This array has a dual-polarization sensitive Hilbert inductor for directly absorbing incident photons. We present the optical response calculated from a transmission line model, simulated with HFSS and measured using a Fourier transform spectrometer. We have estimated the energy absorbed by individual component of a pixel, such as the inductor. The difference between the absorption efficiencies is expected to be 20% from the simulations. The Fourier-transform spectroscopy measurement, performed on the actual NIKA2 arrays, validates our simulations. We discuss several possible ways to increase the absorption efficiency. This analysis can be used for optimization of the focal plane layout and can be extended to other kinetic inductance detector array designs in millimeter, submillimeter, and terahertz frequency bands.
关键词： superconducting microresonator,optical response,millimeter astronomy,Kinetic inductance detector
更新于2025-09-23 15:22:29
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Increased multiplexing of superconducting microresonator arrays by post-characterization adaptation of the on-chip capacitors
摘要： We present an interdigitated capacitor trimming technique for fine-tuning the resonance frequency of superconducting microresonators and increasing the multiplexing factor. We first measure the optical response of the array with a beam mapping system to link all resonances to their physical resonators. Then, a new set of resonance frequencies with uniform spacing and higher multiplexing factor is designed. We use simulations to deduce the lengths that we should trim from the capacitor fingers in order to shift the resonances to the desired frequencies. The sample is then modified using contact lithography and re-measured using the same setup. We demonstrate this technique on a 112-pixel aluminum lumped-element kinetic-inductance detector array. Before trimming, the resonance frequency deviation of this array is investigated. The variation of the inductor width plays the main role for the deviation. After trimming, the mean fractional frequency error for identified resonators is (cid:1)6.4 (cid:2) 10(cid:1)4, with a standard deviation of 1.8 (cid:2) 10(cid:1)4. The final optical yield is increased from 70.5% to 96.7% with no observable crosstalk beyond (cid:1)15 dB during mapping. This technique could be applied to other photon-sensitive superconducting microresonator arrays for increasing the yield and multiplexing factor.
关键词： interdigitated capacitor trimming,lumped-element kinetic-inductance detector,superconducting microresonators,multiplexing factor,resonance frequency tuning
更新于2025-09-23 15:21:01
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Fabrication of OMT-Coupled Kinetic Inductance Detector for CMB Detection
摘要： Future cosmic microwave background (CMB) experiments, including the large scale ground-based Stage Four CMB Experiment (CMB-S4), satellites, and balloons, aim to map the CMB to an unprecedented precision in order to answer several key questions in cosmology. However, to reach the target noise sensitivity, more than 100,000 detectors will be needed. Arrays of kinetic inductance detectors (KIDs) are a promising alternative for experiments that require large number of detectors due to the intrinsic multiplexing capabilities. We present the fabrication procedure for a prototype planar orthomode transducer (OMT)-coupled multi-color KID array optimized for 220/270 GHz frequency bands. These devices are made from silicon-on-insulator wafers to provide a low-loss substrate for the KIDs. The OMT couples the two polarizations of light from a wide-band feedhorn to separate Nb/SiN/Nb microstrip lines, which are then coupled to Al/Nb lumped-element KIDs (LEKIDs). The silicon on the backside of the OMT is etched away using deep reactive ion etch to release the OMT membrane to enable operation over a wide bandwidth. Finally, the buried oxide is removed underneath the KID capacitors in order to minimize two-level system noise and loss mitigation. We achieved a good yield (> 80%) on our prototype devices.
关键词： Kinetic inductance detector,Fabrication,Cosmic microwave background
更新于2025-09-23 15:21:01
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Complex Field Mapping of Large Direct Detector Focal Plane Arrays
摘要： Complex ?eld mapping is a powerful tool to characterize the optical performance of astronomical instruments, and has become the standard for characterizing heterodyne array cameras. Recently, an adaptation of the heterodyne beam mapping technique was demonstrated on a single pixel of a direct detector instrument. We present novel measurement apparatus and data acquisition techniques to e?ciently reconstruct the complex ?eld pattern of individual pixels across a direct detector focal plane array. These techniques are scalable to high pixel counts as the technology maturation and scienti?c requirements push to larger arrays. For this demonstration, we used an engineering model of the low frequency band of the Apex Microwave Kinetic Inductance Detector (AMKID) camera with a center frequency of ν = 350 GHz. Amplitude and phase radiation patterns were measured from all 880 pixels of the test array in two orthogonal polarizations. We also discuss an updated post-processing pipeline using the complex ?eld data to characterize the optical performance of the array. Using the measured complex ?eld pattern, we extract the co- and cross-polarization pattern, Gaussian beam parameters, and propagate the beam from the measurement plane to additional planes of interest across all pixels in the test array. Complex ?eld measurements of direct detectors allow more precise characterization of beam parameters when compared to thermal measurements, particularly for individualized ?tting in post-processing not reliant on the accuracy of the probe system alignment. These techniques enable high-precision characterization of individualized beam parameters as well as the overall optical system to very large format arrays with modest computational processing power. These results demonstrate the diagnostic power of the presented measurement and analysis techniques.
关键词： optical characterization,kinetic inductance detector,near to far ?eld transformation,complex ?eld mapping,Gaussian beam analysis
更新于2025-09-11 14:15:04
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Investigation of Single-Crystal Niobium for Microwave Kinetic Inductance Detectors
摘要： The Advanced Technology Centre (ATC) of National Astronomical Observatory of Japan is developing microwave kinetic inductance detectors (MKIDs) for large-array pixel cameras for millimeter and sub-millimeter astronomy. We investigated single-crystal Nb thin layers to form superconducting microresonators. We compared the performances of MKIDs based on crystalline Nb structure and those based on poly-crystalline Nb. We carried out the entire manufacture of the detectors in the ATC clean room. DC magnetron sputtering is used to grow single-crystal Nb films on r-plane sapphire substrates at an elevated temperature of 800 °C. The residual resistivity ratio (RRR) measured on these single-crystal Nb layers reached values ranging from 40 to 80. We made MKIDs with this crystalline Nb layer, and we measured internal quality factors of the detectors up to 106. The measurement of the noise power spectral density of these MKIDs gave a low value of ? 95 dBc/Hz from 100 Hz to 100 kHz. The internal quality factor Qi and the fractional resonance frequency change δf r/f r of MKIDs with respect to the temperature variation are usually following the extended Mattis–Bardeen equations. However, we noticed a deviation from the theoretical prediction for temperature lower than 1 K (in our case). This deviation has already been observed on Al MKIDs and explained by a theory taking into account the Kondo effect and the kinetic inductance contribution. We demonstrated that our measurements on single-crystal Nb MKIDs are also in agreement with the same theory.
关键词： Microwave kinetic inductance detector,Single-crystal niobium,Superconducting thin films
更新于2025-09-09 09:28:46