اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe design of the Ali CMB Polarization Telescope receiver
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Ali CMB Polarization Telescope (AliCPT-1) is the first CMB degree-scale polarimeter to be deployed on the Tibetan plateau at 5,250m above sea level. AliCPT-1 is a 90/150 GHz 72 cm aperture, two-lens refracting telescope cooled down to 4 K. Alumina lenses, 800mm in diameter, image the CMB in a 33.4{deg} field of view on a 636mm wide focal plane. The modularized focal plane consists of dichroic polarization-sensitive Transition-Edge Sensors (TESes). Each module includes 1,704 optically active TESes fabricated on a 150mm diameter silicon wafer. Each TES array is read out with a microwave multiplexing readout system capable of a multiplexing factor up to 2,048. Such a large multiplexing factor has allowed the practical deployment of tens of thousands of detectors, enabling the design of a receiver that can operate up to 19 TES arrays for a total of 32,376 TESes. AliCPT-1 leverages the technological advancements in the detector design from multiple generations of previously successful feedhorn-coupled polarimeters, and in the instrument design from BICEP-3, but applied on a larger scale. The cryostat receiver is currently under integration and testing. During the first deployment year, the focal plane will be populated with up to 4 TES arrays. Further TES arrays will be deployed in the following years, fully populating the focal plane with 19 arrays on the fourth deployment year. Here we present the AliCPT-1 receiver design, and how the design has been optimized to meet the experimental requirements.
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The Cosmic Microwave Background (CMB) Polarization plays an important role in current cosmological studies. CMB B-mode polarization is the most effective probe to primordial gravitational waves (PGWs) and a test of the inflation as well as other theo
ries of the early universe such as bouncing and cyclic universe. So far, major ground-based CMB polarization experiments are located in the southern hemisphere.Recently, China has launched the Ali CMB Polarization Telescope (AliCPT) in Tibetan Plateau to measure CMB B mode polarization and detect the PGWs in northern hemisphere. AliCPT include two stages, the first one is to build a telescope at the 5250m site (AliCPT-1) and the second one is to have a more sensitive telescope at a higher altitude of about 6000m (AliCPT-2). In this paper, we report the atmospherical conditions, sky coverage and the current infrastructure associated with AliCPT. We analyzed the reanalysis data from MERRA-2 together with radiosonde data from the Ali Meteorological Service and found that the amount of water vapor has a heavy seasonal variation and October to March is the suitable observation time. We also found 95/150 GHz to be feasible for AliCPT-1 and higher frequencies to be possible for AliCPT-2. Then we analyzed the observable sky and the target fields, and showed that Ali provides us a unique opportunity to observe CMB with less foreground contamination in the northern hemisphere and is complementary to the existed southern CMB experiments. Together with the developed infrastructure, we point out that Ali opens a new window for CMB observation and will be one of the major sites in the world along with Antarctic and Atacama.
In this paper, we will give a general introduction to the project of Ali CMB Polarization Telescope (AliCPT), which is a Sino-US joint project led by the Institute of High Energy Physics (IHEP) and has involved many different institutes in China. It
is the first ground-based Cosmic Microwave Background (CMB) polarization experiment in China and an integral part of Chinas Gravitational Waves Program. The main scientific goal of AliCPT project is to probe the primordial gravitational waves (PGWs) originated from the very early Universe. The AliCPT project includes two stages. The first stage referred to as AliCPT-1, is to build a telescope in the Ali region of Tibet with an altitude of 5,250 meters. Once completed, it will be the worldwide highest ground-based CMB observatory and open a new window for probing PGWs in northern hemisphere. AliCPT-1 telescope is designed to have about 7,000 TES detectors at 90GHz and 150GHz. The second stage is to have a more sensitive telescope (AliCPT-2) with the number of detectors more than 20,000. Our simulations show that AliCPT will improve the current constraint on the tensor-to-scalar ratio $r$ by one order of magnitude with 3 years observation. Besides the PGWs, the AliCPT will also enable a precise measurement on the CMB rotation angle and provide a precise test on the CPT symmetry. We show 3 years observation will improve the current limit by two order of magnitude.
The six-meter Atacama Cosmology Telescope (ACT) in Chile was built to measure the cosmic microwave background (CMB) at arcminute angular scales. We are building a new polarization sensitive receiver for ACT (ACTPol). ACTPol will characterize the grav
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