arXiv subjects

Yong-Ping Li

Publications and source records attributed to Yong-Ping Li.

5 recordsLinked to original sources

arXiv2026

Design and characterization of W-band and D-band calibration sources for the AliCPT-1 experiment

Ali Cosmic Microwave Background Polarization Telescope (AliCPT-1) is the first Chinese cosmic microwave background experiment aiming to make sensitive polarization maps of the potential B-mode signal from inflationary gravitational waves. The telescope was deployed on the Tibet Ali site at 5250 m above sea level in early 2025. Before and after each observation season, the instrument performance must be carefully calibrated, including the far field beam performance, far sidelobe, spectral response, polarization angle, and cross-polar beam response. To characterize these optical performances, several calibrators have been developed. We developed a W-band source and a D-band source for the AliCPT-1 telescope's beam characterizations. We present the design and performance of the two calibration sources.

astro-ph.IM↗

arXiv2018

Tibet$^\prime$s Window on Primordial Gravitational Waves

As an essential part of Chinaâ€™s Gravitational Waves Program, the Ali CMB Polarization Telescope (AliCPT) is a ground-based experiment aiming at the Primordial Gravitational Waves (PGWs) by measuring B-mode polarization of Cosmic Microwave Background (CMB). First proposed in 2014 and currently in fast construction phase, AliCPT is Chinaâ€™s first CMB project that plans for commissioning in 2019. Led by the Institute of High Energy Physics (IHEP) under the Chinese Academy of Sciences (CAS), the project is a worldwide collaboration of more than fifteen universities and research institutes. Ali CMB Project is briefly introduced.

astro-ph.IM↗

arXiv2018

Probing Primordial Gravitational Waves: Ali CMB Polarization Telescope

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 China's 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.

astro-ph.CO↗

arXiv2017

Tibet's Ali: A New Window to Detect the CMB Polarization

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 theories 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.

astro-ph.IM↗

arXiv2015

Cosmic Reionization Study : Principle Component Analysis After Planck

The study of reionization history plays an important role in understanding the evolution of our universe. It is commonly believed that the intergalactic medium (IGM) in our universe are fully ionized today, however the reionizing process remains to be mysterious. A simple instantaneous reionization process is usually adopted in modern cosmology without direct observational evidence. However, the history of ionization fraction, $x_e(z)$ will influence cosmic microwave background (CMB) observables and constraints on optical depth $τ$. With the mocked future data sets based on featured reionization model, we find the bias on $τ$ introduced by instantaneous model can not be neglected. In this paper, we study the cosmic reionization history in a model independent way, the so called principle component analysis (PCA) method, and reconstruct $x_e (z)$ at different redshift $z$ with the data sets of Planck, WMAP 9 years temperature and polarization power spectra, combining with the baryon acoustic oscillation (BAO) from galaxy survey and type Ia supernovae (SN) Union 2.1 sample respectively. The results show that reconstructed $x_e(z)$ is consistent with instantaneous behavior, however, there exists slight deviation from this behavior at some epoch. With PCA method, after abandoning the noisy modes, we get stronger constraints, and the hints for featured $x_e(z)$ evolution could become a little more obvious.

astro-ph.CO↗