Source: School of Physics and Astronomy
Written by: School of Physics and Astronomy
Edited by: Wang Dongmei

On 8 December 2016, 19:00 Geneva time, the Alpha Magnetic Spectrometer (AMS) Collaboration announces the fifth anniversary of the AMS Experiment on the International Space Station (ISS) and summarizes its major scientific results to date.

The AMS Experiment is the most powerful and sensitive physics detector ever deployed in space and is exploring a new and exciting frontier in physics research. As a magnetic spectrometer, AMS is unique in physics research as it studies charged particles and nuclei from original sources in the cosmos before they are annihilated in the Earth’s atmosphere. The improvement in accuracy over previous measurements is made possible through its long duration time in space, large acceptance, built in redundant systems and its thorough calibration in the CERN test beam. These features enable AMS to analyze the data to an accuracy of ~1% and thereby requiring new theories to be developed by the physics and astrophysics community.

Since its installation on the ISS in May 2011, AMS has collected more than 90 billion cosmic ray events. The data is analyzed at the AMS Science Operations Center (SOC) located at CERN as well as at AMS universities around the world. Over the lifetime of the Space Station, AMS is expected to measure hundreds of billions of primary cosmic rays. Among the physics objectives of AMS is the search for antimatter, dark matter, and the origin of cosmic rays. Over the first five years on the ISS, the AMS Collaboration has conducted precision measurements of cosmic rays to study elementary particles and nuclei. The latest AMS measurements of the positron spectrum and positron fraction, the antiproton/proton ratio, the behavior of the fluxes of electrons, positrons, protons, helium and other nuclei provide precise and unexpected information on the production, acceleration and propagation of cosmic rays. The accuracy and characteristics of the data, simultaneously from many different types of cosmic rays require the development of a comprehensive model. In the coming years, with more data, one of our main efforts is to ascertain the origin of the Z = -2 events. Most importantly, AMS will continue to collect and analyze data for the lifetime of the Space Station. As the results to date have demonstrated, whenever a precision instrument such as AMS is used to explore the unknown, new and exciting discoveries can be expected.

Led by Nobel Laureate Dr. Samuel Ting, AMS is an international collaboration made up of 56 research institutions from 16 countries and regions with more than 1,500 researchers participating in the project. Sun Yat-sen University (SYSU) is one of the five universities in China that participate in the project.

SYSU is responsible for developing the precision temperature control system of the silicon tracker, which provides a stable thermal environment for the tracker. After AMS was launched, SYSU research team participated in the adjustment of the tracker as well as its on-orbit operational control and maintenance in the past five years. It is this precision temperature control system that makes such high precision measurements possible.

Up till now, SYSU has sent 5 PhD students to participate in the AMS data analysis and they have made recognized contributions. Among them, Dr. Weng Zhili who participated in the first published physics paper of AMS02 has graduated from SYSU and is doing postdoctoral research at MIT, continuing with his AMS data analysis work. The other four PhD candidates Feng Jie, Li Xiang, Li Ziyuan and Lu Senquan are still doing research in different groups in the AMS lab at CERN.