title: G measurements with time-of-swing method at HUST.
abstract: We review the G measurements with time-of-swing method at HUST. Two independent experiments have been completed and an improved experiment is in progress. The first G value was determined as 6.6699(7)×10-11m3kg-1s-2with a relative standard uncertainty (ur) of 105 ppm by using a long period torsion pendulum and two cylindrical source masses. Later, this result was corrected to be 6.6723(9)×10-11m3kg-1s-2with ur=130 ppm after considering the density distribution of the cylinders and the air buoyancy, which was 360 ppm larger than the previous value. In 2009, a new experiment by using a simple block pendulum and spherical source masses with more homogeneous density was carried out. A series of improvements were performed, and the G value was determined to be 6.67349(18)×10-11m3kg-1s-2with ur=26 ppm. To reduce the anelasticity of the torsion fibre, fused silica fibres with Q's of approximately 5×104are used to measure G in the ongoing experiment. These fibres are coated with thin layers of germanium and bismuth in turn to reduce the electrostatic effect. Some other improvements include the gravity compensation, reduction of the coating layer effect, etc. The prospective uncertainty of the next G value is 20 ppm or lower.
authors.affiliation: MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People's Republic of China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.affiliation: MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People's Republic of China.
authors.forename: Jian-Ping
authors.initials: JP
authors.lastname: Liu
authors.affiliation: MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People's Republic of China.
authors.forename: Hui-Hui
authors.initials: HH
authors.lastname: Zhao
authors.affiliation: MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People's Republic of China.
authors.forename: Shan-Qing
authors.initials: SQ
authors.lastname: Yang
authors.affiliation: MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People's Republic of China.
authors.forename: Liang-Cheng
authors.initials: LC
authors.lastname: Tu
authors.affiliation: MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People's Republic of China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Liu
authors.affiliation: MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People's Republic of China.
authors.forename: Cheng-Gang
authors.initials: CG
authors.lastname: Shao
authors.affiliation: MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People's Republic of China.
authors.forename: Zhong-Kun
authors.initials: ZK
authors.lastname: Hu
authors.affiliation: Moscow State University, Sternberg Astronomical Institute, Moscow 119992, Russia.
authors.forename: Vadim
authors.initials: V
authors.lastname: Milyukov
authors.affiliation: MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People's Republic of China junluo@mail.hust.edu.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Luo
keywords: CODATA; gravitational constant G; precision measurement; time-of-swing method; torsion pendulum