Preliminary determination of Newtonian gravitational constant with angular acceleration feedback method

Phil. Trans. R. Soc. A 2014 372, 20140031

Chao Xue1, Li-Di Quan1,2, Shan-Qing Yang1, Bing-PengWang1, Jun-FeiWu1, Cheng-Gang Shao1, Liang-Cheng Tu1, Vadim Milyukov3 and Jun Luo1

1MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People's Republic of China

2School of Automation, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People's Republic of China

3Sternberg Astronomical Institute, Moscow State University, Moscow 119992, Russia

e-mail: junluo@mail.hust.edu.cn

This paper describes the preliminary measurement of the Newtonian gravitational constant G with the angular acceleration feedback method at HUST. The apparatus has been built, and preliminary measurement performed, to test all aspects of the experimental design, particularly the feedback function, which was recently discussed in detail by Quan et al. The experimental results show that the residual twist angle of the torsion pendulum at the signal frequency introduces 0.4 ppm to the value of G. The relative uncertainty of the angular acceleration of the turntable is approximately 100 ppm, which is mainly limited by the stability of the apparatus. Therefore, the experiment has been modified with three features: (i) the height of the apparatus is reduced almost by half, (ii) the aluminium shelves were replaced with shelves made from ultra-low expansion material and (iii) a perfect compensation of the laboratory-fixed gravitational background will be carried out. With these improvements, the angular acceleration is expected to be determined with an uncertainty of better than 10 ppm, and a reliable value of G with 20 ppm or below will be obtained in the near future.