The MTV-G (MTV-Gravity) experiment is aiming to test an existence of a strong gravitational field at around nuclear scale, utilizing an electron polarimeter of the MTV (Mott Polarimetry for T-Violation) experiment at TRIUMF, which is searching a large T-Violating electron transverse polarization emitted in a polarized Li-8 beta decay.From 2011, we have started the MTV-G experiment utilizing the MTV detectors, successfully examined the strong gravitational field at the microscopic scale for the first time.We are trying to set new constraint on the possible new Yukawa interaction at sub-mm scale, where violation of gravitational inverse square law is predicted.

The MTV-G project was started in 2011 to explore a strong gravitational field at a nuclear scale in an electron double scattering experiment, utilizing an experimental technique of the MTV experiment, which searches a electron’s T-Violating transverse polarization in nuclear beta decay at TRIUMF-ISAC. In addition to this new experiment, we have also performed a re-analysis of spectroscopic data of exotic atoms, in a gravitational point of view. From these two studies, we set new constraints on possible new Yukawa interaction at sub-mm scale, as a test of gravitational inverse square law.

The MTV-G project has started in 2011 to explore a strong gravitational field around nuclei utilizing an experimental technique developed to search time reversal symmetry violation in nuclear beta decay experiment at a radioactive beam facility. A large electron spin-precession due to a possible strong gravitational field, which has been predicted by a large extra dimension model, is investigated in an electron-nuclear scattering experiment at TRIUMF. The experimental design, which use a spin polarized electron source and a Mott-spin analyzer, the commissioning experiment, the preliminary results, together with an introduction to the next generation device, are described in this article.