PT2 - Equivalence Principle Tests |
Speaker_ |
Iafolla, Valerio |
Co-autors |
V Iafolla1, D. Lucchesi1, S. Nozzoli1, F. Santoli1,E.C. Lorenzini3,2, I.I. Shapiro2, J. Ashenberg2, C. Bombardelli4,2, P.N. Cheimets2, S. Glashow5 |
Talk _ |
Development of accelerometer prototypes for testing the Equivalence Principle in free fall |
Abstract _ |
Development of accelerometer prototypes for testing the Equivalence Principle in free fall V Iafolla(1), D. Lucchesi(1), S. Nozzoli(1), F. Santoli(1), E.C. Lorenzini(2,3), I.I. Shapiro(2), J. Ashenberg(2), C. Bombardelli(2,4), P.N. Cheimets(2), S. Glashow(5) 1Institute of Interplanetary Space Physics (IFSI), Rome, Italy; 2Harvard-Smithsonian Center for Astrophysics (CfA), Cambridge, MA, USA; 3University of Padova, Padua, Italy 4European Space Agency, ESA/ESTEC, Noordwijk, The Netherlands 5Boston University, Boston, MA, USA Abstract The paper describes a proposed free-fall test of the Equivalence Principle (EP) and the associated development of differential accelerometer prototypes for laboratory testing. The flight experiment to test the EP will be carried out in free-fall inside a capsule released from a stratospheric balloon (Einstein elevator). The accuracy goal of the experiment is a few parts in 10^15 obtained after a free fall time of typically 25 s. This accuracy would imply an improvement of two orders of magnitude with respect to the state of the art in testing the EP. A differential accelerometer with a noise level better than 10^-14g/sqrt(Hz) is required to achieve in free fall the experiment design accuracy. The differential accelerometer (detector) will be cooled down to the temperature of liquid helium and spun up at a rate of 0.5 Hz about the horizontal axis before free fall. The detector is then released to free fall for about 25 s inside the co-moving capsule shortly after the capsule has benn released from the balloon. When compared to proposed future satellite experiments (which could reach higher accuracy) and to classic ground experiments, this free-fall experiment is a good compromise that could potentially improve significantly the present accuracy level of the EP tests and provide the option to repeat the experiment at month-long intervals. The paper then describes the development of two differential accelerometer prototypes (operated at room temperature) that are being used to test key aspects of the experiment in the laboratory. Key experimental issues are the rapid abatement of transient oscillations after release and the ability (espressed by the common-mode rejection factor) of the differential accelerometer to reject accelerations that affect equally the two test masses. Results obtained in the laboratory on two differential accelerometer prototypes are briefly discussed in the paper. |