Application of LTS-SQUIDs for testing the weak equivalence principle at the Drop Tower Bremen

Abstract

Free fall tests to prove the weak equivalence principle were rarely be done in history. Presently, very precise fall tests in the 10 −13 range are possible and under preparation to be carried out on Drop Tower Bremen during free fall over 109 m. A level of accuracy of 10 −18 will be achieved in the current satellite test of the equivalence principle space mission of NASA/ESA. Both kinds of experiments require position detectors with an extremely high resolution to measure infinitesimal displacements of freely falling test masses. On the basis of the LTS SQUID system of the Jena University an experimental setup was developed containing a pair of superconducting levitated test masses installed in a vacuum chamber at 4.2 K. The resolution of the SQUID position detector was measured to be as high as 4×10 −14 m/ Hz . This whole apparatus was successfully tested and dropped at the Drop Tower Bremen providing a free fall height of 109 m corresponding to a flight time of 4.7 s. Recent results of this measurements are described in this work.