Testing Einstein's Equivalence Principle at Bremen drop tower using LTS SQUID technique

Free fall tests to prove the Weak Equivalence Principle (WEP) were rarely b e done in history. Although they seem to be the natural experiments to test the equivalence of inertial and gravitational mass, best results for WEP-p roofs could be attained with torsion pendulum tests to an accuracy of 10(-1 2) because these pendulum tests are long term periodic experiments. otherwi se, free fall tests on Earth can be carried out only for seconds causing ce rtain principle limitations. Nevertheless, very precise fall tests in the 1 0(-13) range are possible and under preparation to be carried out on Drop T ower Bremen during free fall over 109 m, A level of accuracy of 10(-18) wil l be achieved in the current STEP (Satellite Test of the Equivalence Princi ple) 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 m asses. On the basis of the LTS SQUID system of the Jena University an exper imental set-up 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 x 10(-14) m/root 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 tim e of 4.7 s. Recent results of this measurements are described in this work.