Tests of Newtonian Gravitation and the Equivalence Principle and Cryogenic Torsion Pendulum Development

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A program of laboratory experiments in gravitation is to be continued and expanded, in parallel with continued development of the cryogenic torsion pendulum as a general tool for research in gravitational physics. Much of this work will be done in collaboration with the gravitational physics group of Professor Paul Boynton at the University of Washington. Research to be conducted includes:Completion in the first year of a precision measurement of the gravitational constant G, withtarget accuracy of 15 ppm.Jointly with Professor Boynton's group, a test of the inverse square distance dependence of the gravitational force for mass separation on the order of 15 centimeters.Jointly with Boynton's group, tests of the equivalence principle over various distance ranges,for gravitational field sources which include laboratory masses, a nearby mountain, and thesun.These projects will be conducted in an underground laboratory that has been prepared with support from the Pacific Northwest National Laboratory in a former Nike missile bunker on an isolated environmental preserve nearRichland, Washington. In conjunction with these projects, the performance of the cryogenic torsionpendulum will be progressively improved through development and refinement of seismic isolation, tilt control, temperature control, and fiber choice and preparation techniques. The cryogenic torsion pendulum being developed is of potential value to any research in gravitation or other fields which requires the measurement of extremely small slowly varying forces.This project provides research experience and training in a variety of widely applicable technologies, to undergraduate and graduate students as well as to a postdoctoral researcher.