Contains a summary of research.National Science Foundation (Grant MPS75-04033)M.I.T. Sloan Fund for Basic Researc

Kramer, Peter B.

Weiss, Rainer

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XVII. GRAVITATION RESEARCHAcademic and Research StaffProf. Rainer WeissDr. Peter B. KramerNational Science Foundation (Grant MPS75-04033)1I. I. T. Sloan Fund for Basic ResearchRainer Weiss, Peter B. KramerOur research objective is to make an experimental study of the post-Newtonianeffects of relativistic gravitation. At present, the major emphasis is placed on a feasi-bility study of gravitational radiation detectors based on the principle of the interactionbetween free masses and gravitational waves. Gravitational wave antennas of this type,when used with large baselines and sensed interferometrically, give some promise ofbeing able to detect the gravitational radiation from stellar binaries. Preliminary cal-culations with a 1-km baseline system using 1-ton masses in space indicate that thedominant noise for periods longer than 100 s may be stochastic force attributable tohigh-energy protons. The antenna employing a 1-W laser would be able to detect thegravitational radiation from several short-period binary systems in several months ofintegration time. Because of laser amplitude noise, the limiting strain sensitivity forperiods shorter than 100 s corresponds to (A£/1) 2 ~ 10-42/Hz.A prototype interferometric antenna with a 1-m baseline is being constructed in thelaboratory. The sensitivity at frequencies higher than 100 lHz is limited by laseramplitude noise and corresponds to (Ak/!) 2 ~ 10_36 Hz. In the present design, at fre-quencies lower than 100 Hz, the noise is dominated by seismic and acoustic noise. Withthis antenna we should be able to set significantly lower limits on the gravitationalradiation spectrum but not on a level where any reasonable astrophysical process couldbe measured.Construction of the prototype is still in progress. At present the vacuum systemhas been assembled and tests of the optics have been carried out. Interferometry usingmultiple-pass delay lines was demonstrated within a factor of four of the shot-noiselimit.The program has been transferred to the Department of Physics.PR No. 120

Gravitation Research

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Gravitation Research

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