Multi-Nested Pendula: a new concept for vibration isolation and its application to gravitational wave detectors

Adequate vibration isolation is of great importance for the design of any sensitive experiment measuring mechanical motions. The so-called multistage or multipole mechanical low pass filter is a common artifact used for the construction of highly effective vibration isolation. However, the problem with it is the vertical clearance needed inside the vacuum chambers for the construction of numerous, long pendulum stages necessary for effective horizontal vibration isolation. The purpose of this work is to introduce a new concept, called the multi-nested pendula concept, which solves this problem. The attenuation performance of an ideal multistage nested pendula filter is better than that of an ideal multistage common equal pendula filter by a factor of N^{N}, where N is the number of stages used, making this idea of a multi-nested pendula a very interesting one. The initial results (of stability and system resonances) measured for a prototype reinforce the viability of the practical implementation of such idea. A detailed study for the realization of a cryogenic and fully operational version to be used in LIGO is going to be done in a future study.