Other Resonant Gravitational Wave Detectors
● Weber's surprising results in 1969 led to many detectors similar to his bar design
being built and operated in the 1970s - 1990s. None of these instruments has
detected a gravitational wave event to date.
PAGE 9
Material
● The detection of gravitational waves relies upon the detection of vibrations
produced in the bar/antenna by the wave. The longer the vibrations can continue,
the better the measurements will be.
● For the best performance of a resonant gravitational wave detector, the Q factor
must be combined with the material's density and sound velocity. 5056
aluminium was found to be better by a factor of about 16.
Cooling
● Cooling the detector will reduce thermal noise and improve Q factor. The early
experiments operated at room temperature.
PAGE 10
Mechanical Noise Reduction
● Mechanical noise is due to vibrations of the antenna induced by nongravitational
wave effects. Ground vibrations remain a major noise source, even with
sophisticated vibration isolation systems.
Detection
● The cryogenic instruments use superconducting transducers, which have lower
noise levels than Weber's devices. The positioning of the transducers on the bar
has been improved, and some devices split their bars into two halves and place
the transducers between the halves.
PAGE 11
Detectors
● Following Weber's detectors, dozens of other resonant gravitational wave
instruments were constructed, but all produced negative results.
● Weber's surprising results in 1969 led to many detectors similar to his bar design
being built and operated in the 1970s - 1990s. None of these instruments has
detected a gravitational wave event to date.
PAGE 9
Material
● The detection of gravitational waves relies upon the detection of vibrations
produced in the bar/antenna by the wave. The longer the vibrations can continue,
the better the measurements will be.
● For the best performance of a resonant gravitational wave detector, the Q factor
must be combined with the material's density and sound velocity. 5056
aluminium was found to be better by a factor of about 16.
Cooling
● Cooling the detector will reduce thermal noise and improve Q factor. The early
experiments operated at room temperature.
PAGE 10
Mechanical Noise Reduction
● Mechanical noise is due to vibrations of the antenna induced by nongravitational
wave effects. Ground vibrations remain a major noise source, even with
sophisticated vibration isolation systems.
Detection
● The cryogenic instruments use superconducting transducers, which have lower
noise levels than Weber's devices. The positioning of the transducers on the bar
has been improved, and some devices split their bars into two halves and place
the transducers between the halves.
PAGE 11
Detectors
● Following Weber's detectors, dozens of other resonant gravitational wave
instruments were constructed, but all produced negative results.
