|Resonant Gravitational Wave Detectors|
I do need to clarify my mistake on the spelling of Joseph Weber and the double bb I had given his last name.
A simple device to detect the expected wave motion is called a Weber bar – a large, solid bar of metal isolated from outside vibrations. This type of instrument was the first type of gravitational-wave detector. Strains in space due to an incident gravitational wave excite the bar’s resonant frequency and could thus be amplified to detectable levels. Conceivably, a nearby supernova might be strong enough to be seen without resonant amplification. Modern forms of the Weber bar are still operated, cryogenically cooled, with superconducting quantum interference devices to detect vibration (see for example, ALLEGRO). Weber bars are not sensitive enough to detect anything but extremely powerful gravitational waves.
|The MiniGRAIL detector is a cryogenic 68 cm diameter spherical gravitational wave antenna made of CuAl(6%) alloy with a mass of 1400 Kg, a resonance frequency of 2.9 kHz and a bandwidth around 230 Hz, possibly higher. The quantum-limited strain sensitivity dL/L would be ~4×10-21.|
MiniGRAIL is a spherical gravitational-wave antenna using this principle. It is based at Leiden University, consisting of an exactingly machined 1150 kg sphere cryogenically cooled to 20 mK. The spherical configuration allows for equal sensitivity in all directions, and is somewhat experimentally simpler than larger linear devices requiring high vacuum. Events are detected by measuring deformation of the detector sphere. MiniGRAIL is highly sensitive in the 2–4 kHz range, suitable for detecting gravitational waves from rotating neutron star instabilities or small black hole mergers.
AURIGA is an ultracryogenic resonant bar gravitational wave detector based at INFN in Italy. It is based on a cylindrical bar detector. The AURIGA and LIGO teams have collaborated in joint observations.
|1. Side view of the AURIGA suspension for run2. The columns and the bar are clearly visible. Also the liquid Helium vessel and the thermal shields, which come unchanged from run1.|
List of Resonant Detectors
|NAUTILUS (Rome, Italy)|
|ALLEGRO (Louisiana State University)|
|AURIGA (Padova, Italy)|
|EXPLORER (Geneva, Switzerland)|
|Mario Schenberg (Gravitational Wave Detector)|
|MiniGRAIL (Leiden, The Netherlands)|
|NIOBE (Perth, Australia)|