Allegro was a ground-based, cryogenic resonant Weber bar, gravitational-wave detector run by Warren Johnson, et al. at

Louisiana State University Louisiana State University (officially Louisiana State University and Agricultural and Mechanical College, commonly referred to as LSU) is a public land-grant research university in Baton Rouge, Louisiana. The university was founded in 1860 near ...

Baton Rouge Baton Rouge ( ; ) is a city in and the capital of the U.S. state of Louisiana. Located the eastern bank of the Mississippi River, it is the parish seat of East Baton Rouge Parish, Louisiana's most populous parish—the equivalent of countie ...

Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a U.S. state, state in the Deep South and South Central United States, South Central regions of the United States. It is the List of U.S. states and territories by area, 20th-smal ...

. The detector was commissioned in the early 1990s, and was decommissioned in 2008.

Mechanical design

The resonant bar in Allegro is 2300 kg of aluminum, 3 meters in length. Suspended in a cryogenic vacuum tank at 4.2 Kelvin, the bar's natural resonant frequency (the lowest longitudinal mode) is near 904 Hz. The strain on the bar is measured by coupling a second, much lighter, suspended mass to the main heavier mass as a mechanical transformer at the same resonant frequency. Therefore, small motions of the primary mass generate much larger motions in the smaller mass. The differential displacement of the two masses is recorded using an inductive transducer and amplifier (a

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Collaboration with LIGO

Due its close proximity to the

LIGO The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory designed to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. Two large o ...

Livingston Detector (one in the array of three, large-scale, laser interferometric detectors), Allegro has partnered with the LIGO Scientific collaboration to produce several results during the fourth science run of LIGO.

References

{{coord missing, Louisiana Gravitational-wave telescopes Astronomical observatories in Louisiana