ALLEGRO
Encyclopedia
ALLEGRO was a ground-based, cryogenic resonant Weber bar, gravitational wave detector
run by Warren Johnson, et. al at Louisiana State University
in Baton Rouge, Louisiana
. The detector was commissioned in the early 90's, and was decommissioned in 2008.
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 (SQUID).
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.
Gravitational wave detector
A gravitational wave detector is any experiment designed to measure gravitational waves, minute distortions of spacetime that are predicted by Einstein's theory of general relativity. The existence of gravitational radiation is a prediction of Einstein's general theory of relativity. Gravitational...
run by Warren Johnson, et. al at Louisiana State University
Louisiana State University
Louisiana State University and Agricultural and Mechanical College, most often referred to as Louisiana State University, or LSU, is a public coeducational university located in Baton Rouge, Louisiana. The University was founded in 1853 in what is now known as Pineville, Louisiana, under the name...
in Baton Rouge, Louisiana
Louisiana
Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...
. The detector was commissioned in the early 90's, 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 (SQUID).
Collaboration with LIGO
Due its close proximity to the LIGOLIGO
LIGO, which stands for the Laser Interferometer Gravitational-Wave Observatory, is a large-scale physics experiment aiming to directly detect gravitational waves. Cofounded in 1992 by Kip Thorne and Ronald Drever of Caltech and Rainer Weiss of MIT, LIGO is a joint project between scientists at MIT,...
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.