MiniGRAIL is a type of Resonant Mass Antenna,[1] which is a massive sphere that used to detect gravitational waves. The MiniGRAIL is the first such detector to use a spherical design. It is located at Leiden University in the Netherlands. The project is being managed by the Kamerlingh Onnes Laboratory.[2] A team from the Department of Theoretical Physics of the University of Geneva, Switzerland, is also heavily involved.
Gravitational waves are a type of radiation that is emitted by objects that have mass and are undergoing acceleration. The strongest sources of gravitational waves are expected to be compact objects such as neutron stars and black holes. This detector may be able to detect certain types of instabilities in rotating single and binary neutron stars, and the merger of small black holes or neutron stars.[3]
Design
A spherical design has the benefit of being able to detect gravitational waves arriving from any direction, and it is sensitive to polarization.[4] When gravitation waves with frequencies around 3,000 Hz pass through the MiniGRAIL ball, it will vibrate with displacements on the order of 10−20 m.[5] For comparison, the cross-section of a single proton (the nucleus of a hydrogen atom), is 10−15 m (1 fm).[6]
To improve sensitivity, the detector was intended to operate at a temperature of 20 mK.[2] The original antenna for the MiniGRAIL detector was a 68 cm diameter sphere made of an alloy of copper with 6% aluminium. This sphere had a mass of 1,150 kg and resonated at a frequency of 3,250 Hz. It was isolated from vibration by seven 140 kg masses. The bandwidth of the detector was expected to be ±230 Hz.[3]
During the casting of the sphere, a crack appeared that reduced the quality to unacceptable levels. It was replaced by a 68 cm sphere with a mass of 1,300 kg. This was manufactured by ItalBronze in Brazil. The larger mass lowered the resonant frequencies by about 200 Hz.[7] The sphere is suspended from stainless steel cables to which springs and masses are attached to dampen vibrations. Cooling is accomplished using a dilution refrigerator.[8]
Tests at temperatures of 5 K showed the detector to have a peak strain sensitivity of 1.5 × 10−20 Hz−1⁄2 at a frequency of 2942.9 Hz. Over a bandwidth of 30 Hz, the strain sensitivity was more than 5 × 10−20 Hz−1⁄2. This sensitivity is expected to improve by an order of magnitude when the instrument is operating at 50 mK.[4]
A similar detector named "Mario Schenberg" is located in São Paulo. The co-operation of the detectors strongly increase the chances of detection by looking at coincidences.[9]
References
Schutz , Bernard (2009-05-14). A First Course in General Relativity (2nd ed.). Cambridge. pp. 214–220. ISBN 978-0521887052.
de Waard, A; et al. (2003). "MiniGRAIL, the first spherical detector". Classical and Quantum Gravity. 20 (10): S143–S151. Bibcode:2003CQGra..20S.143D. doi:10.1088/0264-9381/20/10/317.
Van Houwelingen, Jeroen (2002-06-24). "Development of a superconducting thin-film Nb-coil for use in the MiniGRAIL transducers" (PDF). Leiden University. pp. 1–17. Retrieved 2009-09-16.
Gottardi, L.; De Waard, A.; Usenko, O.; Frossati, G.; Podt, M.; Flokstra, J.; Bassan, M.; Fafone, V.; et al. (November 2007). "Sensitivity of the spherical gravitational wave detector MiniGRAIL operating at 5K". Physical Review D. 76 (10): 102005.1–102005.10. arXiv:0705.0122. Bibcode:2007PhRvD..76j2005G. doi:10.1103/PhysRevD.76.102005.
Bruins, Eppo (2004-11-26). "Listen, two black holes are clashing!". innovations-report. Retrieved 2009-09-16.
Ford, Kenneth William (2005). The quantum world: quantum physics for everyone. Harvard University Press. p. 11. ISBN 0-674-01832-X.
de Waard, A.; et al. (2005). "MiniGRAIL progress report 2004". Classical and Quantum Gravity. 22 (10): S215–S219. Bibcode:2005CQGra..22S.215D. doi:10.1088/0264-9381/22/10/012.
de Waard, A.; et al. (March 2004). "Cooling down MiniGRAIL to milli-Kelvin temperatures". Classical and Quantum Gravity. 21 (5): S465–S471. Bibcode:2004CQGra..21S.465D. doi:10.1088/0264-9381/21/5/012.
Frajuca, Carlos; et al. (December 2005). "Resonant transducers for spherical gravitational wave detectors" (PDF). Brazilian Journal of Physics. 35 (4b): 1201–1203. Bibcode:2005BrJPh..35.1201F. doi:10.1590/S0103-97332005000700050.
External links
MiniGRAIL on the internet
vte
Gravitational-wave astronomy
Gravitational wave Gravitational-wave observatory
Detectors
Resonant mass
antennas
Active
NAUTILUS (IGEC) AURIGA (IGEC) MiniGRAIL Mario Schenberg
Past
EXPLORER (IGEC) ALLEGRO (IGEC) NIOBE (IGEC) Stanford gravitational wave detector ALTAIR GEOGRAV AGATA Weber bar
Proposed
Past proposals
GRAIL (downsized to MiniGRAIL) TIGA SFERA Graviton (downsized to Mario Schenberg)
Ground-based
Interferometers
Active
AIGO (ACIGA) CLIO Fermilab holometer GEO600 Advanced LIGO (LIGO Scientific Collaboration) KAGRA Advanced Virgo (European Gravitational Observatory)
Past
TAMA 300 TAMA 20, later known as LISM TENKO-100 Caltech 40m interferometer
Planned
INDIGO (LIGO-India)
Proposed
Cosmic Explorer Einstein Telescope
Past proposals
AIGO (LIGO-Australia)
Space-based
interferometers
Planned
LISA
Proposed
Big Bang Observer DECIGO TianQin
Pulsar timing arrays
EPTA IPTA NANOGrav PPTA
Data analysis
Einstein@Home PyCBC Zooniverse: Gravity Spy
Observations
Events
List of observations First observation (GW150914) GW151012 GW151226 GW170104 GW170608 GW170729 GW170809 GW170814 GW170817 (first neutron star merger) GW170818 GW170823 GW190412 GW190521 (first-ever light from bh-bh merger) GW190814 (first-ever "mass gap" collision)
Methods
Direct detection
Laser interferometers Resonant mass detectors Proposed: Atom interferometers Indirect detection
B-modes of CMB Pulsar timing array Binary pulsar
Theory
General relativity Tests of general relativity Metric theories Graviton
Effects / properties
Polarization Spin-flip Redshift Travel with speed of light h strain Chirp signal (chirp mass) Carried energy
Types / sources
Stochastic
Cosmic inflation-quantum fluctuation Phase transition Binary inspiral
Supermassive black holes Stellar black holes Neutron stars EMRI Continuous
Rotating neutron star Burst
Supernova or from unknown sources Hypothesis
Colliding cosmic string and other unknown sources
Hellenica World - Scientific Library
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