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MiniGRAIL Online
An anonymous reader writes "MiniGRAIL - the first spherical resonant mass gravitational wave detector in the world - is now taking data!!! The MiniGRAIL (Gravitational Radiation Antenna In Leiden) detector is located at the Kamerlingh Onnes Laboratory of the Leiden University (The Netherlands). 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 ~4x10-21. The antenna will operate at a temperature of 20 mK. An other similar detector is being built in São Paulo, which will strongly increase the chances of detection by looking at coincidences. The sources we are aiming at are for instance, non-axisymmetric instabilities in rotating single and binary neutron stars, small black-hole or neutron-star mergers etc."
They are looking for gravitational waves. The kind
that are predicted to exist by various versions of
relativity.
This is why they are looking for things like black
hole mergers - because those are supposed to give
off major gravity ripples that could hopefully be
seen by our puny labs on Earth.
I am curious how their theoretical resolution
measures up to the bigger projects like LIGO. I am
also curious how much it costs to keep that much
mass this cold continuously. You need a huge
dilution fridge which would consume some unholy
amount of liquid Helium 4. That's assuming you
got no He 3 leaks. Costs please...
Gravity waves show up as (very) slight distortions of everything. So, for instance things might get a bit longer North-South and a bit shorter East-West for a bit, and then the other way for a bit, and so on.
The changes are VERY tiny, something like 1 part in 10^20, so detecting them is not easy.
Existing detectors measure tiny changes in the length of bars of metal. Results are borderline at best.
Straight-forward detectors like LIGO and the much larger space-based proposal whose name I have forgotten for the moment use lasers to measure changes in much longer lengths (a few km for LIGO, a few million km for the space-based one.
I surmise that this detector looks for waves whose frequency is just right to set this sphere "ringing" at one of its fundamental frequencies. This "ringing" can dramatically amplify the oscillation, producing something that might just barely be detected after a series of further stages of mechanical and electrical amplification. I guess the sphere needs to be so ultra-cold to stop thermal oscilations masking the signal.