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."

Comments

so tread carefully!

[ghostlibrary]

Okay folks, since MiniGRAIL is now taking data in the Netherlands and its partner is doing that in São Paulo, a cautionary.

Please, those of you located equidistant from the two, don't jump, stomp your feet, or drop heavy books. They rely on asymmetry to weed out false signals, and you folks straddling the middle could throw it off.

Remember, we must all do our bit for science.

Google Translation Please

[Anonymous Coward]

Dammit.. they don't have this translation option yet.

What?

[Muda69]

Did anybody at all understand exactly what in the world this GRAIL thing is supposed to do? In layman's terms please....

And oh, the name is kinda lame. They could have at least brainstormed a bit and come up with another acronym like holyGRAIL or something.

Re:What?

[Compuser]

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...

Re:What?

[Compuser]

Hate to reply to myself but my first post was before
I RTFA'ed.
Looks like for some frequencies they will be in the
same ballpark of sensitivity as GEO which is nice
since I always doubted theoretical estimates from
GEO and LIGO as being too optimistic. If they can
get to these sensitivities then maybe the big boys
can get there too.
Oh, and given what I heard about Kadel (their dewar
maker of choice) I reiterate my doubts about He 3
leaks. Why not Oxford? And how much does their
setup cost to run continuously?

Re:What?

[stevelinton]

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.

Whoa.

[BigZaphod]

This has to be one of the most densely packed slashdot stories ever. I understand the words--just not so much the meaning of them in that order. :-)

Someone bring me the Holy Hand Grenade of Antioch! "Bless this, O Lord, that with it thou mayst blow thine slashdot posting to tiny bits, in thy mercy."

We Don't Need This

[christopherfinke]

We've already got one; it is a-very nice!

What's the frequency, Kenneth?

[__aavljf5849]

So, the gravitational waves has to have a frequency pretty close to 2.9kHz to be detected, then? Why that specific frequency? The site seems to offer no clues. Is it just random? It seems awfully high to me...

Detection parameters?

[david.given]

Since this thing is fundamentally a gravity wave antenna, what's the range of frequencies it can usefully detect? Is it just limited to 2.9kHz waves (plus or minus 115Hz)? What about harmonics? Could it be tuned for other frequencies or would that require a redesign?

The reason I ask is that not only does this thing have immense cool value, similar detectors might be very handy for SETI. We know practically nothing about the gravity wave spectrum; it's perfectly possible that the reason we can't find any alien communications with radio telescopes is because everybody's communicating with gravity waves.

So I'm eager to find out what this thing is capable of seeing.

Incidentally, I'm getting slightly disturbed how similar modern gravity wave detectors are getting to those described in David Brin's Earth. If anyone invents a strange new form of physics for manipulating singularities called cavitronics, I for one wish to emigrate to Mars.