Fastest rotating man-made object created (600 million RPM!)

Circularly polarized light carries angular momentum (not OAM, photon spin).

A 10 MHz rotation rate is going some. It's interesting that the surface velocity was omega R ~= 125 m/s at failure, when the centripetal acceleration was omega**2 R ~=800 million gees.

Cheers

Phil Hobbs

what is the energy?

Not very big. The rotational KE is 1/2 I * omega**2, where I is the moment of inertia. For a uniform sphere,

V = 4/3 pi R**2 I = 2/5 M R**2 = 8/15 pi R**5 rho .

For calcite, rho = 2.7e3 kg/m**3, so

KE = 4/15 pi**3 (10 MHz)**2 (2 um)**5 2.7e3 ~= 70 pJ.

Cheers

Phil Hobbs

Volume is R**3 of course. I think the rest is right.

Cheers

Phil Hobbs

Boy, I thought we were spinning stuff fast, up to 5000 RPS. We are spinning little ceramic thimbles in an air bearing, and it has little teeth machined in the side so an air jet spins in.

Jon

I made a "smear camera" driver once-upon-a-time (~1960, MIT Building

NMR samples, especially solids, are spun at speeds up to 70 KHz. They mostly use air motors.

Mechanical streak cameras can be pretty impressive. With a lever arm of

Cheers

Phil Hobbs

Our film carrier arc was only about 0.5m away. I had a toooob photocell read off of the mirror so the shock tube was fired synchronous with mirror position. ...Jim Thompson

Modified dentist's air drills? Dentists drills themselves don't spin nearly fast enough (500Hz), but it's a nice compact package designed to go into a confined space ...

but it's a nice compact package designed to go into a confined space ...

How fast can you spin a strong diamond, or carbyne even stronger apparently:

before it structurally fails?

cheers, Jamie

Yes, that's exactly what these are, solid NMR samples. I sure haven't heard of 70K RPS, and since we have some pretty strong magnets, I doubt anyone is doing 70K RPS. The spin speed scales with the strength of the superconducting magnet field. I think our strongest one is almost 10 T, and few go above that.

Jon

There are some 1 GHz magnets around, 250T. They have a spiral staircase wrapped around them so you can get to the top to load samples. A couple of megabucks or some such.

Wiki mentioned the 70 KHz value

I think my customers usually run maybe a tenth of that.

Whose stuff do you use? Varian? Bruker?

No, I meant 25T, 250K gauss.

A 1 GHz proton nmr magnet is 23.5 T, not 250.

There are some 1 GHz magnets around, 250T. They have a spiral staircase wrapped around them so you can get to the top to load samples. A couple of megabucks or some such.

Wiki mentioned the 70 KHz value

I think my customers usually run maybe a tenth of that.

Whose stuff do you use? Varian? Bruker?

Any idea what the tensile strength of calcite is? I note the comment from one of the investigators: "The rotation rate is so fast that the angular acceleration at the sphere surface is 1 billion times that of gravity on the Earth surface? it's amazing that the centrifugal forces do not cause the sphere to disintegrate!".

Somewhat OT, but around 50 years ago I remember looking through a textbook of electronic circuits, published in the mid-50s. IIRC, one was used to spin a small aluminium rod, I think about 10 mm long and 5 mm across (hexagonal cross-section), to 5 million rpm in a vacuum. The rod was levitated above a coil by a magnetic field, and another coil applied a spin to it. It's many years ago, so my memory may be incorrect, but I think it took at least 2 hours for the rod to reach maximum speed. Is that possible, or is my imagination working overtime?!

Sounds reasonable. The torque you can get that way isn't that big, unless you have a lot of iron (as in a squirrel cage motor).

Small single crystals can be quite a bit stronger than bulk material, especially if they're prepared so as to have a very smooth surface. (It's the largest crack that limits the ultimate strength, just like the proverbial weakest link in a chain.)

Cheers

Phil Hobbs

Interesting that an 'aluminium' rod was levitated by a coil.

or, even iron, makes one wonder how much 'drag' is then exerted upon the rotation by the earth's field. Maybe gone faster?

Good conductor and not too heavy, eddies swirl happily inside to create a response to the alternating magnetic field.