I What are the limits of particle accelerators?

[accdd]

What prevents making a particle accelerator better than the LHC but only a few centimeters big? After all, you accelerate objects with very small masses. Are there insuperable physical limits? What are the physical limitations?

 

[PeroK]

What prevents making a particle accelerator better than the LHC but only a few centimeters big? After all, you accelerate objects with very small masses. Are there insuperable physical limits? What are the physical limitations?

Have you looked on the CERN or Fermilab websites?

 

[antonantal]

The acceleration which increases the speed is provided by an electric force $F_E=qE$. Since $q$ of a particle is small, in order to have a strong $F_E$ you need strong electric field $E$. But there are limits to how strong an electric field can be generated, and this limits the acceleration. So, to reach the high speed you need more time, that is more distance. This distance can be either a long line, or a circle that is traversed multiple times. To make the trajectory a circle you need a centripetal force that is provided by a magnetic force $F_B = q(v \times B)$, but this is also limited by the maximum strength of the magnetic field $B$ provided by the superconducting magnets, so the circle has a large radius.

 

[malawi_glenn]

Furthermore, Synchrotron radiation - the accelerator will "leak" energy and will not be efficient. The smaller the radius, the bigger the centripetal acceleration and higher amount of synchrotron radiation is emitted.

Note that Synchrotron radiation can be a desired outcome, one can use it to study structure of materials and molecules and such. But, not in an accelerator where you wish to attain maximal center of mass energy and high luminosity for particle creation.

This, and the limitations of magnets, causes lot of gain for a large radius for your accelerator

 

[Vanadium 50]

Centimeters?

1. Please work out the electric fields needed to accelerate a particle in a few centimeters.
2. Please calculate the electric fields needed to ionize an atom. Hint: when the applied field exceeds the field of the nucleus, what happens to the electron?
3. Given the answers to (1) and (2) what will you make your accelerator out of?

 

[malawi_glenn]

Given the answers to (1) and (2) what will you make your accelerator out of?

Nuclear matter of course, atomic matter is for suckers!

 

[mfb]

Centimeters?

1. Please work out the electric fields needed to accelerate a particle in a few centimeters.
2. Please calculate the electric fields needed to ionize an atom. Hint: when the applied field exceeds the field of the nucleus, what happens to the electron?
3. Given the answers to (1) and (2) what will you make your accelerator out of?

Plasma wakefield acceleration shows this is not a limit.
We still can't build centimeter-sized multi-TeV accelerators, but it might be possible to shrink the length to a kilometer or so in the future.

 

[Vanadium 50]

Plasma wakefield acceleration shows this is not a limit.

That is the answer to my last question then - don't build it out of atoms.

However, while plasmas can have gradients taht are very high, if you want the beam, you know, actually focused, you need a much larger system than centimeters.

 

[malawi_glenn]

it might be possible to shrink the length to a kilometer or so in the future

How would one minimize synchrotron radiatio then, or are you thinking of linear acclerators?

 

[Vanadium 50]

I think he's talking about a linear machine. High gradients make it more feasible. But plasma wakefields have notoriously poor quality beams. Essentially you have a beam energy spread that is more or` less equally populated from zero to the maximum energy. Totally unbsuitable for collision science. Staging has been demonstrated for stunts, but it isn't realistic.

If you use dielectric wakefields, these problems go away. Beam quality is high, and the machine can be staged. But you're back to atoms. You can get a gradient a factor of 2 better than copper today, and maybe ultimatley an order of magnitude or more. But not hundreds of thousands. Because atoms.

 

[ohwilleke]

What prevents making a particle accelerator better than the LHC but only a few centimeters big? After all, you accelerate objects with very small masses. Are there insuperable physical limits? What are the physical limitations?

While you can't get a tiny size, if you build it in deep space, you can build a simpler one with fewer materials. In space, a very simple linear accelerator with an immense length is no big deal.

 

[malawi_glenn]

if you build it in deep space

When NASA and CERN unite!

build a simpler one with fewer materials

Free vacuum! This will sound great for the funding proposals!

 

[berkeman]

When NASA and CERN unite!Free vacuum! This will sound great for the funding proposals!

And now that we have a proven Sun Shield technology, you can cut way down on the energy it takes to keep the superconducting magnets superconducting!