# Largest conceivable particle accelerator ?

1. Oct 12, 2005

### oldtobor

What would be the largest possible particle accelerator if all the matter-energy of the universe was used to build it ? How far down in sizes could we probe ? I think as of now we can probe 10^-10 mm (?) but to probe even 10 times smaller you would need an accelerator 10 times bigger so it would already be 100 km. Now if we had a trillion km long accelerator in theory how far down could we see , 10^-100 mm ? what are the physical limits ?

2. Oct 12, 2005

### nameta9

In the year 3 million we may have a particle accelerator of 10^9 km. So then we may see 10^-10*10^-10=10^-20 mm. Planck scale is 10^-40 mm. So we still won't see space-time fluctuations. At 10^-100000 mm there will always be a mystery, the observable universe is actually limited in HOW SMALL WE CAN SEE!

3. Oct 12, 2005

### ZapperZ

Staff Emeritus
There is something odd about this question. There is no physical reason why particle accelerator has to be "BIG". The reason that we do now is because the conventional accelerating mechanism depends on using copper cavities as the accelerating structure. We can only put so much gradient within such a structure before copper breaks down (~30 MV/m). That is why if we use such a thing, we have to keep making it larger and larger to achieve higher energies.

There are several centers around the world that are working on research on new accelerating structures that may go beyond the copper limit. The UCLA/USC group is heavily working on plasma wakefield. Another center in Germany just released a paper on using laser acceleration. I am part of a group that works on wakefield in a dielectric structure as the accelerating structure. If we manage to not encounter any potential breakdown problem in our dielectric, we believe we might get to 100 MV/m gradient. Any one of these new accelerating mechanism could easily make an accelerator "shorter" than current technology requires.

So within the physics itself, there's no limit or requirement on "size" of an accelerator.

Zz.

4. Oct 12, 2005

### mezarashi

That's good to know. Although too bad I won't be seeing any solar system scaled particle accelerators to probe Planck lengths then :P

5. Oct 12, 2005

### oldtobor

Thanks for the ideas. But are there theoretical limits to how "powerful" an accelerator can be ? Imagine using all the energy in the universe to accelerate particles, what would be the limits size wise ? Could we in theory reach the planck level and see what is going on at that level with such a science fiction technology or are there real physical limits to how far we can see ? I don't think we can get passed 10^-100 mm.

6. Oct 12, 2005

### ZapperZ

Staff Emeritus
You missed making a major connection between "powerful accelerator" and "how small we can see".

Particle colliders [I'm guessing you want to use particle accelerators for particle collision in high energy physics] do not really LOOK at the physical size of anything. Unlike an electron microscope, for example, where the deBroglie wavelength could be the physical limit of the imaging resolution, particle colliders do not image nor probe "sizes". In fact, the larger the collision energy, the "heavier" the particle it can generate (look at the theoretical mass for the Higgs, for example).

So this discussion about accelerators and how small we can see using it is a bit puzzling.

Zz.

7. Oct 12, 2005

### mezarashi

Honestly particle physics is not an area that I have studied. However, I have read time and again that the larger the energy of a particle collider, the smaller it can probe. I'm not sure how this works, since I have no idea how you can create all the exotic particles we do create with them in the first place. But looking at the De Broglie equation: $$\lambda = \frac{h}{p}$$, where p is the momentum would suggest that the larger the velocity, momentum or energy we give to a particle, the smaller its wavelength. In an analogy with the microscope you mentioned, the smaller the wavelength of our probing carrier, the better resolution we can get. That's how I would've seen it.

8. Oct 12, 2005

### ZapperZ

Staff Emeritus
But this is what I have said. At SOME point, the particle with THAT much energy will no longer just "probe" the object it is hitting, but rather will CAUSE a particle collision that will disintergrate the object being probed. There's a reason why electron microscopes have energy in the keV range. Get it to GeV, and you're no longer "probing" but causing a substantial electron-ion collision that goes into the high-energy physics particle collider regime.

Zz.