Linear particle accelerator design

[emoney]

I have a qustion about two types of accelerating designs.

In these types of design the plates get longer or spaced apart because the frequency of the RF power is constant but the particle is acclerated so it covers more distance in less time.

The other type of design looks like this:

My question is, is why in these superconducting Rf accelerators that the units do not get place farther apart or grow in length as the beam go through.

What I am thinking is that the design with the plates increasing in spacing is for slow moving particle charged particles where acceleration is very large, and that the other design is for when the particles are already traveling very fast and acceleration very little so spacing is less important.

Is that right? or is there a different reason?
I

 

[ZapperZ]

You need to double check if these are all standing wave structure or if one of them is a traveling wave structure. The rf frequency used can also be a determining factor here. In addition, are these linacs used at the very beginning of the acceleration (i.e. Such as at the photoinjector) or are they where the particle bunches are already relativistic?

There are a lot of details here that are missing.

BTW, topics on accelerator science normally belongs in the Classical Physics forum, since classical E&M is usually the main subject area involved, such as in this one.

Zz.

 

[mfb]

I moved the thread.

What I am thinking is that the design with the plates increasing in spacing is for slow moving particle charged particles where acceleration is very large, and that the other design is for when the particles are already traveling very fast and acceleration very little so spacing is less important.

Right.
The superconducting RF cavities are typically used for electrons in the hundreds of MeV to GeV range, where the difference to the speed of light is negligible. It has to be, because frequency and wavelength in those cavities are linked via the speed of light (with some corrections due to the shape of the cavities).