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### how to build a better electron accelerator/collimator?

Posted: Thu Jun 02, 2016 3:08 pm
if i'm thinking through the physics right - and correct me if i'm not -- whether or not an electron at a given cylindrical coordinate z,r,theta outside the magrid makes it into a magrid of a given charge and current, is completely dependent on the "angle" of its velocity; the ratio of the z-component of its velocity to the r-component. (higher dz/dr is better)

now there are only 2 ways to change this ratio: decrease dr or increase dz.

the former would be a collimator, the latter an accelerator.

so... how to construct?...

bearing in mind energy efficiency is important. if it gets twice as many electrons in, but that takes four times the energy, well that's useless.

(the other 2 control parameters are initial r and initial z. obviously the lower the better, for either of them, but i'm separating the two problems here: initial position vs initial velocity)

### Re: how to build a better electron accelerator/collimator?

Posted: Thu Jun 02, 2016 10:33 pm
The other way would be to have X-cusps at the confluence of the paired fields. An X-Cusp has no field (a funny cusp) at the very center so electrons can leave and enter with ease, but the magnet cans (which are NOT there) are still well shielded.

### Re: how to build a better electron accelerator/collimator?

Posted: Fri Jun 03, 2016 5:24 pm
A plasma tube to bring particles up to speed at SLAC
http://phys.org/news/2016-06-plasma-tub ... -slac.html
In plasma wakefield acceleration, energetic bundles of electrons or positrons traverse a plasma and generate plasma "wakes" for trailing bunches of particles to ride. Since the method can boost the energy of the surfing particles up to 1,000 times more over a given distance than conventional technology, it could pave the way for next-generation accelerators that are more powerful, smaller and less expensive.

However, the technique has yet to overcome a major challenge: Strong forces pointing toward the center of the plasma can degrade the quality of the particle beam, which consists of bunches of electrons or positrons. In the positron case, the particles are defocused and lost in the plasma.

Now, says SLAC's Spencer Gessner, the lead author of the new study, "We've engineered a hollow plasma channel – a tube of plasma with neutral gas on the inside. Due to the particular geometry of the plasma, particles flying through the channel don't experience any of the unwanted forces."

### Re: how to build a better electron accelerator/collimator?

Posted: Sun Jun 05, 2016 7:16 pm
DeltaV wrote:A plasma tube to bring particles up to speed at SLAC
http://phys.org/news/2016-06-plasma-tub ... -slac.html
In plasma wakefield acceleration, energetic bundles of electrons or positrons traverse a plasma and generate plasma "wakes" for trailing bunches of particles to ride. Since the method can boost the energy of the surfing particles up to 1,000 times more over a given distance than conventional technology, it could pave the way for next-generation accelerators that are more powerful, smaller and less expensive.

However, the technique has yet to overcome a major challenge: Strong forces pointing toward the center of the plasma can degrade the quality of the particle beam, which consists of bunches of electrons or positrons. In the positron case, the particles are defocused and lost in the plasma.

Now, says SLAC's Spencer Gessner, the lead author of the new study, "We've engineered a hollow plasma channel – a tube of plasma with neutral gas on the inside. Due to the particular geometry of the plasma, particles flying through the channel don't experience any of the unwanted forces."
i wonder if that would be _too_ fast. want to limit the energy input both for efficiency and confinement.

### Re: how to build a better electron accelerator/collimator?

Posted: Mon Jun 06, 2016 1:57 am
Could be, I don't know. Just posting it as a possible option.