5 ms·

Thanks for the input. I've been hearing about wakefield accelerators for a long time, but never got into the nitty gritty of it. Is the beam quality a fundamen

by fnands 4y ago

Thanks for the input. I've been hearing about wakefield accelerators for a long time, but never got into the nitty gritty of it. Is the beam quality a fundamental limiting factor, or is it solvable (at least theoretically). It sees they're going for the get the energy up and solve the beam characteristics later approach

wolfram74 4y ago
caution: Haven't studied particle accelerator design My understanding of most particle accelerators is that they accelerate their subjects directly with fields, either oscillating or steady. Wakefield accelerators use a combination of fields (the laser pulse) and other particles (the "stationary" ions). My suspicion is that the ion background introduces enough noise/chaos into the process that it would be a great effort to make the output more monoenergetic and retain total brightness. But I dunno, I always found particle physics a little tedious and didn't pay as much attention as I could have.
- noobermin 4y ago
  That is also true, basically target imperfections plus noise in the laser cause imperfection in the acceleration process. Essentially the shape of the bubble can change the accelerating fields uniformity, leading to the divergence and spread issues. They usually cryo their target to minimize just plain chaotic behavior from it being a gas, so generally most of the jitter is due to wings of the laser itself causing perturbations in the gas/plasma (it's a plasma once the peak reaches it). That said, you're totally right about the target itself being a source of noise too.
marcosdumay 4y ago
> Is the beam quality a fundamental limiting factor, or is it solvable (at least theoretically). At least frequency noise is inherent for any accelerator where the particles stay for a very short time.
noobermin 4y ago
Everything is solvable theoretically :) I don't think it's necessary fundamental limitation to the process, but it seems a bit far away just at this moment. I will be a little more charitable to myself and the field generally, some people do care about characteristics, it's just what gets the phys revs+ seem to be higher peak energy. It's just a shame because for applications the general beam quality is a potential show stopper. I think the problem is that as anyone who works with numbers knows, including hackers, the peak value of something is what you put on the slide because it's easy and sounds sexy and is more exciting than a histogram.

by fnands 4y ago

wolfram74 4y ago

caution: Haven't studied particle accelerator design My understanding of most particle accelerators is that they accelerate their subjects directly with fields, either oscillating or steady. Wakefield accelerators use a combination of fields (the laser pulse) and other particles (the "stationary" ions). My suspicion is that the ion background introduces enough noise/chaos into the process that it would be a great effort to make the output more monoenergetic and retain total brightness. But I dunno, I always found particle physics a little tedious and didn't pay as much attention as I could have.

noobermin 4y ago
That is also true, basically target imperfections plus noise in the laser cause imperfection in the acceleration process. Essentially the shape of the bubble can change the accelerating fields uniformity, leading to the divergence and spread issues. They usually cryo their target to minimize just plain chaotic behavior from it being a gas, so generally most of the jitter is due to wings of the laser itself causing perturbations in the gas/plasma (it's a plasma once the peak reaches it). That said, you're totally right about the target itself being a source of noise too.

marcosdumay 4y ago

> Is the beam quality a fundamental limiting factor, or is it solvable (at least theoretically). At least frequency noise is inherent for any accelerator where the particles stay for a very short time.

noobermin 4y ago

Everything is solvable theoretically :) I don't think it's necessary fundamental limitation to the process, but it seems a bit far away just at this moment. I will be a little more charitable to myself and the field generally, some people do care about characteristics, it's just what gets the phys revs+ seem to be higher peak energy. It's just a shame because for applications the general beam quality is a potential show stopper. I think the problem is that as anyone who works with numbers knows, including hackers, the peak value of something is what you put on the slide because it's easy and sounds sexy and is more exciting than a histogram.