afp

The issue with the efficiency begins already with the high-power lasers that are needed for wakefield acceleration, which have a typical wall-plug efficiency of ~0.1%. From that, only about ~1% of the laser pulse energy gets transferred into the accelerated electron beam. And only about ~0.1% of that gets converted into light again during the FEL process.

All together, that would mean an efficiency of ~10^{-8}, which is about a million times smaller than for the ERL (I'm no expert there, but I think in the article they mention 1-10% efficiency).

There are prospects for much more efficient high-power lasers, but there's still a long way to go.

I don't know what would dominate the costs in this particular case, but given the low efficiency and reliability (high-power lasers break often) as well as the other issues, I wouldn't bet on wakefield accelerators as an alternative.

It is already possible to reach 800 MeV (the energy for an EUV FEL according to the article) with single-stage laser wakefield accelerators. The problem is doing so with sufficient beam quality, reproducibility and repetition rate. The energy efficiency would also be a problem, as it is nowhere close to what an energy recovery linac could achieve.

That's very useful, thanks!

Are the tolerances of the optimum important in your case? (i.e., how sensitive it is to errors in the design parameters) If so, did you use any method to incorporate this information into the optimization?

It's also very useful for simulation-based optimization. As an example, we use it extensively for the design of particle accelerators, where the simulations are typically expensive and need to run on supercomputers. We have built our own library[0] for enabling this, which in the end uses BoTorch (through Ax[1]) under the hood.

[0]: https://github.com/optimas-org/optimas [1]: https://ax.dev