[afp]

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.

[amirhirsch]

I'm not an expert in this domain and I really wish I could understand more of the issues on efficiency--it still seems like there are major engineering gaps preventing a table-top FEL from existing. I know a little about beam quality issues, but don't really have any sense for the power scales and efficiencies. Are we talking like 10x more power for the same EUV beam from Laser plasma accelerators over an energy recovery linac or an ASML unit?

If the repetition rate is too low, is it possible to re-use an electron beam and use mutliple undulators for multiple EUV beams with separate lithographic reticles? Is it the chirped-pulse-amplified lasers that have slow rep rate or is it possible to have a single driving laser with multiple plasma targets?

Is there a way it becomes viable if you can make something that is dramatically lower in cost even if it burns 10x the power?

[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.

[amirhirsch]

Thanks for your notes! I've only worked with solid state lasers that are pretty efficient and would have figured 10% aught to be possible for a CPA from wallplug to multi-terrawatt beam. I'm not sure how losses would go in the chirp pulse amplifier, plasma or FEL stages though.

I think we could afford a 10^-6 wall power to EUV beam loss and still be economical probably not 10^-8... my rough estimate is that for your 100W EUV beam equivalent to what ASML provides you can afford to burn on the order of 100MW for four years and still use less dollars to pay for that power than the capital expenditure for your ASML EUV system.