As another poster has already said, the power is reduced 10 times, not by 10%.
At such a power reduction, it should be possible to use a much smaller and cheaper EUV source, allowing the use of multiple lithography systems, or increase a lot the throughput achievable with the current EUV sources.
I hope that they have modeled correctly the losses in the mirrors. Here the incidence angle of the EUV light on the mirrors is much closer to a right angle than in the ASML system. It is likely that this increases the absorption in the mirror in comparison with a mirror on which the light falls at an angle far from perpendicular, as used by ASML.
EDIT:
Unfortunately this paper might be a hoax.
I have read the 2013 paper that they give as reference [2] and as the basis of the claim for the 10 times reduction in power losses.
There the losses in the mirror are given only for incidence angles no greater than 21 degrees, very far from a perpendicular incidence. Moreover the data imply that at higher incidence angles the losses increase a lot.
Therefore the system with 4 mirrors at high incidence angles will have much higher losses than a system with 10 mirrors at low incidence angles, unless better mirror materials were discovered in the future.
So ASML must have analyzed this simple system and dismissed it as impossible to make with the known materials.
Not necessarily. It might just have performed at this peak capacity in ideal lab conditions.
This would need to be reproduced, but like you pointed out ASML and Zeiss most likely tested this configuration out at some point in the last 25 years.
That said, the English is very off on this paper - I did a re-read and it looks like they're proposing that they were able to cut the power down to 20W from 200W
Their reference numbered [1] is a more recent book from 2020.
In this book it is said even if EUV mirrors have typically very poor reflectance at high incidence angles, it has become possible to make mirrors with a 60% to 70% reflectance even for high incidence angles (without specifying how high).
They have computed their power advantage using the 65% value which is a middle value between those from the book, so it is OK.
However they have used the same value for the ASML mirrors, which use low incidence angles, so they may have a higher reflectance.
So according to the book, their system should be feasible nowadays, but the actual improvement in light losses is unknown, because the losses in each mirror depend heavily on both the mirror construction and the light incidence angle, which are not taken into consideration in the paper.
At such a power reduction, it should be possible to use a much smaller and cheaper EUV source, allowing the use of multiple lithography systems, or increase a lot the throughput achievable with the current EUV sources.
I hope that they have modeled correctly the losses in the mirrors. Here the incidence angle of the EUV light on the mirrors is much closer to a right angle than in the ASML system. It is likely that this increases the absorption in the mirror in comparison with a mirror on which the light falls at an angle far from perpendicular, as used by ASML.
EDIT:
Unfortunately this paper might be a hoax.
I have read the 2013 paper that they give as reference [2] and as the basis of the claim for the 10 times reduction in power losses.
There the losses in the mirror are given only for incidence angles no greater than 21 degrees, very far from a perpendicular incidence. Moreover the data imply that at higher incidence angles the losses increase a lot.
Therefore the system with 4 mirrors at high incidence angles will have much higher losses than a system with 10 mirrors at low incidence angles, unless better mirror materials were discovered in the future.
So ASML must have analyzed this simple system and dismissed it as impossible to make with the known materials.