
X-ray pulses with gigawatt peak power from a free-electron laser - bookofjoe
https://www.nature.com/articles/s41566-019-0549-5
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cosmic_quanta
It's worth noting that gigawatt peak power in an ultrafast laser is not
special, but that gigawatt peak power _in the x-ray_ region is special.

In larger wavelangths (i.e. visible or near-IR), you can get this level of
peak power from commercial laser systems (e.g. [https://www.spectra-
physics.com/products/ultrafast-lasers/sp...](https://www.spectra-
physics.com/products/ultrafast-lasers/spitfire-
ace?cat=scientific&subcat=amplifiers))

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est31
IIRC one of the main problems of EUV litography is generation of beams with
sufficiently high power. EUV is not X-ray but very close to it.

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the8472
[https://sci-hub.tw/10.1038/s41566-019-0549-5](https://sci-
hub.tw/10.1038/s41566-019-0549-5)

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Animats
Power of each pulse is tiny. 100GW times a attosecond is 10^11 * 10 ^ -18, or
0.1 microwatt. I wonder how much power they have to put in to get that.

 _" Since the scheme developed in this work is based solely on a passive
modulator, our technique is easily scalable to MHz repetition rates, which are
envisioned for the next generation of XFELs"_

Now that's interesting. This is not only a soft X-ray generator, it's a soft
X-ray _beam_ generator. Could this be used as a light source for extreme
ultraviolet (i.e. soft X-rays) wafer fabs?

The "light source" used now for the newer 7nm and down wafer fabs is a
horrible kludge the size of a house. It works by zapping a falling droplet of
molten tin with optical lasers to produce a plasma. This produces X-rays more
or less omnidirectionally, and some tiny, tiny fraction of them eventually get
bounced through the mask and onto the wafer. It's amazing that it's worth the
trouble, and it makes fabs billion dollar projects.

Comments from anyone in the fab side of the world?

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brummm
Your units don't add up: W = J/s -> W*s = J. What you calculated was 10^(-7)
J, not W.

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sbierwagen
Fortunately, the paper calculates pulse power:

>The median pulse energy is 10 μJ at 905 eV and 25μJ at 570 eV. However, due
to the intrinsic fluctuations of SASE XFELs we observe pulses well above the
mean value (up to 250μJ for 570 eV, corresponding to a peak power in the
hundreds of gigawatts).

The only power consumption number in the paper is an aside that notes the
magnetic chicane in the electron beamline is spiked at 10 kiloamps. (At how
many volts? How much power does the rest of the laser consume?) Free-electron
lasers are many things, but efficient isn't one of them.

