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Free electron laser – A fourth-generation synchrotron light source [video] (ccc.de)
200 points by sasvari on Dec 29, 2017 | hide | past | favorite | 38 comments



This machine is the stringing together major physics, optical, and electronic discoveries of the past century or so into a precision machine with incredible new capabilities. From the electron sources, the RF technologies, vacuum and supercon technology, the Bremstrellung (sp?), to the photon grouping, to the obviously advanced detectors with enormous parallel data throughput. One of the best talks I have seen. Bravo.



CCC.DE is slow for me, here's a youtube link to same video. Worth watching!

https://www.youtube.com/watch?v=RKqof77pKBc


I saw the talk live and the nerdism, physicians humor and the transfered knowledge was really mind blowing. It's an awesome insight into the foundation and building of a really large human made machine. Watch!


I have a friend who worked on the construction of the CMS at CERN. Calibration, actually.

He has a similar ability to very clearly explain the technology and what it is trying to accomplish. And an innate curiosity or interest that causes him to learn that -- beyond just his specific technical area.

In other words, some engineers are very effective networkers and communicators.

When I stop to think about it, they have to be, to ever succeed in building such a large and complex device -- in the company and at the behest of so many other disciplines, both practical and theoretical.

P.S. I should add that he does this with everything that really interests him and/or that he is doing. It's not confined to one topic or things he formally works on.

P.P.S. This may be a "Captain Obvious" comment; nonetheless, the presentation reminded me of him.

And of how some comment science stereotypes really are far from the mark.


My personal observation is that experimental physicists seem to be better (on average) at this than other disciplines.

Maybe something about having to deal with the physical world?


Experimental physics require large teams, thus communicators are more probable to be seen.


It depends... Dirac is a counterexample, while Bohr is a supporting example. It may just be that experimentalist who can explain their ideas with clarity and passion are the ones we notice first/most?


Dirac and Bohr were both theorists, not experimentalists! But you're right that it varies within disciplines.

I'm an experimental physics Ph.D. student working on LIGO, and I have also found that experimental physicists are often very good at motivating engineering from top to bottom. I think having depth of knowledge is part of it. My advisor has told me that some of the best experimentalists have sufficient depth of expertise to be theorists. I can't comment on how this compares to other fields (since I haven't worked outside of academia) but I have been very satisfied with how eloquent and deeply informed experimental physicists usually are.


It would've been even better without the unnecessary political commentary.


I was at the talk. What political commentary are you even talking about?


Not sure how the parent would respond, but early on, while discussing Rosalind Franklin's DNA diffraction findings, he makes an unnecessary comment about the Nobel prize going to "the two white men." It seemed out of place compared to the rest of his talk.

I didn't feel like the talk gave off an overtly political tone.

The New England Journal of Medicine on the other hand...cancelled my subscription due to how political it has become. Still has very good review articles, though.


Silence is political too, you just don't notice because you agree with it.


the snubbing of rosalind franklin seems pretty apolitical to me - she had died, and there are no posthumous nobels. still a damn shame she isn't more of a household name, though.


What sort of political commentary on nejm are you referring to? I usually only read articles if I find them elsewhere, so I don't know much other than that it is a well respected journal in the medical community.


The dig at the beginning that „white men“ got 1962 the Nobel prize for DNA instead Rosalind Franklin was cringey and factually incorrect. Frankin died in 1958 and the Nobel prize is not awarded posthumously. Had she lived she would have gotten it too, there is no question about that.


While the Nobel prize is indeed not awarded posthumously, the characterization of Rosalind Franklin being unfairly dispossessed of credit is very reasonable.

Watson and Crick achieved great fame for "Discovering the double helix structure of DNA". Their original paper:

1) contained no experimental data

2) does not cite Franklin

3) was based on her as-yet unpublished X-ray crystallography


Not sure if this was due to a clash of personalities between Wilkins and Franklin or due to gender issues. Considering that there were many women active in British crystallography (Dorothy Hodgkin, Olga Kennard, Eleanor Dodgson, Kathleen Lonsdale, to name a few) I think it really was a personality issue, and the "white men" was unnecessary, even wrong.


I watched the video and then clapped at the end.

There has been tremendous effort to make the presentation and explain the mechanics that led to the XFEL.

Highly recommended.


Incredible video. I’m a software engineer but I feel I know so much more about physics now.


I agree with all the other comments - this is an excellent video.

Does anyone know how the slides were made? Some of the animations are rather lovely. They look like they were made by a professional TV media company. I'm guess this is not the case.


He mentioned that protein crystals are hard to create. There have been experiments to grow them in space. That possibility could open up soon.


Here's a collage of protein crystals grown in space in 2000.

https://en.wikipedia.org/wiki/File:Protein_crystals_grown_in...


Worth watching just for the visualization of how accelerating electrons leads to radiation emission.


Anyone else having problems with the audio?


Watched all the video.

Really Great.

Thank you!


I still don't understand why we need such a thing. Every single interaction that is involved with protein folding or any chemical or molecular process can be calculated "ab initio" via QED (Quantum Electro Dynamics). So why not just build big computers and be done with it? If there is any macroscopic effect that can be exploited, we still can prove that the theory works and won't need a super powerful FEL for it.


The main problem is scaling. In quantum chemistry, you need electron correlation to get accurate results (comparing your ab initio with experiments) and these methods scale quite badly. Somewhat state-of-the-art CCSD(T) (coupled cluster singles and doubles with triple excitations approximated by perturbation theory) scales formally as N^7, with N being the number of electrons in your system (somewhat simplified). Proteins are huge. Even with some of the newest nearly linear-scaling coupled-cluster methods (which utilize GPUs) running calculations on proteins takes extremely long time. And this is just electron correlation methods. We're still using the Born-Oppenheimer approximation, not taking all excitaions into account, using a finite size basis set, ignoring relativistic effects, not thinking about time evolution and (most of the time) not considering (explicit) solvent effects.

We are still a long way from modelling protein folding in solution with 100% quantum mechanics. Luckily, classical molecular dynamics are quite good at modelling biochemical systems (to a degree). There are a ton of errors that a much bigger than quantum (and relativistic) effects anyway.


Ok now I understand why we need such a thing, thank you very much. My knowledge does not go beyond good old Hatree-Fock on that matter. I thought this is a legitimate question because in theory this device is not build to discover any new physics which I would expect from such a facility.

Edit: Followup question, is it possible to build a ProteinFoldingCoin? Can the problems of theoretical chemistry formulated in a way that is hard to calculate and easy to verify, hence replacing the useless sha256 calculations in Bitcoin with something that makes sense?


>is it possible to build a ProteinFoldingCoin?

I've thought about it, but don't think it's possible. Basically quantum chemical methods like Hartree-Fock or Coupled Cluster is a question of finding eigenvalues to some very very large matrices and/or solving non-linear equation. Verifying a solution (such as electron correlation energy) can, to my knowledge, only be done by using the result and checking if the equations are still valid, which pretty much is just doing the whole work.


Your premise, while theoretically true, is not practicable in reality. To compute the realistic trajectory (more correctly: to estimate the probability of all the transitions between all the states to build up the PDF) would require multiple universe-lifetimes to calculate with enough accuracy to replace what an xFEL can tell you.

It's not just about building bigger computers. If it were, we would make that investment. If you look at the QED and QC calculations done on the world's largest supercomputers, they're not that inspiring.


Exactly. Outsourcing calculations to the rest of the universe is via such experiments is a better alternative


The economy is just made of humans and equipment, which also obey the rules of QED. We should get rid of all these useless economists taking data and just simulate everything!


I admittedly didn't visit the link, but I think it's pretty sweet that i can get one of these "electron lasers" for free.


The use of the laser by non-profit entities is free, but one must write quite the sophisticated (I'm assuming) proposal/experiment to be undertaken in order to actually be given permission to use it. The time and effort required there is of course not free.


wow, you folks hate jokes. It wasn't even an offensive one.


Just as at work, I think a good joke is fine - as long as it comes along with some positive content. Otherwise it's just a distracting, meaningless noise.


Wordplay jokes are very low on the comedy sophistication scale, just above puns, bodily functions, and inherently funny words.

HN is just a tough room. You really have to step it up a notch or two, just to not get downvoted. For example, this is probably not quite good enough:

Electron emancipation is fine and good, but electrons will never truly be free until they have the vote.




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