Brazil's scientists are building a synchrotron, named Sirius.

I'm wondering what the point of building this synchrotron is. From Sirius's Wikipedia page, it reaches an electron energy of 3 GeV. This is several orders of magnitude less than LHC energy of 13 TeV.

I'm not a particle physicist, but my understanding is that higher energies are always better, which is why we've been building larger and larger particle accelerators. But if this is correct, then Sirius should be obsolete even before it's finished. What, then, is the point of Sirius? For that matter, what's the point of any research particle accelerator operating at energies less than LHC energy?

The only thing I can think of is that Sirius is working with electrons while the LHC is working with protons, and because the two have different masses, one cannot use the LHC to collide electrons. However there has also been a Large Electron-Positron Collider that reached energies of 209 GeV, higher than Sirius, so I must be missing something.

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    $\begingroup$ “but my understanding is that higher energies are always better” ::facepalm:: Just no. Intensity, precision, low background probes, event tagging, and radioactive beams to name a few other figures of merit and desirable qualities. $\endgroup$ Oct 1, 2019 at 4:00
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    $\begingroup$ Particle physics is a minority use-case for particle accelerators. There are many more used in medicine and industry: light sources, isotope manufacturing, radiography, radio/particle therapy. $\endgroup$
    – dukwon
    Oct 1, 2019 at 19:15

1 Answer 1


Sirius is being built not as a collider for particle physics research, but as a light source to do other kinds of research.

There are lots of uses for lower energy beams: radiation therapy, sterilizing food and other materials, lithography to great microchips, even in old CRT-style displays.

Even particle physics doesn’t always need the highest energy. Beams for producing neutrinos, studying proton structure and looking for rare mu and K decays are all about intensity, not so much energy.


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