What happens if you stick your head in a particle accelerator? (2017)

Re:What happens if you stick your head in a particle acceler... by changoplatanero on Monday August 09, 2021 @08:43PM (#28124049)

I knew that particle accelerarors require a vacuum to operate so at first I didn't understand how you could stick your head in one without releasing the vacuum and stopping the accelerator. It turns out that the vacuum is only needed to accelerate the particles and then after that they can pass through normal air as they make their way to the sensors.

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Re:What happens if you stick your head in a particle acceler... by jamesmaniscalco on Monday August 09, 2021 @11:04PM (#28124773)

As an accelerator physicist - while some earlier machines were built without vacuum beamlines, nearly all modern[0] accelerators are built with ultra-high vacuum beamlines. Beam quality greatly degrades in contact with residual gas due to scattering. This is especially important in light sources, but really any machine where you want low emittance.

[0] edit - I should specify that I mean high energy machines here (my focus). There are also many low energy machines that don't require high vacuum at the end - medical accelerators for example.

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Re:What happens if you stick your head in a particle acceler... by cperciva on Monday August 09, 2021 @09:52PM (#28124421)

Indeed. So the technical answer to "what happens if you stick your head in a particle accelerator" is "nothing, since without a vacuum particles can't be accelerated to high speeds" -- the question answered by the article is "what happens if you stick your head in a beam originating from a particle accelerator".

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Re:What happens if you stick your head in a particle acceler... by tgsovlerkhgsel on Tuesday August 10, 2021 @12:50AM (#28125237)

How do you get the particle out of a vacuum area into a non-vacuum area?

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Re:What happens if you stick your head in a particle acceler... by azalemeth on Tuesday August 10, 2021 @07:35AM (#28127533)

Very thin, very expensive, very low atomic mass number beryllium windows.

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Re:What happens if you stick your head in a particle acceler... by changoplatanero on Tuesday August 10, 2021 @02:16AM (#28125629)

I'm not an expert but I believe that the particles are traveling so fast and with so much energy that they just blast through the walls of the vacuum chamber

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Re:What happens if you stick your head in a particle acceler... by AndrewOMartin on Tuesday August 10, 2021 @04:45AM (#28126500)

There's probably a material which photons and other sub atomic particles can pass through but the molecules in the air can't.

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Re:What happens if you stick your head in a particle acceler... by the8472 on Tuesday August 10, 2021 @08:15AM (#28127851)

For some applications a plasma window can be used.

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Re:What happens if you stick your head in a particle acceler... by jasonwatkinspdx on Tuesday August 10, 2021 @02:11AM (#28125606)

Probably just a very small hole and beefing up the vacuum equipment near it. From what I recall the LHC beam is on the scale of a couple micrometres.

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Re:What happens if you stick your head in a particle acceler... by zaarn on Tuesday August 10, 2021 @07:00AM (#28127264)

No you just fire it through the wall of the vacuum chamber. When you're going >99% the speed of light a couple inches of metal don't matter that much anymore.

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Re:What happens if you stick your head in a particle acceler... by tibyat on Tuesday August 10, 2021 @04:08AM (#28126272)

Why? Just do it all under vacuum.

But in cases where you must (cost/practicality limitations, dealing with liquids, etc), this is done by passing through a thin film of material that has a small cross section of interaction with the particles, typically "low Z" (low atomic number) elements like Beryllium (its rigidity makes withstanding 1 atm pressure difference easy), or simple hydrocarbon plastics like polyethylene/polypropylene.

But this depends on what particles you're talking about.

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