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

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.

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".

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

I talked to a biologist once that was running experiments on mice in front of a particle accelerator. He was testing to see how well the mice responded to both routine and unfamiliar tasks after receiving some level of dosage from the high energy particles (heavy ions I think). The mice usually responded to routine tasks as well as they had prior to the exposure but had much more trouble responding to the unfamiliar tasks. The theory was that the particles damaged the elastic parts of the brain more than the plastic parts, that the brain had more trouble forming new connections to solve problems but strong connections formed by training survived the exposure. The experiments were to study how space radiation may affect astronauts solve problems when confronted with less familiar or totally new ones.

Steven Keating is another incredible example of what the human brain is capable of. He was very successful doing research at MIT even did a few TED talks after having nearly half his brain removed. Unfortunately he is no longer with us.

https://news.mit.edu/2019/celebrating-curious-mind-steven-ke...

You can read studies of people who had their corpus callosum severed. This cuts off all communication between left and right hemispheres permanently. They maintain full and normal function, but the left and right halves of their bodies seem to take on independent lives mostly unaware of each other. You can ask a question and the mouth will give one answer but the left hand may write out a completely different answer (vocal language processing is controlled by the left hemisphere, where left arm is controlled by the right hemisphere).

This suggests even just half the brain can maintain the full set of higher cognitive abilities of a normal healthy human, but only half the motor control, which is presumably more dependent on hard-coded IO ports between the brain itself and the nerve buses running to the actual body part being controlled.

Which is to say there is an actual "right side of the face" zone, but there is no zone for higher reasoning in general. Unless you destroy the entire frontal cortex, much smaller subsets of it can fully function as if whole.

I think Daniel Dennett used this evidence to argue that the entire notion of self is an illusion. The brain is so highly redundant that it really consists of countless selves, a distributed system that dynamically comes to consensus but each component is fully capable of operating on its own or as part of a smaller distributed system when the network gets partitioned.

When I was a child my father was visited by a former colleague, who previously had a stroke. The colleague was partly paralyzed. He had great difficulties talking and to me it looked like he had also problems thinking straight. It appeared that his brain was severly damaged by the stroke. You cannot imagine my surprise when, as he left, he went into his car and drove away just like that.

The brain is very plastic. Which is why often the first sign of a brain tumor (including in people working mentally intensive jobs like PhD student) is a seizure, or paralysis, or deafness. All signs that plasticity in some part of the brain has reached its limit.

I think the energy deposited is almost all just from the kinetic energy of the particles.

The U-70 Synchrotron from the article produced 76 GeV protons. Electron-volts (eV) are a unit of kinetic energy. That works out to 0.012 microjoules per proton.

This was a pulsed machine, with a repetition rate of 0.11 Hz (9 seconds between pulses). In one pulse there were 1.7×10^13 protons. That adds up to about 200 kJ per pulse: About the same kinetic energy as a Toyota Corolla (1200kg) travelling at 65km/h.

As for exactly how the interaction would happen:

The particles would have bounced around the atoms in Mr Bugorski's head. They would lose energy I think mostly via interactions with atomic electrons. As they decelerated, they would also throw off Bremsstrahlung photons which would create a pencil-beam of x-rays. At that energy there would also be plenty of nuclear interactions which would tend to produce neutrons and prompt gamma rays.

Not all of the kinetic energy in the pulse would have been absorbed by Mr Bugorski's head. The energy deposited into a medium by a proton beam is described by the Bragg Peak. If you look it up, protons of ~200MeV would be almost entirely stopped by a human head (~20cm). But at almost 400 times that energy, I think a large fraction of the kinetic energy would just come out the other side in the form of neutrons, gammas, x-rays, and slightly slowed protons.

The sievert is the SI replacement to the rem, (roentgen equivelent, man). These are units of radiation dose that are scaled according to the health effect of the type of radiation. What you may need is a conversion from a radiometric unit (energy equivalent dose) to sieverts, for the particular frequency of microwaves.

Every type of particle, and band of wavelengths, has its own damage mechanism in the body, making the choice of a unit of measure complicated.

I'm not a nuclear physicist, but remember just a bit from my radiation safety training to work in an accelerator lab for a brief time period. Today I work with optics, and there are formulas in the regulations for laser and UV safety. They are quite definitely scientifically based. For instance, the UV wavelength with the highest weighting factor for hazard determination is the absorbance peak of DNA.

Hope that doesn't answer your question (since I'm not an expert anyway), but sheds some light on the complexity of the problem.

Where I went to grad school, they had one of the earliest accelerator physics programs. I remember a story, that the old timers would adjust the beam by closing their eyes and letting the particles cause scintillation inside their eyeballs. That was when beams were vastly less energetic, and in any event, I don't think they did this for very long without realizing the danger. In addition to the beam itself, an accelerator can give off a lot of X rays due to secondary radiation processes. The entire accelerator lab was behind a labyrinth of brick walls, and had an interlock system to make sure nobody was in the tunnel when the machine got started up.

Not a physicist, but randomly remembered a word that may help you find more about this: https://en.wikipedia.org/wiki/Radiosurgery

I doubt you’ll get an answer from a particle physicist.

The most important factors are energy per particle, number of particles, width of beam, and is it matter or antimatter. The most general case is it’s going to bore right through you, so cancer and heating is a lesser concern than the gaping hole.

A microwave beam is a different story, but again the specifics make a huge difference. A microwave oven isn’t going to do much though heating the eyeballs can cause issues. Cancer isn’t a serious concern, but boost the power enough and you can get serious and eventually fatal burns.

> He didn't know anything was happening at the time but ended up losing a couple limbs.

Surely that would have been reported by the university (PR, damage control) and in the news? Can you confirm?

I'm not sure I understand - how did the injured man actually place himself in the path of the particle beam? Given that particle accelerators are a sealed vacuum environment? Or could you be harmed by simply standing next to the accelerator while it's operating? If so, how is that energy reaching you?

From Wikipedia:

"Bugorski continued to work as a physicist at the Institute for High Energy Physics and held the post of coordinator of physics experiments. Because of the Soviet Union's policy of maintaining secrecy on nuclear power-related issues, Bugorski did not speak publicly about the accident for over a decade. He continued going to the Moscow radiation clinic twice a year for examinations and to meet with other nuclear accident victims. He was described as "a poster boy for Soviet and Russian radiation medicine". In 1996, he applied unsuccessfully for disability status to receive free epilepsy medication. Bugorski showed interest in making himself available for study to Western researchers but could not afford to leave Protvino."

Poor man.

But, uh.. are you and everyone you know dying of fireballs and/or radiation poisoning? If not, you are the one making the clear overstatement.

According to one YouTube video I've seen (so, you know, let's not take it as gospel), the shocking and disturbing (and NSFW/NSFL) image in the second article is a victim of burns and is not the subject of the article.

https://www.youtube.com/watch?v=2TxLrfdMKWY

Those two articles are somewhat in conflict. The latter makes it sound like the doctors were doing experiments on Ouchi, while the Wikipedia article's tone seems more in line with a medical team trying to save him. It also mentions that the doctors were instructed to try to resuscitate him (after multiple heart failures) by his family, but the second article makes it sound like they were doing it on their own, to try and prolong his life so they could study him.

Which is right?

Ok, we've changed the url from https://www.theatlantic.com/science/archive/2017/01/what-hap... to the one it points to.