Very cool! There's some wild ideas about antimatter capture in space via giant arrays of superconducting magnets trapping naturally occurring antimatter.
Apparently, nanograms / micrograms is enough to create a "antimatter catalyzed" fission/fusion propulsion system with enormous specific impulse / efficacy.
Exciting results. The electron's magnetic moment is probably the most precise standard model prediction, and Gabrielse's group has measured it with 13 digits of accuracy. The positron is predicted to have exactly the same magnetic moment, but this has not been measured since 1987. With the new trap, they should be able to finally match the electron's precision.
And yet the lifetime of free "thermal" neutrons is unknown (there are two measurements that give results off by ~1%) between 888 and 878 seconds.
Notably, neutrons are quite unstable outside of a nucleus and decay generating a proton, electron, and a neutrino. There are many theories on the discrepancy.
I don't get how they know they have exactly one in there. I mean they're measuring the magnetic field but how on earth do you make sufficiently precise measurements to detect a single particle!?!
The simple explanation: The positrons fly around the trap center. In the z-direction, this is a simple "up and down" oscillation. There are electrodes in the top and bottom of the trap called the "end-caps". The end-caps are connected to each other with a large resistor (technically, a coil forming an LC resonator with the parasitic capacitance, but on resonance it looks like a large resistor).
When the positrons are at the top, they attract negative charges into the top end-cap. This is called an "image charge". When the positrons are close to the bottom end-cap, the image charge into bottom end-cap. This forms a current, the "image current". The more positrons you have, the larger the image current.
Since the image current (on the order of femtoamperes) has to flow through the large resistor, it is turned into a voltage that can be amplified and measured by cryogenic amplifiers. But it has a second effect: The voltage "back-acts" on the positrons, damping their motion. If you have more positrons in the trap, this damping gets stronger, because each positron experiences the back-action of all other positrons.
In the paper, you can see pictures of the driven axial motion, where you take an RF excitation and sweep the frequency over the resonance, recording the positrons' amplitude as a response. The more positrons you have, the "wider" this resonance, because of the damping effect.
As you reduce the number of positrons by doing a "dip" (making the trap really shallow, hoping that some, but not all, positrons escape), you can see the width getting smaller and smaller in discrete steps. That's how you know you are dealing with individual particles.
I haven't worked on Gabrielse's setup, but I have worked on other, very similar (better, ha!) experiments 10 years ago. I don't see what's so special about this trap, but putting antimatter into it always makes for a nice headline.
> In order to determine ωz and the number of trapped
positrons, the axial oscillation of a positron is driven with
oscillating potentials applied to the trap electrodes. The
frequency of the drive ωd is swept through resonance with
ωz.
> For the center-of-mass axial motion of
more than one positron, the damping (and hence the observed signal width) increases in proportion to the number of particles. A confirmation that only one positron
is trapped comes from spin flip observations that are discussed presently
They let it go and listen for the pop? Let it fall from the magnetic containment and you should see a predictable emission as it collides with some normal matter. Detecting single photons is what detectors are all about.
I think this is a fascinating technology. I wonder if it is currently energy positive (so that we can engineer it into a functional source) or at least if it can be extended to be captured in bulk (antimatter rockets!).
Hope Aristotle with his 'telos' is wrong, and the antimatter particle does not have a purpose to annihilate itself with a +-matter particle. The universe will complain if it doesn't.
It gets complicated, because protons and anti-protons are composite particles.
To simplify somewhat, one quark from each will annihilate, leaving four quarks and a lot of energy, which re-arrange into mesons (two quarks each), which then decay into photons, electrons, positrons and neutrinos.
Annihilation. At low collision energies the antiproton and proton go through an interaction which ultimately results in photons (light energy). Matter is converted into energy as e = mc^2. Though the interaction passes through a number of exotic intermediate stages first.
As the sibling comments say, it's a single positron so the energy released is tiny. I tried to find positrons sources in common life, the best I could find was https://en.wikipedia.org/wiki/Positron_emission_tomography The relevant paragraph are
> For a typical dose (245 MBq) of FDG, one of the most common radiotracers used for PET neuroimaging and cancer patient management,[48] the effective radiation dose is 4.7 mSv.[49]
and
> This limitation restricts clinical PET primarily to the use of tracers labelled with fluorine-18, which has a half-life of 110 minutes and can be transported a reasonable distance before use.
Where "245 MBq" means 2*10^8 positrons per second for. And "110 minutes" means a half disappears every 2 hours, so the total sum is equivalent to 4 hours but I'm missing some small constant and they ae probably averaging the dose. I guess "3 hours" is a good compromise but multiply it by 2 or 4 if you prefer a smaller or bigger number. Anyway, 3 hours are 10^4 seconds, so the total numbers of positrons in a PET is approximately 2*10^8 * 10^4 = 2*10^12.
And whether it’s a positron or an electron (beta+ or beta- decay) doesn’t seem to matter that much as far as equivalent dose is concerned, the energy deposited is only fractionally higher in the case of a positron. (But PET can only work with positrons because it’s exactly the pairs of 0.511 MeV annihilation gammas that it’s designed to detect!)
In addition to knowing how much stuff is released by one particle, we have a decent handle on how much is needed in order to be dangerous, due to us being constantly bombarded by various cosmic rays. That's how we can say that it's not dangerous.
The article is behind a paywall, but it seems likely that the bigger safety concern is whatever produced the large quantity of particles needed to have a chance of trapping just one. And those kinds of experiments are conducted in regulated facilities for good reason.
The end annihilation was actually the electron switching to backwards through time. At the beginning of the experiment the positron switches back to forward and continues on its way.
> Every time they bang into something, there’s a chance of annihilation, but it doesn’t always happen
This goes against everything I've ever been told about antimatter. So a positron and electron can collide and not annihilate each other? How does that work? What happens to them in that case, and why does everybody say otherwise?
Similar work is done at the CERN LHC facility, where they can deliver antimatter to your door. Got a couple of hours? Check out Marco Reps' tour: https://www.youtube.com/watch?v=Yibef6nLCv8
I shudder to think of the paperwork the EU would require for authorization to transport antimatter off-campus. But they have hauled it around for up to 20 minutes (https://www.antimatter.hhu.de/en/about-us/base-step) so in principle it could go a bit farther!
whats up with all the comments making analogies with AI torture repository?
One might measure the "amount of computation going on" as a proxy for consciousness, but "number of dissipative logic gates" can't be right since one can construct larger reversible circuits containing the same computation (and hence dissipation is a poor measure), although one could then use the total number of bits (including trash bits) as the measure.
but I don't understand why particle physics?
having all other comments (at the time of writing) be about consciousness of individual particles, seems to indicate these commenters specifically believe particle physics or antimatter to directly describe consciousness?
Or is this some kind of "disinfo inoculation campaign" to render us immune to "sentient rights propaganda"?
Don’t worry! If the single electron theory is correct, then this torture only represents an infinitesimal portion of its total lifetime, which is actually experienced in reverse and so it may feel increasing relief over time rather than increasing anxiety over being trapped.
That's matter cruelty. We need more ethical ways to study those poor things. Does anyone know what happened after the experiment ? Did they finally let it go?
The parents of the anti-matter particle then freeze time just as the containment is about to explode, allowing Picard and Geordi to wander
around the facility looking for clues - until one scientists head slowly turns - they are also awake !!
Very cool! There's some wild ideas about antimatter capture in space via giant arrays of superconducting magnets trapping naturally occurring antimatter.
Apparently, nanograms / micrograms is enough to create a "antimatter catalyzed" fission/fusion propulsion system with enormous specific impulse / efficacy.
PDF: https://www.niac.usra.edu/files/studies/final_report/1071Bic...
This might be of interest:
https://en.wikipedia.org/wiki/Alpha_Magnetic_Spectrometer
Exciting results. The electron's magnetic moment is probably the most precise standard model prediction, and Gabrielse's group has measured it with 13 digits of accuracy. The positron is predicted to have exactly the same magnetic moment, but this has not been measured since 1987. With the new trap, they should be able to finally match the electron's precision.
And yet the lifetime of free "thermal" neutrons is unknown (there are two measurements that give results off by ~1%) between 888 and 878 seconds.
Notably, neutrons are quite unstable outside of a nucleus and decay generating a proton, electron, and a neutrino. There are many theories on the discrepancy.
https://journals.aps.org/prd/abstract/10.1103/PhysRevD.110.0...
I don't get how they know they have exactly one in there. I mean they're measuring the magnetic field but how on earth do you make sufficiently precise measurements to detect a single particle!?!
Edit: this is explained pretty extensively in the paper (https://cfp.physics.northwestern.edu/documents/2026OnePositr...). I'm gonna need to do some background reading though...
The simple explanation: The positrons fly around the trap center. In the z-direction, this is a simple "up and down" oscillation. There are electrodes in the top and bottom of the trap called the "end-caps". The end-caps are connected to each other with a large resistor (technically, a coil forming an LC resonator with the parasitic capacitance, but on resonance it looks like a large resistor).
When the positrons are at the top, they attract negative charges into the top end-cap. This is called an "image charge". When the positrons are close to the bottom end-cap, the image charge into bottom end-cap. This forms a current, the "image current". The more positrons you have, the larger the image current.
Since the image current (on the order of femtoamperes) has to flow through the large resistor, it is turned into a voltage that can be amplified and measured by cryogenic amplifiers. But it has a second effect: The voltage "back-acts" on the positrons, damping their motion. If you have more positrons in the trap, this damping gets stronger, because each positron experiences the back-action of all other positrons.
In the paper, you can see pictures of the driven axial motion, where you take an RF excitation and sweep the frequency over the resonance, recording the positrons' amplitude as a response. The more positrons you have, the "wider" this resonance, because of the damping effect.
As you reduce the number of positrons by doing a "dip" (making the trap really shallow, hoping that some, but not all, positrons escape), you can see the width getting smaller and smaller in discrete steps. That's how you know you are dealing with individual particles.
I haven't worked on Gabrielse's setup, but I have worked on other, very similar (better, ha!) experiments 10 years ago. I don't see what's so special about this trap, but putting antimatter into it always makes for a nice headline.
Relevant paragraphs, near figure 4, page 3:
> In order to determine ωz and the number of trapped positrons, the axial oscillation of a positron is driven with oscillating potentials applied to the trap electrodes. The frequency of the drive ωd is swept through resonance with ωz.
> For the center-of-mass axial motion of more than one positron, the damping (and hence the observed signal width) increases in proportion to the number of particles. A confirmation that only one positron is trapped comes from spin flip observations that are discussed presently
They let it go and listen for the pop? Let it fall from the magnetic containment and you should see a predictable emission as it collides with some normal matter. Detecting single photons is what detectors are all about.
This made me laugh very hard. Thank you.
I think this is a fascinating technology. I wonder if it is currently energy positive (so that we can engineer it into a functional source) or at least if it can be extended to be captured in bulk (antimatter rockets!).
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Sounds like that classic joke about a hunter finding his friend unconscious - the one where the dispatcher asks if the friend is dead…
Direct link to article: https://arxiv.org/abs/2605.08147
Quantunamo Bay
Hope Aristotle with his 'telos' is wrong, and the antimatter particle does not have a purpose to annihilate itself with a +-matter particle. The universe will complain if it doesn't.
What happens if an anti proton hits a normal hydrogen atom?
It gets complicated, because protons and anti-protons are composite particles.
To simplify somewhat, one quark from each will annihilate, leaving four quarks and a lot of energy, which re-arrange into mesons (two quarks each), which then decay into photons, electrons, positrons and neutrinos.
Annihilation. At low collision energies the antiproton and proton go through an interaction which ultimately results in photons (light energy). Matter is converted into energy as e = mc^2. Though the interaction passes through a number of exotic intermediate stages first.
Someone has done the experiment: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.108.0...
The link is cherry picked from a very good explanation by Gemini https://www.google.com/search?q=antiproton+hidrogen+colissio...
That seems super safe. At least they are wearing gloves.
I kind of want to know how they safely deal with its release (destruction)
As the sibling comments say, it's a single positron so the energy released is tiny. I tried to find positrons sources in common life, the best I could find was https://en.wikipedia.org/wiki/Positron_emission_tomography The relevant paragraph are
> For a typical dose (245 MBq) of FDG, one of the most common radiotracers used for PET neuroimaging and cancer patient management,[48] the effective radiation dose is 4.7 mSv.[49]
and
> This limitation restricts clinical PET primarily to the use of tracers labelled with fluorine-18, which has a half-life of 110 minutes and can be transported a reasonable distance before use.
Where "245 MBq" means 2*10^8 positrons per second for. And "110 minutes" means a half disappears every 2 hours, so the total sum is equivalent to 4 hours but I'm missing some small constant and they ae probably averaging the dose. I guess "3 hours" is a good compromise but multiply it by 2 or 4 if you prefer a smaller or bigger number. Anyway, 3 hours are 10^4 seconds, so the total numbers of positrons in a PET is approximately 2*10^8 * 10^4 = 2*10^12.
And whether it’s a positron or an electron (beta+ or beta- decay) doesn’t seem to matter that much as far as equivalent dose is concerned, the energy deposited is only fractionally higher in the case of a positron. (But PET can only work with positrons because it’s exactly the pairs of 0.511 MeV annihilation gammas that it’s designed to detect!)
> I tried to find positrons sources in common life
Good. Reject electrons. Positive vibes only.
It's one particle. It's not a bomb.
Yes, you'd need another 6x10^15 of them to even act as a trigger for a battlefield thermonuclear weapon to destroy something like a tank, apparently.
Ejecting the warp core is a common strategy.
E=mc*2 but m is really really tiny
If it's a single particle I don't think there's much to worry about?
In addition to knowing how much stuff is released by one particle, we have a decent handle on how much is needed in order to be dangerous, due to us being constantly bombarded by various cosmic rays. That's how we can say that it's not dangerous.
The article is behind a paywall, but it seems likely that the bigger safety concern is whatever produced the large quantity of particles needed to have a chance of trapping just one. And those kinds of experiments are conducted in regulated facilities for good reason.
Does this hurt the positron?
Call PETA (People for the Ethical Treatment of Antimatter)
Physicists for the Ethical Treatment of Atoms
The end annihilation was actually the electron switching to backwards through time. At the beginning of the experiment the positron switches back to forward and continues on its way.
https://en.wikipedia.org/wiki/One-electron_universe
What a crazy and fun idea. Good Wikipedia article. Everything in the Feynman cinematic universe is awesome
I was thinking of trying to spin up a campaign on bluesky to be upset about this.
Poor thing, all alone
It could have been an entire universe, like ours, if some theories/cosmologies are correct :)
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> Every time they bang into something, there’s a chance of annihilation, but it doesn’t always happen
This goes against everything I've ever been told about antimatter. So a positron and electron can collide and not annihilate each other? How does that work? What happens to them in that case, and why does everybody say otherwise?
Similar work is done at the CERN LHC facility, where they can deliver antimatter to your door. Got a couple of hours? Check out Marco Reps' tour: https://www.youtube.com/watch?v=Yibef6nLCv8
Or cut to the chase at the 'antimatter factory', at https://www.youtube.com/watch?v=Yibef6nLCv8&t=3186s
Wonder when this will be done by DoorDash…
where they can deliver antimatter to your door
You mean if you live on the 4km loop 'serviced' by BASE-STEP?
I shudder to think of the paperwork the EU would require for authorization to transport antimatter off-campus. But they have hauled it around for up to 20 minutes (https://www.antimatter.hhu.de/en/about-us/base-step) so in principle it could go a bit farther!
1 reply →
whats up with all the comments making analogies with AI torture repository?
One might measure the "amount of computation going on" as a proxy for consciousness, but "number of dissipative logic gates" can't be right since one can construct larger reversible circuits containing the same computation (and hence dissipation is a poor measure), although one could then use the total number of bits (including trash bits) as the measure.
but I don't understand why particle physics?
having all other comments (at the time of writing) be about consciousness of individual particles, seems to indicate these commenters specifically believe particle physics or antimatter to directly describe consciousness?
Or is this some kind of "disinfo inoculation campaign" to render us immune to "sentient rights propaganda"?
It's definitely just jokes due to using the word 'trap'. You might need to get some sleep lol
Don’t worry! If the single electron theory is correct, then this torture only represents an infinitesimal portion of its total lifetime, which is actually experienced in reverse and so it may feel increasing relief over time rather than increasing anxiety over being trapped.
I don't see comments on SI's website. I assume you mean here. Those are jokes.
To be fair, I can see why they didn't realise that considering none of them are remotely funny.
of course the cyclotron going clockwise.
The title of the research article is "One-Positron Quantum Cyclotron" https://cfp.physics.northwestern.edu/documents/2026OnePositr... so you are right.
South of the equator they go counter-clockwise
...and will have to deal with the consequences
That's matter cruelty. We need more ethical ways to study those poor things. Does anyone know what happened after the experiment ? Did they finally let it go?
It was given freedom at the end of experiment, and was immediately eaten by its abundant natural predator, just like it happens in nature.
Don’t eat Jimmy!
Matter rights matter.
But antimatter rights antimatter? Or do they become lefts.
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I sure hope it doesnt come back for revenge damn
It's worse than that. They annihilated it completely.
Drawing the line at matter welfare when the world still has this much human suffering will never stop being wild to me
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I was going to comment "I bet it's pissed" and then worried about drawing dang on myself, but you started it... Also: https://www.facebook.com/watch/?v=1254917172263794.
"Wild? I was absolutely livid!"
I hope they took precautions against the Camerlengo stealing it
Positrons are just as Catholic as electrons: they both have the same mass!
Except they draw the line at welcoming the other in…
The parents of the anti-matter particle then freeze time just as the containment is about to explode, allowing Picard and Geordi to wander around the facility looking for clues - until one scientists head slowly turns - they are also awake !!
[dead]
The Ackbar Effect
It probably got Copenhagen syndrome