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The researchers noted that the Stellarator—a fusion device—loses electrons as they drift across the magnetic field (normally electrons travel along magnetic field lines). This drift is driven by electrons colliding with each other. These collisions send the electrons moving perpendicular to both the magnetic field and an electric field that the electrons create.
The researchers arranged a set of electrodes to recreate that electric field. But the electrodes have to provide a very precise profile in relation to the magnetic field lines of the trap. It’s not stated in the article, but I suspect that a lot of time was spent on this problem. Stellarator designers faced a similar problem, so the researchers could probably work with a modified version of the code used to optimize the Stellarator (the research was conducted at the same institution).
The result, though, was spectacular: the researchers were unable to detect any positron loss during the trapping process.
The trap was also pretty awesome. It combines magnetic fields and electric fields to confine the positrons. This allowed the researchers to take advantage of the new electric field technique to controllably load and unload the trap.
The trap holds the positrons for about a second, which is pretty amazing. But the researchers wanted to know why they only got a second. So a second paper was devoted to looking at the positrons once they were inside.
To overcome this challenge, researchers performed extensive simulations and then verified them experimentally: a tailor-made electric field at the edge of the magnetic trap ensures that the charged particles can drift into the trap across the magnetic field lines. The electric field is then switched off and the particles are trapped in the magnetic field. An opposite example of this effect is seen in fusion research: electric fields, which can form spontaneously in the plasma, cause unwanted drifting of particles out of the confining magnetic cage – a particle loss which fusion researchers prevent by using a variety of countermeasures.
The current experiments used a prototype trap with a simple permanent magnet, which was attached to NEPOMUC [positron source lab]. To generate an electron-positron plasma, however, the APEX group is working on a superconducting dipole that floats in the middle of a vacuum chamber without touching the walls and generates the confining magnetic field.[ex/]
IPPP.mpg.de (English), Dec. 5, 2018 - A cage full of antimatter.
A little more direct report here. We can now see that they ran simulations, created a prototype permanent magnetic trap to demonstrate the simulation, and thus prove it is possible. That was the previous post's announcement: it has been done.
This goes one step further and explains APEX's net step: a superconducting dipole trap!
Now that is going to be awesome!
Maybe get enough particles to do some real, "mad scientist, total destruction of the lab" type experiments!!
ETA: Had this ready for posting when somebody killed our network by applying an update... in the middle of the day! It took them 12 hours to correct. Not bad for a technology company...
originally posted by: TEOTWAWKIAIFF
Since I can't edit my post to fix it...
@MOD, feel free to remove post = 24031801
To overcome this challenge, researchers performed extensive simulations and then verified them experimentally: a tailor-made electric field at the edge of the magnetic trap ensures that the charged particles can drift into the trap across the magnetic field lines. The electric field is then switched off and the particles are trapped in the magnetic field. An opposite example of this effect is seen in fusion research: electric fields, which can form spontaneously in the plasma, cause unwanted drifting of particles out of the confining magnetic cage – a particle loss which fusion researchers prevent by using a variety of countermeasures.
The current experiments used a prototype trap with a simple permanent magnet, which was attached to NEPOMUC [positron source lab]. To generate an electron-positron plasma, however, the APEX group is working on a superconducting dipole that floats in the middle of a vacuum chamber without touching the walls and generates the confining magnetic field.