Spinning electrons yield positrons for research

Spinning electrons yield positrons for research
The Polarized Electrons for Polarized Positrons (PEPPo) experiment in Jefferson Lab's CEBAF injector demonstrated a new technique for production of polarized positrons. When an energetic electron beam strikes matter, it produces photons that can further convert their energy in pairs of an electron and a positron. If the electron beam is polarized, the polarization can be passed on to the new electrons and positrons. Credit: DOE's Jefferson Lab

Researchers use accelerators to coax the electron into performing a wide range of tricks to enable medical tests and treatments, improve product manufacturing, and power breakthrough scientific research. Now, they're learning how to coax the same tricks out of the electron's antimatter twin - the positron - to open up a whole new vista of research and applications.

Using the Continuous Electron Beam Accelerator Facility (CEBAF) at the Department of Energy's Jefferson Lab, a team of researchers has, for the first time, demonstrated a new technique for producing polarized . The method could enable new research in advanced materials and offers a new avenue for producing polarized positron beams for a proposed International Linear Collider and an envisioned Electron-Ion Collider.

Jefferson Lab Injector Scientist Joe Grames says the idea for the method grew out of the many advances that have been made in understanding and controlling the electron beams used for research in CEBAF.

"We have a lot of experience here at Jefferson Lab in operating a world-leading electron accelerator," Grames said. "We are constantly improving the for the experiments, pushing the limits of what we can get the to do."

The CEBAF accelerator gathers up , sets the electrons to spinning like tops, packs them full of additional energy ("accelerating" the particles to up to 12 billion electron-volts), and directs them along a tightly controlled path into experimental targets. Grames and his colleagues would like to take that finesse a step further and transform CEBAF's well-controlled polarized electron beams into well-controlled beams of polarized positrons to offer researchers at Jefferson Lab an additional probe of nuclear matter. They named the endeavor the Polarized Electrons for Polarized Positrons experiment, or PEPPo.

Positrons are the anti-particles of electrons. Where the electron has a negative charge, the positron has a positive one. Producing positrons that are spinning in the same direction, like the electrons in CEBAF, is very challenging. Before PEPPo, researchers had successfully managed to coax polarized positrons into existence using very high-energy electron beams and sophisticated technologies. The PEPPo method, however, puts a new twist on things.

"From the beginning, our aim was to show that we could use the polarized electron beam we produce every day at CEBAF to create the positrons. But we wanted to do that using a low-energy and small-footprint electron beam, so that a university or company may also benefit from our proof of principle," Grames explained.

The PEPPo system was placed inside the CEBAF accelerator's injector, which is the part of the accelerator that generates electrons. The system consists mainly of small magnets for managing the particle beams, targets for transforming them, and detectors for measuring the particles.

In it, a new beam of electrons from CEBAF is directed into a slice of tungsten. The electrons rapidly decelerate as they pass through the tungsten atoms, giving off gamma rays. These gamma rays then interact with other atoms in the tungsten target to produce lower-energy pairs of positrons and electrons. Throughout the process, the polarization of the original electron beam is passed along. The researchers use a magnet to siphon the positrons away from the other particles and direct them into a detector system that measures their energy and polarization.

"We showed that there's a very efficient transfer of polarization from electrons to the positrons," said Grames.

Further, the researchers found that it is also possible to dial up the degree of polarization that they are interested in by selecting positrons of the right energy. While the more abundant lower-energy positrons are less polarized, the positrons with highest-energy retain nearly all of the polarization of the original electron beam. In PEPPo, the electron beam was 85 percent polarized and accelerated to 8 million electron-volts (MeV).

"Nuclear physicists typically want the highest polarization possible for their experiments," he explained. "Positrons collected at half the original electron energy were about 50 percent polarized, which is still quite high. But, as we approached the maximum energy, we measured 82 percent, showing that a very large portion of the original electron polarization is transferred."

The PEPPo experiment ran for four weeks in the spring of 2012. The result has just been published in Physical Review Letters, and it is featured as an Editors' Suggestion.

Grames and his colleagues say now that they have their proof of principle, they want to design a source that is capable of producing a beam of polarized positrons for research.

"With this result in hand, we are now asking ourselves what's the best way to collect these positrons into a beam that may be used by nuclear physicists in experiments at Jefferson Lab and that may be useful for other facilities. That's the next step."


Explore further

CEBAF beam goes over the hump: Highest-energy beam ever delivered at Jefferson Lab

More information: D. Abbott et al, Production of Highly Polarized Positrons Using Polarized Electrons at MeV Energies, Physical Review Letters (2016). DOI: 10.1103/PhysRevLett.116.214801
Journal information: Physical Review Letters

Citation: Spinning electrons yield positrons for research (2016, June 1) retrieved 17 June 2019 from https://phys.org/news/2016-06-electrons-yield-positrons.html
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User comments

Jun 01, 2016
Damn but I love it when there are actual Science articles on this site. Kudos !!!

Jun 01, 2016
We are talking about a point charge moving. It's polarization will be it's directional vector. Any spin will actually be a coil before release. So whatever, it's the forward directional vector and direction as the tangent to circle of the coil. Maybe modified based upon transition from field to field. The field of the electron is normal to the sphere about it at any given moment added to the velocity vector. The energy transfer is via charge motion, i.e. the response to the electron's field as it travels through the media. There exists only the centers of a positive field and the centers of the negative fields. The normal orbiters are the negative. The positive centers are in the nucleus. So really, what is going on?

Jun 01, 2016
I'd validate the isotope concentration throughout the experiment, something I think would be difficult considering the amount of change would be like counting the number of atoms and simply taking it's weight before an after. Longer the use, say a few ^%^&* positrons that will make a measurable weight differential. But hey, if you got some cool tools that can give you tiny changes such one atom dropping som'n, som'n. The "positrons" are coming from where? Remember? Conservation of charge!

Jun 01, 2016
There's only two spherical electric fields, +&-, and only these create radiation. Maxwell

Please, no argument.

Jun 01, 2016
What's the frequency of the coil? and the gamma freq. positives prior to release from nucleus, oscillate? Gamma coming from somewhere. You talk like it's magic! no neutron splits? i.e. +&-+neutrino. Soo...

Jun 01, 2016
Safety?

Jun 01, 2016
Huh, nice, a new probe to look inside things with. They're right, this will do good things for materials science and nuclear physics as well.

Jun 02, 2016
Particle physics problem : Starts with its misunderstanding of the quantum electron structure,it doesn't have an instrument to see its true quantum design, the have classified it a negatively charged particle,with no substructure , without ever considering that its negative charge they measure,is a dominant charge of the mass construction 33.3 larger then the positive quantum mass in its two level quantum construction ,only because they have not the instruments to read the minor charges in quantum construction,

Jun 02, 2016
That a pure negative charge single level construction of their definition of the electron, would repel other electrons and never be able to field chain with other electrons to make magnetic lines of force , it would be magnetically impossible with out both charges present

Jun 02, 2016
So an electron needs to have both charges present to field chain ,its need to levels one a dominant negatively charged level in its quantum charge mass and another level of a smaller positively charged quantum dominant mass bonded by attraction magnetically to each other to make an electron that will field chain,

Jun 02, 2016
If an electron is a two level quantum construction of both charges one dominant by quantum mass over the other, that means the construction can only be manufactured into one other construction a three level electron with a dominant positive charge and a minor negative charge by quantum mass where the two positive levels have 33.3 more quantum mass then the single level negative mass, and that both electrons together the positive electron and the negative electron has equal charged quantum mass when that are fused together to make a photon,

Jun 02, 2016
And the only parts being ejected out of kinetic collisions of photons is two electrons and a positive quantum level off the positive electron, 33. Percent of the photons positive 3 levels of positive charge leaving a negative electron that it began its life as

Jun 02, 2016
Wow that was from deep space it must have been ejected from a black hole into this dimension, ha ha ha thanks for the laugh that was great

Jun 02, 2016
That when the two level electron and three level electron is not used in photons their other job is the building blocks for the shelled constructions of neutrons and protons in induction environments to manufacture new hydrogen atoms

Jun 02, 2016
Those are unbalanced charge constructions in quantum charged mass's with dominant charged mass make up

Jun 04, 2016
In the quantum dimension of construction, there are single level assembled quantum charged particles you have classified as electrons and positrons these must be combined to transition into the hydrogen atom dimension of particle physics to make our two level electrons and three level electrons ,that those still contain both charges but one dominant by quantum part mass, in both constructions, those to parts magnetically bound make our electron in the hydrogen atom dimension of constructions transitional particle physics

Jun 04, 2016
In that quantum dimension there are only two magnetic forces attraction and repulsion between the quantum assemblies ,no field chaining of particles

Jun 05, 2016
A photons, equal charge is 3 positrons and two electrons ,single level particles in quantum mass assemblies

Jun 05, 2016
In electrons there is a single level and two level electron and there is a single level positive charge and a three level constructions

Jun 05, 2016
That only the multiple level electron constructions are the magnetic building blocks of photons, neutrons,and protons

Jun 05, 2016
The experiments results are not making any particles its decoupling particles off of their magnetic level construction's

Jun 05, 2016
In particles that already exists from your material source in kinetic collisions into individual quantum single level parts

Jun 05, 2016
A like metaphor in mechanical electrics is single phase ,double phase and 3 phases electrical charge operations working together

Jun 06, 2016
Says the troll that's too ignorant to figure out the "edit" option.

Jun 06, 2016
Where's your magnetic mechanical hypotheses, or do you not have any aptitude in mechanics and magnetics your just the troll of ignorance ridicule, to cover that lack of character and your ineptness of mechanical comprehension, and your in abilities in conceptions

Jun 06, 2016
Why don't you explain, how 100 percent negatively charged electrons form connected field lines in magnetics, when their like charges repel each other , in mechanical magnetic terms

Jun 06, 2016
What's your hypotheses of the counter magnetic forces that off set the repulsion magnetic forces , I'm all ears, in learning something new in magnetic mechanical forces that can create electron magnetic field lines, and I will acknowledge your mechanical magnetic genius, with no problems , we can always use more thinkers in particle physics

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