Nearly the Speed of Light in One Millimeter: Presenting a New Type of Particle Accelerator

Hybrid Plasma Accelerator Numerical Rendering

Numerical rendering of the laser-driven acceleration (left side) and a subsequent electron-driven acceleration (right side), forming together the hybrid plasma accelerator. Credit: Alberto Martinez de la Ossa, Thomas Heinemann

Electrons Riding a Double Wave

Since they are far more compact than today’s accelerators, which can be kilometers long, plasma accelerators are considered as a promising technology for the future. An international research group has now made significant progress in the further development of this approach: With two complementary experiments at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and at the Ludwig-Maximilians-Universität Munich (LMU), the team was able to combine two different plasma technologies for the first time and build a novel hybrid accelerator. The concept could advance accelerator development and, in the long term, become the basis of highly brilliant X-ray sources for research and medicine, as the experts describe in the journal Nature Communications.

In conventional particle accelerators, strong radio waves are guided into specially shaped metal tubes called resonators. The particles to be accelerated — which are often electrons — can ride these radio waves like surfers ride an ocean wave. But the potential of the technology is limited: Feeding too much radio wave power into the resonators creates a risk of electrical charges that can damage the component. This means that in order to bring particles to high energy levels, many resonators have to be connected in series, which makes today’s accelerators in many cases kilometers long.

200 MeV Accelerator

200 MeV accelerator. Credit: Arie Irman

That is why experts are eagerly working on an alternative: plasma acceleration. In principle, short and extremely powerful laser flashes fire into a plasma — an ionized state of matter consisting of negatively charged electrons and positively charged atomic cores. In this plasma, the laser pulse generates a strong alternating electric field, similar to the wake of a ship, which can accelerate electrons enormously over a very short distance. In theory, this means facilities can be built far more compact, shrinking an accelerator that is a hundred meters long today down to just a few meters. “This miniaturization is what makes the concept so attractive,” explains Arie Irman, a researcher at the HZDR Institute of Radiation Physics. “And we hope it will allow even small university laboratories to afford a powerful accelerator in the future.”

But there is yet another variant of plasma acceleration where the plasma is driven by near-light-speed electron bunches instead of powerful laser flashes. This method offers two advantages over laser-driven plasma acceleration: “In principle, it should be possible to achieve higher particle energies, and the accelerated electron beams should be easier to control,” explains HZDR physicist and primary author Thomas Kurz. “The drawback is that at the moment, we rely on large conventional accelerators to produce the electron bunches that are needed to drive the plasma.” FLASH at DESY in Hamburg, for instance, where such experiments take place, measures a good one hundred meters.

High-energy combination

This is precisely where the new project comes in. “We asked ourselves whether we could build a far more compact accelerator to drive the plasma wave,” says Thomas Heinemann of the University of Strathclyde in Scotland, who is also a primary author of the study. “Our idea was to replace this conventional facility with a laser-driven plasma accelerator.” To test the concept, the team designed a sophisticated experimental setup in which strong light flashes from HZDR’s laser facility DRACO hit a gas jet of helium and nitrogen, generating a bundled, fast electron beam via a plasma wave. This electron beam passes through a metal foil into the next segment, with the foil reflecting back the laser flashes.

In this next segment, the incoming electron beam encounters another gas, this time a mixture of hydrogen and helium, in which it can generate a new, second plasma wave, setting other electrons into turbo mode over a span of just a few millimeters — out shoots a high-energy particle beam. “In the process, we pre-ionize the plasma with an additional, weaker laser pulse,” Heinemann explains. “This makes the plasma acceleration with the driver beam far more effective.”

Turbo ignition: Almost to the speed of light within just one millimeter

The result: “Our hybrid accelerator measures less than a centimeter,” Kurz explains. “The beam-driven accelerator section uses just one millimeter of it to bring the electrons to nearly the speed of light.” Realistic simulations of the process show a remarkable gradient of the accelerating voltage in the process, corresponding to an increase of more than a thousand times when compared to a conventional accelerator. To underscore the significance of their findings, the researchers implemented this concept in a similar form at the ATLAS laser at LMU in Munich. However, the experts still have many challenges to overcome before this new technology can be used for applications.

In any case, the experts already have possible fields of application in mind: “Research groups that currently don’t have a suitable particle accelerator might be able to use and further develop this technology,” Arie Irman hopes. “And secondly, our hybrid accelerator could be the basis for what is called a free-electron laser.” Such FELs are considered extremely high-quality radiation sources, especially X-rays, for ultra-precise analyses of nanomaterials, biomolecules, or geological samples. Until now, these X-ray lasers required long and expensive conventional accelerators. The new plasma technology could make them much more compact and cost-effective — and perhaps also affordable for a regular university laboratory.

Reference: “Demonstration of a compact plasma accelerator powered by laser-accelerated electron beams” by T. Kurz, T. Heinemann, M. F. Gilljohann, Y. Y. Chang, J. P. Couperus Cabadağ, A. Debus, O. Kononenko, R. Pausch, S. Schöbel, R. W. Assmann, M. Bussmann, H. Ding, J. Götzfried, A. Köhler, G. Raj, S. Schindler, K. Steiniger, O. Zarini, S. Corde, A. Döpp, B. Hidding, S. Karsch, U. Schramm, A. Martinez de la Ossa and A. Irman, 17 May 2021, Nature Communications.
DOI: 10.1038/s41467-021-23000-7

3 Comments on "Nearly the Speed of Light in One Millimeter: Presenting a New Type of Particle Accelerator"

  1. So a 10cm device could comforatbly fit in the hand, perhaps a phaser gun.

  2. Peter M Foster | May 26, 2021 at 12:02 am | Reply

    A wave of water. Surf upon it, a floor of electromagnetic energy walk upon it, the space between the mesh of the marsh and the energies surrounding it fusion is unity fusion is division. Strength in putting together the twisted active matrix now do a room, window, a door, a walk thru, without the requirement of a trusted tool but instead like the gas from tritium, helium, lithium, nitrogen, running on space with world revolving in your sensory perception system, a friend or foe, the thought of the light as you point to clear the way, electromagnetic algorithms, EA if we dont for honor, we can be sure of our extinction, but that was already said. Somesay we haven’t even begun to encompass the parameters of humanity, I might agree as we are sitting in the pile of antiquated methods and patterns of behavior so I ask for those held in bondage to be set free…. ps. Dont use one of those thin razors or lasers that woul cut through our frail flesh like a sharp knife in butter around our children, imagine someone with poor focus, oops was that an arm? Keep that in mind as those who think of dominance have not a clue and those who see the walls of our barriers being opened to keep our life and liberty.

  3. Peter M Foster | May 26, 2021 at 12:15 am | Reply

    I’m thinking of launching a gyroscopic vehicle, I’m looking at the wings of velocity and the magnetic energies associated, ignite them in order, the light? Light them in order, oh… said the three to the right or is it left, there I’m lighting them in order, the chp, the saucer, the light like an almond all of the same beach, against the light, the perpetual one on the middle, leave it! They hollered as we approached. It’s their honor so well grab our coats and see the the forces of the magnetic moments alternating frequencies and soon well be steering the gyroscope by the seat of the steering mechanisms in the middle of the sphere, and say zip on over to the far side, even inside of our neurological cavity. Zip it do dah…. whoa that’s a left up ahead, I hear on the screen of Hal, and Vincent, and so I ease back on the left throttle and push gently ahead on the rite, suddenly feeling like a forth header again a big smile takes over my physiognomy and I start to really enjoy this new mobile vehicle if if gyroscopic proportions… look and hover, the buoyancy calculations pr algorithms are already streaming in, thanks to some on the same tangent, let’s keep the faith and the peace is for all, for who would want war when all can have peace. The whole story .. the whole story… dag nabbit.

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