From MPG Institute for Physics [Max-Planck-Institut für Physik] (DE) : “CERN ‘Awake’ brings proton bunches into sync”

From MPG Institute for Physics [Max-Planck-Institut für Physik] (DE)

April 23, 2021

Dr. Patric Muggli
Max Planck Institute for Physics, München
+49 89 32354-580

Fabian Batsch
Max Planck Institute for Physics, München
+49 89 32354-561

The future of particle acceleration has begun. Awake is a promising concept for a completely new method with which particles can be accelerated even over short distances. The basis for this is a plasma wave that accelerates electrons and thus brings them to high energies. A team led by the Max Planck Institute for Physics now reports a breakthrough in this context. For the first time, they were able to precisely time the production of the proton microbunches that drive the wave in the plasma. This fulfills an important prerequisite for using the Awake technology for collision experiments.

Proton bunches in sync: A train of short proton bunches travels through the plasma field, forming a wave on which electrons can be accelerated. CERN AWAKE

How do you create a wave for electrons? The carrier substance for this is a plasma (i.e., an ionized gas in which positive and negative charges are separated). Directing a proton beam through the plasma creates a wave on which electrons ride and are accelerated to high energies.

The proton source of Awake is the SPS ring at Cern- a pre-accelerator for the 27-kilometer circumference ring of the Large Hadron Collider (LHC). It produces proton bunches about 10-cm long. “However, in order to generate a large amplitude plasma wave, the proton bunch length must be much shorter – in the millimeter range,” explains Fabian Batsch, PhD student at the Max Planck Institute for Physics.

The scientists take advantage of self-modulation, a “natural” interaction between the bunch and plasma. “In the process, the longer proton bunch is split into high-energy proton microbunches of only a few millimeters in length, building the train beam,” says Batsch. “This process forms a plasma wave, which propagates with the train travelling through the plasma field.”

Precise timing allows ideal electron acceleration

However, a stable and reproducible field is required to accelerate electrons and bring them to collision. This is exactly what the team has found a solution for now. “If a sufficiently large electric field is applied when the long proton bunch is injected and the self-modulation is thus immediately set in motion.”

“Since the plasma is formed right away, we can exactly time the phase of the short proton microbunches,” says Patric Muggli, head of the Awake working group at the Max Planck Insstitute for Physics. “This allows us to set the pace for the train. Thus, the electrons are caught and accelerated by the wave at the ideal moment.”

First research projects in sight

The “Awake” technology is still in the early stages of development. However, with each step toward success, the chances of this accelerator technology actually being used in the coming decades increase. The first proposals for smaller accelerator projects (e.g., for example to study the fine structure of protons) are to be made as early as 2024.

According to Muggli, the advantages of the novel accelerator technology – plasma wakefield acceleration – are obvious: “With this technology, we can reduce the distance needed to accelerate electrons to peak energy by a factor of 20. The accelerators of the future could therefore be much smaller. This means: Less space, less effort, and therefore lower costs.”

Science paper:
Physical Review Letters

See the full article here .


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The MPG Institute for Physics [Max-Planck-Institut für Physik](DE) (MPP) is a physics institute in Munich, Germany that specializes in high energy physics and astroparticle physics. It is part of the Max-Planck-Gesellschaft and is also known as the Werner Heisenberg Institute, after its first director in its current location.

The founding of the institute traces back to 1914, as an idea from Fritz Haber, Walther Nernst, Max Planck, Emil Warburg, Heinrich Rubens. On October 1, 1917, the institute was officially founded in Berlin as Kaiser-Wilhelm-Institut für Physik (KWIP, Kaiser Wilhelm Institute for Physics) with Albert Einstein as the first head director. In October 1922, Max von Laue succeeded Einstein as managing director. Einstein gave up his position as a director of the institute in April 1933. The Institute took part in the German nuclear weapon project from 1939-1942.

In June 1942, Werner Heisenberg took over as managing director. A year after the end of fighting in Europe in World War II, the institute was moved to Göttingen and renamed the MPG for Physics, with Heisenberg continuing as managing director. In 1946, Carl Friedrich von Weizsäcker and Karl Wirtz joined the faculty as the directors for theoretical and experimental physics, respectively.

In 1955 the institute made the decision to move to Munich, and soon after began construction of its current building, designed by Sep Ruf. The institute moved into its current location on September 1, 1958 and took on the new name the Max Planck Institute for Physics and Astrophysics, still with Heisenberg as the managing director. In 1991, the institute was split into the Max Planck Institute for Physics, the MPG Institute for Astrophysics [Max-Planck-Institut für Astrophysik] (DE) and the MPG Institute for extraterrestrial Physics [MPG Institut für extraterrestrische Physik] (DE).