Proton beams are utilized in a technique known as wakefield acceleration to generate particle beams. Recent trials have revealed that these beams could fragment into high-density filaments due to their interaction with plasma.
When-Proton-Beams-Strike-Plasma
Scientists at CERN in Switzerland are exploring a potential
method of accelerating electrons by launching a proton beam into plasma within
the AWAKE experiment. However, a challenge with this method, referred to as
wakefield acceleration, arises from its potential to induce instabilities in
the proton beam, thereby weakening its structure and impacting the length and
quality of acceleration.
Livio Verra and
colleagues from the AWAKE Collaboration observed that upon injecting a lengthy
proton beam into plasma, the beam fractured into dense, narrow strips.
Measurements indicate the conditions leading to this phenomenon, termed filamentation
instability.
To initiate their investigations, scientists established
plasma within a lengthy, slender glass tube filled with argon gas. The CERN Super Proton Synchrotron provided
the energy required for the proton beams, injecting 400 GeV high-intensity
proton beams into the tube's end. Metal screens were positioned along the beam
path both before and after the plasma tube to capture proton beam images. From
these transverse profiles, the team discerned the structural alterations caused
by plasma interaction.
Verra and
colleagues noted the emergence of small spots near the beam's core, indicating
filamentation. They determined that proton beams with a radius 1.5 times
greater than the plasma skin depth,
a measure of radiation penetration into plasma, instigated this phenomenon.
The findings suggest that constraining the beam radius below
this threshold can mitigate instability.