Ring-shaped electromagnets, when arranged linearly, can generate magnetic fields similar to a tube with a cone at either end—a structure that can repel charged particles entering into a cone again along their path of entry.
Since the 1950s, these devices, called “magnetic mirrors,” have been noted not only as a comparatively easy way to confine plasma but have also proven to be inherently leaky.
In a study reported in EPJ D, physicists, who were headed by Wen-Shan Duan at Northwest Normal University, and Lei Yang at the Chinese Academy of Sciences, both in Lanzhou, China, demonstrated that the leaks in the plasma could be reduced on fulfilling particular conditions.
The physicists used computer simulations to analyze the dynamic properties of a high-energy proton plasma beam within a magnetic mirror and to fine-tune the simulation settings to increase its confinement.
Initially, Duan, Yang, and their coworkers changed the “mirror ratio,” which is defined as the ratio of strongest magnetic field in the mirror (at each cone’s tip) to the weakest magnetic field (on the tube’s surface). They discovered that higher mirror ratios, which could be achieved using finely tuned electromagnet configurations, were directly proportional to lower loss rates and longer confinement times.
Then, they discovered that there was a significant effect due to the initial conditions of the plasma beam itself, including its temperature, density, trajectory, and velocity. The simulated high-energy beam could travel in a tight spiral pattern within the mirror once all these properties are optimized, thereby ensuring maximum confinement.
The knowledge gained by Duan and Yang’s research team can solve a decades-old issue of high loss rates and low plasma confinement times in magnetic mirrors. This could render them perfect for interesting new particle physics experiments, including the production and confinement of electron-positron plasmas and antihydrogen atoms, as well as the high-energy antiproton deceleration.