Effects of High-collision Plasma on Radiation Protection of Human Brain

Objective: The purpose of this paper is to find a reasonable composite structure of electromagnetic protection device, especially the distribution characteristics of plasma parameters and operation conditions. Methods: Due to its high collision frequency, the high-pressure discharge plasma can be usedas a filling medium to take the electromagnetic protection effect. The strategies and algorithmsare presented to solve the propagation characteristics of electromagnetic wave (EMW) in plasma with complex dielectric constant. When the real and imaginary part of permittivity are of the same order of magnitude, the imaginary part value will impact on the feature of plasma dielectric constant, also affect the behavior of propagation of EMW. The propagation process of EMW in virtual human brain (VHB) model is investigated by finite difference time domain method. By optimizing the layout of plasma layer and air layer, an effective phase regulator is constructed, and the reflected wave amplitude is greatly reduced. Results: The simulation results show that plasma makes the amplitude of the electromagnetic fields in VHB decrease to different degrees. their maximum average decrease is about 25% and the corresponding reduction of SAR value is more than 40% in the frequency range of 1.8-3.6GHz. Conclusion: The existence of plasma can make the scalp and muscle possess the excellent performance in resisting the incident of EMW, so that the amplitude of the electromagnetic field inside the brain body is small, so as to effectively protect the brain tissue. These research results have good reference value and engineering applicability for the structure design of protection equipment with high frequency of EMW.