Absorption of energy from a large amplitude electromagnetic pulse by a collisionless plasma

Abstract

Abstmcr-A seriesof experiments in which an electromagnetic pulse (Em) is propagated through a nitrogen plasma are discussed.The pulse has the general characteristics of an EMP. The pulse is observed as it emerges from the plasma as a function of the plasma parameters. As the electron number density increases, it is found that energy is increasingly absorbed from the pulse, a process due to joule heating. In addition, at higher number densities, ringing of the pulse occurs. The nitrogen pressure in these experiments is sufficiently low so that collisions play only a minor role. Also developed is a theoretical model based on the fluid transport equations. This theory predicts that the electrons of the plasma are attaining a temperature of about 15 eV in that part of the system where .the dc magnetic field is about 80 G. More importantly, it is able to predict the output pulse quite well under the conditions that the ambient nitrogen pressure and the electron number density are low. The theory appears to fail as these parameters are increased.

Transformation of the Shape and Spectrum of an Ultrawideband Electromagnetic Pulse in a “Gigantic” Coaxial Line Filled with Magnetized Plasma

“…Particularly, the theory developed in [4] which leads to simulation criteria like (2) assumes that the pulse duration is significantly less than the period of plasma oscillations f p −1 . For longer pulses, when a significant part of the EMP frequency spectrum is on the order of and below the plasma frequency f p , the contribution of cutoff effects to the transformation of the EMP shape increases [16,17]. If collision effects are considered, then pulse duration τ p should be compared to the electron collision frequency ν.…”

“…On the other hand, it is possible to ensure EMP propagation in plasma along an extended path without refraction losses by using symmetric or coaxial transmission lines installed in the plasma chamber and excited by a pulse generator. This model experiment scenario was first implemented in the late 1970s with compact-about 1 m long-strip lines [17]. However, even in this case estimates and experiments show that the length of the propagation path of nano-and subnanosecond UWB EMPs in plasma should be at least several meters to allow observation of the dispersion and nonlinear effects [16].…”

Gigantic Coaxial Line for Experimental Studies of the Interaction of Nanosecond Electromagnetic Pulses with an Ionized Gas Medium

“…In order to model these phenomena, one has to, first, ensure propagation of an EMP in the form of a transverse TEM mode and, second, create a partially ionized medium with controlled parameters along the path of EMP propagation. The first successful attempts to experimentally study transformations of the EMP waveform during EMP propagation in plasma were made in the USA in the 1970s using pulses, which had durations of about 1 ns, and pulse rise fronts of about 250 ps [18,19]. Within the framework of these studies, the concept of a double plasma-filled transmitting line, which maintained propagation of an EMP in the form of a TEM mode, was realized for the first time.…”

Advanced Radar Absorbing Ceramic-Based Materials for Multifunctional Applications in Space Environment

“…In most cases, stealth technology aims to reduce the radar cross section (RCS) by a suitable shape design and/or by adopting radar absorbing materials and structures [ 8 ]. RAMs are also typically exploited for a variety of applications, such as EM protection from high-intensity radiated fields (HIRF), natural phenomena (lightning), intentional EM interference (IEMI) and nuclear EM pulses (NEMP), as component of shields adopted in particle accelerators, for EM compatibility problems (equipment level shielding, anechoic chambers testing), as well as for human exposure mitigation [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ].…”