Simulation of electromagnetic pulses generated by escaped electrons in a high-power laser chamber

Abstract

Intensive electromagnetic pulses (EMPs) can be generated when a high-power laser strikes a target. The transient electromagnetic field can have an intensity of up to several hundred kV m −1 with a broad frequency of up to several gigahertz, which may affect diagnostics and interfere with, or even damage, electronic equipment. In this paper, the process in which hot electrons produced by the laser−target interaction radiate EMPs is studied and simulated. The physical process is divided into three stages which are: the production of hot electrons; the escape of hot electrons; and the generation of EMPs. Instead of using a general finite difference time domain (FDTD) method to solve the Maxwell equations, a particle-in-cell method together with a timebiased FDTD method is applied in EMP simulation to restrain high-frequency noise. The results show that EMPs are stronger with higher laser intensity and larger target size.

Spatial and temporal evolution of electromagnetic pulses generated at Shenguang-II series laser facilities

“…The results indicate that EMP produced at SG-II series laser facility is strongly related to the laser modes and the distance from the TCC. Firstly, EMPs induced by SG-II ps PW laser are one order intense than that of SG-II laser with the same distance from TCC, in consistence with some previous reports: EMPs with a much larger amplitude can be generated by intense ps laser facilities than ns laser facilities [10,27], which may be attributed to the higher laser intensity of the SG-II ps PW laser (0.8×10 19 W cm −2 ) compared with the SG-II laser (1.25×10 15 W cm −2 ), supported by the conclusion that the EMP amplitude increased with the laser intensity according to the PIC simulations and experimental results, the energy and number of escaping hot electrons increased when the laser intensity was enhanced, which indirectly led to the increase of EMP amplitude [17]. Moreover, EMP amplitude was found to linearly depend on the laser intensity at the 200 TW laser system (VEGA 2) [28].…”

“…Accordingly, investigations into the possible factors that determine EMPs are conducted, including target configuration and materials [16][17][18][19][20][21][22], laser power and pulse duration [16][17][18]23], target stalk geometry [16,18], etc which laid solid experimental basis for the shielding of EMPs. However, most previous reports mainly focus on the features of EMPs inside the target chamber, while the amplitude and distribution of EMPs outside the target chamber remain unexplored to date, although it is significant for the protection of electronic devices surrounding the target chamber.…”

Laser produced electromagnetic pulses: generation, detection and mitigation

“…A similar numerical model of EMP generation caused by electron emission is described in Ref. [72]. In this case, the EMP associated with emitted electrons was computed with a specially designed code EMPIC-2D.…”

Generation and regulation of electromagnetic pulses induced by hybrid laser pulses interacting with solid targets

“…Figure 4 shows EMP amplitude and the total energy of the SWB signals exhibit the same trends at two locations. In previous reports, EMP amplitude is confirmed to be proportional to the laser intensity [21,34,35]. Because of the unexpected laser energy jitter, to deeply interpret the EMP amplitude and ensure the reliability of experimental conclusions, the picosecond laser intensity averaged for each of the different laser modes is also provided in figure 4.…”

“…Secondly, a return current is formed and propagates along with the target holder to the ground because of the accumulation of a large number of positive charges on the target, which is another key source for EMPs [13]. Thirdly, high-energy rays interact with metals or cables to induce photoelectrons also responsible for EMPs [21]. Meanwhile, some other charged particles such as ions and protons created by laser-target interaction result in electromagnetic radiations [22].…”