Electromagnetic pulse emission from target holders during short-pulse laser interactions

Abstract

For the first time, a global model of electromagnetic pulse (EMP) emission connects charge separation in the laser target to quantitative measurements of the electromagnetic field. We present a frequency-domain dipole antenna model which predicts the quantity of charge accumulated in a laser target as well as the EMP amplitude and frequency. The model is validated against measurements from several high-intensity laser facilities, providing insight into target physics and informing the design of next-generation ultra-intense laser facilities. EMP amplitude is proportional to the total charge accumulated on the target, but we demonstrate that it is not directly affected by target charging time (and therefore the laser pulse duration) provided the charging time is shorter than the antenna characteristic time. We propose two independent methods for estimating the charging time based on the laser pulse duration. We also investigate the impact of target holder geometry on EMPs using cylindrical, conical and helical holders. Published as: Minenna et al., Phys. Plasmas, 27, 063102 (2020), https://doi.

Analysis of electromagnetic pulses generated from ultrashort laser irradiation of solid targets at CLAPA

“…Therefore, although both the protons and the EMPs gain energy from the laser, no competitive effect is found between them, suggesting that the energy transfer efficiency from the laser is not high. Since the sources of EMPs are mainly attributed to emitted electrons and the target neutralization current, [4,5,8,17] protons in Fig. 4(b) contribute partially to EMPs.…”

“…[4,5] The intensity and distribution of EMPs are strongly related to the laser energy, [6,7] laser duration, [8,9] target size, [10] target shape, [11,12] target thickness, [13] target materials [14][15][16] and target holder. [17] All these critical factors give rise to significant influences on target polarization, potential barrier and hot electrons escaping, which in turn affect the generation of EMPs. [18] To gain insight into the mechanism of EMP generation, a target charging model including dynamics of charge accu-mulation for short-pulse laser-plasma was proposed to reveal the target electric polarization, which was experimentally verified in terms of the laser energy, pulse duration, and target size.…”

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

“…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.…”

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

“…As previously reported, experimental results and theoretical analysis indicated that the intensity of the radiated magnetic field B a was proportional to the charge Q that accumulated at the target [13,25,34,42]. Considering the charge Q is theoretically equivalent to the escaping hot electrons, the increased electrons leaving the target surface leads to a larger amount of charge accumulation, which causes a larger neutralization current and then generates stronger EMPs.…”

“…Meanwhile, some other charged particles such as ions and protons created by laser-target interaction result in electromagnetic radiations [22]. Based on the characteristics of EMPs, some shielding methods including target modification, target holder design [23][24][25], cable processing have been proposed and implemented.…”