Experimental Evidence of Charge Separation (Double Layer) in Laser-Produced Plasmas

Ludmirsky, A.; Eliezer, S.; Arad, B.; Borowitz, A.; Gazit, Y.; Jäckel, S.; Krumbein, A. D.; Salzmann, David; Szichman, H.

doi:10.1109/tps.1985.4316381

Cited by 26 publications

(13 citation statements)

References 11 publications

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“…The inset shows the corresponding time-resolved FC currents which were transformed to the ion fronts. multi-peak target current occurs (Ludmirsky et al, 1985;Borowitz et al, 1987). Thus, from Figure 3 we can deduce that each double layer reaches a maximum in the charge density ρ(x,t) = e(Zn i − n e ) at the ion front located at a critical distance, x cr from the target, where Z is the ion charge number, n i is the ion density, and n e is the electron density.…”

Section: Resultsmentioning

confidence: 93%

Characteristics of target polarization by laser ablation

et al. 2015

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Experimental results are obtained concerning the target polarization, which aptly characterizes the laser ablation. The charge separation in the laser-produced plasma, structure of the ion front, and the current of fast electrons expanding into the vacuum chamber ahead of ions are of crucial importance for the interpretation of multi-peak structure of target currents appearing much later than the laser pulse. Of particular interest is the correlation between the partial maxima in the time-resolved target current and the square root of mass number of ionized species. The late-time negative charging of targets provides evidence for production of very slow ions by ionization of neutrals ablated at the target crater by radiation from plasma produced by 23 ns excimer krypton fluoride laser.Keywords: Target current in laser-produced plasmas; positive and negative target polarization; space structure of ion front

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Section: Resultsmentioning

confidence: 93%

Characteristics of target polarization by laser ablation

et al. 2015

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“…The existence of the electric fields in plasma surfaces had been shown directly by electron beam probes and from electrostatic acceleration of a small number of the nonlinear force-accelerated ions. A more systematic experiment was done by Eliezer and Ludmirsky (1983), Ludmirsky et al (1985), and Eliezer et al (1986) where the temporal dependence of charge of the expanding plasma and the temporal change of the target potential were measured. A very unexpected observation was that the plasma leaving the target was first positively charged and then negatively charged.…”

Section: Electric Fields and Dl's With Laser Interactionsmentioning

confidence: 99%

A new hydrodynamic analysis of double layers

1987

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A genuine two-fluid model of plasmas with collisions permits the calculation of dynamic (not necessarily static) electric fields and double layers inside of plasmas including oscillations and damping. For the first time a macroscopic model for coupling of electromagnetic and Langmuir waves was achieved with realistic damping. Starting points were laser-produced plasmas showing very high dynamic electric fields in nonlinear force-produced cavitous and inverted double layers in agreement with experiments. Applications for any inhomogeneous plasma as in laboratory or in astrophysical plasmas can then be followed up by a transparent hydrodynamic description. Results are the rotation of plasmas in magnetic fields and a new second harmonics resonance, explanation of the measured inverted double layers, explanation of the observed density-independent, second harmonics emission from laser-produced plasmas, and a laser acceleration scheme by the very high fields of the double layers.

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“…A large-aperture antenna is typically necessary for forming the narrow beam -the beam width θ 1/2 [deg] can be approximated by 70 × λ/D, where λ is the wavelength of radiated microwaves [m] and D is the apeture length [m] [3,4]. We propose a laser-driven GPR (LGPR) using microwaves radiated from a laser plasma [5].LGPR does not require a large-aperture antenna to sense a remote location because it generates a laser plasma that acts as a microwave radiator adjacent to the survey area, which is equivalent to a transmission antenna close to the survey area.Electromagnetic waves at various frequency ranges (from MHz to THz), radiate from laser-produced plasmas [6][7][8][9][10][11][12][13]. The radiation is caused by the following processes.…”

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confidence: 99%

“…Electromagnetic waves at various frequency ranges (from MHz to THz), radiate from laser-produced plasmas [6][7][8][9][10][11][12][13]. The radiation is caused by the following processes.…”

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confidence: 99%

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Nondestructive Sensor Using Microwaves from a Laser Plasma

Nakajima

Shimada

Somekawa

et al. 2009

Plasma and Fusion Research

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Ground penetrating radar (GPR) is a nondestructive sensor technology for detecting underground objects. GPR requires large-aperture antennas to survey a remote location precisely because of the expansion of microwaves. We propose a laser-driven GPR (LGPR) that uses microwave radiation from a laser plasma to achieve remote sensing.LGPR is expected to provide good spatial resolution with a small antenna. We selected a subnanosecond laser pulse as a suitable radiator for LGPR (L-S band). Experimental results show that the LGPR system can detect aluminum disks buried in sand. Ground penetrating radar (GPR) is a well-known nondestructive sensor technology that uses microwave echoes to find objects underground and examine building structures [1,2]. Recently, demand has increased for remote sensing technology for landmine detection. Conventional GPR is effective only at a close range, or near the detection area. This is because an increase in the distance between the GPR and the remote survey area increases the area irradiated by the microwave, which leads to a deterioration in the angular resolution of the GPR. The microwave beam width must be as narrow as possible to prevent such deterioration. A large-aperture antenna is typically necessary for forming the narrow beam -the beam width θ 1/2 [deg] can be approximated by 70 × λ/D, where λ is the wavelength of radiated microwaves [m] and D is the apeture length [m] [3,4]. We propose a laser-driven GPR (LGPR) using microwaves radiated from a laser plasma [5].LGPR does not require a large-aperture antenna to sense a remote location because it generates a laser plasma that acts as a microwave radiator adjacent to the survey area, which is equivalent to a transmission antenna close to the survey area.Electromagnetic waves at various frequency ranges (from MHz to THz), radiate from laser-produced plasmas [6][7][8][9][10][11][12][13]. The radiation is caused by the following processes. An intense laser pulse creates a laser plasma. The generated electrons and ions are accelerated toward the outside of the plasma by thermal pressure or Ponderomotive forces. The light electrons receive greater acceleration than the heavy ions. Charge separations are induced in the plasma by different expansion speeds of electrons and ions, which excite the electric dipole moments. These flickering author's e-mail: nakajima-h@ile.osaka-u.ac.jp electric dipole moments radiate electromagnetic waves. It was reported that the radiation frequency spectrum corresponded to the laser-pulse envelope [8,13]. A subpicosecond laser pulse has an optimal duration for the terahertz range [8][9][10][11]. We chose a subnanosecond laser pulse as the optimal duration for L-S band (0.5-4 GHz), which is regarded as a suitable frequency range for the GPR [3]. In this article, the spectrum of the microwaves radiated from laser plasma created by a subnanosecond laser pulse was measured. Using a LGPR system with a subnanosecond laser pulse, aluminum disks (Φ 7, 15, and 26 cm) were detected under a layer of sand. Figu...

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Experimental Evidence of Charge Separation (Double Layer) in Laser-Produced Plasmas

Cited by 26 publications

References 11 publications

Characteristics of target polarization by laser ablation

Characteristics of target polarization by laser ablation

A new hydrodynamic analysis of double layers

Nondestructive Sensor Using Microwaves from a Laser Plasma

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