Measurement of Fast-Electron Energy Spectra and Preheating in Laser-Irradiated Targets

Hares, J. D.; Kilkenny, J. D.; Key, M. H.; Lunney, J. G.

doi:10.1103/physrevlett.42.1216

Cited by 154 publications

(42 citation statements)

References 8 publications

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“…Kα emission was first observed in the pioneering early work of Zigler et al [1] and Key et al [2]. Kα tracer layers were also used in connection with the first observation of collective effects (due to resistive electric fields) in hot electron penetration in matter in 1982, i.e., long before the advent of short-pulse high-intensity lasers.…”

Section: Introductionmentioning

confidence: 99%

Effects of target heating on experiments usingKαandKβdiagnostics

et al. 2015

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We describe the impact of heating and ionization on emission from the target of Kα and Kβ radiation induced by the propagation of hot electrons generated by laser-matter interaction. We consider copper as a test case and, starting from basic principles, we calculate the changes in emission wavelength, ionization cross section, and fluorescence yield as Cu is progressively ionized. We have finally considered the more realistic case when hot electrons have a distribution of energies with average energies of 50 and 500 keV (representative respectively of "shock ignition" and of "fast ignition" experiments) and in which the ions are distributed according to ionization equilibrium. In addition, by confronting our theoretical calculations with existing data, we demonstrate that this study offers a generic theoretical background for temperature diagnostics in laser-plasma interactions.

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Section: Introductionmentioning

confidence: 99%

Effects of target heating on experiments usingKαandKβdiagnostics

et al. 2015

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“…They found that enhanced intensities of the satellite lines can be explained by the presence of non-thermal energy distributions that have higher and narrower peaks than the Maxwell distribution. This type of distribution functions has been used in the analysis of non-thermal distribution in laboratory plasma (Hares et al 1979) as well. In this paper we refer to them as n-distributions.…”

Section: Introductionmentioning

confidence: 99%

Diagnostics of non-thermal distributions in solar flare spectra observed by RESIK and RHESSI

Kulinová

Kašparová

Dzifčáková

et al. 2011

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Context. During solar flares an enormous amount of energy is released, and the charged particles, like electrons, are accelerated. These non-thermal electrons interact with the plasma in various parts of solar flares, where the distribution function of electrons can therefore be non-Maxwellian. Aims. We focus on the non-thermal components of the electron distribution in the keV range and analyse high-energy resolution X-ray spectra detected by RESIK and RHESSI for three solar flares. Methods. In the 2-4 keV range we assume that the electron distribution can be modelled by an n-distribution. Using a method of line-intensity ratios, we analyse allowed and satellite lines of Si observed by RESIK and estimate the parameters of this n-distribution. At higher energies we explore RHESSI bremsstrahlung spectra. Adopting a forward-fitting approach and thick-target approximation, we determine the characteristics of injected electron beams. Results. RHESSI non-thermal component associated with the electron beam is correlated well with presence of the non-thermal n-distribution obtained from the RESIK spectra. In addition, such an n-distribution occurs during radio bursts observed in the 0.61-15.4 GHz range. Furthermore, we show that the n-distribution could also explain RHESSI emission below ∼5 keV. Therefore, two independent diagnostics methods indicate the flare plasma being affected by the electron beam can have a non-thermal component in the ∼2-5 keV range, which is described by the n-distribution well. Finally, spectral line analysis reveals that the n-distribution does not occupy the same location as the thermal component detected by RHESSI at ∼10 keV.

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“…Early experiments using intense nanosecond neodymium-glass and CO 2 laser irradiation recorded X-ray spectra of low Z elements, typically aluminum, and these studies inferred hot electron energies exceeding 10 keV [18,19]. In addition to electron propagation into buried X-ray fluor layers, lateral energetic electron propagation far outside the focal spot, believed to be guided by strong magnetic and electric fields, was also observed [20,21].…”

Section: Spectra Produced By Picosecond Laser Irradiationmentioning

confidence: 99%

Laser-produced MeV electrons and hard X-ray spectroscopic diagnostics

Seely

Hudson

2010

Nuclear Instruments and Methods in Physics Research Section A:

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Keywords: X-ray source size MeV electron propagation K-shell transitions X-ray spectroscopy a b s t r a c t A new spectroscopic technique for the measurement of the sizes of hard X-ray sources produced by the irradiation of solid-density targets by intense laser radiation is discussed. The technique is based on the source broadening of K shell spectral lines from targets irradiated by intense picosecond laser pulses. The spectra are recorded by a modified Cauchois type spectrometer, where the detector is placed far behind the Rowland circle where source broadening dominates instrumental resolution. The laser irradiation with focused intensity greater than 10 18 W/cm 2 produces relativistic electrons that propagate from the focal spot into the surrounding target material with mm range. The energetic electrons produce 1 s electron ionization and K shell radiation with picosecond duration that can be utilized for transient radiography of dense objects including evolving dense plasmas. However, the hard X-ray source has mm lateral size when extended targets are utilized while a much smaller source size (of order 10 mm) is necessary for high-resolution point projection radiography. The lateral source size can be greatly reduced by using targets with limited aspect to the radiography object such as thin foils and wires, but the brightness of these sources is greatly reduced compared to thick planar targets. Studies indicate that the electron range and source size can also be reduced by utilizing an electrically resistive target material such as teflon. In this case the electron propagation from the focal spot is inhibited by a weak return current and incomplete space-charge neutralization. These experimental results are important not only for producing a small hard X-ray source for picosecond radiography but also for reducing the lateral propagation of energetic electrons that can be detrimental to fast-ignition fusion.Published by Elsevier B.V.

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Measurement of Fast-Electron Energy Spectra and Preheating in Laser-Irradiated Targets

Cited by 154 publications

References 8 publications

Effects of target heating on experiments usingKαandKβdiagnostics

Effects of target heating on experiments usingKαandKβdiagnostics

Diagnostics of non-thermal distributions in solar flare spectra observed by RESIK and RHESSI

Laser-produced MeV electrons and hard X-ray spectroscopic diagnostics

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