Radiation induced by relativistic electron showers in the X-ray spectrum of Active Galactic Nuclei

The iron Kα emitted from accreting black holes is thought to be produced by the reprocessing of hard X-ray radiation illuminating the disk. Mechanisms which could produce this hard X-ray radiation are magnetic reconnection in the disk corona or shocks. Both phenomena produce high energy particles whose contribution is usually ignored. In this work, we analyze how the transfer of mechanical energy from relativistic electrons to the circumnuclear gas (accretion disk, BLR) contributes to the X-ray continuum and the iron Kα emission. It is shown that for gas columns comparable to the Thomson depth, the iron Kα yield is comparable to that observed provided that the electron energy is above ∼600 keV and that the total kinetic luminosity of the beam is around log LKIN = 46.6−47.7; this luminosity is comparable to that observed in radio-loud AGNs. The photon index of the X-ray continuum (8 keV−20 keV) generated in such an electron shower is 1 ≤ Γ ≤ 2. Γ and the continuum strength are strongly model-dependent; they are dependent on both the relative orientation between the electron beam and the observer and the radius of the electron beam compared with the characteristic radius of the absorbing medium. The relevance of particle energy transport compared to photon energy transport in the AGN environment is outlined.Peer reviewe

Effects of self-generated electric and magnetic fields in laser-generated fast electron propagation in solid materials: Electric inhibition and beam pinching

We present some experimental results which demonstrate the presence of electric inhibition in the propagation of relativistic electrons generated by intense laser pulses, depending on target conductivity. The use of transparent targets and shadowgraphic techniques has made it possible to evidence electron jets moving at the speed of light, an indication of the presence of self-generated strong magnetic fields

Radiation induced by relativistic electron showers in the X-ray spectrum of Active Galactic Nuclei

The iron Kalpha emitted from accreting black holes is thought to be produced by the reprocessing of hard X-ray radiation illuminating the disk. Mechanisms which could produce this hard X-ray radiation are magnetic reconnection in the disk corona or shocks. Both phenomena produce high energy particles whose contribution is usually ignored. In this work, we analyze how the transfer of mechanical energy from relativistic electrons to the circumnuclear gas ( accretion disk, BLR) contributes to the X-ray continuum and the iron Ka emission. It is shown that for gas columns comparable to the Thomson depth, the iron Ka yield is comparable to that observed provided that the electron energy is above similar to 600 keV and that the total kinetic luminosity of the beam is around log L-KIN = 46.6- 47.7; this luminosity is comparable to that observed in radio-loud AGNs. The photon index of the X-ray continuum ( 8 keV- 20 keV) generated in such an electron shower is 1 less than or equal to Gamma less than or equal to 2. Gamma and the continuum strength are strongly model-dependent; they are dependent on both the relative orientation between the electron beam and the observer and the radius of the electron beam compared with the characteristic radius of the absorbing medium. The relevance of particle energy transport compared to photon energy transport in the AGN environment is outlined

Experimental investigation of fast electron transport through Kα imaging and spectroscopy in relativistic laser-solid interactions

Abstract The study of the basic physical processes underlying the generation of fast electrons during the interaction of high-intensity short laser pulses with solid materials and the transport of these fast electrons through the target material are of great importance for the fast ignition concept for inertial confinement fusion and for the development of ultra-short X-ray sources. We report on the experimental investigation of fast electron transport phenomena by means of the spatial and spectral characterization of the X-ray emission from layered targets using bent crystal spectrometers and a new diagnostic technique based on a pinhole-camera equipped with a CCD detector working in single-photon regime for multi-spectral X-ray imaging The experiments were carried out at relativistic laser intensities, both in the longer (≃ps) pulse interaction regime relevant for fast ignition studie

On the excitation of the FeK alpha line in AGNs by the impact of beams of highly relativistic electrons on the disk

The propagation of highly relativistic electron beams in dense matter induces a cascade of secondary particles that spreads in the environment redistributing efficiently the beam energy in the medium. Such a highly relativistic beams are expected to be produced in the magnetic reconnection events associated with the flaring activity of the magnetized accretion disks of the AGNs. This contribution presents a quantitative analysis of the possible role of these beams in the excitation of the Fe K alpha line.Unidad Deptal. de Astronomía y GeodesiaFac. de Ciencias MatemáticasTRUEpu

Numerical and Theoretical Studies of Basic Issues for Fast Ignition: from Fast Particle Generation to Beam Driven Ignition

In all recently proposed schemes for laser-driven Fast Ignition (FI) of Inertial Confinement Fusion (ICF) targets, two key elements are the conversion of the energy of a Petawatt laser pulse into a beam of strongly relativistic electrons and its transport through a dense plasma or a solid target. The electron beam may either drive ignition directly or be exploited to accelerate a proton beam which in turn is used to ignite the target. Both approaches to FI involve a number of physical processes that are challenging for theory and simulation. In this paper, theoretical and numerical investigations are presented concerning several fundamental issues of relevance to FI, including electron beam instabilities, electron transport in solid-density materials, and requirements for proton beam driven ignition

Fundamental Issues in Fast Ignition Physics: from Relativistic Electron Generation to Beam Driven Ignition

In recent years, several schemes for laser-driven fast ignition (FI) of inertial confinement fusion targets have been proposed. In all schemes, a key element is the conversion of the energy of a Petawatt laser pulse into a beam of strongly relativistic electrons and the transport of the latter into a dense plasma or a solid target. The electron beam may either drive ignition directly or be used to accelerate a proton beam which is In turn used to ignite. Both ignition scenarios involve a number of physical processes which are widely unexplored and challenging for theory and simulation. In this contribution, we present theoretical and numerical investigations of several fundamental issues of relevance to F1 from the stage of electron generation and transport to that of proton energy deposition, including electron beam instabilities, electron transport in solid-density plasma, proton transport in the coronal plasma, and requirements for proton beam driven ignition