Relativistic Electrons Sources

Although very stimulating for the groups active in the field of LPA, experiments performed using thin foils as targets were soon recognized as having a 

As an example of an experimental setup needed for the kind of experiments discussed above, we give now a brief overview of a recent experiment carried out by our group at the SLIC facility at CEA in Saclay (France) [10]. The laser system was the UHI-10 Ti Sa laser, which delivered 65 fs pulses with energy up to 0.7 J. The laser beam was focused by an //5 off-axis parabolic mirror, producing a quasi-gaussian spot where the field parameter ao = c/l aser/mec2, 

The electron density of the produced plasma was diagnosed by means of a Mach-Zehnder interferometer, operated with a small portion of the main pulse, doubled in frequency [29,30]. The electron density along the pulse path was measured to be ne 2 x 1019 cm-3. At this density, the electron plasma wave has a period Tp 25 fs and wavelength Ap ss 7.5 j,m. 

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Synchrotron radiation provides a convenient source of tunable VUV and SXR radiation. Natural synchrotron radiation, emitted by relativistic electrons, is linearly polarized in the plane of their orbit, which is traditionally the configuration used to collect the radiation. However, it is well known that the polarization becomes elliptical if observed above or below the plane of the orbit. 

An Efficient Source of Relativistic Electrons for Medical Applications... 

The electrons lose energy by radiating and so have a limited lifetime. Tired electrons must somehow be replaced. The continuous source of relativistic electrons is in fact the central pulsar. Indeed, at the centre of the expanding nebula is enthroned a rapidly spinning neutron star (turning at some 33 revolutions per second), as witnessed by the punctuated message we receive on Earth. This star is clearly an excellent electron accelerator. 

Luminescent sources are based on the non-equilibrium spontaneous radiation of atoms, ions, and molecules (Fridman Kennedy, 2004), which are excited by strongly nonequilibrium discharges, electron beams, and soforth (as an example, we can point out excimer VUV lamps on the dimers of inert gases excited by relativistic electron beams). 

Synchrotron (ondulator) sources are based on the bremsstrahlung radiation of the relativistic electrons in continuous magnetic fields (synchrotron sources) and space-time-modulated magnetic fields (ondulator sources). 

Another, linearly polarized, radio source in the Crab nebula, where a supernova explosion was observed in the year 1054, leaving behind a pulsating neutron star, could be of similar origin as the radiation in the Milky Way. The likelihood that the pulsar drives the acceleration of both relativistic electrons and of cosmic rays could imply that most cosmic rays in the Galaxy are also... 

The future prospects for selective chemistry research as an aspect of laser development are not as bright as several years ago. With the exception of the quest for a visible chemical laser, most new laser research is oriented towards systems that are patently nonmolecular. The leading candidate for very high power applications is the free electron laser (PEL). In this device, the interaction of a relativistic electron beam with a periodic magnetic structure produces coherent radiation. Such devices on paper can have substantially higher power and efficiency than electric molecular lasers. For moderate power applications, advances in solid state lasers, nonlinear optical conversion processes, and tunable solid state media offer the prospect of broadly tunable compact sources. At low powers, diode lasers and diode laser arrays are gaining increasing application and hold out the promise, when used with solid state media, of versatile tunable sources. 

For even greater X-ray intensities, an X-ray synchrotron source is necessary. Here X-rays are produced by accelerating relativistic electrons (or positrons) around curved paths. The X-rays produced by these means... 

Summary. This Chapter focuses on the investigation of fast electron transport studies in solids irradiated at relativistic laser intensities. Experimental techniques based upon space-resolved spectroscopy are presented in view of their application to both ultrashort Ka X-ray sources and fast ignition studies. Spectroscopy based upon single-photon detection is unveiled as a complementary diagnostic technique, alternative to well established techniques based upon bent crystals. Application of this technique to the study of X-ray fluorescence emission from fast electron propagation in multilayer targets is reported and explored as an example case. 

An expression for 8 in terms of the source and absorber nonrelativistic s electron densities at the origin, s(0) and a(0), respectively, can be obtained by considering the electrostatic interaction between the s electrons and a nucleus with a uniform charge density. A relativistic calculation yields (7) ... 

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