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Register a new userInvestigation of the longitudinal component of an electron electromagnetic field under condition of the shadowing effect
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In this paper we present the method and experimental results of the investigation of a longitudinal component of relativistic electron electromagnetic field in the shadow area of a transversal component. We show experimentally, that in a region, comparable with the formation length area no shadowing effect of the longitudinal component of relativistic electron electromagnetic field appears. This is important for understanding of possibility of the shadowing effect in Smith-Purcell radiation and some other radiation types.
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The features of electromagnetic field of relativistic electrons passing through a hole in an absorbing screen as a function of the distance from the screen in range of radiation formation length were investigated. The analysis of obtained results allows approving the existence of an unstable state of electron with a particularly deprived its coulomb field, which turns into a stable state of usual electron at a distance of a radiation formation length.
Three dimensional, particle-in-cell, fully electromagnetic simulations of electron plasma wake field acceleration in the blow out regime are presented. Earlier results are extended by (i) studying the effect of longitudinal density gradient; (ii) avoiding use of co-moving simulation box; (iii) inclusion of ion motion; and (iv) studying fully electromagnetic plasma wake fields. It is established that injecting driving and trailing electron bunches into a positive density gradient of ten-fold increasing density over 10 cm long Lithium vapor plasma, results in spatially more compact and three times larger, compared to the uniform density case, electric fields ($-6.4 times 10^{10}$ V/m), leading to acceleration of the trailing bunch up to 24.4 GeV (starting from initial 20.4 GeV), with an energy transfer efficiencies from leading to trailing bunch of 75 percent. In the uniform density case $-2.5 times 10^{10}$ V/m wake is created leading to acceleration of the trailing bunch up to 22.4 GeV, with an energy transfer efficiencies of 65 percent. It is also established that injecting the electron bunches into a negative density gradient of ten-fold decreasing density over 10 cm long plasma, results in spatially more spread and two-and-half smaller electric fields ($-1.0 times 10^{10}$ V/m), leading to a weaker acceleration of the trailing bunch up to 21.4 GeV, with an energy transfer efficiencies of 45 percent. Inclusion of ion motions into consideration shows that in the plasma wake ion number density can increase over few times the background value. It is also shown that transverse electromagnetic fields in plasma wake are of the same order as the longitudinal (electrostatic) ones.
Parametric X-ray radiation (PXR) from relativistic electrons moving in a crystal along the crystal-vacuum interface is considered. In this geometry the emission of photons is happening in the regime of extremely asymmetric diffraction (EAD). In the EAD case the whole crystal length contributes to the formation of X-ray radiation opposed to Laue and Bragg geometries, where the emission intensity is defined by the X-ray absorption length. We demonstrate that this phenomenon should be described within the dynamical theory of diffraction and predict a radical increase of the PXR intensity. In particular, under realistic electron-beam parameters, an increase of two orders of magnitude in PXR-EAD intensity can be obtained in comparison with conventional experimental geometries of PXR. In addition we discuss in details the experimental feasibility of the detection of PXR-EAD.
It is shown that the mathematical form, obtained in a recent paper, for the angular momentum of the electromagnetic field in the vicinity of electric charge is equivalent to another form obtained previously by Cohen-Tannoudji, Dupont-Roc and Gilbert. In this version of the paper an improved derivation is given.
The initial modulation in the scheme for Coherent electron Cooling (CeC) rests on the screening of the ion charge by electrons. However, in a CeC system with a bunched electron beam, inevitably, a long-range longitudinal space charge force is introduced. For a relatively dense electron beam, its force can be comparable to, or even greater than the attractive force from the ions. Hence, the influence of the space charge field on the modulation process could be important. If the 3-D Debye lengths are much smaller than the extension of the electron bunch, the modulation induced by the ion happens locally. Then, in that case, we can approximate the long-range longitudinal space charge field as a uniform electric field across the region. As detailed in this paper, we developed an analytical model to study the dynamics of ion shielding in the presence of a uniform electric field. We solved the coupled Vlasov-Poisson equation system for an infinite anisotropic electron plasma, and estimated the influences of the longitudinal space charge field to the modulation process for the experimental proof of the CeC principle at RHIC.
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