ترغب بنشر مسار تعليمي؟ اضغط هنا

Radiation of a charge moving along a corrugated surface with a relatively small period

90   0   0.0 ( 0 )
 نشر من قبل Sergey N. Galyamin
 تاريخ النشر 2019
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

We consider electromagnetic radiation of a charged particle bunch moving uniformly along a corrugated planar metallic surface. It is assumed that the wavelengths under consideration are much larger than the period and the depth of corrugation. Using the method of the equivalent boundary conditions we obtain the Fourier-transform of the Hertz vector. It is demonstrated that the ultra-relativistic bunch excites the surface waves, whereas the volume radiation is absent. Fourier-transforms of the surface wave components and spectral density of energy losses are obtained and analyzed.



قيم البحث

اقرأ أيضاً

We investigate radiation of a charged particle bunch moving through a corrugated planar conductive surface. It is assumed that the corrugation period and depth are much less than the wavelengths under consideration. In this case, the corrugated struc ture can be replaced with some smooth surface on which the so-called equivalent boundary conditions (EBC) are fulfilled. Using the EBC method we obtain expressions for the electromagnetic field of the bunch which are presented in form of spectral integrals. It is demonstrated that the bunch generates surface waves propagating along the corrugations with the light velocity. Also we present results of numerical calculations for electromagnetic field components of surface waves depending on coordinates and show that these dependences can be used for determination of the bunch size.
A method for producing narrow-band THz radiation proposes passing an ultra-relativistic beam through a metallic pipe with small periodic corrugations. We present results of a measurement of such an arrangement at Brookhavens Accelerator Test Facility (ATF). Our pipe was copper and was 5 cm long; the aperture was cylindrically symmetric, with a 1 mm (radius) bore and a corrugation depth (peak-to-peak) of 60 um. In the experiment we measured both the effect on the beam of the structure wakefield and the spectral properties of the radiation excited by the beam. We began by injecting a relatively long beam compared to the wavelength of the radiation, but with short rise time, to excite the structure, and then used a downstream spectrometer to infer the radiation wavelength. This was followed by injecting a shorter bunch, and then using an interferometer (also downstream of the corrugated pipe) to measure the spectrum of the induced THz radiation. For the THz pulse we obtain and compare with calculations: the central frequency, the bandwidth, and the spectral power---compared to a diffraction radiation background signal.
Radiation of charged particles moving in the presence of dielectric targets is of significant interest for various applications in the accelerator and beam physics. The size of these targets is typically much larger than the wavelengths under conside ration. This fact gives us an obvious small parameter of the problem and allows developing approximate methods for analysis. We develop two methods, which are called the ray optics method and the aperture method. In the present paper, we apply these methods to analysis of Cherenkov radiation from a charge moving through a vacuum channel in a solid dielectric sphere. We present the main analytical results and describe the physical effects. In particular, it is shown that the radiation field possesses an expressed maximum at a certain distance from the sphere at the Cherenkov angle. Additionally, we perform simulations in COMSOL Multiphysics and show a good agreement between numerical and analytical results.
A problem of diffraction of a symmetrical transverse magnetic mode $ text{TM}_{0l} $ by an open-ended cylindrical waveguide corrugated inside is considered. A depth and a period of corrugations are supposed to be much less than the wavelength and the waveguide radius. Therefore a corrugated waveguide wall can be described in terms of equivalent boundary conditions, i.e. a corresponding impedance boundary condition can be applied. Both vacuum case and the case of uniform dielectric filling of the waveguide is considered. The diffraction problem is solved using the modified tayloring technique in Jones formulation. Solution of the Wiener-Hopf-Fock equation of the problem is used to obtain an infinite linear system for reflection coefficients, the latter can be solved numerically using the reduction technique.
We investigate the radiation from a charged particle moving outside a dielectric cylinder parallel to its axis. It is assumed that the cylinder is immersed into a homogeneous medium. The expressions are given for the vector potential and for the elec tric and magnetic fields. The spectral distributions are studied for three types of the radiations: (i) Cherenkov radiation (CR) in the exterior medium, (ii) radiation on the guided modes of the dielectric cylinder, and (iii) emission of surface polaritons. Unlike the first two types of radiations, there is no velocity threshold for the generation of surface polaritons. The corresponding radiation is present in the spectral range where the dielectric permittivities of the cylinder and surrounding medium have opposite signs. The spectral range of the emitted surface polaritons becomes narrower with decreasing energy of the particle. The general results are illustrated for a special case of the Drude model for dispersion of the dielectric permittivity of the cylinder. We show that the presence of the cylinder may lead to the appearance of strong narrow peaks in the spectral distribution of the CR in the exterior medium. The conditions are specified for the appearance of those peaks and the corresponding heights and widths are analytically estimated. The collective effects of particles in bunches are discussed.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا