The development and application of permanent-magnet EDS based on Halbach structure
With the permanent-magnet EDS (Electro-dynamic Suspension) system as the background, rectilineal PM Halbach structure is introduced. The theory and stability of permanent-magnet EDS system are analyzed which concludes that permanent-magnet EDS system is of greater advantage under high speed condition. Then two present projects based on the the permanent-magnet EDS which aim at actual application, the GA urban maglev train and the Inductrack rocket launch assist system in US, are introduced in details. Adopting double layers PM halbach structure#GA urban maglev train solves the shortage that the levitation-drag ratio is smaller in low speed condition. The Inductrack rocket launch assist system can save fuel and send more payloads. Finally, Permanent EDS research development status home is generalized.
Design, optimization and purity of permanent magnet helical wigglers for free-electron lasers
A helical wiggler field can be produced inside a cylindrical waveguide by properly distributing and orienting an array of permanent magnets within an annular shell surrounding the waveguide. The design and optimization of such wigglers is considered herein, along with assessments of the strength and spectral purity achievable under practical constraints of equally and uniformly magnetized rare-earth cobalt magnets. Starting with the optimum continuum magnetization, a design is derived that differs from Halbach's primarily in that it includes axially directed components of magnetization. A comparison of the two approaches to helical wiggler design is made in terms of the field strength and purity each can achieve under similar constraints. The optimized design is shown to generate stronger and purer helical wiggler fields than Halbach's version for typical parameters. A modified design that uses many small magnets and does not fill the annular space is suggested and evaluated.
Free electron lasers and stimulated scattering from relativistic electron beams
Abstract : Free electron lasers based on stimulated scattering from relativistic electron beams show potential for a new class of coherent radiation sources ranging from millimeter wavelengths down to optical wavelengths and beyond which are characterized by continuous tunability, very high power levels and competitive efficiencies. Here we present a comprehensive fully-relativistic treatment of stimulated backscattering from an electron beam with streaming velocity beta(sub zo)c. The incident pump wave is taken to be a static, circularly polarized, periodic magnetic field with wavenumber K sub O; the frequency of the scattered radiation is beta(sub zo) ck(sub O)/1-beta(sub zo). The analysis is linear in the scattered wave fields, but contains the pump field to all orders. The physical mechanism of the backscattering is provided by the v X B ponderomotive forces acting on the beam electrons in the presence of both the pump and the scattered waves. This force produces a longitudinal charge bunching which in turn gives rise to source currents for the scattered waves.