Advanced design of a low energy electron source
A multiphysics-based modeling design of a low energy electron source using a thermionic cathode is described in this paper. The proposed device produces a narrow beam employable in delicate applications where dimensions are critical. The effects of multiple physics influencing factors due to the cathode heating over the beam dynamics have been predicted through a multiphysics design approach. This paper would provide the needed knowledge for virtual prototyping of such devices. For this aim, several strategies have been adopted to obtain a simple model, which shows clearly the investigated mechanisms. According to this study, the appropriate materials and shapes can be chosen.
Multiphysics Design of a Klystron Buncher
The Multiphysics design of a 130 GHz klystron Buncher cavity is described in this paper. In this high frequency range, dimensions are critical and expose the device to multiple physics effects, due to the power dissipations, affecting the electromagnetic performances. The proposed device is integrated with a carbon nanotube cold cathode in order to reduce thermal expansion and an opportune airflow controls the temperature. The multiphysics design is performed on COMSOL in order to ensure the desired behavior in operative conditions. Electromagnetic fields and scattering parameters have been computed when the Buncher is subjected to multiple physics factors. The appropriate geometries and materials and can be found.
A Formulation of Convection for Stellar Structure and Evolution Calculations without the Mixing-Length Theory Approximations. II. Application to alpha Centauri A and B
We have constructed a series of models of Alpha Centauri A and Alpha Centauri B for the purposes of testing the effects of convection modeling both by means of the mixing-length theory (MLT), and by means of parameterization of energy fluxes based upon numerical simulations of turbulent compressible convection. We demonstrate that while MLT, through its adjustable parameter alpha, can be used to match any given values of luminosities and radii, our treatment of convection, which lacks any adjustable parameters, makes specific predictions of stellar radii. Since the predicted radii of the Alpha Centauri system fall within the errors of the observed radii, our treatment of convection is applicable to other stars in the H-R diagram in addition to the sun. A second set of models is constructed using MLT, adjusting alpha to yield not the 'measured' radii but, instead, the radii predictions of our revised treatment of convection. We conclude by assessing the appropriateness of using a single value of alpha to model a wide variety of stars.