الفهرس | Only 14 pages are availabe for public view |
Abstract Design, fabrication and utilization of electron sources have gained unique importance in fundamental research and industrial applications. In any electron gun the geometry of the electrodes decides the main beam optics comprising of uniform flow of electrons and beam waist. So that, in the present work, A Pierce-type electron gun with spherical anode has been numerically analyzed and validated experimentally. The regulated output beam is applied to poly (ethylene terephthalate) PET membrane to improve its surface wettability. In the simulation study of the electron gun, it has been proven that, around a certain value of the aspect ratio, the resultant beam geometry could be suitably controlled. The minimum electric field required to prevent beam expansion due to space charge effect has been estimated and it is found to be proportional to the cubic root of the distance from the anode to the target. Also, it is proved that the minimum beam radius is realized at the minimum beam perveance and the maximum beam convergence angle. As a result, this reveals that, the gun geometry controls the beam emittance. The gun design analysis proposed here helps to choose the better operating conditions suitable for low energy electron beam bombardment and/or injection applications into plasma medium for plasma acceleration. Experimentally, an investigation has been made for the extraction characteristics and beam diagnosis for the electron gun. The accelerating voltage increases the electron beam currents up to 250 mA at accelerating voltage 75kV and decreases the beam perveance, beam waist and beam emittance. The minimum beam radius could be found at the minimum beam perveance and maximum convergence angle. Also ii Abstract the increase of the accelerating voltage increases the beam fluence rate up to 1.3 x 1019 e/min.cm2 due to the increase of the extracted current. Tracing the electron beam profile by X-Y probe scanner along the beam line at two different places reveals that the spherical anode produces an convergent beam. The electron beam could be suited for the two suggested experiments in our lab, surface modifications of polymers and plasma acceleration. By using a low energy electrons a number of investigation are being carried out in several areas such as, irradiation effects on surface properties of semiconductors, metals and polymers. In this work, the PET membranes were treated by low energy electron beam with different fluence. The induced surface modifications and the wettability of the electron beam treated PET membranes are studied and analyzed by different methods. CASINO V2.481 Monte Carlo based simulation software is used to investigate the electrons diffusion into the PET membrane which is found to diffuse to the range 70m at accelerating voltage 75kV. Also it is used to study the deposited energy distribution into PET membrane. It shows that the deposited electron energy is Gaussian distributed. Fourier transform infrared spectroscopy (FTIR) shows the creation of hydrophilic groups on the surface which are responsible for the increase of surface hydrophilicity and wettability. The atomic force microscopy (AFM) observation reveals that the surface topography changes after electron beam treatment. The increased wettability of the PET membrane is studied by employing the contact angle method and surface free energy analysis. The contact angle decreases and the surface free energy increases upon electron beam treatments. Electron beam treatment of PET film improves its wettability, adhesion and then its biocompatibility. |