الفهرس 
CHAPTER 1Only 14 pages are availabe for public view
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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
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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.