الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 287 |  |  |
| | | from | 287 | | |
Abstract
This thesis includes three parts: the first part involving
design, fabrication and construction of a 2.5 kJ coaxial plasma
discharge device, the second part involving the electrical
parameters and efficiency of 2.5 kJ coaxial plasma discharge
device, the third part involving plasma current sheath dynamical
behavior along the coaxial electrodes system
A coaxial plasma discharge device used in this experiment
has the following parts :The discharge chamber consists of two
stainless steel coaxial electrodes separated by an insulator perspex
cylinder of 1.5 cm length at one end, where the breakdown of the
gas discharge takes place. The negative inner electrode is made of
16.5 cm length cylinder of diameters of 3.18 cm. The Positive outer
electrode is made of 35 cm length cylinder of minor diameters of
15.7 cm. The coaxial plasma discharge device is powered by a
capacitor bank of 50 μF . The filled gas is helium gas of pressure in
the range from 0.81 to 3.2 Torr and charging voltage ch V of 10 kV.
Many diagnostic techniques are used in this work, including
a Rogovsky coil, miniature Rogovsky coil, magnetic probe and
voltage divider to measure the discharge current, the radial plasma
current sheath density, the magnetic field induction in axial and
azimuthal directions along the coaxial electrodes, and the voltage
between the coaxial electrodes during the discharge process.
Results of the discharge current measurements and the
voltage between the coaxial electrodes during the discharge process
showed that the maximum discharge current value = 103.64 kA
and 83.14 kA at P = 1.6 Torr and P = 3.2 Torr during the first and
second half cycles of discharge respectively and the maximum
voltage during the first and second half cycles = 2.89 kV at P = 3.2
Torr and 1.85 kV at P= 2 Torr respectively.
Results of the time distribution of power P(t) and energy
( ) 1 E t flow through the coaxial plasma tube cleared that max P(t) and
1 max E (t) = 167.23 MW and 161.3 Joule at t ≈ 3 μ s respectively
during the first half cycle, while at the second half cycle max P(t) and
1 max E (t) = 92.45 MW and 86.39 Joule at ≈ 13 μ s . Gas pressure
distribution of P(t) and ( ) 1 E t showed that max P(t) and 1 max E (t) are
detected at P = 1.6 Torr and 2 Torr during the first and second half
cycles respectively.
Results of total inductance L(t) and total resistance R(t)
cleared that t (min) L and t (max) R are detected at P = 1.6 Torr , 1.2 Torr
and 2.4 Torr for the first, second and third half cycles of discharge
respectively.
The maximum axial velocity of centre of gravity of plasma
current sheath, z V = 1.8 ×105 m/s and 1.44 ×105 m/s at P = 2
Torr at the coaxial electrodes muzzle end, during the first and
second half cycles respectively.
Calculations of the efficiency of the device under
consideration and the drive parameter, D cleared that the maximum
efficiency is obtained at P = 1.6 Torr and its equal to 52.93 % and
that D is decreased with increasing of gas pressure .
Axial distribution of the azimuthal magnetic field induction
θ B and axial plasma sheath velocity z V and acceleration z a along
the coaxial electrodes, showed that the magnetic field induction
reaches a maximum value (Peak ) Bθ = 0.629 Tesla at axial Z = 6 cm
in the third half cycle, and that the maximum velocity was detected
= 3×104 m/s in the third half cycle at Z = 14.5 cm.
Radial plasma current sheath density and axial plasma
sheath velocity z V results at Pressure = 1.8 Torr and different axial
Z distances showed that the maximum radial plasma current sheath
density = 1. 27 ×104 (kA / m2) at Z = 4.75 cm for the second half
cycle, and the maximum z V = 6.25 ×104 m/s at Z = 5 cm for the
second half cycle.
.
Radial plasma current sheath density r J results at axial Z
distance = 9 cm and at different gas pressures showed that the
maximum radial plasma current sheath density = 1×104 kA/m2 in
the second half cycle for pressure = 1.6 Torr.
Maximum axial magnetic force z F = 7×10 6 Newton /m3 and
maximum azimuthal magnetic force F = 2.67×10 6 Newton /m3 θ were
obtained at axial Z distance = 4.75 cm in the second half cycle.
The maximum induced axial magnetic field induction in
axial phase z B was found to be 0.317 Tesla at axial distance Z =
3.5 cm during the first half cycle.
The maximum value of PCS axial velocity is found
≈ 8.8 cm /μ s at Z = 14 cm, r = 5.7 cm from IE axis and at P = 2
Torr.
The axial velocity along the coaxial electrodes was found to
decrease with radial distance from inner electrode axis to outer
electrode inner surface Also, that the device is best optimized for
different material applications with 2.4 Torr filling helium gas
pressure.