filamentary structure performance in dense plasma focus
TRANSCRIPT
University of Toyama, Japan
Hamid Reza Yousefi
Filamentary Structure Performance
in Dense Plasma Focus
IWPDA2009
2-3 July
1-Current filaments formation and application in
dense plasma focus(DPF)
2-Hot spots formation and mechanisms in
dense plasma focus(DPF)
Auroral filaments derived from
Birkeland currents Solar Coronal Streamers
Comet tailSolar Coronal Streamers
NGC 6751, enlarged structure
Filamentary structures in cosmos
Most PNe show evidence of filamentary
micro-structures
NGC 6751, the Glowing Eye Nebula. Credit: NASA,
Nebula is a cloud of gas ejected several thousand years
ago from the hot star
Intense lightning and Solar flare
Intense lightening shows current
filaments
Solar flare driven by very strong
magnetic field
Core Part of DPF Device
50
100
242
AnodeInsulator
unit: mm
Core Part of DPF Device
10050
100
AnodeInsulator
Cathode, consist of 24 rods
230
unit: mm
Initial breakdown Coaxial stage Coaxial to radial stage
Radial compression Final constriction or Focus
Prof. Maria Magdalena Milanese IEEE transaction on plasma science 2007,
1 2 1 2
1
2
3
4
5 67
8
9
10
1112Radial compression
Focus
Our result
shows current
filaments
track on the anode
head
Current filaments penumbra in DPF
1234
56
7 89 1011
12 13 1415
1617
1819
2021
Anode
1Radial filaments in a plasma layer during its axial motion and its
radial collapsein DPF, M.Sadowski etal,Plasma Sources Sci. Technol.
17 (2008) 024001 (13pp)
plasma filaments during the
radial collapse phase and quasi-
axial filaments
Filamentary structure in plasma focus
W.H.Bostick, IEEE Transactions on plasma science.vol.ps-14,No.6.1986
Current Filament inDPF from top viewBy W.H.Bostick
Current- Carrying loops in Plasma
Focus
W. H. Bostick, et al., "Pair production of plasma vortices," Phys. Fluids, vol. 9, p. 2079, 1966.
J.W.Mather and A.H.Williams, Phys. Fluids, vol. 9, p. 2081, 1966.
3W.H.Bostick, IEEE Transactions on plasma science.vol.ps-14,No.6.1986
Our result:
Current filament track on the anode head
Mather and Bostick both believed the filamentary structure in plasma focus, but Bostick
concluded in his paper that the mechanism of neutron production from the dense plasma
focus is the coalescing of “paired “filaments at the end of the center electrode which
was in contrast with Mather's idea: Mather also believe the filamentary structure and
paired effect but he also believed that at 1 µs , the filamentary pattern diminishes and
uniform glow devoid of any noticeable filamentary structure
3W.H.Bostick
Initially, proton, boron and electron plasmas are uniformly
distributed throughout the system. In order to produce the
current in the z direction, we drive the electric field Ez
uniformly in the simulation domain.
Other scenario of current filamentation
PIC simulation of current filamentation
driven by external electric field in proton-boron-electron plasma
During the period between ωpet = 2.5 and 25.0 when the external
electric field is imposed in the system, the current induced
in the system alternative current and its intensity is
weak with small scale structure
ωpet = 50 ωpet = 60
ωpet = 70 ωpet = 80
Time evaluation of the spatial distribution of current density Jz/(neqc)
ωpet
Time history of Magnetic
field energy
ωpet
ωpet= 110 ωpet= 130
ωpet= 150 ωpet= 170
ωpet= 170
Time evaluation of the spatial distribution of current density Jz/(neqc)
Magnetic field vector Electron density
Proton density Boron density
ωpet = 170
ωpet = 170
Current density at ωpet = 1000.
ωpet = 1000.
Magnetic field vector Bx vs. By ωpet = 1000.
We found that after turning of the external electric field, the system becomes
unstable against the Weibel-like instability, resulting in the formation of many
small current filaments, In the nonlinear stage of the instability,the current loops
continue to coalesce and finally two current filaments with shell structure of which
current is reverse each other are formed..
The initial phase of the current generation with the cell structure is similar in
Character to the well-known Weibel instability that is caused by the
temperature anisotropy..
1
2
3
4
25mm,
45kV
Next experiment we did, is another scenario of current
filamentation in the atmospheric pressure
Time interval between two frame
10ms
High Voltage
d
Ф=6.25cm, d=2.5cm
Atmosphere pressure
5
6
Low temperature plasma (Te< 5ev) constitutes a mixture
of electrons, ions and neutral atoms
High temperature plasma (with Te>10ev) Almost completely
ionized a mixture of electrons, nuclei
Initial temperature in dense plasma focus
(DPF) is around 5-10ev
Therefore, in the initial phase of DPF energy is not
enough to completely ionized the current sheath
then current filamentation driven, can be the result of a
minimal energy configuration in which the current
circulates mainly in to the channels to produce current
filaments.
One assumption for current filamentation in DPF
Cathode rodCathode rod
Anode
We can conclude schematic diagram of current
filamentation , current coalescences and pinch
formation in DPF
Anode
Insulator
Magnetic reconnection and Plasmoid formation when
two current filaments approach each other and collide
J
Bθ1Bθ2
J Current-loop
Magnetic energy
convert to kinetic
energy
After Magnetic
reconnection
BθT=0
From top
view
Magnetosonic shock
waveMagnetosonic shock
wave
Plasmoid
Plasmoid
Hot spots
When two current-loops or two current filaments approach each other
and collide, the plasma between them compressed and plasma column is
formed then magnetic reconnection occurs. When two current-loops or
filament collide in the case of complete reconnection plasmoid can
Originate And inside of this region host spots are formed.
This plasmoid can move outward
One might suspect that such hot spots are
formed during the magnetic reconnection
of current filaments in DPF
Therefore we can say,
Our suggestion
Anthony L.Peratt simulated the spiral galaxy formation by interaction of
parallel current-carrying magnetic field filaments
Spiral galaxy taken
with the Spitzer
Space Telescope
When two current filaments with angular
momentum approach each other
Anode
CR-39
film
12µm Al filterPinhole
ф=0.3mm
263 m
m91 m
m15 degree
Experiment condition:
D2 gas , 30kV,
peak current 700kA,
5 focus shot,
Cathode
Ion pinhole camera using SSNTD (CR-39)
(a) at 15o (b) at 10o
(c) at 5o(d) at 0o
Ion tracks obtained with the 12µm aluminum filtered pinhole camera with CR-39
film at different angles with respect to the anode axis. (a) At 15o (b) at 10 o (c) at
5o to the electrode axis inside the PF facility and (d) on the electrode axis inside
the PF facility
Helical armHelical arm
Ring shape
with two shell
Image shows NGC 4736
Galaxy, credit by NASA.
We interpret this as a
vortex of ions like the
Whirlpool galaxy,
with central
concentration
Ion tracks obtained with the 12 µm aluminum
filtered single pinhole camera with CR-39 film
Our recent result of single pinhole camera
We can also interpret,
particles wrap into a spiral due to the fact
that the inner part particles will revolve around the
center faster than the outer part particles
Thank you for your attention
The plasma universe may be eternal and infinite, directly contradicting the Big bang model. In this picture,
swirling streams of electrons and ions form filaments that span vast regions of space. Where pairs of these
filaments interact the particles gain energy and at narrow “pinch” regions produce the entire range of
galaxy types as well as the full spectrum of cosmic electromagnetic radiation. Thus galaxies must lie
along filaments, as they are observed to do on a large scale. The bulk of the filaments are optically
invisible from a distance, much like the related Birkeland currents that reach from the Sun and cause
auroras on Earth. —Credit: A. Peratt, Plasma Cosmology, 1992