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