Filamentary Structure Performance In Dense Plasma Focus

Filamentary Structure Performance in Dense Plasma Focus

Hamid Reza Yousefi University of Toyama, Japan

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

Solar Coronal Streamers

Comet tail

Filamentary structures in cosmos NGC 6751, the Glowing Eye Nebula. Credit: NASA, Nebula is a cloud of gas ejected several thousand years ago from the hot star

NGC 6751, enlarged structure

Most PNe show evidence of filamentary micro-structures

Intense lightning and Solar flare

Intense lightening shows current filaments

Solar flare driven by very strong magnetic field

Core Part of DPF Device

Insulator

Anode

50

100 242

unit: mm

Core Part of DPF Device Cathode, consist of 24 rods

Insulator

Anode

50

100

100 230

unit: mm

Current filaments penumbra in DPF Prof. Maria Magdalena Milanese IEEE transaction on plasma science 2007, 5

6

4

7 8

Anode

3 9 2 1

Radial compression Initial breakdown

1 2

1 2

Radial compression

10

11 12 Coaxial stage Focus 9 10 12 13 14 7 11 6 8 15 16 5 17 4 18 3 19 2 20 1 21

Final constriction or Focus

Coaxial to radial stage

Our result shows current filaments track on the anode head

Filamentary structure in plasma focus

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)

Current Filament in DPF from top view By W.H.Bostick

plasma filaments during the radial collapse phase and quasiaxial filaments

W.H.Bostick, IEEE Transactions on plasma science.vol.ps-14,No.6.1986

Current- Carrying loops in Plasma Focus 3W.H.Bostick

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 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

Other scenario of current filamentation

PIC simulation of current filamentation driven by external electric field in proton-boron-electron plasma 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.

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

Time evaluation of the spatial distribution of current density Jz/(neqc) ωpet = 50

ωpet = 70

ωpet = 60

ωpet = 80

Time history of Magnetic field energy

ωpet

ωpet

ωpet= 110

ωpet= 150

ωpet= 130

ωpet= 170

ωpet= 170

Time evaluation of the spatial distribution of current density Jz/(neqc)

Magnetic field vector ωpet = 170

Proton density

ωpet = 170

Electron density

Boron density

ωpet = 1000.

Current density at ωpet = 1000.

Magnetic field vector Bx vs. By ωpet = 1000.

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..

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. .

Next experiment we did, is another scenario of current filamentation in the atmospheric pressure 1

3 Atmosphere pressure 25mm, High45kV Voltage d

2

Time interval between two frame Ф=6.25cm, d=2.5cm 10ms

4

5

6

One assumption for current filamentation in DPF 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.

We can conclude schematic diagram of current filamentation , current coalescences and pinch formation in DPF

Anode

Anode

Cathode rod

Insulator Cathode rod

Magnetic reconnection and Plasmoid formation when two current filaments approach each other and collide Plasmoid

J

J

Current-loop

Bθ2

Bθ1

Magnetosonic shock wave

Magnetosonic shock wave

Plasmoid

From top view

Hot spots

After Magnetic reconnection

BθT=0

Magnetic energy convert to kinetic energy

Therefore we can say, 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

Our suggestion One might suspect that such hot spots are formed during the magnetic reconnection of current filaments in DPF

When two current filaments with angular momentum approach each other

Spiral galaxy taken with the Spitzer Space Telescope

Anthony L.Peratt simulated the spiral galaxy formation by interaction of parallel current-carrying magnetic field filaments

Ion pinhole camera using SSNTD (CR-39) 91 mm

CR-39 film

12µm Al filter

263 mm

Pinhole ф=0.3mm

15 degree

Cathode Anode

Experiment condition: D2 gas , 30kV, peak current 700kA, 5 focus shot,

Helical arm

Helical arm (a) at 15o

(b) at 10o

Ring shape with two shell (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

Our recent result of single pinhole camera

We interpret this as a vortex of ions like the Whirlpool galaxy, with central concentration

Image shows NGC 4736 Galaxy, credit by NASA.

Ion tracks obtained with the 12 µm aluminum filtered single pinhole camera with CR-39 film

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