Físicos mais influentes (teóricos, contando 3 papers)

1

2

Falando de Física dos

Plasmas...

O que é o plasma?

•

Gás ionizado, com o mesmo número de

elétrons e íons (neutro), que apresenta

um comportamento coletivo;

•

Susceptível aos campos elétrico e

magnético externo;

Plasmas na Medicina

Plasmas empoeirados

32

Capture by porous aerogel targets in space & lab



Silica (SiO

) aerogels composed of clusters of 2 -5 nm solid silica

spheres with up to 95 % empty space, an average pore size is 2-50

nm and mass density 20-100 kg/m

_.

17

[**]S.Ratynskaia et al,Plasma Phys. Control. Fusion

50

(2008) 124046

Stardust,

1999-2004 ”

[*]S. Ratynskaia,e

t al

_{2009 Nucl.lFus.}

₄₉

₁₂₂₀₀₁

(mm scale on the figure below)

[“]F. Hortz

et al.

_{2006 Science 314}

TEXTOR tokamak* **

33

100nm

35

IMAGING:Fast Camera Detection of Dust*

_(DIII-D

₎

Time history of dust

(

a)–(d)

. two particles enter

SOL and disintegrate

(e)–(h).particles released

after an ELM impact on the

outer wall

(dust is incandescent)

Dust released by upward-going

38

Aplicações de plasmas no

Centrífugas

8

_×

10

_{radians per second;}

Separação de isótopos;

GROSSMAN AND SHEPP: PLASMA ISOTOPE SEPARATION METHODS ₁₁₁₇

FI anode

cathode

Fig. 3 . Plasma centrifuge from reference [16].

Discharge pulse forming

n e t w o r k Magnet Coils

m-

Cathode target

Grounded Vacuum Vessel

\

\

u p

Laser

Fig. 4. _{Vacuum arc centrifuge from reference [13].}

TABLE I1

PREDICTED VALUES OF c ) *

ions n

H-D 150 D-T 28 NeZ0-NeZ2 2.5

u 2 3 5 - u 2 3 8 1.134

‘From reference [21].

Then

~4 3; I B / p , (16)

In the context of a weakly ionized plasma, the viscosity is due to neurtal-neutral collisions. Argon and xenon plasmas were studied (see Fig. 3) and rotational velocities as high as 1.4 x 103m/s were obtained. It was found that the value of 8 is limited by the viscous damping, so that higher rota- tional velocities result in higher temperatures maintaining the condition:

8 5 1 and thus limiting the value of cy.

A number of interesting papers have been published deal- ing with the laser-initiated vacuum arc plasma centrifuge, [17]-[20]. A fully ionized plasma is produced and transported through an axial magnetic field. For most of the papers published in this area, a so-called rigid rotor model is used [22]. This represents one of the cases treated in [21], where there is no net ion diffusion out of the plasma column. Further, the magnetic field is assumed to be axial and uniform, and a

constant radial “self-consistant” electric field, E, is assumed to exist. This is due to the ambipolar diffusion of the ions in the radial direction [20], and in turn produces an E, x B,

drift or rotation with frequency or the order of E,/B,. _A

three-component system is considered, composed of electrons, and ions 1 and 2. Each component has a corresponding radial Euler-type equation (or momentum conservation) in which a steady state is assumed. (Unlike in [21], viscosity is neglected.) In this case, for each plasma component one has the following:

m u ; / , = e Z ( E ,

+

In [22], a parameter E is defined as the ratio of the centrifugal-

to-electodynamic force:

E = ( m u ~ / r ) / ( Z e w @ , ) = ( v 4 / r ) / ( z e B Z / m ) = w / A ,

(18) where Ai is the cyclotron frequency, and w is the plasma

rotational frequency. In [22], separation of zirconium (mass numbers 96, 94, 92, 91, and 90) was studied. Here, B, =

0.4 T, z = 3, and w = lo5 rad/s. Thus E = 0.08, leading to

the conclusion that both the pressure gradient and centrifugal force terms are small corrections to the ion motion. The ion velocity is, to first order in E ,

Z I ~ S - E r / B z ( l - 2 ~ ) . ₍₁₉₎

Princípios

The principal idea of ICR-method is the following. A

_!

ux of collision free

plasma comes into heating area in which the aimed isotope ions advantageous

acceleration is executed on resonance frequency:

ω

=

ω

=

eB

M

.

To provide heat selectivity it is necessary to realize several conditions. It is

obvious the requirement of stable magnetic ˇeld uniformity in the heating area:

∆

_B

B

<

∆

_M

M

.

(1)

R lines and dealin

(

∆

_B/B

_∼

₁₀

−

3

) i

to the mass of isotopes

The other condition of heating selectivity is the requirement of smallness of

cyclotron absorption line widening due to the heated ions collisions:

ν

ω

<

∆

_M

M

Fig. 1. Block diagram of the plant for

ICR-method isotope separation:

1

_{Å substance}

feeding system,

2

_{Å vacuum chamber,}

3

_{Å plasma source,}

4

_{Å plasma source}

magnetic coil,

5

_{Å the plant magnetic coil,}

6

_{Å HF-antenna,}

7

_{Å plasma}

_!

_ux,

8

_Å

Fig. 2. Elemental cell of product collector:

1

_{Å front}

screens,

2

_{Å plates for product collection,}

3

_{Å plates}

for atom capture in case of spent material dispersion,

4

_{Å receiver of depleted plasma}

_!

_ux

X,.,D ,L/3=.3%(3F (%.)3F $,./,="3 h&3U'*,-+J !"&3) h&3U'*,-+% $/3#*')+ @38&%*+J ',) G,)

# )'5",J !)%&8'%J

K*-3/0)3F $/3#*')3

K**3/"'-3?9'J $,*%)E'3/(_%')X

#

Processamento de materiais

para a indústria

49

Material

Vapor

Pressure

Material

Unit Value

low

high

low

high

glass

Mag.

storage

S/C

Vapor pressure limit for vacuum operation

50

Material/Substrate

Plasma Component

Desired Product

Semiconductor substrates

Active neutral and ionic

species generated by

electron impact

Etching, thin film

deposition, stripping,

cleaning

Magnetic Storage Media

Sputtered atoms generated

by ion bombardment of the

target

Magnetic thin films,

anti-corrosive coatings

Glass

Thin film chemical

precursors, neutrals

Energy efficient coatings

Textiles

Ion bombardment, active

neutrals

Increased wettability, wear

properties,

Industrial Cleaning

Oxygen atoms, ions

Oxidation and removal of

organic films

Food Processing/

Decontamination of CBW

Agents/Medical Equipment

Sterilization

O, O2

, H, OH: chemical

reactions initiated by

plasma chemistry

Destruction or denature of

pathogens, prions; chemical

destruction of toxins

Water/Wastewater

Treatment

O, O2

, O3, OH: chemical

reactions initiated by

plasma chemistry

Removal or destruction of

water contaminants,

51

Plasma generation

of active species

e

-

_{+ CF}

4

→

CF

3

+ F

Plasma etching/

ashing/cleaning

4F + Si

→

SiF

_{4 (g)}

Si

Plasma deposition

of thin films

e

-

_{+ SiH}

4

→

Si

(s)

+ 4H

Si

Plasma

decontamination

of CBW agents

substrate

contaminant

O + organic

→

H

O + CO

Plasma surface

treatment

substrate

(ion induced surface change)

+

+

Plasma sterilization

(chemical destruction of

pathogens)

a)

b)

_c)

d)

e)

_f)

52

V

P

p

s

x

V

53

a. Dielectric

Barrier discharge

b. Corona Discharge

c. DC Plasma torch

Gas In:

RF Electrode

He

O

feed gas fast flow

Contaminated

Surface

evolved products

d. Atmospheric pressure

plasma jet

54

a. D o w n stre am P ro ce ssin g

b . In -S itu P ro c essin g o f w afe rs

su b str a te

g r o u n d e le c tr o d e

r f e le ctr o d e

w a fe r

p la s m a

c. In -S itu P ro ce ssin g o f T ex tile s

rf

electro de

g r o u n d e le c tr o d e

te x tile

d . m ed ic al sterilizatio n &

d ec o n ta m in atio n

B lo w er R F E lec tro d e

G n d

p la sm a

Materiais Micro e Nano

estruturados

55

56

Example:

2

XeF

₂

+

Si

Ar

+

57

Building Units (BUs) are

- generated in plasma

discharge bulk

-

accelerated

(when

charged)

in

plasma

sheath

- transported to the

sur-face

-

sometimes

able

to

drive surface activation

(no

external

heating