Chapter 3

Laser Absorption in Plasmas

OMEGA EPLLE, U of Rochester, USA

t

B

E

t

EjB 00

jEBEEBBE

0

2

0

20

11

2

1

t

jEBEBE

0

2

0

20

11

2

1

t

3.1 Electromagnetic Waves in Plasmas

m

e

dt

d Ev vj en

EEEkk2

22

2

ck p

0

22

m

nep

2222 pck

Current induced by Electron Motion

Dispersion Relation

Plasma Frequency

Cut-off Frequency

Earth Ionosphere

21

2

2

1

pp c

kv

21

2

2

1

pg c

dk

dv

202

1EEW

0

2

2

1

B

BW2

2

1mnvWe

Phase Velocity

Group Velocity

Energy Densities

3.2 General Formulation of Absorption

3.3 Classical Absorption (Inverse-Bremstrahlung)

dk

dt

r

dr

dtvg c2 k

2 p2 r c2k2

r k constant

ILk IL,0

k exp S

S abs dt S abs

Ý r dr

Ray-tracing and laser absorption

r2 Ý h : constant

2 p2

2

c2 Ý r 2 h2

r2

S 1

cabs 1

p

2

h2

c2r2

1/ 2

dr

abs

4 3 e6Z2nen i

32 2mTe 3/ 2 nIB

p

2

n r ncr

r2

S abs

c

r

rt

2

1

/ 1

1 / 2

rt2

h2

c2

/ 1

15

Classical absorption

1

cK

2peei

abs

2/3

eB2

2e

63

)Tmk2(c3

lnZne422/3

e

2e

T

Zn

Heating rate Relaxation rate

Hiper-Maxwell Distribution

Announcement

You can download the viewgraphs from Chapter 1 to Chapter 5

At http://ips.physics.sjtu.edu.cn/

Chapter 6 to 8 will be able to be download from

Wednesday in this week

3.4 Resonance Absorption and Wave Breaking

Gintzburg Curve

21

Experimental Data

Wave Breaking

24

Wave-breaking

26

High Energy Electron Production

Temperature Effect

Density Modification by Ponderomotive Force

EjBEBE

)()](2

[ 02220 cc

t

cIWc /42

2220

BE

IIIt

Energy Conservation Equation of EM Wave

Energy Density of EM Wave

Transport Equation of Radiation

3.5 Conservation Law (Summary)