Time-dependent of recombining Plasma with Pulse Plasma flow

T.Torada, Naoki mine, Hiroyasu Komukai, Tomohiko Ono, Akira Tonegawa, Kazutaka Kawamura

Introduction Time-dependent of emission intensity with Plasma flow

Conclusions

pulse width ：0.3ms

Emission Current：70A

Gas pressure：1.0Pa（Recombining Plasma）

① Emission intensity by electron-ionrecombining (EIR) becomes weak because thenumber of excitation atoms decreases. After,emission intensity increases by electron-impactexcitation with the electron temperatureincreases.

② Emission intensity becomes weak againbecause electron-impact excitation decrease bythe electron temperature decreases. After,emission intensity increases by recombiningwith the number of excitation atoms increase.

Experimental Results of ƒe(ʋ)

Photograph around experiment region

Pulse plasma style control

-20 -10 0 10 20

-5

0

5

applie

d v

oltage

[Ｖ

]

time [ms]

When electrode connected

earth ground

The plasma flows in the

floating electrode.

↓

stationary plasma is

generated

(Low energy)

When electrode

disconnected earth ground

Plasma flows out from the

electrode.

↓

Plasma flow is generated

(High energy)

Floating

voltage

Earth

ground

Stationary plasma Plasma flow

Switching circuit

ElectrodeElectrodeAnode Anode

Plasma flowLends

Gas feeder

Langmuir probe

Spectrometer

Magnetic field Water

Cooling

Target plate

Experimental region

The research on the dynamic behaviors of plasma against the pulse plasma flow

with bursts of heat and particles is a topic in space plasma, and fusion related

edge plasma physics. In particular, the time-dependence of recombination

processes with pulse plasma flow has become important for characteristics of

plasma detachment, in which the transitions from recombination to ionization

plasma have been identified in divertor region of fusion device.

The transient behavior of the recombination plasma with pulse plasma flow has

been studied by observing the short double minimum (negative) spike in Dα/Hα

emission from the plasma. This response in Dα/Hα emission is explained by the

electron temperature increase associated with pulse plasma flow with bursts of

heat and particles along the magnetic field. However, it is required that

experiments which will aid the understanding of the role of the high energy

electron with pulse plasma flow are carried out.

In this study, we have carried out the experimental observation of the time

evolution of electron density ne, electron temperature Te, electron velocity

distribution function ƒe(u), and hydrogen Balmer series spectra in hydrogen

recombination plasma in a liner plasma device, TPD-SheetIV.

Experimental and Modeling results of Hα intensity

Ionization Plasma

（High temperature ）Recombination Plasma

（Low temperature）

-0.10.00.10.20.30.4

0.5

0.6

0.7

0.8

[eV]21

023

21

23

　　

p

p

ep

e

e

e VddV

dIV

e

m

nT][m

2 3-

023

21

23

　　

p

p

eee Vd

dV

dJ

e

mn

Time-dependent of the electron temperature and the electron

density is calculated by using ƒe(ʋ) because of non-Maxwellian.

It is reported by nuclear-fusion device “JET”, the recombination

plasma with pulse plasma flow has been studied by observing the short

double minimum (negative) spike in Dα/Hα emission from the plasma.

Magnetic coil

500l/s

Pump500l/s

Pump

1500l/s

Pump

Gas feeder

Water-cooled

Target

Cathode

Anode

Discharge regionExperimental

region

square-wave

pulse

switching circuit

(MOS-FET transistor)

Function

Generator

Linear plasma device(TPD-Sheet IV)

-0.2 0.0 0.2 0.4 0.6 0.8 1.010-3

10-2

10-1

100

Experim

enta

l in

tensity I [

a.u

.]

Calc

ula

ted inte

nsity I [

a.u

.]

Time [ms]

Calculated

1

Experimental

Ion

cu

rren

t [A

/cm

2]

Time [ｓ]

A.Loarte et al., Fucl.Fusion 38,331(1998).

①

②

Dα

in

ten

sit

y[a

.u.]

( ( ( 0),(2)(

pnipAnnpkdt

pdn

pi

e

0.0 0.5 1.0

0

4

8

12

Ele

ctr

on t

em

pera

tue

Te [

eV

]

Time [ｍｓ]

0.0

2.0

4.0

6.0

8.0

Bulk plasma Hihg energy

electron

Bulk plasma Hihg energy electron

Ele

ctr

on d

ensi

ty

n e [1

017 m

-3 ] •Electron density

Bulk plasma:5.5×1017

→8.0×1017[m-3]

High energy electron :

→6.5×1016[m-3]

•Electron temperature

Bulk plasma: 0.8 → 1.6 [eV]

High energy electron :

→ 13.1[eV]

Modeling: corona model

Experimental observations of the time evolution of the electron density ne,the electron temperature Te, the electron velocity distribution function ƒe(u),and hydrogen Balmer series spectra have been carried out on hydrogenrecombination plasma with plasma flow. The emission intensity of Ha iscalculated by using coronal model.

(1) The short double minimum (negative) spike in Hα emission from the

plasma is observed in recombination plasma with pulse plasma flow.

(2) In the pulse plasma flow, the high energy electrons except for bulk

plasma are appeared.

(3) The high energy electrons are dominant for the emission intensity of Ha

in comparison with experimental and modeling results.

( :pk

( :pn

:),( ipA

rate coefficient

Einstein coefficient

population of level “p”

enpkqnA

AhcI

)()(

Department of Physics, School of Science, Tokai University, 411 Kitakaname, Hiratsuka, Kanagawa, 259-1292, Japan

Comparison with experimental

and modeling results

Electron density: ne Electron temperature: Te

0.0 0.5 1.0 1.5 2.0 2.50.0

1.0

2.0

3.0

4.0

Ele

ctro

n ve

loci

ty d

istr

ibut

ion

func

tion

[x10

11]

velocity [106m/s]

Bulk plasma

High energy

electron

ƒe

(ʋ)