A SPECTRAL CHRONOGRAPHIC AND EQUIDENSITOMETRIC INVESTIGATION OF A PULSE BLENDED DISCHARGE

(1)

HAL Id: jpa-00219408

https://hal.archives-ouvertes.fr/jpa-00219408

Submitted on 1 Jan 1979

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

A SPECTRAL CHRONOGRAPHIC AND

EQUIDENSITOMETRIC INVESTIGATION OF A PULSE BLENDED DISCHARGE

A. Petrakiev, I. Koleva, J. Ganeva

To cite this version:

A. Petrakiev, I. Koleva, J. Ganeva. A SPECTRAL CHRONOGRAPHIC AND EQUIDENSITOMET-

RIC INVESTIGATION OF A PULSE BLENDED DISCHARGE. Journal de Physique Colloques,

1979, 40 (C7), pp.C7-845-C7-846. �10.1051/jphyscol:19797408�. �jpa-00219408�

(2)

JOURNAL DE PHYSIQUE CoZZoque C7, szcppldment au n07, Tome 40, J u i Z l e t 1979, page C7- 845

A SPECTRAL CHRONOGRAPHIC AND EQUIDENSITOMETRIC INVESTIGATION OF A U S E BLENDED DISCHARGE

A. Petrakiev,

I.

Koleva, 3. ^Ganeva.

University o f Sofia, Department o f Physics, Chair o f Optics a d Speectroscopy, Bulgaria.

ABSTRACT: A method of space-and- time diagnostication of capillary pulse discharges on the basis of spectral equidensitometric investigations, is proposed.

INTRODUCTION

The specific peculiarities of the localized pulse discharges, such as the obtainment of relatively small volumes of high temperature plasma (up to 1 0 9 ~ ) within very short ( f r o m p s to fl5 parts) duration, good reproducibility, simplicity of the scheme, etc.

,

have made imperative the use of such discharges on a large scale.

I n the field of spectroscopy capillary pulse discharges are utilized for exciting the spectra of elements which are difficult to excite, and ions with high degree of ionisation. I n the process of the development, testing and calibration of standard light sources, elaborated on the basis of capillary pulse dischargesrf,21, several essential features and advantages of such sources, wers elucidated. The chemical composition of the plasma jet corresponds to the composition of the walls of the capillary, a fact which enables the study of the properties of such plasma of a dif- f erent chemical composition. The capillary pulse discharge is character.ized dy a strong space-and-time heterogenety, which makes impossible the utilization of the common spectral methods of plasmzediagnostic In the present work an attempt is made at investigating the space-and-time development of the temperature by means of spectral-and-equidensitometric and hagh speed chronographic methods.

EXPERIMENTAL

The electric circuit parameters are C=420pF

,

U=250 k V , and L=1.2pH

.

^The

discharge are carried out i n air at atmos- pheric pressure. The discharges are ape- riodical

,

with two well-shaped half -pe- riods of a total duration of about 180J.d

.

The amplitude of the current intensity at the maximum of the first half-period is u p to

5

kA. The localization of the dis-

charge channel is achieved with the aid of two 1.8mm thick flat parallel dielec--- tric plates with dia 2.5 mm coaxial aper- tures at a distance of 2 m m from one another. Since no independent discharge intervened with the voltage and the gap with which we operated, we applied a powerful brief initiating pulse, synchro- nized with a SFR (USSR) superhigh- speed cinema-picture camera. The latter was used i n a regime of stills extension of a speed of 95000 pictures per sec in a two- and four-raster system. The linear field of the stills was of 1 0 mm- The combining of the SFR camera with the narrow-band interference filters has ma*

it possible to sepapate and retrace i n time the excitation zones of the respective spectral lines. On Fig 1 the schema of the experiment is shown. 1% allows to

obtain a complete space-and-time informa- tion from one single shot for the two ( A . and

h2

) or the four (

A i , A,, h 3

andh,,) lines. The data about the lines that we have used are given on Tab1 e 1

.

^{The last}

column of the table shows the normal temperature values for the corresponding lines l 3 . 9,5]

2

C A M E R A

Fig. I

Table 1

t'

RESULTS AND DISCUSSION

The superhigh-speed photographs thus obtained, enable to retrace the structural changes i n time i n the discharge plasma. With pulse discharges the substance enters the interelectrode gap i n the shape of vapour jets or flares. In localized pulse discharges the electrodes are stream-lined by contrary plasma jets from the channel in the direction of the electrodes. The formation of such jets is related to the evaporation of material from the walls of the capillaries in the rapid heating and expantion of thevapours The high-speed capillary jets ( Mach num- ber up to

3)

create compacted zones i n the electrodes'stream-lining. Intensity pulsations are observed. This structure could be explained on the basis of the hydrodynamic phenomena arising in the outflow of supersonic speed plasma j&t s from a nozzle. From the stills thus obtained it can also be seen that coaxial plasma in the shape of a disk of a radius of some

4

mm is created between the c a p s laries. After some 2 0

)CS

after the beginning of the pulse; the bright central area ceases to grow in dimention. When we compare the stills extension of theflasmta

Line ,nm 0 I 604.6 C I1 437.4 XJ ^NI11

409.7

El

,

^eV

1

^E2,^eV

10.99 /

^13.04

24.65

:

27.49 27.44

1

^30.46

Txl O - ~ O K 1.8

3.3 4.8

X q C I V 580.1; 37.55139.68

1

^6.0

--

I Î Î Î

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797408

(3)

glow of the capillary pulse discharge with use of various electrodes, great diffkrences i n the mechanism of entry of the vapours into the gap.

Spectral investigations. of the discharge by zones show that i n the spectrum of the central sector symmetrical to the axis there are lines of components of the composition of the capillaries, though not of the electrodes. I n this area a n excitation of lines with a different degree of ionization (or up to 0 V, C V),and a very good spatial distribution, are observed.

The emission of lines of a different rate occurs from very narrow concentric zones of a different thickness (parts of the m m ) I n the area between the fronts of the bright zones and the surfaces of theplates, lines of the components forming part of the composition of the plexiglass, the air medium, and the electrodes, with a low

degree of ionization, are observed.

Besides the good spatial distribution of the lines of a different frequency, a time extension is also observed. It is seen that the C I V 580.1 nm line is excited only during the first half-period, and that it achieves its maximum intensity about the 18th p s as from the beginning df the discharge. For the N 111

409.7

nm

line I m w is observed about the 42th&s, for the I1

437.4

nm, about the 50th PS, while the 0 I

604.6

nm line achieves a maximum value between. the 64th and 70th.

The simultaneous knowledge of the intensity I&= li'(x,y,z,t) of lines of a different degree of ionization has enabld u s to follow up the space-and-time development of the temperature. Use was made of the temperature functions of excZtation of the respective lines with such a sel- ection as to allow to include both the high-temperature areas of zhe discharge channel and the peripheral zones. The t ernperature f unctionS~3,~.5~are determined.

with a n accuracy of up to

15

per cent, and are normalized to unit. From the photographs obtained through the combined use of the SFR film camera and the interference filters only the stills corresponding to the maximum of the temperature functions of excitation of the respective lines (~igg.2) were selected, and were

P aphic

e

* 4 , f 4

Fig. 2

i f ' 4 z 0.5

All stages of the process of otaining the Sabatier effect, were observed. A calibration of the equidensities was carried out and the blackening curves and the sensitometric properties of the photo- graphic material utilized, were taken into account. A family of the equidensities of the lines of a different ionization rate was obtained for time instants corresponding to their normal temperatures; the difference i n the blackening densities of the individual equidensities is AS=const

( ~ i g . 3 a

---

-i[

CONCLUSIONS:! The proposed method can be successfully used with plasmas, with which it is impossible, or very dif- f icult

,

to determine the plasma parameters with the aid of other diagnostication methods.

By means of a rmmerical solution of

..

m's integral equation f 87 the radial distribution of the intensity was obtained. The results of space-and-time development of the temperature, obtained i n the conditians of a capillary pulse discharge, is shown i n -Table 2.

1

O r y p q o ~ a H.

,IIoJ~AoIIIBHcKH~ I*I. ,OMII,li,~Q80 2 Klatt H,,Staatsexamensarbeit,Kie1,1967 3 Larenz R . ,Zeit.Phys.

,x,

^327,

1951 4

Krempl H. ,Zeit.Phys.

,a,

^{302, 1962}

5

Petrakiev A.,V6r6s T.,S~ectroch.Acta

'1

2

1 3

4 5 6

8 10

.

-

UB,

369, 1969

6

Lau E.,-,Krug W. ,Equidensitometry, 1968

7 BA~ZHMHPOB

C.,

ACTPOHOM.~HP.

977,197'7 8 Bockasten K., JOSA,

2 ,

9, 943, 1961

604.6

nm t , r 6 6 r s

Im

re.

15 2 8 . 5

5.2 3.8 2.9 2.1

71.7 1.4

9 1 . 2 1.1

T P K

' 4 XI 0- 1.8 1.5 1.45

1.4

1.3 1.25 1-23 1.2 1.15 1 ~ 1

437.4

nm t2f

50

p s

= ( r j vet.

26 2 0 13

9

6

4.4

2.5

-

1.8 TOK

0-4

3.3 2.2 1.5 1.3 1.2 1.1

3-71.0 0.9 -

0.8

409.7

nm t3=42 jus Icr)

rd.

3 5 2 4 16 9 6.3

4.7

2.8 2.2

'

TOK

0-4

4.8 3.8 3.0 2.7 2.4 2.3 3.72.2 2.1 2.42.0 1.9

580.1 n m t4=1 8 p s T(r)r0K

re€.

55

4

6.0 3 7 3.7 26

/

^3.4

1 8

14

7..8

4.9 -

2.3 2.9 2.8 2.7 6.22.6 2.5

-

2.4

d