USE OF TIME-RESOLVING HIGH RESOLUTION SPECTROSCOPY IN THE INVESTIGATION OF PULSE HOLLOW-CATHODE DISCHARGES

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USE OF TIME-RESOLVING HIGH RESOLUTION SPECTROSCOPY IN THE INVESTIGATION OF

PULSE HOLLOW-CATHODE DISCHARGES

S. Mohamad, A. Petkov

To cite this version:

S. Mohamad, A. Petkov. USE OF TIME-RESOLVING HIGH RESOLUTION SPECTROSCOPY

IN THE INVESTIGATION OF PULSE HOLLOW-CATHODE DISCHARGES. Journal de Physique

Colloques, 1979, 40 (C7), pp.C7-195-C7-196. �10.1051/jphyscol:1979796�. �jpa-00219502�

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JOURNAL DE PHYSIQUE CoZZoque ~ 7 , suppzgment au n07, Tome 40, JuiZZet 1979, ^pageC7- 195

USE OF TIME-RESOLVING HIGH RESOLUTION SPECTROSCOPY IN THE INVESTIGATION OF PULE HOLLOW-CATHODE DISCHARGES

5.2. Mohamad, A.P. Petkov.

University of Sofia, Dept. of Physics, Bulgaria.

I n t r o d u c t i o n

R e c e n t l y t h e hollow-cathode discha.- r g e w i t h p u l s e s u p l a y i s q u i t e o f t e n made u s e f o r t h e purposes of atom-absorption

spectroscopy.%e time dependences of t h e s p e c t r a l - emission c h a r a c t e r i s t i c s of t h e p u l s e f e e d hollow-cathode d i s c h a r g e , a r e

of a g r e a t i n t e r e s t ( 1 - 3 ) .Tkeir d e t a i l e d study y i e l d s v a l u a b l e i n f o r m a t i o n on t h e p h y s i c a l p r o c e s s e s i n t h e hollow-cathode source depending on t h e f e e d i n g regime, b e s i d e s t h e s e v e r a l i n t e r e s t i n g a p p l i c a - t i o n p o s s i b i l i t i e s t h a t i t o f f e r s .

I n *he p r e s e n t work an examination i s made of t h e dependences of t h e i n t e n s i t - i e s and t h e h a l f - w i d t h of c e r t a i n s p e c t - r a l l i n e s of chromium depending on parameters of t h e f e e d pulse,namely t h e dura- t i o n of t h e c u r r e n t p u l s o ~ ( t ) , t h e d u r a t -

P

i o n of t h e p a u s e s ( ~ p ) , t h e frequency of -the p u l s e s f , e t c . T h e s e dependences a r e co-

mpared w i t h analogous parameters i n d i r e - c t - c u r r e n t f e e d w i t h c u r r e n t i n t e n s i t y v a r i a t i o n s of between 5 t o 20 mA and acc- o r d i n g l y p u l e s - c u r r e n t v a r i a t i o n s of b e t - ween 100 t o 400 mA. On t h e b a s i s o f ' t h e s e measurements temperature d e t e r m i n a t i o n s of t h e plasma were made depending on t h e p u l s e i n t e n s i t y of t h e c u r r e n t and t h e i n t e n s i t y of t h e d i r e c t c u r r e n t , and on t h e .frequency of t h e p u l s e s .

The diagram showing t h e p r i n c i p l e s of o p e r a t i o n of t h e experimental s e t t i n g i s shown on Fig. 1 -The hollow-cathode d i s -

charge i s s u p p l i e d from a p u l s e g e n e r a t o r while t h e r e c o r d i n g of t h e l i n e and i t s width i s done with a u n i v e r s a l Fabry-Pe- r o t UFPS-1 i n t e r f e r o m e t e r " C a r l - Z e i s s W - Jena w i t h piezoceramic scanning.For t h e r e c o r d i n g proper an o s c i l l o g r a p h or c h a r t r e c o r d e r i s used,depending on t h e t y p e of t h e discharge.Use was made of t h e G5-15 (USSR) p u l s e generator.%e f e e d i n g of t h e c u r r e n t i s done w i t h t h e a i d of r e c t a n g u - l a r p u l s e s of a d u r a t i o n of between

5

t o 10 p s e c and pause between them of a du- r a t i o n i s from 156 t o 600 p s e c , i . e w i t h a

n - e p e t i t i o n frequency of between 1 t o

7

KHz.The d.c b i a s c u r r e n t was 0.5 mA,and t h e p u l s e c u r r e n t , a s much a s up t o 400 mA.

For t h e sake of o b t a i n i n g c o r r e c t r e s - u l t s a d e t a i l e d study was n e c e s s a r y of fIie a p p a r a t u s f u n c t i o n of t h e Fabry-Perot

i n t e r f e r o m e t e r . T o t h a t end s e v e r a l metho-

. ,

ds were u s e d . ~ h e one w i t h t h e u s e of h e l - ium-neOn l a s e r 7 o p e r a t i n g i n a Single-mode regime, proved t h e b e s t ( 4 ) 111 the treatme-

n t of t h e p r o f i l e s t h e methods of Minkow- s k i and Bruck ( 5 ) ,were used.

R e s u l t s

O n Fig.2 t h e dependences of t h e i n t - e n s i t y I of t h e s p e c t r a l l i n e of chromium with

h

⁼⁴²⁵⁴ a r e shown depending on t h e p u l s e ( c u r v e 2 ) and d i r e c t ( curve 4 ) cu- r r e n t s , and depending on t h e h a l f -width a l s o on t h e p u l s e ( _{curve 1}) and d i r e c t ( curve 3

9

c u r r e n t s . I n t h e s e measurements t h e d u r a t i o n Of t h e p u l s e s t = 1 0 P s e c , a n d t h e d u r a t i o n of t h e pauses Tz200 Psec,rem- P

a i n c o n s t a n t . P

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979796

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On

Fig.3 analogous dependences are presented,but with fixed values of Tp=200

Psec and a pulse current of Cp=300 mA,and Corresponding variations of the duration of the pulses and the direct current intensity. curves 1 and

3

givs the half-width

for a pulse and direct-current regimes, and curves 2 and 4,the intensities for pu lse and direct-current regimes.

Fig.4

On Fig.4 the dependences are given of the intensity and the haif-width-of

*he same line as a function of

Tp

and Cdc with fixed values for the pulse current Cp= 300 &,and the duration of pulses tp 1 0 psec.Curves 1 and 3 relate to the half widths 43 of the line, and 2 and

4,

to the

intensities i n pulse or direct-current su- P P ~ Y

With the aid of the f ormula4k7. 16.

1 0 - 7 ~ O ~ ~ , w h e r e M is the mass of the atom of the chromium =51.99,and assuming that the other interactions are negligibly minute and that the line has a Doppler pr-

5 0 0 0 0 5 200 11, 100 15 20

7%;;

d.c.

Fig.5

of ile, the discharge temperatures 9 ^were determined as a function of the pulse current, the intensity of the direct current and the frequency of the pulses (~ig,5,6).

On. both figures the curves 1 refer to Pu- lse feed,and 2,to direct-current feed.

2600

h

EREKCES Fig. 6