ON THE VUV RADIATION OF TOWNSEND AVALANCHES

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ON THE VUV RADIATION OF TOWNSEND AVALANCHES

V. Peskov

To cite this version:

V. Peskov. ON THE VUV RADIATION OF TOWNSEND AVALANCHES. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-331-C7-332. �10.1051/jphyscol:19797163�. �jpa-00219139�

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JOURNAL DE PHYSIQUE Colloque C7, suppldment au n07, Tome 40, J u i l l e t 2979, page C7- 331

ON THE VUV RADIATION W TOWNSEND AVALANCHES

V.D. Peskov.

I n s t i t u t e for Physical Problems Moscow, U.S.S.R.

Gas s c i n t i l l a t i o n counters of r a d i a t i o d Results : Constant e l e c t r i c f i e l d

i ~ t e n h v e l y developed i n l a s t y e a r s , a r e Rare gases The measurement show t h a t advanced compared t o proportional gas coun- s p e c t r a of C O ~ ~ ~ ~ U O U S stream of A were t e r s by t h e i r enhansed energy r e s o l u t i o n [I] due t o molecular r a d i a t i o n of the r a r e I n sueh a counters t h e r e i s r e g i s t e r e d VW gase. Table I p r e s e n t s t h e i n t e n s i t y r a d i a t i o n of t h e Townsend avalanches (A) i n d i s t r i b u t i o n of s i n g u l a r ^A r a d i a t i o n i n c o n t r a s t t o charge c o l l e c t i n g i n the con- r e l a t i v e photon numbers a t d i f f e r e n t v e n t i o n a l counters. This work concerns t h e s p e c t r a l i n t e r v a l s , measured by narrow-

s t u d . of t h e VUV s p e c t r a of A i n r a r e gases band counters. _Table and H2 at pressures P=0.1-30 atm.

Method : An i n s t a l l a t i o n f o r s p e c t r a recor- ding of a s i n g l e A i s presented i n Fig.4.

A was i n i t i a t e d in t h e c y l i n d r i c a l counter (7) by55~e. Their r a d i a t i o n a t

h

4 1050 was recorded by open counter (12) with a narrow s p e c t r a l s e n s i t i v i t y v a r i e d from 500 t o 1000

1

by means of changing t h e working gas is counter and f i l t e r before

t h e counters. Radiation with

>

1050 A Comparison of t h e s e data with energy dis- t r i b u t i o n in molecular s p e c t r a ( s e e f o r was recorded by t h e narrow-band counter

example ¹²¹) r e v e a l s their q u a l i t a t i v e with I,@ windows (2). Spectra of the l a r g e

agreement. Therefore, A in r a r e gases (continuous) stream of A

,

i n i t i a t e d by

55Fe ( a c t i v i t y 0.1 c) were recorded by t h e e x c i t e p r e f e r a b l y the molecular spectra.

vacuum spectrograph. To expbore t h e e f f i c i e n c y of t h e e x c i t e d Fig.? I-high molecules formation and, t h e r e f o r e t h e

'@

pressure chamber, brightness of A r a d i a t i o n we have measu- 2-counters with r e d t h e r a t e s of t h e r a r e gases molecule LiF window ( 9 ) , formation i n t h e t h r e e - p a r t i c l e c b l l i s i o n + t a p , & p u r i f i e r , processes. For t h i s purpose t h e r e was 5-calibrated measured t h e r i s e time of t h e e l e c t r i c a l source of VW, and VW s i g n a l s i n t h e counters with a

&manometer, 7- t h i n wire ( 0.01 mm)

-

see Fig.2. The s c i n t i l l a t i o n pulse f r o n t consisted of t h e e l e c t r o n counter with wire, ( ) and i o n ( ) components, F a s t ( 8 ) , 10-spectrograph, 11-tap f o r gas flow- component of t h e VW pulse f m n t

5

was i n g , 12-open counter, 1 + d i f f e r e n t i a l cham- due t o formation - . of t h e e x c i t e d molecules b e r , 14-tap f o r flowing impurity gas. and slow

- -

t o t h e i r r a d i a t i v e de-

* - - - C - - - - ' - - -

I n r a r e gases t h e accumulation of e x c i t e d cay. The experimental r e s u l t s a r e pre- atoms i s p o s s i b l e 131

,

so due t o the s t e p sented i n Table 2. The r a t e c o e f f i c i e n t s i o ~ i z a t i o n t h e s p e c t r a of singular A and a c a l c u l a t e d by t h e s e d a t a a r e : for

l a r g e stream of A , i n g e n e r a l , may be &if-

f e r e n t

.

^(4.5*2) ^cm6 ^s-' and f o r Xe

-

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797163

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' I '

Fig.2 Electrical&Jand l i g h t

~~1

sigmls from

counter f i l l e d with Ar+CR4 (b) and A r (c) Table 2

Next experiment was held i n a f i x e d vo- lume where t h e e x c i t e d atoms concentration was supported a t a constant l e v e l . The dis-

charge chamber with ^@;asa t p r e s s u r e s . 1-40 t o r r was i r r a d i a t e d with 5 5 ~ e s o u r c ~ ~ h i s chamber was j o i n t e d t o t h e i o n i z a t i o n cham- ber. The VW photon counter (flowing o r with LiF window) were placed perpendicularly t o t h e a x i s of t h e i o n i z a t i o n chamber. The concentration of e x c i t e d atoms and d i s t r i - bution of the V W brightness was evaluated by t h e method, described i n [3]

.

^{The con-}

s t a n t . ~ of t h e e x c i t e d molecule formation c a l c u l a t e d by t h e s e d a t a were f o r A&

-

-10-32 cm6 a-"

,

^{f o r Xe}

-

³ ^em6 ^s-I

.

b) H2 Spectroscopic measurements i n H2 '-that i n v i s i b l e and VUV regions only

weak molecular spectrum i s excited. O n the o t h e r hand, i n t h e H2 counter with a t h i n wire (diameter 0.1 mm) t h e e l e c t r i c f k e l d s t r e n g t h may grow up t o 16 V/cm and t h e e l e c t r o n energy s t o r e d at t h e i r l a s t f r e e path n e a r the filament may be increased up t o 100 eV. I n t h i s case t h e emission of t h e bremsstrahlung r a d i a t i o n f ror t h e anode, analogous t o t h e spectrum of the e l e c t r o n gun, i s possible. We have measured such a spectrum by means of multiwire counters [4]

and discovered t h e weak bremsstrahlung radia%ion of electrons from t h e anode.

I1 A l t e r n a t i n g e l e c t r i c f i e l d T.n t h e

-

'paper

[51

t h e r e wqs described t h e scin- t i l l a t i o n counter with HF e l e c t r i c f i e l d . Such a counter advantageously d i f f e r s from

counters with a constant f i e l d , because it can measure simultaneously a l l t h r e e coor- d i n a t e s of t h e photons o r p a r t i c l e s . We k v e stuPyed s p e c t r a of A both i n t h e ca- v i t y and in t h e f l a t spark counter with a HF feeding. Electrons m u l t i p l i c a t i o n i n t h e HF e l e c t r i c f i e l d caused t h e propagation of i o n i z a t i o n wave with v e l o c i t y of

lo6 -

lo7

cm/s from t h e p o i n t of t h e i n i t i a l io- n i z a t i o n . The experiments with narrow-badd counters show t h a t propagation of t h i s wave r e s u l t e d from d i f f u s i o n of resonance photons ( a t short d i s t a n c e s ) and with mo-

* *

l e c u l a r r a d i a t i o n

-

a t long d i s t a n c e s

.

References :

I A.J.P.L.Policarpo, Space S c i . I n s t r ,

2 ,

77, 1977

2 A.N. Zaidel, E .Ya.Shreider

,

"Vakuumnaya .

spectroskopiya i ee primenenie"

,

Nauka, 1

976

3 V.D.Peskov, X I 1 1 ICPIG, B e r l i n ,

2 ,

455, 1

977

4 I.P.Tindo, Sb,"Itogi nauki", v.9, Astronomiya VINITI, 88, 1974, p.173

* *

The p r i n c i p l e of s p h e r i c a l i o n i z a t i o n wave propagation was used t o construct t h e X-ray d e t e c t o r , where t h e coordinates of t h e initial photons were determined by t h e VUV r a d i a t i o n delay t i m e measured n e a r t h e opposite edges of t h e counters.