STUDY OF A NITROGEN-NEON NUCLEAR INDUCED PLASMA

(1)

HAL Id: jpa-00219174

https://hal.archives-ouvertes.fr/jpa-00219174

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.

STUDY OF A NITROGEN-NEON NUCLEAR INDUCED PLASMA

D. Auphelle, F. Euve, M. Fitaire, A. Pointu, M. Vialle, L. Wartsky

To cite this version:

D. Auphelle, F. Euve, M. Fitaire, A. Pointu, M. Vialle, et al.. STUDY OF A NITROGEN-NEON NUCLEAR INDUCED PLASMA. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-397-C7-398.

�10.1051/jphyscol:19797195�. �jpa-00219174�

(2)

JOURNAL DE PHYSIQUE ColZoque C7, suppl6rnent au no?, Tome 40, J u i l l e t 1979, page c7- 397

STUDY ff A MTROGEN-NEON NUCLEAR INDUCED PLASMA

D. Auphelle, F. Euve, M. Fitaire, A.M. Pbintu, M. Vialle and L. wartsky*.

Laboratoire de Physique des Caz e t des Plasmas. Bdtiment 212, Universite' Paris-Sud, 91405 Orsay Cedex, K ~ r m c e .

I n s t i t u t drEZectronique FondamentaZe. Bdtiment 220, Universitg Paris-Sud, 92405 Orsay Cedex, France.

The importance of energy-transfer from neon in Ne-N nuclear induced plasmas is well known. Lasing

2 effect was observed in a Ne-N mixture with a very 2

low rate of N2 impurity, and it was shown that la- sing occurs form a Ne-N2 energy transfer'') . ^In

this communication the role of nitrogen in a sta- tionary neon plasma induced by a 2.3 MeV proton- beam is reported. The proton-beam intensity,

Ib' was varied from 0.5 to 3.5 uA. The neon pressure was in the range of 50 to 700 torrs. The nitrogen concentration-rate (10 to -4 lo-') was measured with a mass-spectrometer. The influence of nitrogen on the densities of the charged particles of the plas- ma and an evaluation of ion-temperature are repor- ted.

1. K N energy-transfer_

:

Visible plasma spectrum 2

was observed and first negative bands of N were encountered. The most intense band corresponds to a wavelength of 391.4 nm. Due to the low nitrogen

2 +

concentrations the excitation of

3 C

state

of

ni- trogen cannot be explained by direct proton excita- tion, but is the result of Ne-N energy transfer.

2 It has been established that the excitation of +

2 +

N2(B

C )

state in Ne-N2 mixtures follows from an energyUtransfer from neon ions(2). In our experi- ment Ne+ ions are produced by the proton-beam with a rate S

dE/dx

:

proton energy-loss per unit length W

:

average energy required for an electron-ion

pair production

j

:

proton-beam current-density

Ne+ ions disappear through the following reactions:

(1) ~ e + + 2Ne 8 ^{Ned +} ^{Ne, 8}

⁼

5 . 1 0 - ~ ~ c m ~ . s - ~ ( ~ ) (2) Ne++ N2+ Ne k -+I ..., ^k

⁼

5.31 l ~ - ~ ~ c m ~ . s - ~ ( ~ )

1 (3) Ne++ N2+ N2 t2...,k 2

=

7.5 -7 3.s-1 (9) (4) Ne++ e ~ e * + Ne, a

=

1.8 10 cm

2 (5) Ne> N2 5 ^N;+ ^{2Ne, k}

⁼

⁹ 1 0 - ~ ~ c m - ~ s - ~ (3) In the worst conditions for reaction (5) i.e. for maximum value of n

=

10llcm and minimum value of -3 measured N2 concenzration IN2]= 2 10' 6cm-3 the pro- bability of reaction (5) is lo3 higher than the

,

probability of reaction (4). We may conclude that Ne-N energy-transfer process involves Ne; ions ac-

2 cording to successive reactions (1) then (5). A quantitative study of these reactions taking into account measured densities of the involved species shows that N+ ions are created with a rate equal to

2 the rate of production of Ne*, i.e. S. Futhermore 2 +

we assume that all N; ions are created in B

Z

sta- + 2 +

te. The N (B

C )

ion disappears owing to the follo- 2 u

wing reactions

:

This simple model agrees with the observed de- creasing of 391.4 nm line intensity versus increa- sing N pressure. This can be shown on figure (1)

2 which gives the variations of I /(k3+k4 [NJ) (a) and the observed 391.4 nm (b) line intensity versus ni- trogen pressure with a neon pressure of 7 0 torrs.

~ e + molecular-ions created by reaction (I) dissap- 2

pear through the following reactions

:

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797195

(3)

+ 2 +

2. Measurements of the N (B

C )

rotational tempera- 2 u

ture

:

The ~ t u d y of 391.4 nm R-branch rotational

-

spectrum allows us to determine the rotational tem- '~(5) perature, Trot, of the (B,vv=o) state of N2 .

The following table gives the results obtained for various neon pressures and two proton-beam intensi- ties.

The highly exothermal behaviour of reaction (5) ex- PNe (torrs)

plains that the N; ions temperature is much higher than the nhtral gas temperature measured else- where (6) .

343

C

10 440

2

23 456 1 1 510

C

40 512

L'

14 448

f

20 ---

50 100 310 500 600 700

4

3. The influence of N on the electronic den*

2 and ionic equilibrium

:

On measuring the electro- nic density, ne, with a microwave cavity, we noti- ced that an increasing ratio of N2 from to

-

1

1 0 leads to a decreasing electronic density down to a ratio of 113. This ratio is roughly indepen- dant on the Ne pressure and of the beam intensity.

In the experimental pressure range, the value of n arises from an equilibrium between the creation rate S and the recombination rate. If we assume the existence of a dominant ion with a concentration

"i' ni= "e' and n

=

m, where a is the recombi- nation coefficient. At low nitrogen density the do- minant ion is N ;, ^a

⁼

^a

⁼

2-10 cm .s -7 3 -1(9) and n

=

n . Due to decreasing ratio to 1/3 of electro-

e eo

nic density at the high N2 densities we deduce that N+ is becoming the dominant ion with

:

4 a

=

a

=

2.10-~cm~.s-'(~). The observed electronic 1

density n would be consequently n

=

and 1

therefor2'nel/ao = 113. This agrees with previous studies made in afterglow plasmas, that indicate

+ .

at least the existence of N+ and

N

Ions in mixtu-

2 4

res having about the same concentration that we have (7) .

Thus we may conclude that even for low nitrogen concentrations the dominant ion is

N;

and for hi- gher concentrations, heavier ions ( ) ' N appear.

4 520

f

34

497

f 18

528

f

6 527 + ¹⁶

558

f

28 516

f

19 Acknowledgements

:

We would like to acknowledge E. Le Duc for his technical assistance.

This work has been supported by Direction des Recherches, 6tudes et techniques (D.R.E.T.) and by Centre National de la Recherche Scientifique.

References

:

STUDY OF A NITROGEN-NEON NUCLEAR INDUCED PLASMA

HAL Id: jpa-00219174

https://hal.archives-ouvertes.fr/jpa-00219174

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.

STUDY OF A NITROGEN-NEON NUCLEAR INDUCED PLASMA

D. Auphelle, F. Euve, M. Fitaire, A. Pointu, M. Vialle, L. Wartsky

To cite this version:

D. Auphelle, F. Euve, M. Fitaire, A. Pointu, M. Vialle, et al.. STUDY OF A NITROGEN-NEON NUCLEAR INDUCED PLASMA. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-397-C7-398.

�10.1051/jphyscol:19797195�. �jpa-00219174�

JOURNAL DE PHYSIQUE ColZoque C7, suppl6rnent au no?, Tome 40, J u i l l e t 1979, page c7- 397

STUDY ff A MTROGEN-NEON NUCLEAR INDUCED PLASMA

D. Auphelle, F. Euve, M. Fitaire, A.M. Pbintu, M. Vialle and L. wartsky*.

Laboratoire de Physique des Caz e t des Plasmas. Bdtiment 212, Universite' Paris-Sud, 91405 Orsay Cedex, K ~ r m c e .

I n s t i t u t drEZectronique FondamentaZe. Bdtiment 220, Universitg Paris-Sud, 92405 Orsay Cedex, France.

The importance of energy-transfer from neon in Ne-N nuclear induced plasmas is well known. Lasing

2

effect was observed in a Ne-N mixture with a very 2

low rate of N2 impurity, and it was shown that la- sing occurs form a Ne-N2 energy transfer'') . In

this communication the role of nitrogen in a sta- tionary neon plasma induced by a 2.3 MeV proton- beam is reported. The proton-beam intensity,

1. K N energy-transfer_

Visible plasma spectrum 2

was observed and first negative bands of N were encountered. The most intense band corresponds to a wavelength of 391.4 nm. Due to the low nitrogen

2 +

concentrations the excitation of

state

ni- trogen cannot be explained by direct proton excita- tion, but is the result of Ne-N energy transfer.

2

It has been established that the excitation of +

N2(B

state in Ne-N2 mixtures follows from an energyUtransfer from neon ions(2). In our experi- ment Ne+ ions are produced by the proton-beam with a rate S

dE/dx

proton energy-loss per unit length W

average energy required for an electron-ion

pair production

j

proton-beam current-density

Ne+ ions disappear through the following reactions:

(1) ~ e + + 2Ne 8 Ned + Ne, 8

5 . 1 0 - ~ ~ c m ~ . s - ~ ( ~ ) (2) Ne++ N2+ Ne k -+I ..., k

5.31 l ~ - ~ ~ c m ~ . s - ~ ( ~ )

1 (3) Ne++ N2+ N2 t2...,k 2

7.5

-7 3.s-1 (9) (4) Ne++ e ~ e * + Ne, a

1.8 10 cm

2

(5) Ne> N2 5 N;+ 2Ne, k

9 1 0 - ~ ~ c m - ~ s - ~ (3) In the worst conditions for reaction (5) i.e. for maximum value of n

10llcm and minimum value of -3 measured N2 concenzration IN2]= 2 10' 6cm-3 the pro- bability of reaction (5) is lo3 higher than the

probability of reaction (4). We may conclude that Ne-N energy-transfer process involves Ne; ions ac-

2

cording to successive reactions (1) then (5). A quantitative study of these reactions taking into account measured densities of the involved species shows that N+ ions are created with a rate equal to

2

the rate of production of Ne*, i.e. S. Futhermore 2 +

we assume that all N; ions are created in B

sta- + 2 +

te. The N (B

ion disappears owing to the follo- 2 u

wing reactions

This simple model agrees with the observed de- creasing of 391.4 nm line intensity versus increa- sing N pressure. This can be shown on figure (1)

2

which gives the variations of I /(k3+k4 [NJ) (a) and the observed 391.4 nm (b) line intensity versus ni- trogen pressure with a neon pressure of 7 0 torrs.

~ e + molecular-ions created by reaction (I) dissap- 2

pear through the following reactions

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797195

+ 2 +

2. Measurements of the N (B

rotational tempera- 2 u

ture

The ~ t u d y of 391.4 nm R-branch rotational

-

spectrum allows us to determine the rotational tem- '~(5) perature, Trot, of the (B,vv=o) state of N2 .

The following table gives the results obtained for various neon pressures and two proton-beam intensi- ties.

The highly exothermal behaviour of reaction (5) ex- PNe (torrs)

plains that the N; ions temperature is much higher than the nhtral gas temperature measured else- where (6) .

343

10 440

23 456 1 1 510

40 512

low rate of N2 impurity, and it was shown that la- sing occurs form a Ne-N2 energy transfer'') . ^In

(1) ~ e + + 2Ne 8 ^{Ned +} ^{Ne, 8}

5 . 1 0 - ~ ~ c m ~ . s - ~ ( ~ ) (2) Ne++ N2+ Ne k -+I ..., ^k

(5) Ne> N2 5 ^N;+ ^{2Ne, k}

⁹ 1 0 - ~ ~ c m - ~ s - ~ (3) In the worst conditions for reaction (5) i.e. for maximum value of n

m, where a is the recombi- nation coefficient. At low nitrogen density the do- minant ion is N ;, ^a

^a

6 527 + ¹⁶

G. Bekefi - John Wiley - ^New-York.