AGLAE : AN EFFICIENT PULSED keV RANGE X-RAY SOURCE AND ITS SPECTROSCOPY DIAGNOSIS

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AGLAE : AN EFFICIENT PULSED keV RANGE X-RAY SOURCE AND ITS SPECTROSCOPY

DIAGNOSIS

C. Bruno, Jacques Chevallier, J. Delvaux, Y. Cauchois, R. Kherouf, C.

Senemaud

To cite this version:

C. Bruno, Jacques Chevallier, J. Delvaux, Y. Cauchois, R. Kherouf, et al.. AGLAE : AN EFFICIENT

PULSED keV RANGE X-RAY SOURCE AND ITS SPECTROSCOPY DIAGNOSIS. Journal de

Physique Colloques, 1987, 48 (C9), pp.C9-107-C9-110. �10.1051/jphyscol:1987917�. �jpa-00227284�

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JOURNAL DE PHYSIQUE

Colloque C9, suppl6ment au n012, Tome 48, decembre 1987

AGLAE : AN EFFICIENT PULSED keV RANGE X-RAY SOURCE AND ITS SPECTROSCOPY DIAGNOSIS

C. BRUNO, J. CHEVALLIER, J. DELVAUX, Y. CAUCHOIS*, R. KHEROUF*

and C. SENEMAUD"

CEA, Centre d 'Etudes d e Valduc, F-21120 Is-sur-Tille, France

* L C P , Universite Pierre et Marie Curie, F-75005 Paris, France

It i s known t h a t h i g h energy low impedance pulsed e l e c t r o n generators produce exploding w i r e s o r gas-puff Z-pinch plasmas which r a d i a t e i n t e n s e X-ray pulses.

These e x p e r i m e n t s were p i o n e e r e d i n t h e 7oth b y N.R.L.l. T h i s paper presents Z-pinch experiments conducted w i t h t h e generator Aglae 2 . I t s inductance was lowe- r e d t o about 20 nH i n order t o ensure a f a s t c u r r e n t r i s e time (3.1013A x s-1 f o r 40 ns). E i t h e r aluminium wires a r r a y o r gas-puff have been used t o extend t h e X-ray l i n e s range from 1 t o 4 keV. F i g u r e 1 shows geometries w i t h t h e f i g h t l i n e s which a l l o w plasma diagnosis by means o f i t s r a d i a t i o n .

cathode anode

Fig. 2 : Time-integrated p i n h o l e camera Fig. 1 : Diode and gas i n j e c t o r images

nozzle geometries f i l t e r s : Be 11 p ( a ) , A1 5 pm ( b ) T i 6 pm ( c )

The X-ray images shown i n f i g u r e 2 were taken through a t r i p l e t i m e - i n t e g r a t e d p i n h o l e camera behind t h r e e d i f f e r e n t f i l t e r s : Be 11 p, A1 5 pm, Ti 6 pm. The low energy range contour p l o t shows f l a r i n g areas which probably do n o t occur a t t h e same time along the plasma. The harder e m i t t i n g zones on a x i s are thought t o be

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987917

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C9-108 JOURNAL DE PHYSIQUE

responsible of a high energy bremsstrahlung component created by energetic runaway electrons. The plasma length ( 3 cm) i s equal to the cathode-anode gap. The emitting plasma column diameter i s

w i t h i n 1

and 5

mm,

depending on the i n i t i a l conditions

(gas-puff pressure, e l e c t r i c a l power delay, i n i t i a l diameter, imploded mass).

-I I

0 so .loo IS0 LOO t (nsl

Fig. 3: Visible l i g h t streak Fig. 4

:

X-Ray waveforms through photographs of Ne-implosion different f i l t e r s

Implosion dynamics i s followed with the help of a streak camera. I t observes a plasma length of

1

mn i n the middle of the cathode-anode space. Figure 3 shows

2

v i s i b l e 1 ig h t streak photographs recorded on 30

mn

diameter neon-puff imp1 osions.

The f i r s t one i s taken i n the case of a high imploded mass due t o a l a t e e l e c t r i c a l power injection in the diode. The plasma motion i s l a t e and slow. The other case shows a high velocity up t o 4 . 1 0 ~ cm. s-l.

A

simple mathematical model (internal r e p o r t ) was s e t up t o explain experimental r e s u l t s . I t allows us t o estimate the imploded mass. As an example, calculated times and v e l o c i t i e s corroborate measu- rements i f 25 pg neon a r e imploded in the Z-pinch process i t s e l f . Furthermore the model shows a b e t t e r coupling of imploding load t o the generator f o r a reduced gas-puff diameter.

Implosion timing i s a l s o deduced from X-ray diodes measurements. The XRD1s cathodes a r e made of a1 uminium and associated with f i l t e r s , e i t h e r a1 uminium (0.8

pm

or 5

~JII

thick) or beryl1 ium (10 thick). Figure 4 shows X-ray wave-forms from

Ne-puff implosion. The hard X-ray burst i s roughly 30 ns a t

F.W.H.M.

while the

over-all emission l a s t s about 150 ns due t o low energy X-ray and

U.V.

Bursts are

not well reproducible. Their energy, measured with a

5 pm

thick tantalum calori-

meter placed behind an 11

^pm

thick beryllium f i l t e r , i s within

1

t o 3 kJ.

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X-ray spectra were p r e v i o u s l y c o l l ected i n the 0.8

-

4 keV range w i t h a convex curved c r y s t a l spectrograph 3. A new instrument was r e c e n t l y b u i l t ( f i g u r e 5). It incorporates two independent convex c r y s t a l s which analyse simultaneously t h e X-ray b u r s t e i t h e r i n the same energy range o r not. Bent c r y s t a l s , manufactured by Q u a r t z e t S i l i c e o r L.C.P., i n c o r p o r a t e d i n our spectrggraph were p r i n c i - g a l l y : Rb AP (2d = 26.J2 A) KAP (2 d = 26.64

4 )

mica ( 2 d = 19.90 A) and L i F ( 2 d = 4.03 A ) . Narrow PIN diodes have been a l s o used i n t h e spectrograph t o c o l l e c t some choosen 1 ines. An independant study o f t h e r e f l e c t i - v i t y p r o p e r t i e s o f these types o f c r y s t a l s , e i t h e r plane o r convex, was performed w i t h an X-ray tube. It appears t h a t the r e f l e c t i v i t y i s n o t s i g n i f i c a n t l y modified by t h e s t r o n g curvature.

F i g . 5 : Schema o f t h e spectrograph

Figure 6 showstypical spectra e m i t t e d from Ne and Ar plasmas. A l l e x h i b i t both

He-1

i k e and H-1 i k e series, however the l a t e r i s weak on t h e Ar spectrum. Some e v i - dence o f t h e L i - l i k e s e r i e s appears a l s o on each record. Temperatures and densi- t i e s were i n f e r e d from comparisons w i t h pub1 i s h e d c a l c u l a t i o n s 4, 5 . T y p i c a l l y Ne plasmas h o t areas l i e i n the 0.1 t o 0.5 keV range and 1019 t o

l o z 0

e-. w h i l e f o r Ar, temperature i s h i g h e r than 1 keV and d e n s i t y i s l e s s than 1019 e-. ~ m - ~ .

Fig. 6 : Ne and Ar spectrum ^I

*

;

^-e(ke~)4 ³^:^s ³

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C9-110 JOURNAL D E PHYSIQUE

A narrow PIN diode gives the s i g n a t u r e o f H - l i k e resonance l i n e i n f i g u r e 4.

The Ne X formation i s much s h o r t e r than the o v e r - a l l plasma duration, however t h e diode s i g n a l does n o t a l l o w t o o b t a i n temporal i n f o r m a t i o n concerning t h e Ne I X and Ne X i o n s occurence. The i n t e g r a t e d r e f l e c t i v i t y data were used t o estimate the r a d i a t e d resonance l i n e energy : a value between 0.2 and 1 k J was obtained.

References

1. D.Mosher, S.J.Stephanakis, J.M.Vitkovitsky, C.M.Dozier, L.S.Levine and D.J.Nage1, Appl. Phys. L e t t .

-

23 (81, 429, (1973)

2. A.Bernard, C.Bruno, J.Delvaux, P.Eyl

,

A.Nicolas and G.Raboisson, i n Procee- dings o f t h e 1983 Pulsed Power Conference, (Albuquerque, N.M. 1983)

3. C-Bruno, Y-Cauchois, J. Cheval l i e r , R.Kherouf, C.Senemaud, Nucl

.

^Instrum.

Methods,

222,

601, (1984)

4. R.Mewe, Sol. Phys.,

22,

459, (1972)