J. Trebes et al- Progress Report on the Lawrence Livermore National Laboratory Soft X-Ray Laser...

8/3/2019 J. Trebes et al- Progress Report on the Lawrence Livermore National Laboratory Soft X-Ray Laser Program

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UCRL- 96365PREPRINThiif-mitf-

Progress Report on theLawrence Livermore National LaboratorySoft X-Ray Laser Pr ogram

J. Trebes, S . Brown, E.M. Campbell, N. CeglioD . Eder, D . Gaines, A. Hawryluk, C. Keane, R. London

B. HacGowan, D . Matthews, S. Haxon, D . NilsonM. Rosen, D . Stearns, G. Stone, and D . Whelan

This pap er was prepared for submittal toSPIESan Diego, CaliforniaOttober 17-21, 1987

August 1987

This is a preprint of a paper intended for pu blication in a journal or proceedin gs. Sincechanges may be made before publication, this preprint is nude available with theunderstanding that it will not be cited or reproduced without the permission of theauthor.

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OiSTiiibL'iiofi (IF T H I S onr.uurr,


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DISCLAIMERThis dt c n l n u prepared as in ircoM l tf work sponsored bj >w ot** Q of th +United States Government. Neither (he United States G T


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PROGRESS REPORT ON THE LAHRENCE LIVERHORE NATIONAL LABORATORYSOFT X-RA Y LASER PROGRAM*

J . Tre be s , S . B row n, E . M . C a m pbe l l , N . C e g l l o , D . E de r ,D. Ga ines , A . Hawry luk , C . Keane , R. London, B. MacGowan,D . Ma t t he w s , S . Ma x on , D . N l l s on , M . R os e n ,D . S t e a rn s , G . S t o ne , a nd 0 . H he l a nLa w re nce L l v e rm ore N a t i o na l La b ora t o ryU n i v e r s i t y o f C a l i f o r n i a

L 1 vern iers , CA 94550O C R L - - 9 6 3 6 5

A B S T R A C T D E 8 8 0 0 1 8 8 8S i g n i f i c a n t p r o g r e s s t o w a r d t h e g o a l o f p r o d u c i n g h i g h p o w e r , h i g h

c o h e r e n c e x - r a y l as e r s h a s b e e n m a d e . L a s l n g at w a v e l e n g t h s as l o w as6 6 A h a s b e e n a c h i e v e d in a n i c ke l l i k e l a s e r s c h e m e w h i c h 1s s c a l a b l et o s u b - 4 4 A w a v e l e n g t h s . In a d d i t i o n , x - r a y l a s e r c a v i t i e s , x - r a yh o l o g r a p h y , a n d an a p p l i c a t i o n s b e a m l i n e h a v e b e e n d e m o n s t r a t e d .

' W o r k p e r f o r m e d u n d e r t h e a u s p i c e s o f t h e U . S . D e p a r t m e n t o f E n e r g y byt h e L a w r e n c e L l v e r m o r e N a t i o n a l L a b o r a t o r y u n d e r c o n t r a c t n u m b e rW - 7 4 0 5 - E N G - 4 8 .

MASTER01STRIBUTI0H OF THIS DOCUMENT IS UNUiiUUb , N \


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I N T R O D U C T I O NT h e L a b o r a t o r y S o f t X - r a y L a s e r P r o g r a m a t t h e L a w r e n c e L i v e r m o r e

N a t i o n a l L a b o r a t o r y N o v a L a s e r F a c i l i t y h a s b e e n p u r s u i n g s o f t x - r a yl a s e r r e s e a r c h w i t h t h e go a l o f p r o d u c i n g h i g h l y c o h e r e n t , h i g h p o w e rs u b - 4 4 A l a s e r s . A ge n e r al r e v i e w o f t h i s e f f o r th a s b e e n p r e s e n t e d b y D . M a t t h e w s e t a l . , p r e v i o u s l y . S i g n i f i c a n t n e wp r o g r e s s h a s b e e n m a d e t o w a r d t h i s g o a l s i n c e t h e n . S p e c t r a l l y r e s o l v e ds o u r c e s i z e m e a s u r e m e n t s h a v e s h o w n t h a t t h e t ot a l o u t p u t e n e r g y o f t h eN e - l i k e S e l a s e r 1 s n o w g r e a t e r t h a n t h e c a l c u l a t e d s a t u r a t i o n o u t p u te n e r g y . M u l t i - p a s s a m p l i f i c a t i o n u s i n g t h e S e l a s e r ha s a l s o b e e nd e m o n s t r a t e d 1 n a l a s er c a v i t y . L a s l n g h a s b e e n d e m o n s t r a t e d 1 n N 1 - 1 i k eE u a t w a v e l e n g t h s a s l o w a s 6 6 A . T h i s s c h e m e 1 s s c a l a b l e t o s u b - 4 4A w a v e l e n g t h s . R e s e a r c h on r e c o m b i n a t i o n l a s e r s c h e m e s w h i c h a r e a l s os c a l a b l e t o s h o r t e r w a v e l e n g t h s h a s b e e n i n i t i a t e d . A n x - r a y l a s e ra p p l i c a t i o n s b e a m l i n e ha s b e e n c o n s t r u c t e d a n d u s e d 1 n ap h o t o - 1 o n 1 z a t 1 o n p h y s i c s e x p e r i m e n t . F i n a l l y , x - r a y h o l o g r a p h y u s i n g a nx - r a y l a s e r h a s b e a n d e m o n s t r a t e d f o r t h e f i r s t t i m e .

N E O N L I K E S E L E N I U MT h e N e - I 1 k e S e l a s e r i s p r o d u c e d w h e n a p o w e r f u l o p t i c a l l a s e r p u l s e

1 2i o n i z e s a n e x p l o d i n g fo il g e o m e t r y t a r g e t . ' T h e p o p u l a t i o n i n v e r s i o nI s p r o d u c e d b y b o t h c o l l l s l o n a l e x c i t a t i o n a n d d i e l e c t r o n i c r e c o m b i n a t i o nd u r i n g t h e o p t i c a l l a s e r d r i v e p u l s e . 1 , 3 T h e t yp i c a l I r r a d i a n c e o n t hef oi l 1 s 5 x 1 0 1 3 H / c m 2 o f 0. 5 u m l i g h t 1 n a 5 0 0 p s g a u s s l a n p u l s e .T h i s p r o d u c e s l a s e r e m i s s i o n a t fi v e w a v e l e n g t h s r a n g i n g f r o m 1 8 2 t o2 6 3 A . T h e d o m i n a t e e m i s s i o n o c c u r s a t 2 0 6 a n d 2 0 9 A . T h e e m i s s i o n


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at these wavelengths Is more than five orders of magnitude greater thanthe spontaneous emission le v e ls . Ti;e la se r source s iz e has been measuredto be 50 urn 1n dia m ete r.* With th is source s iz e, the output energyof about 150 raj from a 4 cm long las er have been shown to be g re ater than4the pre dicte d sa tu rat ion output energy of 70 mO.

LASER CAVITIESLaser cavity development 1s Important for the improved efficiency,

divergence, and coherence of soft x-ray la se rs . For the f i r s t tim e,multi-pass am plific atio n o f a so ft x -ray laser has been demonstrated.The cavi ty r e s is te d of a spherical m ult l - la yer mirror and a f la tm ul ti- lay er b eam splitter placed at e ith er end of the Se las er . Thespherical mirror was a Si/Ho multi-layer deposited on a glass substrate.The beamsplitter was a Si/Ho multi-layer deposited on a 400 A si l iconni tr id e substra te. The thin si l ico n n itr id e substrate has high soft x-raytransmission . The measured re fl e c t iv it ie s at 206 A were 201 for thesph erical m irror and 151 fo r the be am sp litte r. The measured bea ms plittertransmission was 5%.

Both double pass and triple pass amplification experiments wereconducted. A time resolved s pectrometer was used to monitor the las eroutput from the ca v it y . In the double pass exp erime nts, the second passwas about seven times more Intense than the I n i t i a l am plifie d spontaneousemission. In the tr ip le pass experiments, the In it i a l laser emission, thesecond pass due to reflection off the mirror, and the third pass due tore fle ct io n o ff the beam splitter and the mirror were time resolved . Thesecond pass was about 20 times more intense than the f i r s t pass, wh ile


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the th ir d pass was comparable to the f i r s t p ass. The drop in the t h ir dpass output was due to the rapidly decreasing gain as a function of timelat e 1n the laser t ime evolution .

NICKEL LIKE LASERSThe s c a la b il it y o f U se r schemes to sh orter wavelengths is important

for such ap plic at ion s as holography of bi olo gi ca l specimens where thela se r wavelengths need to be in the "w ater window" (44 -23 A ) . TheNe-like schemes are estimated to require drive laser intensities of morethan 1 0 1 6 H/cm 2. These In te n s it ie s , over foca l spots severalcentimeters in length necessary for saturation, ar2 beyond theca pa bil i t ie s f current opt ical las ers . Nickel l i k e las ers , however,w il l only req uire approximately 4 x 10 H/cm for U si ng at 43 A.The N1 -Hk e lase r 1s an analog to the Ne-I1ke las er except 4-4 tra ns itio nsare used as laser tra ns it ion s instead of the 3-3 tr an sit i on s 1n theHe -lik e la se rs . The 4-4 tran sit io ns In N1-H ke ions have a shorterwavelength for a given Ionizatio n pot ent ial than the 3-3 tra ns it ion s InNe-I1ke systems. This res ults In less power being required for U si ng tobe achieve d. Laslng at 66 and 71 A has bean demonstrated i n M i- li k eEu. Evidence for gain a t SO.5 A has been obtained 1n Nl - li k e Yb.These experiments a re discussed in more d e ta il 1n Ref. 4 (thes eproce edings ). Experiments using N 1- lik e W, with U se r emission a t 43 Aare planned.


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R E C O M B I N A T I O N L A S E R SR e c o m b i n a t i o n l a s e r s su c h a s t h o s e d e m o n s t r a t e d b y S u c k e w e r ,

e t a l . , 7 a n d K e y e t a l . , h a v e si m p l e a t o m i c p h y s i c s a n d a r a p ids c a l i n g to s ho r t w a v e l e n a t h s . H y d r o g e n l i k e A l h a s p r e d i c t e d g a i n s o f5 c m - 1 o n t h e 3 - 2 t r a n s i t i o n a t 3 9 * u s i n g a d r i v e l a s e r I n t e n s i t y o f3 x 1 0 1 5 W / c m 2 . T h e o u t p u t p u l s e l e n g th I s p r e d i c t e d t o b e 1 0 p s 1 nd u r a t i o n . 9 L i t h i u m l i k e C r 1 s p r e d i c t e d t o a l s o h a v e l a s e r e m i s s i o n a t3 9 A w i t h a d r i v e l asfir p o w e r o f 3 x 1 0 H / c m . I o n i z a t i o n b a l a n c eant! s p e c t ra l I d e n t i f i c a t i o n e x p e r i m e n t s a r e u n d e r w a y a s a p r e l i m i n a r y s t e pt o p r o d u c i n g s u b - 4 4 A l a s l n g u s i n g r e c o m b i n a t i o n l a s e r s y s t e m s .

A P P L I C A T I O N S B E A M L I N ET h e S e x - r a y l a s e r w a v e l e n g t h s ( - 2 00 A ) , p u l s e l e n g t h (- 20 0 p s )

a n d o u t p u t e n e r g y ( 0 - m j ) a r e w e l l m a t c h e d t o t e s t t h e p o p u l a t i o ni n v e r s i o n p h y s i c s f or a 3 7 2 A p h o t o - 1 o n 1 z a t i o n l a s s r I n N a p r o p o s e db y H . S l l f v a s t a n d 0 . H o o d . " I n o r d e r t o u t i l i z e t h e S e l a s e r , a na p p l i c a t i o n s b e a m l i n e w a s c o n s t r u c t e d t o c o l l l m a t e , r e l a y , a n d f o c u s t h e

1 2x - r a y l a s e r b e a m I n t o a N a c e l l . A s c h e m a t i c d r a w i n g s o f t h e s y s t e mI s s h o w n in F 1 g . 1 . T h e b e a m l l n e c o n s i s t e d o f t w o s p he r i c a l m u l t i - l a y e r sa nd a th i n A l f i l t e r . T h e s p h e ri c a l m i r r o r s h a d a p e a k r e f l e c t i v i t y o f~ 2 6 i at 2 0 8 A an d a r a d i u s o f c u r v a t u r e o f 4 m e t e r s . T h e n a r r o wb a n d p a s s (~10X> o f tiie m i r r o r s w a s u s e d t o e l i m i n a t e t h e b a c k g r o u n de m i s s i o n d u e t o t h e n o n - l a s 1 n g p r o c e s s e s . T h e 1 0 0 0 A t h i c k A l f i l t e rw a s u s e d t o e l i m i n a t e s t r a y 0 . 5 urn v i s i b l e l i g h t f r o m t h e d r i v e l a s e rs c a t t e r e d b y t h e S e e x p l o d i n g fo il t a r g e t . A m e a s u r e d s p o t s i z e o f


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3 0 0 ym I n d i a m e t e r was ob t a i ne d us i ng t h i s o p t i c s s y s t e m . Th i sm e as ure m ent w as done w i t h t he op t i c s s l i g h t l y de f oc u s e d . Th i s s po t s i zeI s c on s i s t e n t w i t h a s po t s i ze o f 1 0 0 \im 1 n d i a m e t e r , a t b e s t f o c u s .The Se l a s e r be a m l l ne has be en us ed 1n a p re l i m i n a r y pho t o - 1 on 1 za t 1 one x p e ri m e n t w i t h A r . 1 3 E x pe r im e nt s w i t h N a a re p l a n ne d .

HOLOGRAPHYX - r a y h ol og r a ph y o f f e r s t h e p o s s i b i l i t y o f o b t a i n i n g h i g h r e s o l u t i o n

( < 5 0 0 A ) t h r e e - d i m e n s i o n a l Im ag es o f l i v e b i o l o g i c a l s p ec im e n s o nt l n e s c a l e s s h o r t c om pa re d t o b i o l o g i c a l p r o c e s s e s . T h i s r e q u i r e s h i g hp o w e r, h i g h l y c o h e r e n t , s u b -4 4 A l a s e r s . H 1 t h t h e d e m o n s t r a t i o n o fN 1 - I 1 k e l a s e r s , th e d e m o n s t ra t io n o f l a s e r c a v i t i e s , an d t h e p o s s i b i l i t yo f o s c i l l a t o r - a m p l i f i e r x - r a y l a s e r c h a i n s , such h ig h q u a l i t y l a s e r smay s oo n b e a v a i l a b l e f o r h o l o g ra p h y o f b i o l o g i c a l s p e ci m e ns . As a f i r s ts tep toward the goa l of mak ing holograms o f b io lo g ic a l spec imen s, a proofo f p r i n c i p l e x - ra y l a s e r ho log ra phy e x pe r i m e nt ha s bee n de m ons t ra t e d .

The Se U s e r a t 206 and 209 A was used 1n a m od i f ie d Gaborgeom et ry . A schem at ic o f the system is shown in F i g . 2 . An u l t ra -sm oo th


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a v e r a g e i n t e n s i t y a c r o s s t h e d a t a a s a f u n c t i o n o f p o s i t i o n , t h e b o t t o mp o r t i o n s h o w s a c a l c u l a t e d f r i n g e p a t t e r n f o r t h e w i r e . A g r e e m e n t i sq u i t e g o o d e x c e p t a t l a r g e d i s t a n c e s f r o m t h e c e n t e r o f t h e h o l o g r a mw h e r e t h e s p a t i a l f r e q u e n c y o f t h e f r i n g e s i s t o o h i g h c o m p a r e d t o t h es p a t ia l r e s o l u t i o n o f t h e f i l m . H o l o g r a m s o f t h r e e - d i m e n s i o n a l g o l d b a rf i g u r e s w e r e a l s o o b t a i n e d a n d r e c o n s t r u c t i o n s u s i n g a H e - N e l a s e r w e r es u c c e s s f u l l y p r o d u c e d . A l t e r n a t i v e h o l o g r a p h y s y s t e m s w h i c h o f f e rp o t e n t i a l l y h i g h e r r e s o l u t i o n s a r e b e i n g p u r s u e d . R e q u i r e m e n t s f o rm a k i n g h o l o g r a m s o f b i o l o gi c a l s p e c i m e n s w i t h s u b - 4 4 X l a s e r s a r e a l s ob e i n g s t u d i e d .

C O N C L U S I O N ST h e L L N L s o f t x - r a y U s e r p r o g r a m 1 s n o w f o c u s i n g o n t h e d e v e l o p m e n t

o f s u b - 4 4 A l a s e r s c h e m e s w h i c h c a n b e s c a l e d t o h ig h p o w e r a n d h i g hc o h e r e n c e . T h e t e c h n o l o g i e s f o r t h i s , s u c h a s c a v i t i e s , o s c i l l a t o ra m p l i f i e r d e s i g n s , a n d x -r a y o p t i c s a r e b e i n g d e v e l o p e d . T h e r e 1 s a l s oa n i n i t ia l e f f o r t 1 n d e v e l o p i n g x - r a y l a s e r h o l o g r a p h y a s a u s e f u l t o o l1 n h i g h r e s o l u t i o n m i c r o s c o p y .


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R E F E R E N C E S1 . D . H a t t h e w s , e t a l . , J . O p t i ca l S o c .2 . D . M a t t h e w s , e t a l . , P h y s . R e v . L e t t . 4 . H O ( 1 9 8 5 ) .3 . M . R o s e n , e t a l . . " O n t he D y n a m i c s o f C o l l i s l o n a l E x c i t a t i o n X - r a y

L a s e r s , " t o b e p u b l i s h e d .4 . D . H h e l a n , e t a l . , t h e s e p r o ca e d lr s c s.5 . N . C e g l i o , e t a l . . " M u l t i - p a s s A m p l i f i c a t i o n o f S o f t X - r a y s I n a

L a s e r C a v i t y , " s u b m i t t e d t o O p t i c s L e t t e r s .6 . B . H a c G o w a n , e t a l - , " D e m o n s t r a t i o n o f S o f t X - r a y A m p l i f i c a t i o n i n

N i c k e l - l i k e I o n s , " s u b m i tt e d t o P h y s . R e v . L e t t .7 . S . S u c k e w e r , e t a l . , P h y s . R e v . L e t t . 5 5 . 1 7 5 3 ( 1 9 6 5 ) .8 . K . K e y . e t a l . , J. d e P h y s i q u e , , 71 ( 1 9 8 5 ) .9 . 0 . E d s r , e t a l . , " R e c o m b ^ i i t l o n X - r a y L a s e r s U s i n g H - H k e M a g n e s i u m

a n d A l u m i n u m , " s u b m i t t e d t o J O S A B .1 0 . C . K e a n e , e t a l . , to b e p u b l i s h e d .1 1 . H . S i l f v a s t , e t a l . , " S ho r t W a v e l e n g t h C o h e r e n t R a d i a t i o n :

G e n e r a t i o n a n d A p p l i c a t i o n s , " D . A t w o o d a n d J. B o k o r , e d s . ( A I P , N Y ,1 9 8 6 ) .

1 2 . 0 . N i l s o n , e t a l . , t o b e p u b l i s h e d .1 3 . H . S i l f v a s t , 0 . H o o d , e t a l . , t o be p u b l i s h e d .1 4 . M . R o s e n , e t a l . , C o n m . P l a s m a P h y s . C o n t r o l l?--1 f u s i o n , V } 2 4 5

( 1 9 8 7 ) .1 5 . J . T r e b e s , e t a l . , s u b m i t te d t o Sc ir -n ce .


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F T G J R E C A P T I O N S1 . S c h e m a t i c o f t h e x - r a y l a s e r a p p l i c a t i o n b e a m l l n e .2 . S c h e m a t i c a r r a n g e m e n t c f t h e m o d i ' l e d G a b o r h o l o g r a p h y g e o m e t r y

s h o w i n g t h e n a r r o w b a n d p a s s x - r a y m i r r o r .3 . U p p e r f r i n g e p a t t e r n f r o m h o l o g r a m o f 8 ins w i r e . M i d d l e

a v e r a g e I n t e n s i t y a s a f u n c ti o n o f p o s i t i o n I n t h e f r i n g e p a t t e r n .L ow er c a l c u l a t e d I n t e n s i t y a s a f u n c t i o n o f p o s i t i o n f o r ah o l o g r a m o f a n 8 jim w i r e .


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75 mm dia. multi-layerx-ray mirrors

tnsertable beamsplitterSelenium x-ray-

laser at 2 06 & 209 A. Two multi-layer mirrors focus the x-ray laserto a 300 nm dia. point. The laser can be pointed with a 75 urad accuracywith this mirror configuration.


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101 Film Detector

Multi- layer X-ray MirrorR - 25 % @ 208A

Selenium X-ray Laser


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i t * - t ' '

> . -

-200 -100 0 100 200X-posWen (umj

-200 -100 0 100 200X-pottlon (microns)

J. Trebes et al- Progress Report on the Lawrence Livermore National Laboratory Soft X-Ray Laser...

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