ECRIS - CLOSING REMARKS

HAL Id: jpa-00229396

https://hal.archives-ouvertes.fr/jpa-00229396

Submitted on 1 Jan 1989

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.

ECRIS - CLOSING REMARKS

R. Geller

To cite this version:

R. Geller. ECRIS - CLOSING REMARKS. Journal de Physique Colloques, 1989, 50 (C1), pp.C1-

887-C1-892. �10.1051/jphyscol:1989195�. �jpa-00229396�

C o l l o q u e C l , s u p p l 6 m e n t au n o l , Tome 50, j a n v i e r 1 9 8 9

ECRIS

-

CLOSING REMARKS

R. GELLER

CENG

-

D R F / P A D S I , 8 5 X , F-38041 Grenoble Cedex, France

Let me begin with some g e n e r a l information : t h i s was t h e 9 t h ECRIS meeting.

The t o t a l number of p u b l i c a t i o n s concerning ECRIS

-

s i n c e 1979

-

reaches 170. Recently I t r i e d t o count papers o f Atomic Physics done with ECRIS and published i n t h e l i t t e r a t u r e . I stopped a t 200.

A s f o r papers of Nucl. Phys. done with ECRIS t h e r e a r e s o many t h a t I dropped t h e counting.

This g i v e s you an i d e a about t h e importance of ECRIS i n general. Of course I cannot summarize a l l t h e involvements of ECRIS. Therefore I w i l l only analyze what w e heard since yesterday i n t h e f i e l d o f ECRIS s c i e n c e & technology. I n o r d e r t o organize t h e concluding remarks I w i l l ask q u e s t i o n s and t r y t o respond. I know t h a t , on a p h i l o s o p h i c a l point of view, such a method is u n f a i r because one can guide t h e conclusions towards t h e f i e l d s one p r e f e r s . Well t h a t i s e x a c t l y what I want and I t h i n k t h a t another time when somebody e l s e w i l l do t h e same kind of job he w i l l do t h e same t h i n g .

Let u s now consider r e c e n t ECRIS Developments : There i s a t f i r s t a family of ECRIS b u i l d e r s f o r i n d u s t r i a l Reasearch and Developments applied t o Ion implantation, Lithography and a l l kind of Ion Engineering. They now c o n s t i t u t e an independant ECRIS community and have t h e i r own s p e c i a l i z e d meetings. I w i l l not speak about t h e i r business. Then t h e r e i s a second family of ECRIS b u i l d e r s f o r more fundamental research

-

^{t h a t} is our community

-

and t h i s family now d i v i d e s i n t o two groups.

a ) low charged i o n s , b ) and high charged i o n s .

The low charged i o n s people want t o t a k e advantage of t h e tremendous i o n i z a t i o n efficiency.

achievable with ECRIS and have developped Isotope and on l i n e ECRIS, p o l a r i z e d ion ECRIS, n e g a t i v e i o n ECRIS, E c r i s f o r a g r e s s i v e m a t e r i a l s , e t c . . . Generally they need low e l e c t r o n energy and n o t extremely good confinement. Karlsruhe h a s always been a pionner i n t h i s f i e l d and they s t i l l a r e . But high performances a r e now a l s o achieved i n Louvain. Grenoble, Canada and Japan, and cusped ECRIS a r e a l s o developped. The F o r e f a t h e r of a l l t h e s e sources were t h e simple and double mirror ECRIS which worked i n our group a l r e a d y 20 y e a r s ago but t h e ECRIS of today reach a kind of u n p a r a l l e l e d p e r f e c t i o n and deserve s p e c i a l congratulations.

The t h i r d ECRIS family d e a l s with h i g h l y charged i o n s f o r fundamental R & D and involves t h e most advanced research. The F o r e f a t h e r of a l l t h e s e sources i s SUPERMAFIOS o p e r a t i n g from 1974 t o 1977. U n t i l now more than 30 sources of t h i s kind were b u i l t a l l over t h e world with some r e c e n t newcomers : t h e two Japanese 10 Ghz ECRIS

-

a t RIKEN and TOKYO

-.

The Argonne High Voltage ECRIS which now works f i n e and i s a master piece of engineering. The Neomafios High Voltage 8 GHz ECRIS which enables easy s e t up on high v o l t a g e platform and t h e recent CW 16.6 GHz Minimafios.

But a t l e a s t 9 new ECRIS a r e underway. Most of then w i l l work a t higher frequencies than u s u a l . In.1990 45 w i l l work a l l around t h e world ( f i g . 1) and hopefully among them t h e 30 GHz Supra-conducting ECRIS, which w i l l need a tremendous t e c h n o l o g i c a l e f f o r t and whose performance should l e a d t o o t h e r break throughs provided t h a t gyrotrons work as well a s D r Mathews t o l d us. Personnaly I do b e l i e v e .

Anyhow i t was very impressive a t t h i s meeting t o hear about t h e ECRIS developments and performance from a l l over t h e world : from t h e pionneering work a t MOSCOU with h o t e l e c t r o n r i n g s and b a s i c high l e v e l r e s e a r c h t o c l a s s i c a l developments i n JAPAN

-

and t h e fundamental work done a t MIT

-

^and "SPIRE" ( a p r i v a t e company) begins a l s o t o ponder high performance ECRIS f o r i n d u s t r i a l a p p l i c a t i o n s .

What is new about o u r knowledge i n ECR plasma 7

F i r s t of a l l we have improved our p r a c t i c a l knowledge :

-

Of d i f f e r e n t ways f o r coupling RF i n t o t h e c a v i t y with c o a x i a l f e e d e r s

-

perpendicular, a x i a l o r o u t of axe waveguides.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1989195

Cl-888

JOURNAL DE PHYSIQUE

-

^{A l l} t h e ECRIS u t i l i z e r s presently know how t o handle gas mixing but a l s o systematic w a l l coating becomes routine i n LBL and Grenoble. The understanding of a l l t h a t i s not complete and discussions are open.

-

^We know how t o obtain s o l i d material vapors with ovens and pistons. In t h i s case Jacquot's diagram showing vapor yields linked t o boiling temperature of the material i s a good canvas.

-

People a l s o begin t o miniaturize o r suppress the f i r s t stage.

-

and gradual increase of B up t o 2 m, has been checked i n MSU. Also some ion chromatism measurements were done a t MSU i n connection with gas mixing

-

and may explain some phenomena.

Good emittance measurements were done a t MSU and D r Vienet proposes more complete and systematic emittance measurements linked t o space-charge-effects i n the extraction zone.

-

once more overdense plasmas was studied a t Moscow and gave clear-cut answers : they are not good f o r high charge ion production. A s soon as the RIKEN ECRIS began t o operate.

E1ect:ron g6ns were added f o r t r i a l . Let us wait f o r c l e a r cut answers...

What about our t h e o r e t i c a l knowledge of ECRIS operation 7 This was and remains the weakest p a r t of our a c t i v i t i e s :

a) We s t i l l cannot f i g u r e out the e l e c t r o magnetic RF f i e l d i n an ECR zone inside a plasma and therefore cannot evaluate the electron energy aquired i n a resonnance.

b) and even i f we could. t h i s i s not relevant i n a stochastic heating mechanism which prevails i n the multimirror source.

In short we are not able t o predict the electron energy o r velocity d i s t r i b u t i o n as a function of RF input power i n a given ECR plasma.

During t h e l a s t year, here i n Grenoble. D r Lieberman from Brazil and D r Melin worked on that topic but progress is very slow

-

and the problem very d i f f i c u l t .

People have t o admit t h a t our lack of understanding and modeling of ECR stochastic heating is not due t o laziness but has i t s roots i n plasma theory, where d i f f e r e n t famous theoreticians already t r i e d t o tackle t h e problem. I have i n my f i l e s more t h a t 1000 printed pages about t h a t topic. I n general they show a l i n e a r increase of electron energy with RF power a t the beginning and then a saturation. But up t o where t o what numerical values is t h i s l i n e a r increase v a l i d ? Nobody knows. I n my scalings l a s t year I proposed a l i n e a r r e l a t i o n between Electron Energy and RF leading t o q,,, increasing with P,, on t h i r d power.

I 'am a f r a i d t h a t such r e l a t i o n s a r e not relevant i n many s i t u a t i o n s , because power ponderative e f f e c t s such as wall coating a r e not taken i n t o account and because, as mentionned previously above, a given RF power threshold, electron heating becomes a nonlinear business.

Thus W, a P,, is only t r u e a t the beginning of t h e RF power increase a s seen on f i g . 2 and qop ^{oc piL3} is therefore very over simplified.

I n f a c t I am presently sure t h a t mathematics w i l l not provide a p r a c t i c a l r e l a t i o n between electrbon energy and RF power before I get r e t i r e d .

So what ? Should we s t o p t o predict ECRIS scalings ? Not a t a l l : i f theory i s not yet good, let us t r y a purely experimental approach. This can be a s h o r t e r way.

And f o r t h a t one has t o develop new methods of measuring the electron energy i n the plasma versus RF input power.

We have already t r i e d t h a t 15 years ago on Supermafios with X-rays and diamagnetism and so did Yves Jongen on the ECREVIS i n 1982. We got some r e s u l t s but not enough. We have now to do i t b e t t e r with additional new methods l i k e Electron Cyclotron Emission. D r Melin who w i l l soon replace me i s presently preparing such measurements. Let m e r e c a l l t h a t he is a s p e c i a l i s t of plasma diagnosis.

However Grenoble would be happy t o share such an e f f o r t with other labs of plasma diagnosis

-

f o r instance Berkeley and MIT.

Persomaly I think t h a t t h i s is now what we need the most : a r e l i a b l e l i n k between Electron energy and RF power.

Now l e t us look f o r the next scalings ; we have proposed

-

t h a t density n i s proportionnal t o 02 f o r reasons of wave cut off

-

and confinement time T proportionnal t o B ' . ~ ( B is the average magnetic f i e l d ) f o r reasons of quasi quiescent diffusion.

kk/

PRF

input

F i g . 1 : The high q ECRIS numbers vs ( t ) F i g . 3 : Q u a s i l o g Sncrease of q vs(nv'C ) - .

r i g . 4 MINIMAFIOS p u l s e d regime 1 Hz-100 m s

-

^{Aq vsw}

q is compatible w i t h q

op ta ^{l o g w 3 p 5} n r v a w3'5

4+

F i g . 4 a : Comparative Tantalum S p e c t r a f o r Cornparatlve Argon S p e c t r a f o r Fig.4b

a / 10 GHz a / 10 GHz

b/ 1 6 , 6 GHz:Mixt. 0 2

b/ 1 6 , 6 GHz:Mixt 20% A r . 90 % 0 2 q o p t : l 0 GHz TaL8+ 30 e pA _q o p t : l O GHz A r 8+ 30 e FA

q o p t : 1 6 , 6 GHz ~ a ~ ~ ~ 50 e pA q o p t : 1 6 , 6 GHz ~ r " 260 e pA

F l g . 4 ~

4oFrT3i

¹⁰

^{fa @}

4

, > I v

l+ 18 22 26 30323% 9+

44

48 2

25

503134

Comparative Uranium S p e c t r a f o r Comparative Xenon S p e c t r a f o r

a/ 10 GHz a / 10 GHz

b/ 1 6 , 6 GHz

q o p t : l o GHZ

u18+

12 e FA q o p t : 1 6 , 6 GHz

uZ5+

^{30 e} FA

b/ 1 6 , 6 GHz l i x t 20 % Xe 80 % 0 2 q o p t : 10 GHz xe18+ 16 e pA q o p t ; 1 6 , 6 GHz ~ e ~ ~ + 4 0 epA

I f v is t h e a v e r a g e e l e c t r o n v e l o c i t y w e f i n d t h a t n w is p r o p o r t i o m a l t o B'.~ when only B is i n c r e a s e d . Knowing more o r less ^{n and T,} s o a g a i n ,

if

w e could e v a l u a t e t h e e l e c t r o n v e l o c i t y v, t h e n t h e b a t c h c a l c u l a t i o n s would g i v e us a good approach t o q optimum which is t h e peak c u r r e n t c h a r g e i n an Ion Spectrum.

n s v a w3.5 ^-+ q o p t o l o g w 3 . 5 n r v a -v q,,, o l o g B'.~

Cl-890 JOURNAL DE PHYSIQUE

But a s long as we cannot e v a l u a t e numerically nrv we can only say t h a t according t o t h e batch c a l c u l a t i o n s q o P t i n c r e a s e s roughly l i k e t h e l o g of n r v t h a t means q o p t i n c r e a s e s l i k e t h e l o g o f 03. 5 .

Why l i k e t h e l o g 7 AS seen on t h e f i g u r e

3

t h e l o g is not a t h e o r e t i c a l by-product but a pragmatic observation. I n many batch f i g u r e s i n o r d e r t o i n c r e a s e q by a f a c t o r of 2 , nrv has t o i n c r e a s e by a f a c t o r of roughly 10 and t h i s because t h e s t e p by s t e p i o n i z a t i o n c r o s s s e c t i o n d e c r e a s e s by 10.

AVCO and EBIS people provided us with some batch f i g u r e s which h e l p u s p r e s e n t l y b u t f o r t h e next f u t u r e w e have not enough of them. Therefore. I i n v i t e ECRIS and Atomic P h y s i c i s t s t o i n v e s t i g a t e more t h i s f i e l d , f o r d i f f e r e n t elements, with a b i g v a r i e t y of reasonnible e l e c t r o n e n e r g i e s .

How p r a c t i c a l l y , t h e s e s c a l i n g s behave is seen on f i g . 3 where we consider an i n c r e a s e of w from 10 GHz t o 16.6 GHz on t h e Minimafios source f o r i n s t a n c e i n pulsed regime f o r Argon Xenon Tantalum and Uranium.

Again t h e l a c k of information on t h e p r e c i s e v a l u e s of nrv and t h e absence o f adequate batch c a l c u l a t i o n s hinder any a c c u r a t e comparisons ; t h e r e f o r e f o r rough e v a l u a t i o n s w e p r e f e r t o u t i l i z e t h e quasi-logarithmic s c a l i n g (which i s uneasy t o apply). Looking a t f i g . 4 t h e only t h i n g we can s a y i s t h a t qoPt increases slowly with o a s expected by such s c a l i n g s .

So t h e s e s c a l i n g a r e n o t wrong b u t j u s t n o t p r e c i s e .

They g i v e a good o r d e r of magnitude f o r upgrading and b e t t e r knowledge of n r v and batch c a l c u l a t i o n should improve them.

Remember t h a t

3

y e a r s ago some people believed t h a t miracles w i l l happen when w i s decreased.

My next q u e s t i o n d e a l s with t h e s c a l i n g which g i v e s i o n c u r r e n t s v s Ion mass and frequency :

I n order t o compare i t t o experimental r e s u l t s I employed t h e s i m p l e s t method. For i n s t a n c e I took t h e l a s t CW r e s u l t s from LBL

-

Grenoble and Riken sources

-

^i.e. t h e peak c u r r e n t s f o r d i f f e r e n t elements of each source, and p l o t t e d i t v e r s u s M. These rough experimental p o i n t s a r e s i t u a t e d with r e s p e c t t o a 1 / M graph p a s s i n g through an experimental reference p o i n t ( M = 1 6 , Oxygen). Fig. 5 shows t h a t t h e 1 / M s c a l i n g looks very r e a l i s t i c (except f o r Argon c u r r e n t s which a r e always b e t t e r than p r e d i c t e d ) . For a p p r e c i a t i n g t h e dependance w e p l o t on f i g . 6 t h e s l o p e of I v s 02 and then compare i t t o t h e s l o p e o f experimental CW i o n c u r r e n t s o f h i g h l y charged s p e c i e s (such a s ~ r l

xeZ5

~ a

uZ5

' ~e t c ) i s s u i n g from t h e LBL source ( a t 6.4 GHz), t h e Caprice and Minimafios source ( a t 10 GHz) and t h e upgraded Minimafios ( a t 16.6 GHz). Once again we n o t i c e t h a t t h e w square law looks very r e a l i s t i c

...

But even i f t h e s e s c a l i n g look a l r e a d y decent, one should n e v e r t h e l e s s continue t o make them b e t t e r and every new i n i t i a t i v e , experimental o r t h e o r e t i c a l , h a s t o be encouraged.

F i n a l l y I want t o i l l u s t r a t e t h e impact of highly charged ECRIS on modern nuclear and p a r t i c l e physics. ( I t s impact on atomic physics has been debated e a r l i e r a t t h i s meeting).

For t h a t l e t us consider a diagram where y i s t h e a c c e l e r a t i o n energy of t h e p r o j e c t i l e s varying from 1 MeV/U t o 500 GeV/U and X i s t h e atomic number of t h e p r o j e c t i l e s from Hydrogen t o Uranium. On t h e diagram we a l s o l o c a t e some well-known f i e l d s of heavy i o n research. and some w e l l known p a r t i c l e a c c e l e r a t o r s , c y c l o t r o n s , l i n a c s synchrotrons and compound a c c e l e r a t o r complexes. A t f i r s t w e s e e t h e s i t u a t i o n i n 1980 before ECRIS were employend. Then w e show t h e s i t u a t i o n i n 1987 with soqe 20 ECRIS already working and e v e n t u a l l y what w i l l be t h e s i t u a t i o n i n 1992 when CERN. GSI, MSU, GANIL. IMP RIKEN e t c . w i l l work with upgraded ECRIS. Nearly a l l t h e diagram w i l l be f i l l e d thanks t o the u t i l i z a t i o n o f ECRIS. Conclusion : ECRIS b u i l d e r s a r e n o t numerous b u t a r e tremendous people

...

I hope t o s e e you soon.

M

-0- L 8 L ECRfS 6.4 GHz

--+

^{CAPRICE 10GHi}

-+

^{RlKEN 10 GHz}

-U- MINIMAFIOS 16.6 GHz

50

^-

----__

0

Ne ArCc S*

Fig5

: optimum i o n c u r r e n t s v s i o n mass f o r f o u r d i f f e r e n t E C R I S .

~ i 9 , 6

: CW h i g h q c u r r e n t s v s ( W 2 ) f o r LBL 6 , a GHz, C a p r i c e and M i n i m a f i o s 10 Chz a n d M i n i r n a f i o s 16,6 GHz.

The Trnpzct of ECF.IS on Nuclear & Particle Physics

without ECRIS

W

SUPER DENSE SUPER HOT MATTER

with ECRIS

z z

GANIL, 1' MSU

,

2 UNILAC

,

^2'SUPERHILAC, Accelerators :

3 & 4 Various Cyclotrons : LBL, KVI, JULICH, GRENOBLE etc.. 5 DOUBNA, S'INDIANA

1

6 Synchrotr.SATURNE, 7 Synchrophas. DOUBNA, 8 BEVATRON, 9,CERN: PS+SPS