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LA-uR--f34-295l

llE85002037

TITLE: CAPABILITIES OF THE LOS ALAMOS NATIONAL LABORATOKiIN NUCLEAR TARGET TECHNOLOGY

AUTHOR(S): Judith C. Gursky

SUBMITTEDTO 12th World Conference of International NuclearTarget Development Society

DISCLAIMER

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~~~~k)~~s ~osAlam.sNewMexi-08754S1os Alamos National Laboratory

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CAPABILITIES OF THE LOS ALAMOS NATIONAL Laboratory

IN tWJCLEARTARGET TECHNOLOGY

Judith C. Gurakv

Los Alamos National LaboratoryPhysics Division

LOB Alamoe, NM 97545

ABSTRACT

Targets are made at Loe A!amoa for exDerimente at the Ion Beam Facilitv (Van

de GraaFf), the ~edium Fnergy Phvaica Facility (LAMPF), and for experiments COG-

ducted at many other accelerators in the U.S. ●nd EuroDe. Thin, ii30roDic

taruets are made hv eDuttering and evaporation. Versatile, large-scale facili-

tie~ exist for ceramica and Dlastics fabricatiorl, electroDlatinQ, Dow<*r

metallur~v, fabrication bv Dressing, caatinrz and rollins, chemical and mygical

vaDor deDosicion and smtterinu. SDecial develocmence include lJICra-O(eCiSiO!I

machlnine, cr:~ogenic targets ~nd Sham?d-foil tarRets.

1. Introduction—.

The demand It

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this Laboratory for targeta for accelerator experiments varies

from ultrathin targets for heavy-ion exDerimente to fairly maaeive blocks of

ieotoDic material for bombard=nt bv 900 ~eV Darticlea. In addition tc work at

the Ion Beam Facilitv and LAMPF, the Nuclear Phyeicm RrouDs in the Phv.aics

!)ivigion mount experiments at many other arceleratore: GSI, CERN, Oak Ridge

Hoi;.field Heavy Ion Accelerator, Berkelev ~R-jn Cyclotron, SuDerhilac and

~evalac, !lroo~haven ACS, and Indiana Cvclorron.

The Phvsicd Division Taruet Laboratory ciroducee moat of the thin targeta [11,

and for cthera we call on the reaourcee of a large and diverse material%

techn~lo~v erouD, MST-6. A wate~-cooled grnDhite :areet for LAMPF was described

at the INTDS 19~0 Conference [2]

?. p~vgica ~lvi.gion Target Laboratnr?—.—

This Laboratory (fig. 1) contair!d equiument for DhVRical vaDor deDo!3ition

~D1’F, and gbdtterinu. A Danfysik aooarat~s with minor moGificationa is used for

!fi k’! focused-icm-beam aDutterinR [3]. In addirion to d broad ranQe of thin,

lsotnuic targets ( for examDle, ?n, Cd, 0s, ir, Ru, Cr, rare earth oxides), a

t-idfoi,,aed he~q hag Dtoduced larue-area (20crn2) 23611 cl~Dooitg of un to 1 mR!cm2.

A stainlesa-steel, diffusion-DumDed @:-stern reachinu 5 x 10-) corr contain~ a

!rin!?+earch ver~i~fl of t$e VarianfTtlermionics* ?-kw electron Rtin. This ~S

,Jq&~ for a~Dardte~ isotooea and seauenLial ●vaDoration8

qtriODing auenc for utic on heated auhstratee, followed hV ●n

~,Jch ag N1 or Ti.

— .—

*Thermionicmn Inc, 72R15 ~utro St., Vavward, CA Qk5~L

of an inoraanic

iaotone of a metal

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The aeneral tmrDose evaporator has a L5.7 x 76.2 cm qlass bell iar, oumDed by

a cT-R crvopumD* (15001/s for air), and has a 5 WA filament-heating Dawer

SUDDl~ and 6-kW Airco-Temeecal electron gun with variable size hearth

inserts. It ooerate~ at 5 x 10-8 torr. Rcth of these avatems have

Guartz-crvstal deoosit thickness monitors and eubstrate heating or coolinE.

The Laboratory now includes a vacuum evaporation svacem inside n controlled

atmo!3Dhere Rlove hox (fiR. ?). The Kewaunee** 85 l/rein purification svgLem

reduces water and oxygen to less than 1 DDm. NitroRen COIltent Of <~ DDm ~9 not

removed but is aflequatelv low for work with lithium. The 25.L-cm-diameter

vacuum enclosure is diffusion-DunIDed to L x 10-7 torr and hag a ~ kVA fiiament

9UDD1V. A 2-kW electron Run can be installed if needed: the system ic uged for

.wark with reactive and hvgroscoDic materialg. Transfer can he made from a D@i”t

into a transfer mechanism and to an ion-oumDed storage chamber ooerating ac 10-7

torr.

The Laboratory also includes a SWISII hvdropen reductinn filrnace, q-tonne hand

hvdraulic Dress, balances, oDtical microscopes, fume hoods, and ec?uiDmeat for

thicknegg measurement bv ener~v 10SS CIE alDha earticlea.

● CTI-crvoRenicq, Walthmn, MA 0225LI

●*Kewaunce ~cientific FquiDrnent Corn., Lockhart, TX ‘H6~~

3. Materials Technology Grour

A general description of the

the sco De of their capabilities.

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MST-6 facilities will Rive a partial picture of

Ceramics work includes DtessinR and molding, slip-casting of very large parts

of MgO and other oxides and growth of SiC and Si3NM whiskers for reinforcement

of ceramica and plastics. A recent development by T. T. Meek et al. is

bonding of ceramics and production of low-density (0.08 R/cm3) ceramics bv

microwave proceaaing [4,51. The power required for bonding alumina substrates

with sealing glass can he less than 1% of that used in conventions

heating. The result i8 a diffusion bond instead of a tiurface bond. A tvDica

low denaitv ceramic is achieved hv filling the ceramic, lithium silicate glass

with Rlass or metal microfialloons, with potae9ium silicate water glaS9 DrovidinR.

foaming ant-1 bonding. Heating rates of UD to 33 000 OC/h have heen

3 density has compressive strength of ‘5 MDa.observed. Material of 0.1 U/cm

The Dowder metallurgy facility inclu ’es a complete powder characterization

laboratory, measuring surface area, size distribution and Dvcnometer

densitv. Plaema 9praving and hot-pressin~ at UD to 2500°C are among the

capacities. Two new hot isos~-tic presseg are on order and will be installed in

the next year. Re6ctive and radioactive materials are Droceaeed in

inert-atmo.sDhere glove boxes,

Direct rolling of powder into sheet is done on a mill !Jith 20.3-cm-diameter

rl)llerfi. A Dure powder (W, Cu, Ta, end other metals) or a mixture is poured

into th~ rollers under accurate feed control [61. The maximum width is 15 cm,

the minimum thickness ia from 0,0025 cm to 0,025 cm depending on the

mat-rial. A fuEitive binder such aa cetvl alcohol cun he used and the sheets

ar? usua]lv eintered in a reducinR atmosphere,

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Metal fabrication is done by Warforrrrinq, hvdroforming, suDer-Dlastic formirig,

rollinfz, and laser and electron-beam weldinu.

CaDahility also includes SEM, metallography and surface analysis. There i9 a

Dlaatics section, a foundry with Comriuter-contro lled vacuum and arc meltinz

eqtiiment, ehoos machining metals, ceramics, uranium and ~ranhite, ana a

500f)-tonne Dress with 3- diawter caDacitv.

The coatings section has larue scale equiDment for Dhvsical vaDor

cleDosi~ion. ~ig. 3 8;..as some of the electron beam pVD equiDmnc . The

9DtitterinR equiDrrrent include? planar triode units and several chambers wiLh

Sloan S-31O SDutcerguna.* A cryoD~mDerl chamher 122-cm-dia and 122-cm-lonz is

used for ion imp~anaticn and a190 for focused-ion sputtering. Another unit

contains twc focu9able sputtering sources that can deoosit on a sr~bstrate

9irrrultaneouslv.

The coatinu9 section i9 areatly enlaruin~ ita sdrface analvsis cacabilitv bv

the desi~n and construct~.on of a m~ltiDrobe svstem. It will oDerate at ~n..,c

E@rr and will include ~ Hitachi S-520 scanninm electron rnicroscore, AE~ ~Auger

electron srre~troscoov), ED&.. (enerRv-di90ersive analvsis bv Y-rav5~, F~rA

Lelectrlon snectroscoDv for chemical analvfrig), 1ss (ion-g~a[[erirru

q@e:troscnov), TnS (thermal de90rDtion 3Dectro8coDv) and SIYS (seconclar:< i3n

maas sDecLroscoDv). Data aca~isi.ion and analvsis will he handled by a ~p-l~n~

com~dter.

A maior effort is devoted to Dr.jduction and characterization of laser-fusion

microhalloon ta:.acts. A detailed di?SCriDtic)n of thig work is too le!IEthv for

thi9 DaDer. Iiowgver, I will indicate some tidvanced techniques devel?Ded for

●Sloan Technology CcrD., Santa Barbara, CA

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inertial confinement fusion (ICF). Mayer and Catlett [7] have coated

microsphere of 50 to 500 IJIDdia with metal layers of excellent ul~iformity, as

shown in figs. 4a and 4b. Armstrong, Flick and Perry [81 have fabricated

cylindrical gold targets (see FiR. 5) of wall thicknesses 50 and 100 Urn, ucing

electroplating and micromachining. Similar cylinders have heen made as thin as

51Jm.

The Mechanical Fabrication Division has develoDed ultra preci9ion machining

caoahilities that can produce surface finishes of 30nm Desk-to-valley and

pro~rammed surface profiles [9,101. Figs. 6 and 7 ahow an overall view and

scanning electron micrograDhs of a mandrel for a hollow cylindrical ICF tarRet

200Dm-dia and 700Um-lonR. The longitudinal profile of khe piece is an accurate

sine-wave of 25Pm wavelength and 1}1~ amoliturle, machined with a

cornDuter-cont rollecl diamond tool. The mandrel was coated with 2- and 5-Lm

conDer bv electron beam PVD and the mandrel was dissolved, leaving the cooDer

cvlinder.

Novel methods have been develoDed for larger Darticle-beam imDlosion targets

which are required to be of cvlinrlrical symmetrv.

~ Cylindrical Targets—-

Carroll and McCreary [111 have used a fluidized-bed chemical vapor deposition

(CVD) Droce~s to Droduce 3 urn-thick, l,O-cm-diamet ertunRsten cvlinders for use

as imploeion tarqets for beam diaRnostic9 for ICF at Sandia National

Laboratories, Hollow cylindrical mandrels are placed in a hed of dense,

sDht?rical particles. Hydrogen gas flowing through the bed causes the mandrels

to move in a rnndom manner. When the reaction temperature

hexafluoride is admitted. ‘Jsing the reaction klF6 + 3M2

tunR,?ten coatinRs with fine grain structure are cleooaited.

ie reached, tuoR9ten

72~K W + 6 HF, smooth

Acid leachinR of the

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preparation and adhesive. A mechanical refrigerator liquefies the appropriate

gas.

The flask is supported inside a vacuum vessel for heat insulation. If the

flask desiRn includes a flat wall, the pressure differential between the inner

liquid and the vacuum cau8ea bulging of the surface. To eliminate bulRing, one

can enclose the flask in another flask filled with Ras at the same Dressure as

the liquid. Fig. 12 shows the components of such a target.

Additional heat shielding is frequently provided by multiDle layers of

aluminized 0.0067rmI mylar. A 20-layer blanket only duplicates the amount of

Dolymer in the shell of the flask. Liquid helium targets normally require a

much more effective radiation barrier, which is provided by a shell around the

flask, cooled by liquid nitrogen.

3He, ‘He, 14N, ‘5N, 160, and‘arRet 9 of H, !), T, ‘“70 have been used in

experiments as Drimsry targets, to Drovide secondary beams or as analyzing

devices. Target volumes have ranRed from 10 m~ to 17 i. Rare gases are handled

in a sealed svstem, The neutron production target is a rapid-circulation-rate

stainless-steel flask of liquid deuterium, with 76~m-thick walls. Metal flasks

are also used for cryogenic targets of tritium, with containment and safety

considerations taking precedence over cryogenic problems. Stainless steel is

also used for ‘He becau9e of the substantially lower diffusion rate Lhrough the

walls compared to Mylar.

6. Polarized Targets

Several targets Drovidinx Droton Polarization of about 80% by the method of

dvnamic nuclear polarization have been in uae at LAMPF [18,191. The target

designed and built in the Physics llivision is described in detail in ref. 20.

-1o-

7. Acknowledgements..——k

The work described above was performed by many DeoDle. The enclosed

evaporator in the tarqet laboratory was designed and constructed with assistance

from William Teasdale and Edward Robinson. Jerome T. Rowen constructs all of

Lhe plastic cryogenic target flaaks used at LAMPF. The cryogenic targets are

desiEned by Jan Novak’s grouD in MP-7. Much helpful information and advice was

Drovided by Haskell Sheinber.g and Richard Mah, in addition to the Deople whose

work is cited.

-11-

Referencee

[11

[21

[31

[41

[51

[6]

[7]

[R]

[9]

[10]

[111

[12]

[13]

[14]

[151

[]6]

[17]

[18]

[19]

J. C. Gursky, Proc. 10ch World Conf. of International Nuclear TargetDev. Sot., Rehovot, (1981) p. 83.

R. D. Brown, Nucl. Instr. and Meth. 200 (1982) 91.

G. Sletten and P. Knudsen, Nucl. Instr. and Meth. 102 (1972) 459.

T. T. Meek, R. D. Blake, F. H. Cocks, and D. T. Vaniman, MicrowaveProcessing of Terrestrial Materials and the Potential for ProcessingExtraterrestrial Materials, to be published.

T. T. Meek and R. D. ‘Ilake, Ceramic-Ceramic Seals by ?licrowave Heating, tobe vuhlighed.

W. H. Lenz and C. F. Peterson, The Powder Rolling of Molybdenum andTungsten, Los Alamos Scientific Laboratory Report LAMS-2612 (1961).

A. Mayer and D. S. Catlett, Plating and Surface Finishing 65 (1978) 42.

s. Armstrong, F. F. Flick, and(4) (1982) 10S5.

R. L. Rhorer, A. L. Cauler, E. W.

F. Perry, J. Vac. Sci. Technol. 20

Colston and J, R. Ruhe, Proc.Sot, Photo-Optical Instrum. EnE., San DieEo 306 (1981) 122.

R. L. Rhorer, Proc. Sot. Photo-Optical Instrum. Eng., San Dieejo 433(1983) 107,

D. W. Carroll and W. J. McCreary, J. Vat. Sci. Technol. 20(4) (1~82) 1087.

David V. Duchane and Barry L. Barthell, Thin Solid Films, 107 (1983) 373.

R. W. Springer and D. S. Catlett, Thin Solid Films, 54 (1978) 197,

R, W. SDringer, B. L. Barthell, and D. Rohr, J, Vat. Sci. Technol.17 (1) (1980) 437.

R. w. SprinRer and C. D, Hosford, J. Vat, Sci. Technol. 20 (3)(1982) 462.

J. K. Novak, Progress at LAMPF, Los Alamos Scientific Laboratory rePorLLA-R994-PR (1981) 75.

E. E. Eaton, E. p. Ehart, and D. J. Kelly, Fabrication Techniques forLiquid H Accelerator Targets, Los Alamos Scientific Laboratory reportLA-4R62 t1972),

J. J. Jarmer, Progress at LAMPF, Los Alamos Scientific Laboratory reportLA-8994-PI? (1981) 73.

M, V, McNaughton et al., Phys, Rev. C 23, (1981) 838.

-12-

[20] C. R. Newsom, Free Neutron-Proton Analyzing Power at Medium Energies,Dissertation, University of Texas at Austin, 1980.

-13-

Figure CaDtionf3—— —

Fig. 1. Physics T)iviaion Target Lab ratory.

Fig. 2. Controlled atmosphere glove box containing vacuum evaporator.

Fi~. 3. Equipnwnt for electron beam evaporation.

Fig. 4. Metallograohic cross sections of metal microsuheres. (a) Electro~latedwith 22bm nickel (200X). (h) Electroplated with 250 Pm gold.

Fig. 5. Thin walled gold cylinders, 3-, 6-, and 9- dia.

Fig. 6. Machined aluminum mandrel 200Pm-dia, 700-pm-long, with sine-waveeurface.

Fig. ~. ScanninR electron micrographs of cmofile of 200Pm dia aluminum m~lldrelwith eine-wave eurface. (a) 250X. (b) 1000X.

FiR, R. Thin walled tungsten cylinders,

rig. 9. SEM ohotoKraphs of CVD tungoten surface. (a) conventional deoosit at100ox. (b) fluid-bed deposit at 3000X. Note gram refinement.

Fig. 10, lJnhacked 0.2 Lm-thick alumil,um foil mounted on rinR electrode fixture

afler dissolving of rmlv vinyl alcohol backing. The surface is smoothand shiny.

FiR.11, Crvogenic target flask ehowinR completed assembly and, below,components sand-blasted before bonding.

Fig, ]2. Components of cryogenic tarRet, showing thin disk Mylar flask tocontain liquefied Eas and epherical caps to surround it and containpressure-equalizing Eaa.

. .

fig. 7

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