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Abstract The diamon

Neutron SourcMay 3, 2009, wsystem failure~840 kW. Thethought to beincoming H− balso reflect bacbreakdown frosecondary electhese and othimprovements

The Spallacomprises a 11.5 MW designring with charglong pulses fropower is tNanocrystallinuse from the These foils weMay 3, 2009, ~840 MW. Themore, and theprevent furthertwo days latechange (a firstmodified foil fail.

A team wasrecommend mthe next run modified foilssingle foil lasproduction rupower of 1 MWof the foil systprevent them.

SNS The nomina

foils have threbrackets that mechanism. A_____________________________

*ORNL is manage00OR22725 for the

NS STRIPP

M. Plum, J. GO

R. MaceD. Ra

nd stripper foce worked succwhen we startees after incree main contre 1) convoy ebeam, that strick from the eleom the chargctron emissionher failure me

we have made

INTRODation Neutron1 GeV, 60 Hzn beam powerge-exchange inom the linac totypically abone diamond str

beginning of ere successfullshortly after ine first failure w

e beam power r foil system fer after anotht for SNS) wasbracket, but t

s assembled tomodifications, w

cycle startins and brackets sted for the enun, which incW. In this paptem failures, an

STRIPPERally 17 mm x 4ee free edges a

hang from A photo of a fir

_______________

ed by UT-Battelle, e U.S. Department

PER FOIL

Galambos, S.Oak Ridge Naek, Los Alamaparia, Brook

oils in use at cessfully with ned experiencineasing the beributors to thelectrons, stripike the foil brectron catcher, e developed o

n. In this paperechanisms, ande to mitigate th

DUCTION n Source a, H− ion beam

r, followed by njection to como ~700 ns. Theout 1 MW ripper foils [2

f formal operaly used with nncreasing the was quickly fowas reduced

failures, and ther failure. A s executed on Mthe foil system

o investigate thwhich were pug in Septembperformed ve

ntire Septembeluded operatiner we will discnd the modific

R FOIL SYS5 mm x 0.30 m

and are mountepins on the

rst generation fLLC, under contrat of Energy.

L FAILUR

Kim, P. Ladational Labo

mos Nationalkhaven Nati

the Spallationno failures unting a rash of foieam power tohe failures arpped from thracket and mayand 2) vacuum

on the foil byr we will detaid describe th

hem.

accelerator [1m linac with an accumulato

mpress the 1 me present beamat 925 MeV

] have been inations in 2006no failures untibeam power to

ollowed by twoto ~430 kW to

hen to ~400 kWmid-cycle foi

May 19 using m continued to

he failures andut in place fober 2009. Thery well, and er – Decembeng at a beamcuss the causecations made to

STEM mg/cm2 strippeed on L-shaped

foil changingfoil and brackeact DE-AC05-

RE MODE

dd, C. Luck,oratory*, Oakl Laboratoryonal Labora

n il il o

re e y

m y il e

] a

or ms m V. n

6. il o o o

W il a o

d or e a

er m es o

er d g et

is shown inside a beam lossfield causbeam to ctilted lontrajectorieideally enmore enecatcher isto intercepback up in

Figure. 1.foil-changshaped bacross thecase).

FOIL S

Convoy The fir

portion ofso the corevolutionstressed thfailure, nobracket (tfailures)bracket isbracket shelectrons the loweattached bmelted, ca

ES AND T

C. Peters, Yk Ridge, TN

y, Los Alamoatory, Upton,

in Fig. 1. Whstrong (~0.25s caused by Hses the convoycircle with a gygitudinally byes drop ~16 mmnough to miss ergy into the fs mounted to thpt the electronsnto the path of

. A first generger mechanismbracket are dee span to suppo

SYSTEM D

electrons strrst failure mef the L-shapednvoy electrons

n around the mhat this failureot a foil failurethe type in usis shown in

s shown in Fighows the meltistriking the b

er right showbefore the maausing the coun

THEIR CU

Y. Polsky, R. N, USA os, NM, USA, NY, USA

hen in use, thT) magnetic 0 excited statey electrons str

yroradius of 12y ~200 mrad sm in the first rthe foil and thfoil [4]. A wahe bottom of ths and prevent t

f the beam.

ration foil bracm. The long armesigned to strort foils if need

DAMAGE M

rike the bracechanism is sd bracket was ts struck the b

magnetic field e mechanism ie. A photo of se at the timesFig. 2. An ex

g. 3. The bottoing that occurrbracket. The laws where a aterial around nterweight to f

URES*

Shaw,

A

he foil is positfield to contros [3]. The magripped from th mm, but the fi

so that the elerevolution, wh

hus avoid depoater-cooled elehe vacuum chathem from refle

cket mounted om and leg of tretch carbon ded (not used i

MECHANIS

cket imple – the too close to thracket on theilines. It shou

is actually a bra second genes of the first xample of a m-left corner red from the coarge melted arcounterweightthe mounting

fall off.

tioned ol the gnetic he H−

field is ectron hich is ositing ectron amber ecting

on the the L-fibers in this

SMS

lower e foil, ir first uld be racket

eration set of failed of the onvoy rea on t was g hole

Proceedings of IPAC’10, Kyoto, Japan THPEB039

04 Hadron Accelerators

T12 Beam Injection/Extraction and Transport 3969

R

eevTccee

Fbb

FT~

Reflected coThe second

electrons. If thelectron catchvacuum chamThe electron composite (sincoefficient), welectrons are selectrons in the

Figure. 2. A beam power inbracket show v

Figure. 3. A This foil laste~840kW.

Figure. 4

onvoy electrod failure mechhe electrons areher, some ma

mber and strikecatcher ma

nce carbon hawith angled supposed to hite downward di

used second-gn this case wasvery little dama

failed second-ed for a few

4. A used third

ons hanism is refe not properly cay reflect bace the foil and/aterial is a as a relatively

undercut fact in order to aimirection.

generation foi only 400 kW, age.

-generation foihours at a b

-generation foi

flected convoycaptured by thk up into th/or the bracket

carbon-carbonlow reflection

ces where thm any reflected

il bracket. Thso this foil and

il and bracketbeam power o

il bracket

y he e t. n n

he d

e d

t.

of

Howevsurfaces othe foil afoil and removed they travemelting dthe brackedroop dowcorner is some of tthe brackepart of the

Vacuum The thi

breakdowplace in aanode (foto secondthermioniThe nextcathode (due to ththe foil. Tthe gasebreakdowin the bracshows a cSeveral hclamped through tshows simsubstrate breakdow

Figure. 5bracket sh

In addivacuum bthe breakdportion ofof this typ

er, some elecof the electron and bracket. F

bracket. The so that the con

el down to the damage on the et has also sofwn. We believe

due to reflecthese reflectedet arm, they cae bracket.

breakdownrd failure mech

wn. This form a perfect vacuuil) first develo

dary electron emic electron emit step is evap(bracket) that e strong electrThe evaporateeous environ

wn. Each breakcket, and over close up photoholes can be s

to the brackethe bracket armilar material ehad sharp edg

wn events.

5. A close-up hown in Fig. 4.

ition to damagbreakdown candown events stf the foil. We hpe of damage to

ctrons can hit catcher and ref

Figure 4 showslower leg on

nvoy electronselectron catchlower left cor

ftened enough e that the melticted convoy e

d electrons alsoannot explain a

hanism is cathof electrical b

um. To initiate ops a positive emission. If theission can furtporation of shbecome hot fric field betwe

ed cathode mament needed

kdown event crtime large hol

o of the same bseen where theet. One hole rm. The top oerosion at loca

ges that helped

view of the .

ge to the brackn also cause datart and/or end have not obsero the foil.

the upward-fflect back up tos a third-genen this brackets would not hiher, yet it still srner, and the ato allow the a

ing on the lowelectrons. Altho strike the foll the damage t

hode-spot in-vabreakdown can

the breakdowelectrical charge foil is hot enther charge theharp points ofrom field emeen the bracke

aterial then prod to sustainreates a smalles develop. Figbracket as in Fe foil substrate

passes compof the bracketations where th

initiate the va

foil clamp fo

ket, cathode-spamage to the fon the free-ha

rved strong evi

facing oward

eration t was it it as shows arm of arm to er left hough il and to this

acuum n take

wn, the ge due nough, e foil.

on the mission

et and ovides n the crater

gure 5 Fig. 4. e was

pletely t also he foil acuum

or the

pot in-foil, if anging idence

THPEB039 Proceedings of IPAC’10, Kyoto, Japan

3970

04 Hadron Accelerators

T12 Beam Injection/Extraction and Transport

B

igacHrtbatffe

ac

abntl

lld

midemp

eefe

mcetmlnTctpb

Bracket pincThe foil bra

itself gets hgenerations 1 aluminium dconductivity, However, alumrelatively highthe temperatubetween the clapplies tensionthe silicon subfoil to fracturefree-standing pedges that cont

Other mechaIn addition

already discucontribute to a

The silicon and some portbeam aperture not predict thathe closed orblow level (othe

Trailing edglevel in the rlongitudinal bdetailed at the strike the foil a

Sudden beamomentary eqin the ring injedue to beam sexample of thiminutes and problems with

Another heaeddy current electric fields flow in the foevidence for th

During the smade to the fochanged from expansion coeto that of silimelting pointlightweight. Hnot as good asThe bracket aclamping the fthe clamp arepoints that cabreakdown. So

ching acket will get

hot enough tthrough 3 f

due to its elight weight,

minium also hah coefficient of ure increases lamp and the bn along the widbstrate that sup, which can theportion of thetribute to the v

anisms to the foil s

ussed, there at least a minor

substrate thattions of the brof the ring. Pa

at any particlebit, yet beam herwise there woge multipactingring, due to t

beam profile. Los Alamos P

and bracket andam excursion

quipment failurection area. Sostriking the stris type of phenlasted for sevthe Ring rf sy

ating mechanisheating due tof the beam,

oil bracket. Whis type of heat

SOLUsummer of 200il and the bracaluminium to

fficient of titanicon. Also tita, good electr

However, the rs aluminium duand clamp arefoil to the brace carefully poan contribute ome of the foi

hot simply bo emit visibfoil brackets wease of mac, and low ras a low melti

f thermal expanit pinches th

bracket arm andth of the foil. ports the uppeen lead to rips e foil, and alsvacuum breakd

system damagare others degree.

t supports theracket, are locarticle trackinges will be this halo is certainould be no bea

g is also likely pthe triangular This phenomeSR [5]. These d cause additio

ns in the rinre, can cause lome of the beamripper foil and/nomenon occuveral days instem. sm that we into the pulsed causing electri

We have not oting.

TIONS 09 several modcket. The bracko titanium, sinnium is much anium has a rical conductivradioactivationue to its high ae machined flket, both the blished to remto cathode-sp

ils we installed

ecause the foible light. Thwere made ochining, goodradioactivationing point and nsion, so that ahe stripper foind at same tim

This can causer portion of thand tears in th

so create sharpdown.

ge mechanismthat probably

e diamond foilcated inside thg simulations do

far away fromnly present atam loss). present at som

nature of thenon has beenelectrons could

onal heating. ng, caused bylarge beam losm loss is likely/or bracket. An

urred every fewn 2009 due to

nvestigated wanature of th

ical currents toobserved strong

difications werket material wance the therma

better matchedrelatively highvity, and it i

n properties aratomic numberlat, and beforbracket arm and

move any sharppot in-vacuumd in Septembe

il e

of d

n. a

as il e e

he e p

ms y

l, e o

m a

e e n d

y ss y n w o

as e o g

re as al d h is re r.

re d p

m er

2009 wer~0.025 mmcontact bealso moveto improelectrons,made as sthat couldelectrons.added to bsupported

The foifree-standbeam halthe substr

A new half withDecemberwith the entire run1 MW. Thfoil was 4power recof damagupstream understootwisted, athe end oafter it waFor the pusing a fofunctioned

Figure 6.entire Sep

[1] S. He[2] R. Sh[3] J. We[4] L. W[5] R. M

re also sandwim thick to helpetween the foied 1 cm furtheve the cleara and the armshort as possibd be struck by Note that somboth the arm a

d foils. il itself was m

ding length (sho and reflecte

rate. set of foils, hahout, were inr 2009 run cycgold foil mou

n cycle, even ahe total charge4820 C, to becord of 978 C.e, although thside of the bra

od at this timand wrinkled, bf the run cycleas removed in resent Februar

oil mounted wid well.

Photo of thept. – Dec. 2009

REFenderson, PAChaw et al., PACei et al., PRST-

Wang et al., PRSMacek et al., PA

iched betweenp improve the il and the bracer out on the aance for the

ms and legs ofble to remove y beam halo o

me additional lend the leg in o

modified to hahorter silicon sed convoy elec

alf with the golnstalled for cle. The first founting method

after increasinge delivered to te compared to The used bracere is an unknacket and foil

me. The foil ibut it was stille. A photograpFebruary 2010ry to June 201ithout gold, an

e foil and brac9 run cycle at h

FERENCESC07, p. 7. C07, pg. 620. -AB 3, 081010ST-AB 8, 0942

AC01, p. 688.

n layers of gollarge-area elec

cket. The foilsarms of the bracirculating co

f the brackets any excess maor reflected coength will needorder to mount

ave up to a 3substrate) to prctrons from str

ld foil mountinthe Septemb

oil selected wad, and it lasteg the beam powthe target usin the previous cket shows no

nown coating osubstrate that itself is blackl performing wph of this foil, 0, is shown in F0 run cycle, w

nd to date it ha

cket that lastehigh beam pow

S

0 (2000). 201 (2005).

ld foil ctrical s were ackets onvoy

were aterial onvoy d to be

fiber-

5-mm revent riking

ng and er to as one ed the wer to ng this

high- signs on the is not

kened, well at

taken Fig. 6. we are as also

ed the er.

Proceedings of IPAC’10, Kyoto, Japan THPEB039

04 Hadron Accelerators

T12 Beam Injection/Extraction and Transport 3971