Compact Photon Source · 1. The raster is 2 mm x 2 mm (requires pol. target rotaCon) Power...

CompactPhotonSource

updates&ideasfor10/31/2017

B.WojtsekhowskiforthecollaboraCon

10/31/17 1

γ-Source

210/31/17

1.2µA e- γ

e-

8.8 GeV

Beam Dump in the magnet

B ~ 1.5T

3cm NH3

Distance to target ~200 cm photon beam diameter on target ~0.9 mm

Initial MC simulation shows acceptable background rate on SBS and NPS Detailed analyses of radiation level are in progress

2mm hole

fromtheNovember2014talkattheNPSmeeCng

10%X0

fromthetechnoteforthe2015WACSproposal

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4


3 mm x 3 mm hole 2 mm x 2 mm raster

Current model of the γ-Source

W-powder

Radiator

Cu-core

2.7 µA e-

11 GeV

10%X0

B ~ 3.2 T

10/31/17

5


3 mm x 3 mm hole

Current model of γ-Source

Cu-core

10/31/17

6


3 mm x 3 mm hole

Current model of γ-Source

Cu-core

10/31/17

7

Graphical view of changes in the source

W-powder

Cu-core

2.7 µA e- 11 GeV

10/31/17

Cufillerin100cmlongmagnet

Fe-shield

1.2 µA e- 8.8 GeV

W-Cufiller40cmlongmagnet

Concreteshell

W-Cu-core

2015model 2017model

NewdevelopmentsthelistfromourpreviousmeeCng

1.  Therasteris2mmx2mm(requirespol.targetrotaCon)2.  ThemagnetpoleisshapedtoboosttheBfieldto3.2T->length

reducConwhichallowsalongerfrontshieldandawedgedabsorber.3.  ThecentralabsorberofCuhas1.9xbeXerheatconducCvity,4.2x

longerradiaConlengththantheW-Cu(20%)alloy.4.  W-powderexternalshield(16g/cm3density)forbeXershielding.5.  Gradual“stepped”openingofthebeamlineforrad.leakreducCon6.  Shieldingrequirementlogic:TheradiaConfromthesourceshouldbe

afewCmeslowerthanthatfromthephotonbeaminteracConwiththematerialofapolarizedtarget.

10/31/17 8

ConsideraConsfora6-pointlist

1.   Therasteris2mmx2mm(requirespol.targetrotaCon)PowerdeposiConinthepolarizedtargetforahighenergyphotonbeamdefinedbyphotonintensityis160mWper1µAelectronbeam(10%X0radiatorandnolossduetocollimaCon),seep.18inPR12-15-003toPAC43andp.21intheTNonCPSforGeant4calculaCons.Theprojected2.7µAbeamona0.1X0radiatorleadstoapowerdeposiConof0.43WaXwhichalsocorrespondstoan80nAelectronbeamonthepolarizedtarget-almostatthelimitfortheUVaNH3targetfortheopCmumFigure-of-Merit.FOMenhancementduetotheCPScouldbecalculatedas:R=2.7x0.10/[0.08x(0.10+0.02)]=28,whereweusedthesameradiaConlengthoftheconvertor(+1/2target)andincludedaneffecCvefluxofvirtualphotons(0.02)forelectronbeam.

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2.ThemagnetpoleisshapedtoboosttheBfieldto3.2Tesla->lengthreducCon,whichleadstoabeXerfrontshieldandwedgedabsorber.ThisopCmizaContookintoaccountthatforasmallhorizontalrastersizethedistancebetweenthemagnetpolesneartheradiatorcouldbereduced.However,thedistanceneedstobemuchlargerintheareaofthebeampowerdeposiContoallowforheattransferintheabsorber.ThewedgeshapeofthepoleleadstoconcentraConofthemagneCcfluxatthefrontofthemagnetandhelpsfasterdeflecConoftheusedbeamtotheabsorber.Thespacebetweenmagnetpolesisfilledwithawedgedcooperabsorber.

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Bvs.z

Z

3.ThecentralabsorberofCuhas1.9xbeXerheatconducCvity,4.2xlongerradiaConlengththantheW-Cu(20%)alloy.

IntheoriginaldesignweusedtheWCu(20%)alloyforfasterabsorpConofthebeamenergyandsecondaryneutrons.Theoriginal2015CPSschemeassumed10kWbeampoweranda20mmx2mmrasterpaXernwithseveralslots.However,thecurrentplanrequiresapowerof30kWandreducedrastersizeto2mmx2mm.HigherheatconducCvityandlongerradiaConlengthofthepurecopperabsorberallowsustoachieveacceptablepowerdensityintheabsorber.AlsotheneutronyieldperkWislowerinCurelaCvetoWbyafactoroftwo.

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3.ThecentralabsorberofCuhas1.9xbeXerheatconducCvity,4.2xlongerradiaConlengththantheW-Cu(20%)alloy.AnesCmate:Thepowerdistributedover30cmwithdiameterof2cm.UsingawedgeshapeoftheCu(inx-yplane)withangleof90degreesandcoolingat12cmdistancefromthepowersourcewecanesCmatethetemperatureprofile:600+140x(1-r2)forr<1cmandalog.profileforr>1cm240ln(12/r).A3DcalculaConwouldbeuseful.

10/31/17 12


ΔTatahotcenter=600+140C

water

3.ThecentralabsorberofCuhas1.9xbeXerheatconducCvity,4.2xlongerradiaConlengththantheW-Cu(20%)alloy.

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GabrielfoundfortheWCuabsorber:Tmax~700C

Att

enua

tion

leng

th (

g cm

2 )Neu t ron Energy (MeV)

Concrete!= 2.4 g cm 3

High energy limit

1 2 5 10 20 50 100 200 500 1000 0

25

50

75

100

125

150

4.W-powderexternalshield(16g/cm3density)forbeXershielding.OpCmizaConoftheCPSshieldingwillconCnueunClfullengineeringiscompleted.ThereareseveralgeneralconsideraCons:a)  ThetotalthicknessneededforneutronabsorpConisabout1000g/cm2

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Fordistance2meterfromthesourceand30kWbeamDoserateis1krem/kW*30kW/(4πr2)=0.60krem/hArerapplyingashieldingfactorof1000=>0.60rem/h

4.W-powderexternalshield(16g/cm3density)forbeXershielding.OpCmizaConoftheCPSshieldingwillconCnueunClfullengineeringiscompleted.ThereareseveralgeneralconsideraCons:a)  ThetotalthicknessneededforneutronabsorpConisabout1000g/cm2.b)  Thetotalweightislowerforthehighermaterialdensity.c)  ThecostofthematerialwillbethemainfactorfortheCPSproject.

Solidtungstenistooexpensivefortheoutershielding;W-powderismoreaffordableanditsdensity(16g/cm3)issCllhigherthanforironbyafactoroftwo.

d)Thereisasignificantsurplus(200tons)ofleadbricksatSLACwhichcouldbeobtainedforaverylowcost(mainlytransportaCon).

e)Thereisapossibilityofusingironplatese.g.forKLcase(noweightlimit).

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5.Gradual“stepped”openingofthebeamlineforrad.leakreducCon.Theprofileoftheopeningisthesubjectcurrentlyongoingwork.TheGeant4MCpresentedintheCPSTN(seep.24-25)isshownbelow:

Powerdensityatanangle>0.4degree (distanceisabove10cmfrombeamaxis) islowerbyafactorof105thaninthe center,butitissCllleadtoradiaConon thelevelofseveralkRad/hour.

Therecentstudyshowsthatastepped profileofthegamma-beamexitline helpstoreduceradiaConlevel.

10/31/17 16

r [cm]0 1 2 3 4 5 6 7 8 9 10

/el.]

2 r

dr)/e

lect

ron

[MeV

/cm

E/(2

210

110

1

10

210

Photon Energy Density vs radius @15mPhoton Energy Density vs radius @15m


6.Shieldingrequirementlogic:TheradiaConfromthesourceshouldbeafewCmeslowerthanfromthephotonbeaminteracConwiththematerialofapolarizedtarget.Withthegamma-beamonthepolarizedtarget,significantradiaConwillbeproducedinbeam-targetinteracConwhichdefinestheunavoidableradiaConlevel.RadiaConlevelisproporConaltoL γ n=photonflux\Cmestargetmass.IntheTNfor2015proposal(p.26)weprovidedacomparisonoftheCPSoperaConontheUVatargetwiththeradiaConlevelduringGEP/SBSandGEnE02-013experiments:ArercorrecConforthehigherpower(30kW)ofthepresentplan,theradiaConlevelesCmatedtobe10CmeslowerthanintheGEpexperimentand2.5Cmeshigherthaninthe2006GEnexperiment.NewcalculaConsareneededforthecurrentdesignoftheoutershielding.

10/31/17 17


10/31/17 18

RCS - Feb. 2002: Ee- = 3.48 GeV!

Average Dose Rate = 441. mR/hr at 100 µA!i.e., for a steady e- beam of 100 µA at Ee-=3.48 GeV onto !

6%X0 Cu radiator followed by 2%X0 (15 cm) LH2 target, !the Hall A radiation monitor would record 441. mR/hr.!

0.00!

100.00!

200.00!

300.00!

400.00!

500.00!

600.00!

0.00! 10.00! 20.00! 30.00! 40.00! 50.00!

Neu

tron

Dos

e R

ate

(mR

/hr)

@ 1

00 µ

A!

Average Current (µA)!

Dose Rate (mR/hr) @100 µA!2/23/02!

2/22/02!

2/21/02!

2/24/02!

2/25/02!

2/26/02!

2/27/02!

2/28/02!

3/1/02!

2/21/02!

ConsideraConsfora6-pointlist6.ProjectedradiaConinthehallduetoaphotonbeamandtargetinteracCon

RadiaConmonitor~15mfromthetargetin120deg.direcCon

Fromthis4mrem/h/µAfor1)effecCvetarget-1.7g/cm2

2)effecCveradiator–7%projectedlevelforWACSfor1)target–3g/cm2

2)radiator10%

is10mrem/h/µAat15morat2mfromtarget~500mrem/h/µA=>

total1.5rem/hTheshieldingfactorofCPSneedstobe1000tokeepCPScontribuConof1/3comp.unavoidable1.5rem/h

KLongCPSarea

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~12m

KLongCPSarea

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KLongCPSarea

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~10m

EsCmatedlengthof10metersallowstheCPStypesourcewiththebeampowerof60+kW

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Geant4model(GEMCframework)Marco,MaurizioBW

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Geant4model(GEMCframework)

Muon11GeV

10/31/17 24

Geant4model(GEMCframework)

11GeVe-Yv=-1mm

11GeVe-andaphoton

Compact Photon Source · 1. The raster is 2 mm x 2 mm (requires pol. target rotaCon) Power...

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