capture simulation for ilc electron -driven positron source

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Capture Simulation for ILC Electron -Driven Positron Source. Y. Seimiya, M. Kuriki, T. Okugi, T. Omori, M . Satoh, J. Urakawa, and S. Kashiwagi. 14 May 2014. Why do we need e-driven e+?. ILC is an international big project. It should be “fail-safe”. - PowerPoint PPT Presentation

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Capture Simulation for ILC Electron-Driven Positron SourceY. Seimiya, M. Kuriki, T. Okugi, T. Omori, M. Satoh, J. Urakawa, and S. Kashiwagi14 May 2014ILC is an international big project.It should be fail-safe.It should be implemented by the latest technology which is sometimes with unexpected risks. To control the risk, a technical back up is necessary. The e-driven e+ source is the backup. Why do we need e-driven e+?The electron driven e+ source is however not conventional. Amount of e+ is 50 times larger than that for SLC.To implement the e+ source with the minimum risk, it should be designed in operable regime, 35 J/g PEDD (Peak Energy Deposition Density) on target.In this study, we demonstrate that an enough amount of e+ can be generated with this condition. Purpose of this studyChart of Positron Source for ILCDRCapture SectionBooster Linace-e+ECSCapture Section: AMD and solenoid up to several hundreds MeV (L-band).Booster Linac: Acceleration up to 5GeV (L-band+S-band).ECSEnergy Compression System: matching in longitudinal phase space. 4Chart of Positron Source for ILCDRCapture SectionBooster Linace-e+ECSYield(e+/e-): The number of e+/ The number of e- at the targetDesign guideline is Yield 1.5 (3.0e+10 e+) in DR acceptance (50% margin).5Capture SectionBeam parameters & TargetDrive beam energy6 GeVBeam size4.0 mm (RMS)Target thickness14 mmAMDSolenoide-Target (rotate)e+Accelerating StructureAccelerating Structure RF Gradient25 MV/mRF frequency1.3 GHz (L-band)Length10mAperture (radius)20mmAMD parametersMax AMD field7 TTaper parameter60.1 /mmAMD length214 mmSolenoidSolenoid Field0.5 T

Positron distribution at the exit of Capture SectionPositron distribution simulated by GEANT4 just after the Target. (T. Takahashi)The number of e-: 1000, The number of e+: 12696

Booster Linac

Booster LinacRF Peak Gradient40 MV/mRF frequency1.3 GHz (L-band)Length323.6 mAperture (radius)17mmBasic structures are FODO cells consisted of 4 QMs and some RF.Positron distribution at the exit of Booster Linac7Energy Compression System (ECS)

ECSRF Peak Gradient38 MV/mRF frequency1.3 GHz (L-band)Length90.5 mAperture (radius)17mmBase structures are 3 chicanes and some RF.Positron distribution at the exit of ECSParameters for optimizationRF phase at Capture SectionRF phase at Booster Linac, ECSAperture at Capture SectionAperture at Booster Linac, ECSAperture and magnetic strength at AMD, and distance between AMD and targetDrive beam energy, target thickness, and beam sizeRF gradient at Capture SectionPositron energy at the exit of Capture SectionFix at the realistic largest apertureOptimized automaticallysmall impactCapture RF phase

Aperture at Capture Section (X2+Y2)1/2 < 20 mmAperture at Booster Linac (X2+Y2)1/2 < 17 mmAcceptance at DRLongitudinal Acceptance: (E-E0)/E0 < 0.75 %, (z-z0) < 37.5 mmTransverse Acceptance: (Wx+Wy)* < 70 mmDec. captureAcc. captureYield is Max. at 270310Adiabatic Matching Device (AMD)

dZAMD Aperture (RAMD) 6mm(radius)AMD Max. field strength (BAMD) : 7TPlace of BAMD and end surface of Target (dZ) : 5mm (giving 3.5T)Z (m)Bz (T)AMD and Target configurationsYield is greatly depended on RAMD and dZ.But not so much on peak BAMD. Yield is saturated at dZ 8mm.BAMD=7T, dZ=3mm, and RAMD=8mm are a feasible parameter set.

dZ=5mmdZ=3mm

RAMD(mm)RAMD(mm)Aperture in Booster Linac

Capture eff. is saturated at 17mm . 17mm is optimum.cDrive beam and Target configuration1

E=6GeV, T=20mm E=6GeV, T=14mm E=3GeV, T=14mm RAMD(mm)RAMD(mm)RAMD(mm)Ne=2.0e+10 (fixed).Yield is better for smaller spot size.Drive beam and Target configuration2EnergyThicknessBeam sizePEDD YieldTotal deposit3 GeV14 mm4mm15 J/g0.71.8 J6GeV14 mm4mm23 J/g1.32.6 J20 mm4mm27 J/g1.54.9 J3 GeV14 mm6mm 7 J/g0.41.8 J6GeV14 mm6mm10 J/g0.82.6 J20 mm6mm12 J/g0.94.9 JNe- =2.0e+10RAMD=8mm

Larger spot size gives larger # of e+.6GeV-thickness14mm might be optimum.Drive beam and Target configuration3E=6GeV, T=20mm E=6GeV, T=14mm E=3GeV, T=14mm RAMD(mm)RAMD(mm)RAMD(mm)# of positron giving PEDD 23 J/g.16Drive beam and Target configuration4EnergyThicknessBeam size# of cap. e+Total deposit3 GeV14 mm4mm2.110102.7 J6GeV14 mm4mm2.610102.6 J20 mm4mm2.610104.2 J3 GeV14 mm6mm2.910106.1 J6GeV14 mm6mm3.410105.9 J20 mm6mm3.310109.5 JPEDD=23 J/g, Ne- is scaled. RAMD=8mm

1-6 Cell = (2FODO +RF)7~18Cell = (2FODO+2RF) 19~40Cell = (2FODO+ 4RF)

19Cell

20Cell (starting point of S-band)Exit of Booster LinacL-band(1~19)S-band(20~40)Replacing L-> S-bandCapture SectionL-band RF Aperture: 20 mmBooster LinacL-band RF Aperture: 17 mmS-band RF Aperture: 10 mmECS Aperture: 17mmL-band RF= 6+12*2+(Nc-18)*4 S-band RF= (40-Nc)*4Nc=26 giving L-band: 62 and S-band: 56

Red: considered only Sband Aperture (1.3GHz)Green: considered S-band Aperture and RF frequencyReplacing L->S-band1-6 Cell = (2FODO +RF)7~18Cell = (2FODO+2RF) 19~40Cell = (2FODO+ 4RF)Nc :Cell number where S-band startsHorizontal number express the cell number where L-band is changed to Sband. If horizontal=19, 1~19=L-band, 20~40=S-band.19Magnetic field distributions of FC

Bz(T)Z(m)A=-1/6 ~ 1Many electrons are also generated by the target.These electron are captured in RF phase opposite to that for positron .Total beam loading becomes roughly twice of that by positrons.The electrons can be eliminated by a chicane. However, the chicane at low energy causes a significant loss on the capture efficiency. The position of the chicane is compromised between the beam loading and the capture efficiency.Beam loading by electron Positron Capture for ILC Electron-Driven Positron Source is simulated.Yield(e+/e-) is greatly depended on AMD aperture, target position, and beam size. When E=6GeV, T=20mm, >5mm, dZ=5mm, RAMD >7mm, and BAMD=5T, enough e+ is obtained. Yield is reduced greatly when FC field is distorted. Time variation should be carefully investigated. The chicane position should be optimized.SUMMARY backupRF phase dependenceAfter Booster LinacAperture of Capture Section (X2+Y2)1/2 < 0.02 mAperture of Booster Linac (Transmitted): (X2+Y2)1/2 < 0.017 mLongitudinal Cut: (E-E0)/E0 < 0.75% (z-z0) < 37.5 mmTransverse Cut: (Wx+Wy)* < 0.07 m

Target is placed in maximum field of AMD (7T). Ignore AMD aperture

20 triplets, rep. = 300 Hz triplet = 3 mini-trains with gaps 44 bunches/mini-train, Tb_to_b = 6.15 n secDRTb_to_b = 6.15 n sec2640 bunches/train, rep. = 5 Hz Tb_to_b = 369 n sec e+ creation go to main linacTime remaining for damping = 137 m secWe create 2640 bunches in 63 m secBooster Linac5 GeV NC300 HzDrive LinacSeveral GeV NC300 HzTargetAmorphous TungstenPendulum or Slow Rotation2640 bunches60 mini-trains StretchingConventional e+ Source for ILCNormal Conducting Drive and Booster Linacs in 300 Hz operation29Beam after DR

Extraction: fast kicker ( 3 ns kicker: Naito kicker) the same as the baseline

35J/g500k100kParameter Plots for 300 Hz schemePEDD J/gcolored bandaccepted e+/e-there seems to be solutions dT max by a triplete- directly on to Tungstens=4.0mmNe-(drive) = 2x1010 /bunch313-5m/sec required (1/20 of undulator scheme)2 possible schemes being developed at KEK Moving Target2013/8/30 ILC monthly, Yokoya32bellows sealvacuumairferromagneticfluid sealairvacuum5Hz pendulum with bellows sealrotating target with ferromagnetic sealmain issue: life of bellowsmain issue: vacuumFirst step prototype fabricatedHILC KEK KEKDESY, CERN, IHEP

Dependence on Drive beam sizes of the Drive e- Beam (mm)35J/ge+/e- =1.5, Ne-/bunch = 2x1010 33

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