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Capture Simulation for ILC Electron -Driven Positron Source

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”.

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Capture Simulation for ILC Electron -Driven Positron Source

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  1. 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

  2. Why do we need e-driven e+? • ILC 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.

  3. Purpose of this study • 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.

  4. Chart of Positron Source for ILC DR e- e+ Capture Section Booster Linac ECS • Capture Section: • AMD and solenoid up to several hundreds MeV (L-band). • Booster Linac: • Acceleration up to 5GeV (L-band+S-band). • ECS（Energy Compression System）: matching in longitudinal phase space.

  5. Chart of Positron Source for ILC DR e- e+ Booster Linac ECS Capture Section Design guideline is Yield 1.5 (3.0e+10 e+) in DR acceptance (50% margin). Yield(e+/e-): The number of e+/ The number of e- at the target

  6. Solenoid Capture Section AMD e- e+ Accelerating Structure Target (rotate) Positron distribution at the exit of Capture Section • Positron distribution simulated by GEANT4just after the Target.(T. Takahashi) • The number of e-: 1000, The number of e+: 12696

  7. Booster Linac Basic structures are FODO cells consisted of 4 QMs and some RF. Positron distribution at the exit of Booster Linac

  8. Energy Compression System (ECS) Base structures are 3 chicanes and some RF. Positron distribution at the exit of ECS

  9. Parameters for optimization • RF phase at Capture Section • RF phase at Booster Linac, ECS • Aperture at Capture Section • Aperture at Booster Linac, ECS • Aperture and magnetic strength at AMD, and distance between AMD and target • Drive beam energy, target thickness, and beam size • RF gradient at Capture Section • Positron energy at the exit of Capture Section Optimized automatically Fix at the realistic largest aperture small impact

  10. Capture RF phase Yield is Max. at 270〜310° Dec. capture • Aperture at Capture Section • (X2+Y2)1/2 < 20 mm • Aperture at Booster Linac • (X2+Y2)1/2 < 17 mm • Acceptance at DR • Longitudinal Acceptance: • (E-E0)/E0 < 0.75 %, (z-z0) < 37.5 mm • Transverse Acceptance: • (Wx+Wy)*γ < 70 mm Acc. capture

  11. Adiabatic Matching Device (AMD) • AMD Aperture (≡RAMD)： 6mm(radius) • AMD Max. field strength (≡BAMD) : 7T • Place of BAMD and end surface of Target (≡dZ) : 5mm (giving 3.5T) Bz (T) dZ Z (m)

  12. AMD and Target configurations dZ=3mm dZ=5mm RAMD(mm) RAMD(mm) • Yield is greatly depended on RAMDand dZ. • But not so much on peak BAMD. • Yield is saturated at dZ<3mm and RAMD > 8mm. • BAMD=7T, dZ=3mm, and RAMD=8mm are a feasible parameter set.

  13. Aperture in Booster Linac Capture eff. is saturated at 17mm . 17mm is optimum. c

  14. Drive beam and Target configuration（1） E=3GeV, T=14mm E=6GeV, T=20mm E=6GeV, T=14mm RAMD(mm) RAMD(mm) RAMD(mm) • Ne=2.0e+10 (fixed). • Yield is better for smaller spot size.

  15. Drive beam and Target configuration（2） • Ne- =2.0e+10 • RAMD=8mm

  16. Drive beam and Target configuration（3） # of positron giving PEDD 23 J/g. E=3GeV, T=14mm E=6GeV, T=20mm E=6GeV, T=14mm RAMD(mm) RAMD(mm) RAMD(mm) • Larger spot size gives larger # of e+. • 6GeV-thickness14mm might be optimum.

  17. Drive beam and Target configuration（4） • PEDD=23 J/g, Ne- is scaled. • RAMD=8mm

  18. Replacing L-> S-band（１） 19Cell L-band(1~19) S-band(20~40) 20Cell(starting point of S-band) 1-6 Cell = (2FODO +RF) 7~18Cell= (2FODO+2RF) 19~40Cell= (2FODO+ 4RF) • Capture Section • L-band RF Aperture: 20 mm • Booster Linac • L-band RFAperture: 17 mm • S-band RFAperture: 10 mm • ECSAperture: 17mm Exit of Booster Linac

  19. Replacing L->S-band（２） • Red: considered only S−bandAperture (1.3GHz) • Green: considered S-band Aperture and RF frequency Nc :Cell number where S-band starts 1-6 Cell = (2FODO +RF) 7~18Cell= (2FODO+2RF) 19~40Cell= (2FODO+ 4RF) L-band RF= 6+12*2+(Nc-18)*4 S-band RF= (40-Nc)*4 Nc=26 giving L-band: 62and S-band: 56

  20. Magnetic field distributions of FC Bz(T) A=-1/6 ~ 1 Z(m)

  21. Beam loading by electron • Many electrons are also generated by the target. • These electron are captured in RF phase opposite to that for positron . • Total beam loading becomes roughlytwice 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.

  22. SUMMARY • 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, σ>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 positionshould be optimized.

  23. backup

  24. RF phase dependence（After Booster Linac） • Target is placed in maximum field of AMD (7T). • Ignore AMD aperture • Aperture of Capture Section • (X2+Y2)1/2 < 0.02 m • Aperture of Booster Linac • (Transmitted): • (X2+Y2)1/2 < 0.017 m • Longitudinal Cut: • (E-E0)/E0 < 0.75% • (z-z0) < 37.5 mm • Transverse Cut: • (Wx+Wy)*γ < 0.07 m

  25. Conventional e+ Source for ILC Normal Conducting Drive and Booster Linacs in 300 Hz operation e+ creation go to main linac 20 triplets, rep. = 300 Hz • triplet = 3 mini-trains with gaps • 44 bunches/mini-train, Tb_to_b = 6.15 n sec 2640 bunches/train, rep. = 5 Hz • Tb_to_b = 369 n sec Drive Linac Several GeV NC 300 Hz Booster Linac 5 GeV NC 300 Hz DR Tb_to_b = 6.15 n sec Target Amorphous Tungsten Pendulum or Slow Rotation 2640 bunches 60 mini-trains Time remaining for damping = 137 m sec We create 2640 bunches in 63 m sec Stretching

  26. Beam after DR Extraction: fast kicker ( 3 ns kicker: Naito kicker) the same as the baseline

  27. Parameter Plots for 300 Hz scheme e- directly on to Tungsten s=4.0mm colored band accepted e+/e- PEDD J/g dT max by a triplet Ne-(drive) = 2x1010 /bunch １ ２ ３ ４ ５ 35J/g 500k there seems to be solutions 100k

  28. KEK、広大、DESY, CERN, IHEP Moving Target 5Hz pendulum with bellows seal rotating target with ferromagnetic seal • 3-5m/sec required (1/20 of undulator scheme) • 2 possible schemes being developed at KEK bellows seal air ferromagnetic fluid seal vacuum main issue: vacuum main issue: life of bellows 今年度：既存のＸ線発生装置の基本構造を利用して真空度（リークレート、到達真空度）など基礎実験を行い、データを取る。オイルの対放射線特性データーも測定 air vacuum First step prototype fabricated KEK 工作センター、広大 H２６−２７：ILC の実機とほぼ同じターゲットの制作し真空試験。 リガク、原研高崎

  29. Dependence on Drive beam size , Ne-/bunch = 2x1010 e+/e- =1.5 35J/g s of the Drive e- Beam (mm)

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