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Christopher Gerth , Michael R ö hrs, Holger Schlarb DESY Hamburg

Optics Layout of the Diagnostic Sections BC1 & BC2. Christopher Gerth , Michael R ö hrs, Holger Schlarb DESY Hamburg. Measurement of the correlated and residual energy spread of the bunch Tuning of 3rd harmonic cavity D = -2m,  OTR = 0.3 m, Res.: ~ 7.9 keV. Off-axis screen design.

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Christopher Gerth , Michael R ö hrs, Holger Schlarb DESY Hamburg

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  1. Optics Layout of the Diagnostic Sections BC1 & BC2 Christopher Gerth, Michael Röhrs, Holger Schlarb DESY Hamburg

  2. Measurement of the correlated and residual energy spread of the bunch Tuning of 3rd harmonic cavity D = -2m, OTR = 0.3 m, Res.: ~ 7.9 keV Off-axis screen design • kicker enable single bunch measurements • Phase space tomography • Slice emittance measurements 3.9 GHz on 3.9 GHz off E=500MeV 15mm Slice energy spread 7mm time 125keV energy General Layout of Diagnostic Section BC1 Multi-screen slice emittance measurements L = 42.5 m Matching section Acceleration Modules Tcav x Tcav y 500 MeV 100 m 15° OTR1 Wire Scanner ~ N*180° +90° to Tcav. x Transverse Deflecting Structures for bunch profile and slice emittance measurements Slice emittance diagnostics and dump section have major impact on lattice layout

  3. Outline Diagnostic Section BC1 • Optimisation of lattice layout for slice emittance measurement • Optics layout / matching and integration in overall lattice(matching with Mad8) • Add Dump section • Add other special and standard diagnostics • Sensitivity study, integration into S2E simulations (to be done) Diagnostic Section BC2 • Specific requirements (what is different?) • Optics layout / matching

  4. Operation modes for Diagnostic Section BC1 Operation modes and lattice optics:

  5. Layout Optimization for slice emittance measurements 12 m TDSx /TDSy ΨTDS ΨTDS ΨFODO ΨFODO ΨFODO • Main criteria: • Precision of slice emittance values • Longitudinal resolution • Soft criteria (simplicity & flexibility): • Symmetrical FODO lattice (same phase advance in x and y) • Total length < 12 m • max 3 cells • max 6 OTR screens (4 per plane) • OTR screens in the centre of drifts • Variables: • Locations of OTR screens • Phase advance ΨFODO of FODO lattice • Phase advance ΨTDS between TDSs and FODO lattice

  6. Optimization Slice Emittance Measurements 3 FODO cells / 4 screens in each plane Emittance error Longitudinal resolution For each FODO cell phase advance exist several solutions with a specific combination of phase advances from the horizontal and vertical TDS to the FODO lattice!

  7. Optics Layout Diagnostic Section 1Slice emittance measurements (optic 1) TDSx / TDSy 67 deg 3 FODO cells Matching into Linac 45o / 45o 113 deg Resolution in x and y: long. Profile: 15 fs, slice emittance: 37 fs

  8. Optics Layout Diagnostic Section 1Projected emittance/ commissioning (optic 2) 6 FODO cells: All phase advances between 22.5 and 90 deg can be matched! Linac

  9. Optics Layout Diagnostic Section 1Slice emittance measurements 76 deg (optic 3) TDSy ßy = 52m 92o 3 FODO cells 76o / 76o Matching into Linac Resolution only in y: long. Profile: 11 fs, slice emittance: 16 fs

  10. Resolution Slice Emittance Measurement Streak Strength of Transverse Deflecting Structure 1 MHz bunch rep rate rQ : normalised shunt impedence P0 : Input power at TDS A factor of 1.6 would be gained at 1 MHz bunch rep rate Resolution in x and y: long. Profile: 9 fs, slice emittance: 23 fs

  11. Screen / Kicker arrangement (1) Horizontal slice emittance / vertical streak Vertical slice emittance / horizontal streak 45deg 76deg HK1 OTR1 OTR1 HK1 OTR2 OTR3 HK2 OTR4 OTR4 HK2 OTR6 OTR6 45deg 76deg VK1 OTR1 OTR2 VK1 OTR2 OTR3 VK2 OTR4 OTR4 VK2 OTR6 OTR5 3 cells = 11.4 m FODO lattice 6 off-axis OTR screens (y andx) Horizontal kicker Vertical kicker VK1 HK1 VK2 HK2 OTR1 OTR2 OTR3 OTR4 OTR5 OTR6

  12. Screen / Kicker arrangement (2) Horizontal slice emittance / vertical streak Vertical slice emittance / horizontal streak 45deg 76deg HK1 OTR1 OTR1 HK1 OTR2 OTR3 HK2 OTR4 OTR4 HK2 OTR6 OTR6 45deg 76deg VK1 OTR1 OTR2 VK1 OTR2 OTR3 VK2 OTR4 OTR4 VK2 OTR6 OTR5 3 cells = 11.4 m FODO lattice 6 off-axis OTR screens (y andx) Horizontal kicker Vertical kicker HK2 HK1 VK1 VK2 OTR1 OTR2 OTR3 OTR4 OTR5 OTR6 Bend plane of BCs defines the OTR arrangement

  13. Screen / Kicker arrangement (1) Special OTR screen arrangement in FODO section

  14. Screen / Kicker arrangement (1) Special OTR screen stations in FODO section: Camera perpendicular to screen to get full resolution over entire screen (no limitation by field of depth) 15mm 7mm

  15. Max length due to dump location Diagnostic mode 2: Energy Spread (optic 4) Goal: ΔE/E ~ 10-5 → ΔE ~ 5keV from meas. at FLASH Laser Heater (30 keV) Values at screen: ßx = 1.992 m ßy = 0.356 m Dy = -1.327 m → ΔE/E ~ 1.5*10-5 ΔE ~ 7.2 keV εN = 1*10-6 µm Higher order effects? Chromaticity? Needs to be studied

  16. BC Dumps: Thermal Limits Courtesy of M Schmitz, MIN Average Heating

  17. Diagnostic mode 3: Long pulse trains (optic 5) ßx = 1825 m ßy = 1192 m Dy = 3 mm Beam size 1mm

  18. OTR Profile Monitor Sketch of BC1-Dumpmodule (C-Cu version)500MeV Courtesy of M Schmitz, MIN  2.7m 0.4m Concrete all around 8cm 5RM Cu Cu Cu 20cm 13.9x0 Window Graphite 120cm*1.7g/cm³/ 4.8x0 10cm  0.4m  NW63  1.2m 8cm 5RM Vacuum pumping 0.4m  1.4m 0.4m Cooling Water Temp. Sensor Cabling

  19. Diagnostic Dump BC1 Module stay clear

  20. Diagnostic Dump BC1 Courtesy of N Meiners, MEA • Restricted safety route • Restricted operation with full bunch trains due to activation (2 kW @ 1Hz) • Electronics may need local shielding

  21. FODO lattice Diagnostic Section Engineering layout (1) TDS-x TDS-y VK1 Dipole 22 Quads VK2 HK1 HK2 Booster Linac 2.5m

  22. FODO lattice Diagnostic Section Engineering layout (2) BAM T1 Dipole CSR VK1 ABCM EOSD TDS-x TDS-y 22 Quads Alignment laser 9 Vertical / 9 Horizontal Correctors 2 Vertical / 2 Horizontal Kickers VK2 HK1 HK2 Laser table Bread board RES T2 Booster Linac OTR / Wire Scanner Station 3 + 6 special in FODO lattice Beam Position Monitor 18 + 2 orbit feedback SR 2.5m 2 Collimators for kicked bunches ABCM

  23. FODO lattice 3.8 m 10 modules 7.6 m 5 modules Diagnostic Section Engineering layout (3) BAM T1 CSR VK1 ABCM EOSD TDS-x TDS-y Alignment laser Lattice can be divided into modules: VK2 HK1 HK2 RES T2 Booster Linac SR 2.5m ABCM

  24. Layout of Diagnostic Section BC2 • 8 times more streak strength of TDS required:scales with energy (0.5-2 GeV) and bunch length (100-25 um) → operation 1MHz • Only 1 TDS foreseen → horizontal streak given by dump • Optical Replica Synthesizer (ORS) needs to be integrated • FODO cell length = 7.6 m → only 2 FODO cells

  25. TDS-x TDS-x TDS-x TDS-x Diagnostic Section Engineering layout (1) Dispersive Section Modulator Radiator 4.8 m ORS laser FODO lattice VK1 HK1 HK2 VK2 Main Linac 2.5m

  26. Optics Layout Diagnostic Section 1Slice emittance measurements 76 deg (optic 1) TDSy ßy = 47m 2 FODO cells 68o 22o / 76o Matching into Linac Resolution only in y: long. Profile: 11 fs, slice emittance: 11 fs

  27. Max length due to dump location Diagnostic mode 2: Energy Spread (optic 4) Goal: ΔE/E ~ 10-5 → ΔE ~ 5keV from meas. at FLASH Laser Heater (30 keV) Values at screen: ßx = 10.5 m ßy = 8.0 m Dy = -2.2 m → ΔE/E ~ 2.1*10-5 ΔE ~ 40 keV εN = 1*10-6 µm Higher order effects? Chromaticity? Needs to be studied

  28. Conclusions • For which bunch rep rate, 5MHz or 1MHz, shall the on-line slice emittance diagnostics be designed in BC1: • Desired resolution can easily be reached at 1 MHz but is just at the theoretical limit for 5 MHz. • Kickers with the required kick strength for 1MHz are in operation in several machines at DESY (‘off-the-shelf’). 5 MHz would requires new design and prototype development. • If standard FEL operation will be 5 MHz slice emittance diagnostics cannot be operated parasitically if designed for 1 MHz (or might not be used if resolution is not sufficient). • If standard FEL operation will be 1 MHz one would lose at least a factor of 1.6 in resolution if designed for 5 MHz Conclusions (1):

  29. Conclusions Dump defines the horizontal streak direction in BC2. If the BCs are installed vertically slice emittance could be measured in the bend plane of BCs. Conclusions (2): Number of quads in current layout BC1 was 22 now 22 BC2 wsa 13 now 19 New lattice layout requires slightly more space BC1: 1.5 m in BC + 0.9 m in diag section = 2.4 m BC2: 1.0 m in BC + 1.5 m in diag section* = 2.5 m*Additional FODO cell for 45 deg lattice requires 7.6 m more space Layout of the dignostics sections can be arranged in modules. Components can be prealigned and tested. This saves time during installation and commissioning. Layout of BC1 diagnostic section almost finalized. After beam dynamic and sensitivity studies (2 months) the vacuum and engineering layout could be started

  30. Optics Layout Diagnostic Section 1Projected emittance/ commissioning (optic 2) Thanks to Markus Huening (TDS calculations) Norbert Meiners (Tunnel layout) Michael Schnitz (Dump) Frank Obier (Kicker) Dirk Noelle (Standard Diagnostics) Bernhard Schmidt (Special Diagnostics) Albrecht Leuschner (Radiation Safety) Winni, Nina, Vladimir (Lattice layout & matching)

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