1. A special large aperture BPM at FLASH Nicoleta Baboi for Kirsten Hacker BPM Workshop, Lüneburg, Nov. 30, 2006

2. FLASH 0.5-1nC / bunch 1 MHz … 100 kHz, up to 800 s up to 700 GeV (later 1 GeV) RF gun FEL experimental area bypass 4 MeV150 MeV450 MeV1000 MeV undulatorscollimator bunch compressor Laser bunch compressor accelerator modules 250 m

3. Magnetic chicanes bunch compression x = R 16 * E/E

4. Energy stability Energy jitter – position jitter in dispersive sections (e.g. magnetic chicanes) – arrival-time jitter after chicane Requirement –timing jitter < 30 fs energy jitter < 10 -4 (35 m position jitter in BC) Use BPM to measure position jitter –resolution: 5 m (single bunch) –challenge: large horizontal aperture in BC2 unconventional design needed

5. BPM for the Bunch Compressor beam stripline vacuum stripline vacuum StriplineVacuum Beam beam tapering SMA output RF pulses beam tapering SMA output Beam Tapering SMA output RF Pulses cannot reach 5 m res. with analogue electronics use optical method

6. BPM installed in BC2 Compact! Thanks to: Jan Hauschildt Dirk Noelle Silke Vilcins Holger Schlarb Nils Mildner Christopher Gerth And many more…

7. T1-T2=T3 D=T3*c dE/E=D/R16 T1 T2 T3 EBPM ~300mm

8. 40 GHz 8 GHz beam stripline pickup resolution < 3um

9. R16 T166 R3666 ~ 150 um resolution => 5*10 -4 resolution Scope in tunnel

10. Dphase = (-Etot+Egun+Eacc1*cos(pi*phase/180)) Etot

11. R16 T166 R3666 ~ 150 um resolution => 5*10 -4 resolution Scope in tunnel

13. Cable length correction: Red->Black R16 T166 R3666 Out-of-tunnel

14. Cable length correction: Black->Blue Out-of-tunnel

15. -Looked at synch light monitor -Scanned in y -Stopped when beam appeared to be approaching beam pipe