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Electron Bunch Measurements with a Transverse RF Deflector P. Emma ICFA XFEL 2004 Workshop July 29, 2004

Electron Bunch Measurements with a Transverse RF Deflector P. Emma ICFA XFEL 2004 Workshop July 29, 2004. ICFA Future Light Sources Sub-panel Mini-workshop on XFEL Short Bunch Measurement and Timing Stanford Linear Accelerator Center , July 26 - 30, 2004.

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Electron Bunch Measurements with a Transverse RF Deflector P. Emma ICFA XFEL 2004 Workshop July 29, 2004

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  1. Electron Bunch Measurements with a Transverse RF DeflectorP. EmmaICFA XFEL 2004 WorkshopJuly 29, 2004 ICFA Future Light Sources Sub-panel Mini-workshop on XFEL Short Bunch Measurement and Timing Stanford Linear Accelerator Center, July 26 - 30, 2004 ICFA XFEL 2004 - July 29, 2004

  2. R. Miller, IEEE Trans. Nucl. Sci., June 1965. X.-J. Wang, PAC’99, March 1999. J. Frisch, BNL/LCLS Diag. Workshop, March 2000. P. Emma et al., LCLS-TN-00-12, Aug. 2000. R. Akre et al., PAC’01, June 2001. R. Akre et al., EPAC’02, June 2002. H. Schlarb: http://www.desy.de/s2e/ (Aug. 2003). Previous Talks/Publications ICFA XFEL 2004 - July 29, 2004

  3. RF ‘streak’ 2.44 m V(t) sy e- sz D 90° bc bp Transverse RF Deflector in the SLAC Linac S-band V0 20 MV sz 50 mm, E 28 GeV frf = 2856 MHz built in 1960’s (G. Loew…) ICFA XFEL 2004 - July 29, 2004

  4. Existing bends compress to 80 fsec 1.5% 1.5 Å 30 kA compression by factor of 500 80 fs FWHM 28.5 GeV RF Deflector Short Bunch Generation in the SLAC Linac 1-GeV Damping Ring sz 6 mm SLAC Linac FFTB sz 1.1 mm sz 50 mm 30 GeV sz12 mm ICFA XFEL 2004 - July 29, 2004

  5. Linac Installation SPPS: L = 2.4 m f = 2856 MHz TTF-2: L = 3.6 m f = 2856 MHz LCLS: L = 0.5 & 2.4 m f = 2856 MHz P. Krejcik ICFA XFEL 2004 - July 29, 2004

  6. Measurements RF Deflector OFF RF Deflector ON ICFA XFEL 2004 - July 29, 2004

  7. Cavity on -180° 3-Point Bunch Length Measurement sz = 90 mm Cavity on +180° Bunch length reconstruction: measure streak at 3 different RF phases sy2 Cavity off RF deflector phase (deg) Asymmetric parabola indicates incoming beamtilt ICFA XFEL 2004 - July 29, 2004

  8. Extracting rms beam size from non-Gaussian, noisy screen image Screen calibration Limited field of view on screen RF phase drift during measurement Inadequate RF voltage Clumsy software Data acquisition time vs. beam drift time Practical Issues ICFA XFEL 2004 - July 29, 2004

  9. Voltage/Screen Calibration BPM calibration is only accurate to ~10% level: …better to calibrate amplitude on screen and get pixels/deg (P. Krejcik) BPM y-position after deflector (mm) RF phase setting is highly accurate RF deflector phase (deg) ICFA XFEL 2004 - July 29, 2004

  10. (from H. Schlarb’s 2003 talk) Screen Pixel Calibration Errors Simulated Simulated beam position beam position no noise on x-axis: slope = -3.5 exactly noise on x-axis: fitted-slope = -2.6 (true = -3.5) RF phase RF phase Errors on x-axis produce bias in standard linear regression techniques… T. Lohse, P. Emma, SLAC-CN-371, Feb 1989. ICFA XFEL 2004 - July 29, 2004

  11. (from H. Schlarb’s 2003 talk) Screen Pixel Calibration less sensitive to timing jitter BPM y-position (mm) 100% klys. drive: 0.427 mm/deg screen y-position (pix) 50% klys. drive: 4.92 pix/deg BPM y-position (mm) 50% klys. drive: 0.0415 mm/deg ICFA XFEL 2004 - July 29, 2004

  12. RF Deflector as Arrival Time Monitor E0 28 GeV, V0 24 MV, by 50 m At 14 GeV, a 10-mm BPM resolution can resolve <10 fsec timing error – but must also consider RF phase jitter. ICFA XFEL 2004 - July 29, 2004

  13. 5+ energy spread meas. stations (optimized with small b) Location of Main Linac Diagnostics • 5+ emittance meas. stations designed into optics (Dyx,y) • slice measurements possible with transverse RF (L0 & L3) • BPMs at or near most quadrupoles and in each bend syst. • RF deflectors for slice e and sE measurements T-cav. rf gun T-cav. gex,y gex,y gex,y gex,y L0 gex,y gex,y? L1 L2 L3 X ...existing linac sE sE sE sE E E E sE E E ICFA XFEL 2004 - July 29, 2004

  14. RF-deflector at 1 MV sy bunch length Slice-Emittance Measurement Simulation slice OTR 10 times scannedquad ICFA XFEL 2004 - July 29, 2004

  15. = meas. sim. = calc. = y distribution = actual Slice-Emittance Measurement Simulation (slice-y-emittance also simulated in BC1-center) Injector at 135 MeV with S-band RF-deflector at 1 MV (same SLAC slice-e code used at BNL/SDL) slice-5 ICFA XFEL 2004 - July 29, 2004

  16. Slice Energy Spread Measurements in LTU LTU at 14 GeV with S-band RF-deflector at 24 MV sE/E  10-4 sx 12 mm FEL goal ICFA XFEL 2004 - July 29, 2004

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