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Modified Beam Parameter Range

Modified Beam Parameter Range. W. Decking (DESY) 2 nd XFEL Machine Advisory Committee Meeting 05.05.2010. PITZ 2009 results: Nominal 1 nC measurements. 2. Solenoid Scan. Long term(~4 days): ~6-8.5% (stdev) ~16-21% (peak-to-peak). 3.0. 2.5.  y =1.26 um. e y =1.26 mm mrad. 2.0.

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Modified Beam Parameter Range

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  1. Modified Beam Parameter Range W. Decking (DESY) 2nd XFEL Machine Advisory Committee Meeting 05.05.2010

  2. PITZ 2009 results: Nominal 1 nC measurements 2 Solenoid Scan Long term(~4 days): ~6-8.5% (stdev) ~16-21% (peak-to-peak) 3.0 2.5 y=1.26 um ey=1.26 mm mrad 2.0 mm mrad 1.5 1.0 Xemit Yemit 0.5 x=0.76 um ex=0.76 mm mrad XYemit 0.0 378 380 382 384 386 388 390 392 394 Imain, A • Q = 1 nC • Gun phase: +6o off-crest • Booster phase: on-crest • Laser temporal profile: 2.1/23.1/2.4 ps • Laser spot size = 0.36 mm min. exy = 0.98 um 100% RMS emittance (no charge cut in data analysis) 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  3. PITZ 2009 results: Emittance vs. bunch charge 1 nC Study of emittance vs.BSA size and charge 0.5 nC gun of +6 deg off-crest, booster on-crest 0.25 nC 1.8 0.1 nC 1.6 1.4 1.2 Emit-XY (um) 1.0 0.8 0.6 0.4 0.2 0.0 0.1 0.2 0.3 0.4 0.5 Laser spot size (mm) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 BSA size (mm) 3 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  4. PITZ 2009 results: Emittance vs. bunch charge (with charge cut) 4 10% cut ~0.7-0.8 mm-mrad (remove non-lasing electrons) → beyond XFEL requirement 5% cut ~0.4 um (comparable to LCLS result) 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  5. Parameters at Gun 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  6. Bunch Compression Scheme 14 GeV 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  7. Micro-bunching Instability • Longitudinal space charge induced growth of initial current fluctuations • Damping by large uncorrelated energy spread • Smaller initial current -> smaller instability growth • Laser heater scaled to provide same energy spread after final compression • Keep final current ripple < 200 A => initial energy spread ≤ 20 KeV after BC0 after BC1 after BC2 before undulator Example working point with realistic LH and 10 KeV energy spread 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  8. Parameters after Laser Heater – Constant Energy Spread 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  9. Wash Out of Initial Current Ripple • Longitudinal space charge washes out initial density ripple • Effect decreases with decreasing peak current • Add uncorrelated energy spread to counteract instability => ×2 final energy spread at 20 pC 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  10. Parameters after Laser Heater – Increased Energy Spread 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  11. Parameters at Undulator 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  12. Emittance Degradation 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  13. Final Parameter Set 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  14. FLASH S2E Simulations 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  15. FLASH S2E Simulations 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  16. Other Issues • Impact of reduced emittance on baseline layout • Emittance measurement optimized for 1.4 mm => reduced resolution • Impact of reduced charge on baseline layout • Nominal charge range 0.1 to 1 nC with diagnostics resolution optimized at 1 nC • Impact of reduced energy on baseline layout • Less chirp compensation from linac wake field 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

  17. Summary • New baseline parameter set established • Detailed analysis follows, taking into account tolerance considerations, complete set of self- and external fields etc. 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

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