Modified Beam Parameter Range W. Decking (DESY) 2nd XFEL Machine Advisory Committee Meeting 05.05.2010 How to edit the title slide Upper area: Title of your talk, max. 2 rows of the defined size (55 pt) Lower area (subtitle): Conference/meeting/workshop, location, date, your name and affiliation, max. 4 rows of the defined size (32 pt) Change the partner logos or add others in the last row.

PITZ 2009 results: Nominal 1 nC measurements 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 XYemit x=0.76 um ex=0.76 mm mrad 0.0 378 380 382 384 386 388 390 392 394 Nominal 1 nC measurement results in the 2009 run period are shown in this slide. The minimum of 100% rms geometric emittance of 0.98 um was measured. This measurement has been performed for gun 4.2 @ the position of 5.7 m from the cathode with the machine & beam parameters as shown here. 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

PITZ 2009 results: Emittance vs. bunch charge 3 PITZ 2009 results: Emittance vs. bunch charge 0.0 0.1 0.2 0.3 0.4 0.5 Laser spot size (mm) Study of emittance vs.BSA size and charge gun of +6 deg off-crest, booster on-crest 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 0.0 2.0 BSA size (mm) Emit-XY (um) 1 nC 0.5 nC 0.25 nC 0.1 nC Beside the measurements of the nominal 1 nC bunch charge, we also measured the emittance of the other charges. Results of emittance measurement results for different bunch charges are shown here for 100 pC, 250 pC, 500 pC and 1 nC. The emittance values of ~0.9 to 1.2 um were measured for 1 nC beam and shown as the data series in this figure. The smallest emittance value of ~0.4 um for 100 nC with good quality of the beamlet signal can be measured with the emittance measurement system @ PITZ. All measurements showing here are the measurements that used the flat-top temporal laser pulses with short rise/fall time of 2 ps. 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

PITZ 2009 results: Emittance vs. bunch charge (with charge cut) 4 PITZ 2009 results: Emittance vs. bunch charge (with charge cut) 10% cut ~0.7-0.8 mm-mrad (remove non-lasing electrons) → beyond XFEL requirement By applying the charge cut to the emittance analysis of 5 measurement cases. One can see that the emittance of 1 nC beam is about 0.7-0.8 um. This is beyond the XFEL requirement. One interesting case is the 250 pC bunch charge with 5% charge cut, the emittance is about 0.4 um was measured. This value is very comparable to the LCLS emittance measurement result. 5% cut ~0.4 um (comparable to LCLS result) 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

Parameters at Gun Charge nC 1 0.5 0.25 0.1 0.02 RMS Bunch Length fs   RMS Bunch Length fs 8000 6000 5400 4800 4500 simulation Peak Current A 49.8 33.2 18.4 8.3 1.8 Slice Emittance mm 0.7 0.32 0.2 measurement of projected Slice Energy Spread keV 2 0.6 0.8 Compression factor 100 120 162 301 1128 Peak Current A 5000 4000 3000 2500 2000   05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

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

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

Parameters after Laser Heater – Constant Energy Spread Charge nC 1 0.5 0.25 0.1 0.02   RMS Bunch Length fs 8000 6000 5400 4800 4500 simulation Peak Current A 49.8 33.2 18.4 8.3 1.8 Slice Emittance mm 0.7 0.32 0.2 measurement of projected Slice Energy Spread keV 2 0.6 0.8 Slice Energy Spread after LH 20 16.7 12.3 6.7 1.78 Constant Energy Spread after Compression 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

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

Parameters after Laser Heater – Increased Energy Spread Charge nC 1 0.5 0.25 0.1 0.02   RMS Bunch Length fs 8000 6000 5400 4800 4500 simulation Peak Current A 49.8 33.2 18.4 8.3 1.8 Slice Emittance mm 0.7 0.32 0.2 measurement of projected Slice Energy Spread keV 2 0.6 0.8 Slice Energy Spread after LH 20 16.7 12.3 6.7 1.78 Constant Energy Spread after Compression 18.2 15.3 9.8 3.6 Increased Energy Spread after Compression 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

Parameters at Undulator Charge nC 1 0.5 0.25 0.1 0.02   Compression factor 100 120 162 301 1128 Peak Current A 5000 4000 3000 2500 2000  Goal Slice Energy Spread MeV 0.2 0.9 No Laser Heater Slice Energy Spread after LH 2.0 Constant Energy Spread after Compression 2.2 2.5 2.9 4.1 Increased Energy Spread after Compression 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

Emittance Degradation Charge nC 1 0.5 0.25 0.1 0.02   Slice Emittance at Gun mm 0.7 0.32 0.2 from measurement of projected Compression Factor 100 120 162 301 1128 Emittance Degradation % 5.0 10.0 20.0 30.0 100.0 from simulation and LCLS experience Slice Emittance at Undulator 1.05 0.77 0.60 0.42 0.40 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

Final Parameter Set Gun Charge nC 1 0.5 0.25 0.1 0.02 Slice Emittance mm 0.7 0.32 0.2 Peak Current A 49.8 33.2 18.4 8.3 1.8 Slice Energy Spread after LH keV 20.0 18.2 15.3 9.8 3.6 Undulator Compression Factor   100 120 162 301 1128 Peak Current kA 5.0 4.0 3.0 2.5 2.0 Bunch Length (RMS) fs 80 50 33 16 4 1.05 0.77 0.60 0.42 0.40 Slice Energy Spread MeV 2.2 2.9 4.1 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

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

FLASH S2E Simulations Charge nC 1 0.5 0.25 0.1 0.02 Gun   Charge nC 1 0.5 0.25 0.1 0.02 Gun Slice Emittance (RMS) mm 0.8 to 1 0.6 to 0.7 0.4 to 0.5 0.25 to 0.3 < 0.1 Peak Current A 50.0 35.0 20.0 8.0 1.6 Slice Energy Spread (RMS) KeV 0.7 0.2 to 0.3 0.1 to 0.15 Undulator Compression Factor 50 90 150 240 1000 Peak Current kA 2.4 2.5 2.0 1 to 1.5 Emittance Degradation % 20 30 60 1 to 1.3 0.7 to 0.9 0.5 to 0.7 0.3 to 0.4 MeV 0.1 to 0.2 0.2 to 0.4 Initial × Compression 0.05 0.07 0.10 Radiation pulse (FWHM) fs 70.00 30.00 17.00 7.00 2.00 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator

Impact of reduced emittance on baseline layout 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

New baseline parameter set established Summary New baseline parameter set established Detailed analysis follows, taking into account tolerance considerations, complete set of self- and external fields etc. Charge nC 1 0.5 0.25 0.1 0.02 Peak Current kA 5.0 4.0 3.0 2.5 2.0 Bunch Length (RMS) fs 80 50 33 16 4 Slice Emittance mm 1.05 0.77 0.60 0.42 0.40 Slice Energy Spread MeV 2.2 2.9 4.1 05.05.2010, 2nd XFEL MAC W. Decking, DESY, XFEL Machine Layout Coordinator