‘‘S2E’ Study of Linac for S2E’ Study of Linac for TESLATESLA XFEL XFELP. EmmaP. Emma

SLACSLAC

TrackingTracking Comparison to Comparison to LCLSLCLS Re-optimizationRe-optimization TolerancesTolerances JitterJitter CSR EffectsCSR Effects

L = 6 m L = 9 mrf = 38°

L = 330 mrf = 43°

L = 550 mrf = 10°

BC-1L = 6 m

R56= 36 mm

BC-2L = 22 m

R56= 22 mm DL-2R56 = 0

DL-1R56 0

undulatorL =120 m

6 MeVz 0.83 mm 0.1 %

150 MeVz 0.83 mm 0.10 %

250 MeVz 0.19 mm 1.8 %

4.54 GeVz 0.022 mm 0.76 %

14.35 GeVz 0.022 mm 0.01 %

...existing linac

L0

rfgun

L3L1 X

LhL =0.6 mrf=

L2

L 16 mrf 40°

L 72 mrf 40°

L 850 mrf = 0°

BC-2L 14 m

R56= 36 mm

BC-3L 18 m

R56= 11 mm

undulatorL =? m

6 MeVz 2.0 mm 0.1 %

120 MeVz 0.5 mm 2.0 %

375 MeVz 0.1 mm 1.4 %

1.64 GeVz 0.020 mm

0.5 %

20.5 GeVz 0.020 mm 0.01 %

L3L0

LhL 1.4 mrf=

rfgun 3.9 L1

BC-1L 4 m

R56= 76 mm

L = 8 mrf 22°

L2

LCLSLCLS

TESLA-XFELTESLA-XFEL

(parameters only approximate)

Twiss parameters along TESLA-XFELTwiss parameters along TESLA-XFEL

BC1BC2

BC3

undulator

Bunch length and energy spread along TESLA-XFELBunch length and energy spread along TESLA-XFEL

EE//EE

ss

-bunching exaggerated by noise, -bunching exaggerated by noise, but gain may be large (see but gain may be large (see modulated beam study below).modulated beam study below).

BC1+

BC2+

BC3+

Longitudinal phase space at end of TESLA-XFELLongitudinal phase space at end of TESLA-XFEL

-bunching exaggerated by noise-bunching exaggerated by noise(see modulation study below)(see modulation study below)xx 1.3 1.3 3.6 3.6 mm

Slice emittance at end of TESLA-XFELSlice emittance at end of TESLA-XFEL

Slice energy spread at end of TESLA-XFELSlice energy spread at end of TESLA-XFEL

E/E < 0.01%

slice 4D centroid osc. amplitudeslice 4D centroid osc. amplitude Twiss slice mismatch amplitudeTwiss slice mismatch amplitude

Sliced Bunch AnalysisSliced Bunch Analysis

IIpkpk xx,,yy EE//EE00

//

Quad alignment tolerancesQuad alignment tolerances

Quad roll-angle tolerancesQuad roll-angle tolerances

1 mm

10 mrad

Longitudinal-only simulation with Longitudinal-only simulation with LiTrackLiTrack (200k in 66 seconds) (200k in 66 seconds)

no CSRno CSR

00 = 0.2 = 0.2°°

00 = 0 = 0

Ipk 11 kA

Ipk 6 kA

Test rf phase sensitivity:Test rf phase sensitivity:

gun-timinggun-timing chargecharge|| EE /

/ EE| <

0.1

%| <

0.1

%

||ttii| < 0.13 ps| < 0.13 ps ||Q/QQ/Q| < 4%| < 4%

gun-timinggun-timing chargecharge|| II pkpk

// II pkpk| <

12%

| < 1

2%Scan gun-laser timing and charge, monitoring energy and peak currentScan gun-laser timing and charge, monitoring energy and peak current

gun-timinggun-timing chargecharge

||ttii|< 0.13 ps|< 0.13 ps ||Q/QQ/Q|< 4%|< 4%

3.9-phase3.9-phase 3.9-voltage3.9-voltage

||hh|< 0.05|< 0.05°° ||VVhh//VVhh|< 0.3|< 0.3%%

L0-phaseL0-phase L0-voltageL0-voltage

||00|< 0.07|< 0.07°°

||VV00//VV00|< 0.08|< 0.08%%

L1-phaseL1-phase L1-voltageL1-voltage

||11|< 0.05|< 0.05°° ||VV11//VV11|< 0.21|< 0.21%%

L2-phaseL2-phase L2-voltageL2-voltage L3-phaseL3-phase L3-voltageL3-voltage

||22|< 1.1|< 1.1°° ||VV22//VV22|< 1.6|< 1.6%% ||VV33//VV33|< 0.1|< 0.1%%

||33|< 2.2|< 2.2°°

This suggests an increase of the 3.9-GHz voltage This suggests an increase of the 3.9-GHz voltage

Note 2Note 2ndnd-order chirp after BC2-order chirp after BC2

System is very sensitive with System is very sensitive with large 11-kA spike at headlarge 11-kA spike at head(T. Limberg)…(T. Limberg)…

LiTrackLiTrack with 3.9-GHz voltage raised from 16.6 MV to 21.0 MV with 3.9-GHz voltage raised from 16.6 MV to 21.0 MV

previous previous distributiondistribution

no spikesno spikes

00 = 0.2 = 0.2°°

00 = 0 = 0

Ipk 5.5 kA

Ipk 4.5 kA

With 21-MV 3.9-GHz rf,With 21-MV 3.9-GHz rf,again testing rf phase again testing rf phase sensitivity:sensitivity:

……much less sensitivemuch less sensitive

gun-timinggun-timing chargecharge

||ttii|< 6.0 ps|< 6.0 ps ||Q/QQ/Q|< 100%|< 100%

3.9-phase3.9-phase 3.9-voltage3.9-voltage

||hh|< 0.19|< 0.19°°

||VVhh//VVhh|< 1.0|< 1.0%%

L0 phaseL0 phase L0 voltageL0 voltage

||00|< 0.09|< 0.09°° ||VV00//VV00|< 0.20|< 0.20%%

L1 phaseL1 phase L1 voltageL1 voltage

||11|< 0.24|< 0.24°° ||VV11//VV11|< 1.0|< 1.0%%

L3 phaseL3 phase L3 voltageL3 voltage

||33|< 2.2|< 2.2°° ||VV33//VV33|< 0.1|< 0.1%%

L2 phaseL2 phase L2 voltageL2 voltage

||22|< 0.49|< 0.49°° ||VV22//VV22|< 1.4|< 1.4%%

originaloriginaladjustedadjusted3.9-GHz3.9-GHz

3.9-GHz 3.9-GHz & X-band& X-band

Form ‘jitter budget’ based on uncorrelated jitter: Form ‘jitter budget’ based on uncorrelated jitter:

degrees of degrees of X-band or X-band or 3.9-GHz3.9-GHz

3.9-GHz 3.9-GHz & X-band& X-band h-h-

LiTrackLiTrack Jitter Simulation of TESLA-XFEL using ‘jitter budget’ Jitter Simulation of TESLA-XFEL using ‘jitter budget’

6.7 minutes @ 5 Hz6.7 minutes @ 5 Hz(no CSR)(no CSR)

II//II00))rmsrms

13%13%

EE//EE00))rmsrms

0.09%0.09%// 0.18%0.18%

tt))rmsrms

0.2 ps0.2 ps

energyenergy energy spreadenergy spread

peak currentpeak current arrival timearrival time

No CSR

Now test re-optimized setup with full 6D tracking (Elegant)

ElegantElegant tracking tracking with CSRwith CSR (and increased 3.9-GHz voltage) (and increased 3.9-GHz voltage)

xx 1.3 1.3 2.4 2.4 mm -bunching exaggerated by noise, -bunching exaggerated by noise, but gain at but gain at 3 3 m may be largem may be large(see modulation study below)(see modulation study below)

4 keV injector slice 4 keV injector slice energy spreadenergy spread

ElegantElegant tracking with CSR and slice energy spread tracking with CSR and slice energy spread ××6 from gun6 from gun

xx 1.3 1.3 2.0 2.0 mm-bunching damped by large -bunching damped by large intrinsic energy spread (23 keV intrinsic energy spread (23 keV or or 10 1044 at undulator) at undulator)

23 keV injector slice 23 keV injector slice energy spreadenergy spread

slice slice

slice slice EE//E E < 0.01%< 0.01%

-tron oscillation induced by CSR energy loss-tron oscillation induced by CSR energy loss

Full 6D Full 6D ElegantElegant tracking with increased 3.9-GHz voltage and tracking with increased 3.9-GHz voltage and “23 keV”“23 keV”

……xx might be affected might be affected

= 500 = 500 mmAA = = 0.5%0.5%

Add modulation on density Add modulation on density andand energy profile energy profile

Use 10Use 1066 macro-particles and quiet-start bunch population in macro-particles and quiet-start bunch population in xx, , xx, , zz, , EE//EE

at 120 MeVat 120 MeV

1010

22

IIpkpk 5 kA 5 kA

IIpkpk 50 A 50 A

120 MeV120 MeV

20.5 GeV20.5 GeV

CSR CSR -bunching in -bunching in full TESLA-XFELfull TESLA-XFELN = N = 101066,,bins = 500,bins = 500,transient 1D model,transient 1D model,linear optics,linear optics,matched matched ’s,’s,QQ = 1 nC, = 1 nC,xx = 1 = 1 m,m,pk pk //pkpk00 100, 100,EE00 = 4 keV & = 4 keV & 23 keV23 keV

CSR offCSR off

EE//EE 10 1044 at 20 GeV at 20 GeV after BC’safter BC’s

linear opticslinear optics

BC1BC1

BC2BC2 BC3BC3Track full XFEL in Track full XFEL in 4D (4D (xx, , xx, , zz, , EE//EE) ) from pre-BC1 at 120 from pre-BC1 at 120 MeV to just past BC3 MeV to just past BC3 at 1.64 GeV using at 1.64 GeV using ““CSRCSR__calccalc” (PE) and ” (PE) and linearly re-matching linearly re-matching to proper to proper and and energy chirp prior to energy chirp prior to each BC.each BC. re

-mat

ch p

oint

re-m

atch

poi

nt

re-m

atch

poi

ntre

-mat

ch p

oint

injectorinjector = 500 = 500 m,m,AA = 0.5% = 0.5%

post-BC1post-BC1 123 123 m,m,AA 0.5% 0.5%

post-BC2post-BC2 20 20 m,m,AA 6.0% 6.0%

post-BC3post-BC3 6.6 6.6 m,m,AA 50% 50%

EE00 = 4 keV = 4 keV

gain gain 100 100

injectorinjector = 500 = 500 m,m,AA = 0.5% = 0.5%

post-BC1post-BC1 123 123 m,m,AA < 1.0% < 1.0%

post-BC2post-BC2 20 20 m,m,AA < 1.0% < 1.0%

post-BC3post-BC3 6 6 m,m,AA 3% 3%

EE00 = 23 keV = 23 keV

gain gain 6 6

EE00 = 4 keV = 4 keV EE00 = 23 keV = 23 keV

gain ~ 1gain ~ 1gain gain 150 150

= 250 = 250 m,m,

AA = 0.5% = 0.5%

EE00 = 4 keV = 4 keVEE00 = 23 keV = 23 keV

TESLA-XFEL CSR Compound Gain Curve (no LSC)TESLA-XFEL CSR Compound Gain Curve (no LSC)

starting at 120 MeV

Large Large -bunching gain, even without longitudinal space charge -bunching gain, even without longitudinal space charge – adding energy spread is very helpful– adding energy spread is very helpful

Charge jitter in XFEL much looser than Charge jitter in XFEL much looser than LCLSLCLS

Some rf phase tolerances tighter than Some rf phase tolerances tighter than LCLSLCLS

Lack of longitudinal wakefield allows very linear compression, Lack of longitudinal wakefield allows very linear compression, producing nearly uniform current profile – not possible in producing nearly uniform current profile – not possible in LCLSLCLS

Possibly better performance if BC3 were integrated into BC2?Possibly better performance if BC3 were integrated into BC2?

Thanks especially to Yujong, Jean-Paul, and TorstenThanks especially to Yujong, Jean-Paul, and Torsten

Final CommentsFinal Comments