Emittance Preservation in PSI-XFEL Linac with updated ......† : z = 650 m is the minimum length...

Emittance Preservation in PSIEmittance Preservation in PSI--XFEL LinacXFEL Linacwith updated parameterswith updated parameters

G. Amatuni, B. Grigoryan*, V. Tsakanov

07 April 2009 PSI CANDLE – PSI Collaboration 2

IntroductionIntroduction

• Correlated, uncorrelated energy spread in linac.

• Emittance preservation in S-Band linear accelerator.

– Coherent betatron oscillations– Accelerating sections misalignment – The effects of RF phase jitter

– Quadrupole misalignment. One-to-one orbit correction.

Beam Dynamics study for PSI-XFEL Linear accelerator (0.25-6 GeV)


Optimization-III of 6 GeV PSI-XFEL LINAC

Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland

slice parameters at the end of Linac

projected parameters

ASTRA up to exit of SB02 & ELEGANT from exit of SB02 to consider space chare, CSR, ISR, and wakefields !

Meritslowest relative rms projected energy spread, σδ ~ 0.013%low projected emittance, εnx ~ 0.40 µmlow slice emittance, εn,slice ~ 0.33 µmlow rms slice energy spread, σdE,slice ~ 148 keV for whole bunchideal energy chirpings for FEL1 & FEL2 (SASE) and FEL3 (Seeding) beamlines

Demeritssomewhat long bunch length, σz = 14.2 µm and somewhat low peak current, Ipeak ~ 1.6 kAlongest machine length, z = 650 m† at the undulator entrance

† : z = 650 m is the minimum length for 6 GeV Linac, Dog-Leg (DL), DIAG3 in DL, and Switch Yards in LINAC2



Linac 1 Linac 2Linac 1 Linac 2

0.873

10.4

π/3

18.9 / 18.9

LINAC 2LINAC 2LINAC 1LINAC 1TWISS parametersTWISS parameters

1.305K1 (QD / QF) [m-2]

10.3Cell Length [ m]

π/3Phase adv. per cell µ

17.9 / 17.8βmax x / y [ m ]



Machine and electron beam main parametersMachine and electron beam main parameters (updated)(updated)

Parameter Linac 1 Linac 2 Bunch Charge [ pC ] 200 200 Energy [ GeV ] 0.255 –1.47 1.47 –6.1 Bunch Length rms [ µm ] 55 14.2 Initial relative correlated energy spread (rms) init / final [ % ]

1.673 / 0.473 0.473 / 0.013

Peak current [ kA ] 0.35 1.5 Norm. transv. emit. [ mm-mrad ] 0.39 0.38 Nominal accel. grad. [ MV/m ] 22 22 RF frequency [ GHz ] 3 3 Number of accel. Sections 18 68 Number of focusing cells 9 34 Type of the focusing lattice FODO FODO

4.34.3Accel. Structure Length [ m ]


Wakefields Wakefields

Transverse and longitudinal wake potentials for single bunch inTransverse and longitudinal wake potentials for single bunch in SS--band structure.band structure.

Linac 1Linac 1 Linac 2Linac 2*K.Bane, M. *K.Bane, M. TimmTimm, T. , T. WeilandWeiland, SLAC, SLAC--PUBPUB--9798 9798


Correlated Energy SpreadCorrelated Energy Spread

Linac 1Linac 1 Linac 2Linac 2

CorrelCorrel. energy spread 1.673% / 0.473% . energy spread 1.673% / 0.473% 0.473% / 0.013% 0.473% / 0.013%

0.013 %

0.013 %

0.473 %


Coherent Betatron Oscillations. Uncorrelated Energy SpreadCoherent Betatron Oscillations. Uncorrelated Energy Spread

Linac 1 38 Linac 1 38 keV keV ( ~ 0.015% )( ~ 0.015% ) Linac 2 138 Linac 2 138 keV keV ( ~ 0.01 %) ( ~ 0.01 %)


Correlated Correlated EmittanceEmittance Dilution. Wakefield ImpactDilution. Wakefield Impact



Accelerating Sections Misalignments.Accelerating Sections Misalignments.


Random (statistic) misalignment rms offset 500 umRandom (statistic) misalignment rms offset 500 um


Accelerating Sections Misalignments.Accelerating Sections Misalignments.



RF Phase JitterRF Phase Jitter



Quadrupole Misalignment. OneQuadrupole Misalignment. One--toto--one orbit correctionone orbit correction


Quadrupole random Quadrupole random rmsrms misalignments misalignments 100 100 µµmmBPM random BPM random rmsrms misalignmentsmisalignments 100 100 µµmmBPM resolution BPM resolution 2 2 µµmm



Correlated emittance dilutionCorrelated emittance dilutionLinac 1Linac 1 Linac 2Linac 2



Uncorrelated emittance dilutionUncorrelated emittance dilutionLinac 1Linac 1 Linac 2Linac 2




Correlated emittance dilution for Correlated emittance dilution for corrected orbit and nominal RF phases.corrected orbit and nominal RF phases.




Uncorrelated emittance dilution for Uncorrelated emittance dilution for corrected orbit and nominal RF phases.corrected orbit and nominal RF phases.


Summary. Emittance Dilution in PSISummary. Emittance Dilution in PSI--XFEL XFEL LinacLinac

Linac1Linac1 Linac2Linac2Coherent oscillations

uncorrelated 5×10-5 % 2×10-4 %correlated 0.015 % 0.62 %

Misalignments

Accel. Sections 0.1 % 0.52 %

Quadrupoles & BPMs ( 100 µm ). One-to-one correction

uncorrelated 7×10-5 % 0.001 %correlated 0.5 % 2 %

TOTAL < 0.65 % < 3.5 %

For RF phases: For RF phases: --4141°° (linac 1) and 40(linac 1) and 40°° (linac 2) (linac 2)


Further (in-progress) studies

RF phase and amplitude errors.Accelerating sections tilts.Quadrupole field errors and beta mismatch

Summary.Summary. EmittanceEmittance Dilution in PSIDilution in PSI--XFEL XFEL LinacLinac


Summary. OutlooksSummary. Outlooks

Comparison of SComparison of S--band and Cband and C--band options for PSIband options for PSI--XFEL XFEL LinacLinac* * PSIPSI--XFEL XFEL Linac Linac options from Y. Kim.options from Y. Kim.

Emittance Preservation in PSI-XFEL Linac with updated ......† : z = 650 m is the minimum length...

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