P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Linac Commissioning P. Emma LCLS Commissioning...

P. Emma, P. Emma, SLACSLAC LCLSLCLS Commissioning – Sep. 22, 2004 Commissioning – Sep. 22, 2004

Linac CommissioningLinac CommissioningP. EmmaP. Emma

LCLSLCLS Commissioning Workshop, SLAC Commissioning Workshop, SLAC Sep. 22-23, 2004Sep. 22-23, 2004

LCLSLCLS


Linac Commissioning Document AvailableLinac Commissioning Document Available

http://www-ssrl.slac.stanford.edu/lcls/linac/notes/linac_commissioning.ps

>23 page >23 page DRAFTDRAFT document describing: document describing:initial checkoutinitial checkoutsetup of linacsetup of linachow/where to measure beamhow/where to measure beamwhat device to scan and by how muchwhat device to scan and by how muchexpected resolutionexpected resolutionhow/where to correct beamhow/where to correct beametc…etc…

(not complete yet, but close)(not complete yet, but close)


Linac ‘Commissioning’ (Physics)Linac ‘Commissioning’ (Physics)

Initial checkout (tunnel and beam-based)Initial checkout (tunnel and beam-based)

How to setup How to setup IIpkpk = 3.4 kA, = 3.4 kA, 1.2 1.2 m, etc.m, etc.

What to measure and what to adjust (simulations)What to measure and what to adjust (simulations)

Longitudinal phase spaceLongitudinal phase spaceBunch LengthBunch Length

Energy Spread (proj. & slice)Energy Spread (proj. & slice)

Transverse phase spaceTransverse phase spaceProjected EmittanceProjected Emittance

Slice EmittanceSlice Emittance


Initial Machine ConditionsInitial Machine Conditions

Magnets warmed, standardized, and set properlyMagnets warmed, standardized, and set properly

Reasonable quality Reasonable quality ee beam available: beam available:

Rough beam steering establishedRough beam steering established

Rough RF phasing of each klystron (1 or 2 deg)Rough RF phasing of each klystron (1 or 2 deg)

Any beam obstruction and loss issues solvedAny beam obstruction and loss issues solved


Initial Checkout - Initial Checkout - TUNNELTUNNEL

Power-on Power-on polarity checkspolarity checks of all “new” magnets of all “new” magnets

Validate proper Validate proper cabling connectionscabling connections (magnets, (magnets, BPMs, diagnostics…)BPMs, diagnostics…)

Rough Rough alignment inspectionalignment inspection (tape measure, eye) (tape measure, eye)

Verify all insertable devices move in and out, and Verify all insertable devices move in and out, and are finally are finally removedremoved


Initial Checkout - Initial Checkout - BEAM-BASEDBEAM-BASED

Take Take full setfull set of of xx and and yy ‘oscillation’ data (checks ‘oscillation’ data (checks optics and BPM scaling…)optics and BPM scaling…)

Verify all Verify all profile monitor scalingprofile monitor scaling with known with known centroid shifts (wires, OTR, YAG, screens…)centroid shifts (wires, OTR, YAG, screens…)

Repeat above at high dispersion points (DL1, BC1, Repeat above at high dispersion points (DL1, BC1, BC2, DL2) using energy changesBC2, DL2) using energy changes

CalibrateCalibrate all BPM-charge, and toroid readings all BPM-charge, and toroid readings based on one well established referencebased on one well established reference

DocumentDocument all the above for future scrutiny all the above for future scrutiny

CHECKOUT CHECKOUT MUSTMUST BE COMPLETEBE COMPLETE BEFORE MEASUREMENTS AND TUNING BEGIN! BEFORE MEASUREMENTS AND TUNING BEGIN!


Location of Main Linac DiagnosticsLocation of Main Linac Diagnostics5+ energy spread meas. stations (optimized with small 5+ energy spread meas. stations (optimized with small ))

...existing linac...existing linac

L0L0

rfrfgungun

L3L3L1L1 XX L2L2

xx,,yy xx,,yy xx,,yy xx,,yy

xx,,yy

EE EE EEEE

5+ emittance meas. stations designed into optics (5+ emittance meas. stations designed into optics (xx,,yy))BPMs at or near most quadrupoles and in each bend syst.BPMs at or near most quadrupoles and in each bend syst.

RF deflectors for slice RF deflectors for slice and and EE measurements (L0 & L3) measurements (L0 & L3)

EE

EE EEEEEE EE

T-cav.T-cav.

T-cav.T-cav.


Setup of Linac-0 RFSetup of Linac-0 RF

RF-deflector at 1 MVRF-deflector at 1 MV

Phasing L0-LinacPhasing L0-Linac

RF-deflectorRF-deflector

yy bunch length bunch length

minimize energy spread with L0 RF phaseminimize energy spread with L0 RF phase

Establish initial bunch lengthEstablish initial bunch lengthPhase linac-0Phase linac-0



Linac-1 RF phase scanLinac-1 RF phase scan(X-band off, BC1 bends at 295 MeV)(X-band off, BC1 bends at 295 MeV)

Linac-X RF phase scanLinac-X RF phase scan(BC1 bends at 250 MeV)(BC1 bends at 250 MeV)

set phase to set phase to 2525˚̊0.50.5˚̊ set phase to set phase to 160˚160˚0.5˚0.5˚

20-20-m res. BC1 BPMm res. BC1 BPM 20-20-m res. BC1 BPMm res. BC1 BPM

L1 RF phaseL1 RF phase

LX RF phaseLX RF phase

Turn on BC1 energy feedbackTurn on BC1 energy feedbackSwitch off BC2 chicaneSwitch off BC2 chicaneUse sec-25 RF-deflector to meas. bunch length (Use sec-25 RF-deflector to meas. bunch length (zz11))

Adjust S-band RF phase (Adjust S-band RF phase (0.50.5˚̊) to set ) to set zz11 195 195 10 10 mm

Linac-1Linac-1newnew

rfrfgungun

21-1b21-1b21-1d21-1d XX



Linac-2 RF phase scanLinac-2 RF phase scan(BC2 bends at 5.9 GeV, or…)(BC2 bends at 5.9 GeV, or…)

set phase to set phase to 4141˚̊0.50.5˚̊

40-40-m res. BC2 BPMm res. BC2 BPM

L2 RF phaseL2 RF phase

Turn on BC2 energy feedbackTurn on BC2 energy feedbackUse sec-25 RF-deflector to measure length (Use sec-25 RF-deflector to measure length (zz22))

Adjust L2 RF phase (Adjust L2 RF phase (0.50.5˚̊) to set ) to set zz22 20 20 2 2 mm

Linac-3 phasing is trivial (Linac-3 phasing is trivial (5˚)5˚)

5-5-m res. LTU BPMm res. LTU BPM

L2 phaseL2 phase

Scan Linac-2 phase & use LTU BPM to find Scan Linac-2 phase & use LTU BPM to find max. wake-induced energy loss across Linac-3max. wake-induced energy loss across Linac-3

(NO CSR)

L2L2 L3L3


Emittance Meas. Simulation in LCLSEmittance Meas. Simulation in LCLS

OTR1,2,3OTR1,2,3 WS11,12,13WS11,12,13BC1BC1

Multiple OTR screensMultiple OTR screensMultiple wire-scannersMultiple wire-scanners

Quad-scans on single OTRQuad-scans on single OTRQuad-scans on OTR with RF-deflectorQuad-scans on OTR with RF-deflector


135-MeV OTR 135-MeV OTR xx-profiles from tracking-profiles from tracking

xx = 0.75 = 0.75 ±± 0.04 0.04 mmxx = 0.75 = 0.75 ±± 0.04 0.04 mm

xx 118 118 mm xx 49 49 mm

xx 120 120 mm

non-Gaussiannon-Gaussian


xx-Slice-Emittance Measurement-Slice-Emittance MeasurementRF-deflector at 1 MVRF-deflector at 1 MV

slice OTR 10 timesslice OTR 10 times

yy bunch length bunch length

““QE03” quad scannedQE03” quad scanned


xx-Slice-Emittance Measurement Simulation-Slice-Emittance Measurement Simulation

slice-5slice-5

Injector at 135 MeV with Injector at 135 MeV with S-band RF-deflector at 1 MVS-band RF-deflector at 1 MV

= meas. sim.= calc.= y distribution= actual(same SLAC slice-(same SLAC slice- code used at BNL/SDL)code used at BNL/SDL)

DL1 slice-emit on WS02DL1 slice-emit on WS02

“QE03” scanned 20% (centered on 106% of its nominal gradient)


yy-slice-Emittance Measurement in BC1-slice-Emittance Measurement in BC1

3.9 mm3.9 mm

0.1 mm

0.1 mm

““Q21201” scanned Q21201” scanned ±±20%20%


yy-slice-Emittance Measurement Simulation-slice-Emittance Measurement Simulation

slice-slice-yy emittance in emittance in

BC1 using BC1 using xx-chirp-chirp

= meas. sim.= calc.= y distribution= actual

slice-5slice-5

“Q21201” scanned 20% (centered on 92% of its nominal gradient)


Empirical BC1/BC2 Dispersion CorrectionEmpirical BC1/BC2 Dispersion Correction

Residual Residual xx-dispersion (and its angle) is precision -dispersion (and its angle) is precision minimized using ‘tweaker’ quads in the chicaneminimized using ‘tweaker’ quads in the chicane

actual data from SPPS chicaneactual data from SPPS chicane

x /2

SPPS chicane with quadsSPPS chicane with quadsCorrect Correct and ( and (), orthogonally ), orthogonally with 2 quadswith 2 quads


Transverse Wakefield CompensationTransverse Wakefield Compensation

trajectory trajectory afterafter steering steering

xx 2.1 2.1 mm

yy 5.2 5.2 mm

All quadrupoles, RF structures, and All quadrupoles, RF structures, and BPMs misaligned by 300 BPMs misaligned by 300 m rmsm rms

steering coilssteering coils

xx 1.0 1.0 mm

yy 1.1 1.1 mm

Small ‘bumps’ added to Small ‘bumps’ added to correct emittancecorrect emittance


Repeat for 100 Different SeedsRepeat for 100 Different Seeds

// 20% (projected) 20% (projected)

M. BorlandM. Borland


Energy Jitter Measurement (Feedback)Energy Jitter Measurement (Feedback)

undulator…undulator…

relative energy relative energy centroid resolution: centroid resolution:

~0.003%~0.003%

xx11 xx22Two 5-Two 5-m BPMs:m BPMs:

Difference of BPM Difference of BPM xx-readings is proportional to energy -readings is proportional to energy change, and change, and insensitiveinsensitive to incoming trajectory jitter. to incoming trajectory jitter.

xx 125 mm) 125 mm)


Slice-Emittance Configuration for LTUSlice-Emittance Configuration for LTU

nominal opticsnominal optics(proj. emit.)(proj. emit.)

WS31-34WS31-34

undulator…undulator…

slice-emit.slice-emit.meas. opticsmeas. optics

OTR33OTR33stopperstopperinsertedinserted


Slice-Emittance Measurements in LTUSlice-Emittance Measurements in LTU

= meas. sim.= calc.= y distribution= actual

xxxx

zz

yy

LTU at 14 GeV with S-band LTU at 14 GeV with S-band RF-deflector at 24 MVRF-deflector at 24 MV

“QEM3” (or tweaker) scanned 3% (centered on its nominal gradient)


Slice Energy Spread Measurements in LTUSlice Energy Spread Measurements in LTU

LTU at 14 GeV with S-band LTU at 14 GeV with S-band RF-deflector at 24 MVRF-deflector at 24 MV

FEL goalFEL goal

EE//E E 104

x 12 m


SummarySummaryMost diagnostics incorporated into design and Most diagnostics incorporated into design and simulated (1simulated (1stst pass) pass)

Two RF-deflectors allow time resolved Two RF-deflectors allow time resolved measurements at low and high energymeasurements at low and high energy

Tune-up algorithms considered, but more Tune-up algorithms considered, but more refinement neededrefinement needed

Feedback systemsFeedback systems must maintain setup while must maintain setup while tuning progresses (bunch length monitors?)tuning progresses (bunch length monitors?)

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Linac Commissioning P. Emma LCLS Commissioning...

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