Joe Frisch LCLS FAC [email protected] Oct. 30, 2007 1 Linac/BC2 Commissioning (Dec. 2007...

Joe FrischJoe Frisch

LCLSLCLS FAC FAC [email protected]@SLAC.Stanford.edu

Oct. 30, 2007Oct. 30, 20071

Linac/BC2 CommissioningLinac/BC2 Commissioning(Dec. 2007 through Sep., 2008)(Dec. 2007 through Sep., 2008)

J. Frisch, J. Frisch, et al.et al.LCLS FAC MeetingLCLS FAC Meeting

Oct. 30, 2007Oct. 30, 2007

LCLSLCLShttp://www-ssrl.slac.stanford.edu/lcls/internals/commissioning/index.htmlhttp://www-ssrl.slac.stanford.edu/lcls/internals/commissioning/index.html



Oct. 30, 2007Oct. 30, 20072

LCLSLCLS Accelerator Schematic Accelerator Schematic

SLAC linac tunnelSLAC linac tunnel research yardresearch yard

Linac-0Linac-0L L =6 m=6 m

Linac-1Linac-1L L 9 m9 m

rf rf 25°25°

Linac-2Linac-2L L 330 m330 mrf rf 41°41°

Linac-3Linac-3L L 550 m550 mrf rf 0° 0°

BC1BC1L L 6 m6 m

RR5656 39 mm39 mm

BC2BC2L L 22 m22 m

RR5656 25 mm25 mm DL2 DL2 L L =275 m=275 mRR56 56 0 0

DL1DL1L L 12 m12 mRR56 56 0 0

undulatorundulatorL L =130 m=130 m

6 MeV6 MeVz z 0.83 mm 0.83 mm 0.05 %0.05 %

135 MeV135 MeVz z 0.83 mm 0.83 mm 0.10 %0.10 %

250 MeV250 MeVz z 0.19 mm 0.19 mm 1.6 %1.6 %

4.30 GeV4.30 GeVz z 0.022 mm 0.022 mm 0.71 %0.71 %

13.6 GeV13.6 GeVz z 0.022 mm 0.022 mm 0.01 %0.01 %

Linac-Linac-XXL L =0.6 m=0.6 mrfrf= =

21-1b,c,d

...existinglinac

L0-a,b

rfrfgungun

21-3b24-6dX

25-1a30-8c

Injector CommissioningInjector Commissioning Commission in Jan. 2008Commission in Jan. 2008



Oct. 30, 2007Oct. 30, 20073

BC2/Linac BC2/Linac Commissioning GoalsCommissioning Goals

This is the tricky one

No problems expected

Expect we can run at 1nC

No specific problems expected – but lots to do

No problems expected

No known issues, but there could be surprises



Oct. 30, 2007Oct. 30, 20074

OTR screens (3)OTR screens (3)

Dipole magnets (4)Dipole magnets (4)

S-band RF acc. sectionsS-band RF acc. sections

LCLSLCLS BC2-Area Layout BC2-Area Layout

4.3 GeV4.3 GeV(not to scale)(not to scale)

BC2BC2

OTR21OTR21

OTR22OTR22(25-3d)(25-3d)

OTR_TCAVOTR_TCAV(25-9)(25-9)

BXKIKBXKIK

Kicker magnet (1)Kicker magnet (1)

TCAV3TCAV3(25-2d)(25-2d)

4 wire-scanners “de-scoped”4 wire-scanners “de-scoped”

Transverse RF deflector (1)Transverse RF deflector (1)

4 wire-scanners in sec-284 wire-scanners in sec-28(300 m downstream)(300 m downstream)

Can measure Can measure xx,,yy here, here,

with BC2 OFFwith BC2 OFF



Oct. 30, 2007Oct. 30, 20075

Linac/BC2 Commissioning ScopeLinac/BC2 Commissioning ScopeNew 4-dipole chicane in 24-7 – 24-8New 4-dipole chicane in 24-7 – 24-8Adjacent matching quads and new opticsAdjacent matching quads and new optics3 new OTR screens, 1 collimator, 1 BPM, and 2 3 new OTR screens, 1 collimator, 1 BPM, and 2 moved wire-scanners in sec-28 (4 wires in sec-24 moved wire-scanners in sec-28 (4 wires in sec-24 are “are “de-scoped”de-scoped”))Transverse RF deflector at 25-2d + Transverse RF deflector at 25-2d + xx-kicker 25-3d-kicker 25-3dTwo new coherent radiation-based bunch length Two new coherent radiation-based bunch length monitorsmonitorsEnergy and bunch length feedback loop and new Energy and bunch length feedback loop and new SS sub-boosters in 24-1,2,3 + 24-8 (TCAV3)SS sub-boosters in 24-1,2,3 + 24-8 (TCAV3)No new linac BPM electronics in 2008 (or ’09?)No new linac BPM electronics in 2008 (or ’09?)



Oct. 30, 2007Oct. 30, 20076

Manpower and SchedulingManpower and SchedulingTen months of commissioning BC2/Linac (Dec - Sep)Ten months of commissioning BC2/Linac (Dec - Sep)More help with commissioning shifts (H.-D. Nuhn, F.-J. More help with commissioning shifts (H.-D. Nuhn, F.-J. Decker, Z. Huang, Y. Ding, D. Ratner)Decker, Z. Huang, Y. Ding, D. Ratner)Did 3 shifts per week for 5 months in 2007 - exhaustingDid 3 shifts per week for 5 months in 2007 - exhaustingNo weekend shifts (ops only) after 1No weekend shifts (ops only) after 1stst month of startup month of startupOperators now somewhat experienced on injectorOperators now somewhat experienced on injectorNeed two physicists/shift for 10 shifts/week (after 1Need two physicists/shift for 10 shifts/week (after 1stst month)month)Need to cover 20 man-shifts/week - have at least 14 Need to cover 20 man-shifts/week - have at least 14 physicists – requires a total of physicists – requires a total of 1.5 shifts/week/man1.5 shifts/week/man (after 1 (after 1stst month)month)Shutdown LCLS for 2 weeks in March? (new gun probes + Shutdown LCLS for 2 weeks in March? (new gun probes + fix GTL)fix GTL)



Oct. 30, 2007Oct. 30, 20077

Last Run’s Typical Shift ScheduleLast Run’s Typical Shift Schedule



Oct. 30, 2007Oct. 30, 20078

ScheduleSchedule

JJ AA SS OO NN DD JJ FF MM AA MM JJ JJ AA SS OO NN DD JJ FF MM AA MM JJ JJ

linac/BC2 linac/BC2 Install Install

Linac/BC2 Linac/BC2 CommissioninCommissionin

g g

LTU/Und/Dump LTU/Und/Dump FEE/NEH Install FEE/NEH Install

20072007 20082008

LTU/Und/FEE LTU/Und/FEE Commissioning Commissioning

AA SS OONN DD

20092009PPS

PPS

Controls Controls checkout & re-checkout & re-

commission commission injectorinjector

Re-Re-commission commission

Inj/BC2 to SL2Inj/BC2 to SL2

X-Ray tunnel/FEH X-Ray tunnel/FEH Install Install

FEL FEL Commissioning Commissioning

……InjectorInjectorCommissioninCommissioning g

NowNow

PPS

PPS

1st Spont. Light1st Spont. Light1st FEL1st FEL

LightLight 1st Users1st Users

downtime

commissioningtime



Oct. 30, 2007Oct. 30, 20079

BC2 Commissioning ParametersBC2 Commissioning Parameters

ParameterParameter ValueValue CommentsComments

RF rateRF rate 30 Hz30 Hz May test 120HzMay test 120Hz

Beam rateBeam rate ≤≤30 Hz30 Hz 10 Hz 10 Hz eebeam as baseline – short term 30-Hz beam as baseline – short term 30-Hz tests (beyond 30 Hz is unnecessary)tests (beyond 30 Hz is unnecessary)

Drive-laser rateDrive-laser rate 30 Hz30 Hz Possible 120-Hz late in the run?Possible 120-Hz late in the run?

Bunch chargeBunch charge 250 pC250 pC Start at this low charge but later up to 1-nCStart at this low charge but later up to 1-nC

Drive-laser pulse lengthDrive-laser pulse length ~6 ps fwhm~6 ps fwhm Optimum not clear yetOptimum not clear yet

Final beam energyFinal beam energy 13.6 GeV13.6 GeV 13.6 GeV typically with tests down to 4.3 GeV13.6 GeV typically with tests down to 4.3 GeV

May 12, 2007May 12, 2007



Oct. 30, 2007Oct. 30, 200710

BC2 LayoutBC2 Layout

Tw

o ne

w O

TR

scr

eens

+ L

OLA

& k

icke

rT

wo

new

OT

R s

cree

ns +

LO

LA &

kic

ker



Oct. 30, 2007Oct. 30, 200711

BC2 LayoutBC2 Layout

BP

MB

PM

Co

llim

ato

rC

olli

ma

tor

OT

R

OT

R

scre

en

scre

en

23-m long chicane23-m long chicaneTranslates horizontally up to 52 cmTranslates horizontally up to 52 cm



Oct. 30, 2007Oct. 30, 200712

New construction in BC2 (sector 24/25)New construction in BC2 (sector 24/25)

Oct. 11, 2007Oct. 11, 2007



Oct. 30, 2007Oct. 30, 200713

New construction in BC2 (sector 24/25)New construction in BC2 (sector 24/25)

Oct 26



Oct. 30, 2007Oct. 30, 200714

New Pre-Beam Tunnel Check ListNew Pre-Beam Tunnel Check List

17 pages17 pages

etc.etc.etc.etc.

Component bar codesComponent bar codes

Polarity conventionsPolarity conventions

Installation orientationInstallation orientation



Oct. 30, 2007Oct. 30, 200715

Magnet Power Supply ModificationsMagnet Power Supply ModificationsOnly QUAD’s 24201-24501 (4 of original 8) remain on sector-24 bulk Only QUAD’s 24201-24501 (4 of original 8) remain on sector-24 bulk supply (keep 0-20 A boost for each)supply (keep 0-20 A boost for each)Q24601 gets its own supplyQ24601 gets its own supplyDoubled-up Q24701A/B gets its own supplyDoubled-up Q24701A/B gets its own supplyQ24801 quad goes away forever (boost supply is free)Q24801 quad goes away forever (boost supply is free)Doubled-up Q24901A/B gets its own supplyDoubled-up Q24901A/B gets its own supplyNew QM21 & QM22 (46-cm FFTB quads) each get own supplyNew QM21 & QM22 (46-cm FFTB quads) each get own supplyTwo new MCOR6 tweaker quads (Two new MCOR6 tweaker quads (-correction) as in BC1-correction) as in BC1No new correctors here, but all of sectors 20-30 get new MCOR6 No new correctors here, but all of sectors 20-30 get new MCOR6 corrector supplies to replace old SCOR6 suppliescorrector supplies to replace old SCOR6 suppliesControl divided between EPICS and SLCControl divided between EPICS and SLC

Have software to communicate between systems, but adds complexity.Have software to communicate between systems, but adds complexity.Still details to work out for LEM, etc .Still details to work out for LEM, etc .



Oct. 30, 2007Oct. 30, 200716

BC2 Dipole Field Quality OKBC2 Dipole Field Quality OK

No quad field andNo quad field andsextupole is just below tolerancesextupole is just below tolerance



Oct. 30, 2007Oct. 30, 200717

Diagnostics IssuesDiagnostics Issues

Can’t tune on something you can’t measureEngineering issues with the wire scanners

Vibration limits us to slow scan speedsCan be fixed – but no sure solution in hand

Physics issues with the OTR screens

Coherent effects distort imageMay be able to fix with short wavelength filter, but not known.



Oct. 30, 2007Oct. 30, 200718

Wire ScannersWire ScannersMeasured beam size Vs. Motor Steps / second Range is 40-140 microns

With slow scanning, size was reproducible to 5 microns.

May be able to fix problem by adding a gear reducer to wires scanner (cheap), but not tested yet.

For now, limited to slow scans 1 minute / scan, 10 minutes for emittance measurement.



Oct. 30, 2007Oct. 30, 200719

Even “ideal” wire scanner only gives integrated Even “ideal” wire scanner only gives integrated profilesprofiles

Pathological beam shape that wouldNot be apparent on wires



Oct. 30, 2007Oct. 30, 200720

Coherent Effects in OTRsCoherent Effects in OTRs

OTR12 sum signal as QB is varied. BC1 off, L1X, L1S on crest. Y beam sizeVaries with observed intensityNot clear if effect will be worse after BC2.



Oct. 30, 2007Oct. 30, 200721

OTRs - PlansOTRs - Plans

Installing diffraction gratings in front of OTR camerasHope to find that coherence is only in long wavelength signalsIf signal is incoherent below ~400nm can easily add filters to cameras

Installing UV (200nm) and IR (2.5um) detectors on OTRsIR detectors to understand coherence (not seen yet at DESY / FLASH or Spring-8 / SCCS)UV detectors to look for coherence at hard UVIf no coherence at 200nm, can use UV cameras (but $$)

Can not show from beam parameters that we don’t have coherence as short at 100nm – beyond the range of conventional cameras.In future “Laser Heater” will probably fix this problem – but would like to be able to diagnose beam without heater.



Oct. 30, 2007Oct. 30, 200722

Diagnostics – BPMsDiagnostics – BPMs

Existing linac BPMs have 30 – 100 micron resolution depending on beam charge (300pc – 1nC).Readout is through SLC – EPICS communication – slow ~5 seconds.Will need good linac orbit tuning algorithms.

Work underway.

Need initial accuracy ~1mm. OKThen tune on emittance – should work but slow.May wish to tune at high charge (~1nC)

Increase effect of wakefieldsBetter BPM resolution



Oct. 30, 2007Oct. 30, 200723

Diagnostics – where are we?Diagnostics – where are we?

Wire scanners work but:For now, just slow scans – hope for a mechanical fix soonFirst wires located in S28, 300 meters downstream of BC2

OTRsSo far can not be used for quantitative measurementsSome plans that may fix the problem, but not clear a solution exists Discussed at 3-way collaboration meeting at Spring-8 this month. Work underway at other labs.

BPMsUsing old LINAC BPMs. Should be OK, but readout slowNext year (?) replace with epics BPMs.



Oct. 30, 2007Oct. 30, 200724

Emittance Preservation and MeasurementEmittance Preservation and Measurement

Measure emittance after L2:In BC2 (with compressor straight) using OTR

If we do not have coherent effects – otherwise:

Wire scanner in Sector 28 (300M downstream)Orbit Tuning

Minimize orbit on Linac BPMSThen Tune orbit on emittance

In OTR21, or in S28 wiresMight be slow to converge

Then optimize BC2 emittanceThis is probably our most serious technical challenge.



Oct. 30, 2007Oct. 30, 200725

Bunch Length measurementBunch Length measurement

In much better shape than transverse measurementsTCAV in S24 will let us resolve bunch length.

Old cavity in new installation.No problems anticipated.

Cross check with direct compression measurement using phase cavities

Demonstrated in injector

On line mm-wave bunch length monitors similar to injector monitors

Shorter mm wavelengths, but should work

Unique beam conditions – can always have surprises!



Oct. 30, 2007Oct. 30, 200726

Other IssuesOther Issues

LINAC controls split between EPICS and SLC systems.

We have tools in place to make this work, but could be slow to get going

Limited LINAC tunnel access – B-factory running.Limited time to make changes or repairs

Systems designed for “Production”, not R+D. Compact, reliable, and high performance, but difficult ot modify.



Oct. 30, 2007Oct. 30, 200727

Additional Run PlansAdditional Run Plans

Improve performance of injectorBetter BC1 magnet field qualityX-band cavity moved to reduce steeringTry programmable phase ramp in L0A to reduce bunch length / improve emittance

New RF system for phase stabilization over ~1km beamlineNew temperature stabilized transmission linesNeed to compare with beam timing and MDL. Complexities due to path length changes in bunch compressors.

Commission new beam feedbacksEnergy and bunch length throughout machine

Energy at 3 points, bunch length at 2, beam time. Transverse feedbacks throughout machine

Optimize orbit on emittance, then stabilize



Oct. 30, 2007Oct. 30, 200728

SummarySummary

Linac/BC2 Linac/BC2 ee commissioning starts in early Dec. ’07 commissioning starts in early Dec. ’07Large amount of commissioning time available Large amount of commissioning time available (fewer shifts/week & no weekends after 1(fewer shifts/week & no weekends after 1stst month?) month?)Main ’07 goal is to Main ’07 goal is to verifyverify full functionalityfull functionality of of linac/BC2 beamline, plus diagnostics and controlslinac/BC2 beamline, plus diagnostics and controlsOptimizing performance may take longerOptimizing performance may take longerWill need some linac access in first 1-2 monthsWill need some linac access in first 1-2 months

Joe Frisch LCLS FAC [email protected] Oct. 30, 2007 1 Linac/BC2 Commissioning (Dec. 2007...

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