LCLS Commissioning: Results & Plans P LCLS Commissioning: Results & Plans P. Emma, for the LCLS Commissioning Team DOE Status Meeting for the LCLS May 13, 2008 LCLS Phys. Rev. publication: http://prst-ab.aps.org/pdf/PRSTAB/v11/i3/e030703
LCLS Accelerator Layout 6 MeV z 0.83 mm 0.05 % 135 MeV z 0.83 mm 0.10 % 250 MeV z 0.19 mm 1.6 % 4.30 GeV z 0.022 mm 0.71 % 13.6 GeV z 0.022 mm 0.01 % beam parked here Linac-X L =0.6 m rf= -160 Linac-0 L =6 m rf gun L0-a,b Linac-1 L 9 m rf -25° Linac-2 L 330 m rf -41° Linac-3 L 550 m rf 0° 25-1a 30-8c ...existing linac 21-3b 24-6d 21-1 b,c,d undulator L =130 m X BC1 L 6 m R56 -39 mm BC2 L 22 m R56 -25 mm DL1 L 12 m R56 0 DL2 L =275 m R56 0 Injector Commissioned (‘07) Commissioned in Jan. 2008 SLAC linac tunnel research yard
LCLS Injector Layout Commissioned in ‘07 6 MeV 135 MeV 250 MeV OTR screens (7) YAG screens (7) Wire scanners (7) RF Gun Dipole magnets (8) Commissioned in ‘07 Solenoid Beam stoppers (2) S-band RF acc. sections (5) L0a Gun Spectrometer L0b Emittance Screens/Wires Emittance Screen/Wires RF Deflector 2-km point in 3-km SLAC linac L1S X-band RF acc. section 135-MeV Spectrometer BC1 TD11 stopper 135 MeV 250 MeV
LCLS BC2 Area Layout (sector 24/25) OTR screens (3) Collimator jaws (2 Phase monitor cavity (1) New installation in fall ‘07 Dipole magnets (4) Kicker magnet (1) Transverse RF deflector (1) S-band RF acc. sections 4 wire-scanners “de-scoped” 4 wire-scanners in sec-28 (300 m downstream) CE21 BPMS21 OTR21 PH03 BXKIK BC2 TCAV3 (25-2d) OTR22 (25-3d) OTR_TCAV (25-9) (not to scale) 4.3 GeV
Commissioning Highlights Injector commissioning: April through August, 2007 (DONE) Phase-II commissioning: Dec. Complete 3/31/08 (BC2 + Linac) Up to 1 nC of bunch charge now available (0.25 nC used) Great laser uptime (99%) and good performance (again) Emittances 1 mm after BC1 at 1 nC, 250 MeV (fairly routine) Routine e- to 14 GeV (24/7 except Wed., ~90% up-time) BC1 dipoles & chicane motion fixed! No emittance growth in X-band RF cavity when best steered BC2 compression demonstrated (no dipole field quality issues) Long transverse RF deflector at 5 GeV fully operational CSR effects measured in BC1 & BC2 – agree with codes so far Many beam & RF feedback systems running well Coherent OTR observed – compromises nearly all screen data Gun RF probes changed in April ’08 (allows 120-Hz – D. Dowell) More physicists involved in commissioning in 2008 (8 15)
Design and Typical Measured Parameters
“Problems/Issues” from July ‘07 DOE Review Gun Faraday cup broken Gun toroid shorted during installation Some YAG screens not installed properly BC1 motion control limited (300 mm 260 mm) Cathode QE about 5-times lower than design Some controls tools late (orbit displays, fitting, magnet control & alarms) MCOR power supply ADC readback noise (fixed) Laser phase drift and lock trouble until mid-June ALL FIXED
Pre-Beam Check List for BC2/Linac 17 pages, 800 checks - all DONE polarity checks DONE installation orientation controls check component bar codes etc. etc.
Laser Spatial and Temporal Shaping 2R = 1.4 mm 2008 2007 7.2 ps 6.9 ps 2008 7.2 ps 2007 Spatial shape on cathode using iris Temporal shape (6.9 ps FWHM) S. Gilevich, G. Hays, P. Hering, A. Miahnahri, W. White 99% Drive Laser up time!
Powerful Scanning/Correlation Application Watch profiles as scan proceeds H. Loos Quickly minimize emittance by scanning any parameter
b-Matching GUI in Matlab Soon to be extended for undulator matching… C. Limborg before xx = 1.08 sets quads after xx = 1.00 reads meas’d b & a Soon to be extended for undulator matching…
Projected Emittance <1.2 μm at 1 nC (135 MeV) s = 60 μm gex = 1.07 μm meets injector goals gey = 1.11 μm
Injector Emittance Measured Over 3 Days (0.25 nC) OTR screen at 135 MeV gex = 0.91, gey = 1.01 gex injector is stable gey wire-scanner at 250 MeV after BC1 gex = 0.83, gey = 0.83 J. Welch
Laser & Electron-Based Feedback Systems Transverse Loops: Laser spot on cathode (2) Gun launch angle Injector trajectory X-band cavity position Linac trajectory (2 old) Undulator traj. (future) Longitudinal Loops: DL1 energy BC1 energy BC1 bunch length BC2 energy BC2 bunch length Final energy (old loop) now running Laser (bunch length feedback still needs work) BPMs CSR detectors Steering Loop sz1 sz2 V0 gun d0 d3 d1 d2 L0 1 V1 2 V2 V3 D. Fairley J. Wu J. Frisch L1 X L2 L3 DL1 BC1 BC2 DL2
BC1 Dipole Field Quality Fixed Poles were milled off and wider poles were bolted on and then the fields were shimmed. Nov. ‘07 fixed Sext. tolerance Aug. ‘07 ±3s beam J. Welch, S. DeBarger, N. Li, et al.
BC1 Dispersion Measurement & Correction Dex/e0 < 1% Dey/e0 3% hx = -0.64 mm hx = -0.18 mrad hy = 1.62 mm hy = -1.33 mrad gex = 0.88 mm No more BC1 emittance growth Vary energy before BC1 and read BPMs after BC1 h, h Dex/e0 (2nd-order) < 5% Dex/e0 (1st-order) < 1%
BC2 Dipole Field Quality OK Beam energy scans confirm BC2 dipole field quality meets requirements No measurable quad field and sextupole is just at tolerance ±3s beam OK
Operating Point Summary Display Shows operators the main machine parameter targets and their present settings & includes save/restore files H.-D. Nuhn
A Phase shift of -0.4 deg is added to the Elegant curves Bunch length after BC1 measured with transverse RF BPM-Measured CSR Energy Loss in BC1 at 0.25 nC (compares well with tracking) BC2 OFF BSY (14 GeV) TCAV (5.0 GeV) BC1 (250 MeV) L1S BPM e- Elegant CSR energy loss after BC1 measured with BPM A Phase shift of -0.4 deg is added to the Elegant curves Y. Ding, Z. Huang operating point g Chicane Bend BPM
Hor. CSR Emittance Growth after BC1 (250 MeV, 0.25 nC) j = -22º sx = 38 mm sx = 55 mm j = -26º sx = 246 mm j = -27º Vertical emittance after BC1 is almost unaffected Y. Ding, Z. Huang Elegant Horizontal emittance after BC1 vs. RF phase Elegant Meas-1 Meas-2 Data also exists at 1 nC and BC2 data (0.25 nC) also shows decent results Elegant operating point
RF Phase and Amplitude Stability (e.g., L0a) New inj. RF systems meet jitter tolerances 0.05% rms (<0.07%) RF Feedback Running 20-second sample at 10 Hz 0.05º rms (<0.07º) R. Akre, D. Kotturi, J. Craft, V. Pacak, et al.
Stability is not so far off of our goals (~10%) Normalized phase space centroid jitter after BC1 (~5% of rms beam size) RMS AyN = 4.1% RMS AxN = 4.9% Stability is not so far off of our goals (~10%) 1-s beam size D. Ratner … near end of linac (~15% of rms beam size, but sometimes larger) poor BPM resolution RMS AxN = 19.9% RMS AyN = 8.5% Thanks to Controls group for new BPM electronics! Q = 0.25 nC DE/E jitter < 0.1% DQ/Q jitter < 2%
Chicane length 24 m, 4.3 GeV, 2º bends BC2 Chicane in the Linac at 4.3 GeV Bob Fuller Chicane length 24 m, 4.3 GeV, 2º bends
old screen used – poor res. Bunch Compression Measured after BC2 (0.25 nC) Bunch length after BC2 measured with transverse RF -2º shift applied to simulation sz 10 mm sz < 10 mm old screen used – poor res. sz > 25 mm BC2 (4.3 GeV) BSY (14 GeV) TCAV (5.0 GeV) 550 m L2
Longitudinal Phase Space at 14 GeV PR55 LiTrack simulation Bunch is Over-Compressed L2 phase = -41 deg Chirp knob = -450 MeV measurement Vertical scale only approx. PR55 Bunch is Under-Compressed L2 phase = -41 deg Chirp knob = +450 MeV LiTrack simulation Vertical scale only approx. measurement older screen has poor resolution
Results still variable – requires careful work Emittance Measurements at End of Linac Using Wire Scanners sx = 76 mm sx = 38 mm sx = 49 mm sx = 47 mm wire scans F.-J. Decker R. Iverson Emittance measured 300 m after BC2 at 10 GeV with 10 mm bunch length gey = 0.9 mm Q = 0.25 nC Results still variable – requires careful work
Poor Beam Conditions Also Arise… bad X-profile at end of linac Possibly the L2 phase drifted into a strong CSR regime – bunch length feedback not running gex = 5.5 mm Q = 0.25 nC
Emittance Near End of Linac Over a Weekend gex gey Emittance near end of linac during weekend run at 0.25 nC, with no tuning gey stayed at ~1 mm for the next 3+ days
DONE DONE DONE DONE DONE DONE 2008 Commissioning Goals http://www-ssrl.slac.stanford.edu/lcls/internals/commissioning/documents/bc2-commissioninggoals.doc DONE DONE DONE DONE DONE
LCLS Installation and Commissioning Time-Line First Light in FEE First Light in FEH LTU/Und/Dump Install PPS Cert. LTU/Dump Und. Seg. Install FEE/NEH Install X-Rays in NEH FEH Hutch BO CD-4 (7/31/2010) PEP-II run ends FEH Install now J F M A M J J A A S O N D J F M A A M M J J A S O N D J F M A M J J 2008 2009 2010 Down PPS Linac/BC2 Commissioning Re-commission Inj/BC2 to SL2 LTU/Und Comm. FEE Comm. NEH Operations/ Commissioning May 2, 2008
LTU/Undulator/FEE/FEL Commissioning H. Tompkins See break-out presentations: LTU & Undulator Commissioning Plans (H.-D. Nuhn) FEL/FEE Overview Commissioning Plans (H. Tompkins) FEE Diagnostics & Commissioning (R. Bionta)
Problems/Issues End-of-linac x-emittance difficult to minimize and maintain, especially at 1 nC (needs more work – m-bunching?) Some wire-scanner vibration issues (~fixed in April ‘08) Most OTR screens are unusable due to COTR (laser heater should solve this in FY2009) Most linac BPMs need upgrade – 16 of 83 done with great resolution improvement (on AIP list) BC2 bunch length monitor noisy or real jitter – (need beam synchronous acquisition for RF & BPMs or m-bunching?) Bunch length feedback loops need more wring-out (need more time + less noisy monitor)
Summary Drive laser very reliable – performs well (great team) Injector in very good shape – runs well after setup Many measurements made – getting to know machine Emittances at end of linac difficult to tune and maintain, but nice results are possible with effort (gey is maybe there?) We look forward to next phase (LTU, undulator, FEL, …) –preparations have begun (plans, software, checkout, …) Thanks to dedicated Commissioning Team + Controls, RF, Engineering, Operations, ASD, maintenance, etc
DONE
m-Bunching in BC2 May Blow up X-Emittance OTR screen in BC2 OTR21 gex,y measured with wire-scanners 500-m downbeam of BC2 gex gey
COTR After BC2 OTR screen just after BC2 OTR22 OTR22 with BC2 screen inserted (smoothes m-bunching) with BC2 screen OUT (m-bunching present – COTR!)
FY2009 Commissioning Activities Pre-Beam Checkout (Nov-Dec ‘08) – check-list in prep. Re-establish injector & linac beam quality (Nov-Dec ‘08) – have experience First LTU Commissioning with beam (Jan-Mar ‘09) – lots of time ‘Undulator’/Dump Comm. without undulators (Jan-Mar ‘09) Calibrate & commission: RF BPMs, Loss Monitors, BFWs, ADS BBA algorithm testing (without segments) Install undulator segments (Mar ’09, two wks) – optimize linac again First Undulator Segments Commissioning (Mar-Apr ‘09) Care with first transport to minimize radiation on segments Full alignment process (BBA, BFW’s) Commission FEE Diagnostics (Apr-Jun ‘09) Direct Imager, Calorimeter, Slit, Solid Attenuator, Gas Attenuator, Gas Detector Beam-Based K Measurement Components Optimization & characterization of SASE (Jun-Jul ‘09) Optimize linac beam quality (adjust compression, emittance tuning, BBA) Measure gain length