Operational Performance of LCLS Beam Instrumentation. Henrik Loos, SLAC BIW 2010, Santa Fe, NM

Transcription

1 Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Operational Performance of LCLS Beam Instrumentation Henrik Loos, SLAC BIW 21, Santa Fe, NM BIW Henrik Loos

2 Linac Coherent Light Source at SLAC X-FEL based on last 1-km of existing linac Å Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Existing 1/3 Linac (1 km) (with modifications) New e Transfer Line (34 m) Injector (35º) at 2-km point X-ray Transport Line (2 m) Undulator (13 m) Near Experiment Hall BIW 21 Far Experiment Hall Henrik Loos

3 gun L TCAV L1S heater 3 wires 3 OTR DL1 135 MeV L1X BC1 25 MeV LCLS Layout 2 Transverse RF cavities (135 MeV & 5 GeV) 18 BPMs and 13 toroids Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM 3 wires 2 OTR σ z1 σ L2-linac z2 BC2 4.3 GeV 7 YAG screens (at E 135 MeV, one at 14 GeV) 13 OTR screens at E 135 MeV 3 OTR TCAV3 5. GeV 17 wire scanners (each with x & y wires) CSR/CER pyroelectric bunch length monitors at BC1 & BC2 5 beam phase monitors ( MHz) 4 wire scanners L3-linac BSY 14 GeV Gun spectrometer line + injector spectrometer line old screen µ wall 5 wire scanners DL2 14 GeV vert. dump undulator 14 GeV YAG screens OTR screens Wire scanners Phase monitors BIW Henrik Loos

4 Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Strip Line BPM Performance Strip line BPMs 6+ new ones for LCLS, 8+ upgraded from SLC with new electronics Continuous calibration with test pulse between beam triggers Two variable attenuators for charge range 5 pc several nc Beam synchronous data acquisition system at 12 Hz Noise level measurement Measure beam orbits at ~15 BPMs for 5 shots in main linac through undulator SVD eigenvalues to determine orbit jitter and intrinsic BPM noise level Average value for strip-line 3.5 μm, for RF cavity 25 nm at 25 pc Noise at 2 pc ~1 times higher Noise rms (µm) Noise rms (µm) pc Strip Line BPM σ = 3 μm Stripline BPM RF BPM RF BPM σ = 3 nm 2 Strip Line BPM σ = 25 μm 1 2 pc RF BPM σ = 2 μm Position (m) BIW Henrik Loos

5 Undulator RF Cavity BPMs Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Few micron beam orbit straightness in undulator required for FEL operation Sub-micron resolution met with RF cavity BPM design 11.4 GHz dipole cavity Reference cavity for normalization Calibration with beam signals Move supporting girder of undulator Induce known orbit oscillation upstream of undulator BIW Henrik Loos

6 Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Beam Based Undulator Alignment Measure undulator orbit at energies from GeV Fit yields quad + BPM offsets Apply correction to get dispersion free orbit After several iterations, average orbit rms few μm Mainly incoming orbit jitter BFW In/Out Corr Beam Undulator Quad RF BPM Scan Girder Movers Girder y Pos (µm) x Pos (µm) GeV, σ = x 7.3 um 7. GeV, σ x = 4. um 9.25 GeV, σ x = 3.7 um GeV, σ = x 3.8 um 4.3 GeV, σ = y 5.3 um 7. GeV, σ = y 4. um 9.25 GeV, σ = y 6.8 um GeV, σ = y 3.1 um z (m) BIW Henrik Loos

7 Wire Scanner Performance Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Wire card with x, y, 45 wires 2 4 μm tungsten wires Stepper motor driven in open loop, LVDT readback Fast ion chambers + PMTs for beam loss detection Synchronous acquisition of beam orbit, wire position and PMT signal Beam jitter correction Use beam jitter to sample beam size with fixed wire Wire in DL2 with orbit jitter > beam size 15 xmean =.12±.1 mm xrms = 41.9± 4.4 µm xmean =.11±. mm xrms = 3.8±.63 µm 1 5 Raw Jitter corrected WIRE:LTU1:246 Position (µm) BIW Henrik Loos

8 Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Wire Scanner Emittance Measurement Emittance measured with 4 wires at 45 phase advance 4 Accurate beam size 2 measurement for good beta matching Beam Size (µm) Beam Size (µm) 4 2 Emittance upstream of undulator E = GeV Q =.249±.1 nc γε x = 1.14±.1 µm ξ x = 1.4±. γε y = 1.5±.1 µm ξ y = 1.± Position (m) Norm. Angle Norm. Angle Norm. Position BIW Henrik Loos

9 OTR/YAG Profile Monitors Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Common design 1 μm YAG crystal 1 μm OTR foil (Al) Fixed magnification 5 mm telecentric lens ~1 2 mm FOV 1 um resolution (OTR) CCD Camera Mega pixel 12 bit Insertable filters OD1 + OD2 Total system dynamic range > 1 5 Actuator Screen Optics Box BIW Henrik Loos

10 YAG Screen Performance Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM YAG screens at low energy in injector High sensitivity for low charge beam Image cathode emission on YAG at 15 pc 4 CCD Counts x Correlation Plot 14-Nov-28 2:26:46 YAGS:IN2:921:TMIT Electron density (1/µm 2 ) x 1 4 y (mm) x (mm) BIW 21 1 Saturation limits beam size 13 μm at 25 pc Beam size significantly smaller at most locations 1 Henrik Loos

11 Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM OTR Low Charge Slice Emittance Individual Slice Fit Lower limit on OTR slice emittance ~1pC Q E σ z I γε x = 2 pc = 135 MeV = 4 μm = 5 A =.14 μm Norm. Emittance ( µm) Emittance Current Laser Spot Ø.6 mm Time (ps) BIW Henrik Loos

12 Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM OTR Screen Coherent Effects Linear OTR response in injector Coherence effects after bend magnets Factor 2 change in OTR size for % change in beam size Highly compressed beam light intensity x1 5 Distribution fractured or ring shaped Horizontal Beam Size ( µm) OTRS:LI21:291:XRMS Q = 25 pc Quadrupole Strength (kg) OTR12 L L1X gun L1S wire scanner DL1 BC1 L 135 MeV 25 MeV BIW Henrik Loos

13 Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM YAG Screens for High Energy Beam Coherent effects visible on dump OTR foil Recently replaced with YAG crystal YAG fluorescence 1 3 higher than OTR from crystal Small crystal tilt to steer COTR away from camera COTR speckle pattern gone in YAG image Tolerable energy loss in dump area, but concern elsewhere y (mm) Profile Monitor OTRS:DMP1:695 8-Dec-29 13:58: y (mm) Profile Monitor OTRS:DMP1: Apr-21 15:27: YAG crystal in main dump -6-8 OTR foil in main dump x (mm) x (mm) BIW Henrik Loos

14 Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Transverse Deflector Cavity RF Cavity Screen e S-band 2.44 m V(t) RF streak σ y V > 2 MV f RF = 2856 MHz E S = 13.6 GeV σ z β d ψ 9 β s σ 2 y k ev 2 2 RF = σ y + βd βsσ z sin ψ cosφ Es 2 from 196 s Map time axis onto transverse coordinate Simple calibration by scan of cavity phase BIW Henrik Loos

15 YAGS2 RF deflector ON Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Injector Longitudinal Phase Space energy time Laser OFF σ E /E < 12 kev YAGS2 Dec. 1, 28 YAGS2 Laser heater effect on slice energy spread can be studied Laser: 4 µj σ E /E 45 kev Timing between heater laser & electron beam adjusted Laser: 23 µj σ E /E 12 kev BIW Henrik Loos

16 Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Bunch Length with Wire Scanner PMT Signal (Counts) PMT Signal (Counts) Bunch length as small as 3.5 μm rms measured for 25 pc beam Double-horn structure of undercompressed beams visible BPM noise too large for jitter correction at 2 pc and ~1 μm bunch length BIW 21 zrms = 382.5±38.2 µm zrms = 23±. µm Corrected Jitter uncorrected z Position (µm) 16 Bunch length (um) BC2 4.3 GeV σ z2 TCAV3 5. GeV Wire Scanner Correlation Plot 22-Nov-29 14:27:54 WIRE:LI28:144:BLEN L3-linac BSY 14 GeV Bunch Length vs. Compression 3.5 μm L2 chirp voltage (MeV) 16 Henrik Loos

17 Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Pulse Stealing Bunch Length Scan Trigger TCAV at 1 Hz to steal diagnostic bunch 5 fs phase jitter 1 μm orbit jitter Place wire off beam axis, TCAV kicks beam there Signal (1 3 cts) σ y = 6.2±. µm σ y = 44.±. µm σ y = 61.3±. µm -9-9 Off Beam Size (µm) σ y = 43.98± 2.76 µm σ z = 5.8±.755 µm cal = 7.235±.633 µm/µm -9 9 TCAV3 Phase (Degree) WIRE:LI28:444 Position (µm) Use 3 positions.5 mm apart Let jitter sample profile Insufficient jitter when TCAV off BIW Henrik Loos

18 Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Relative Bunch Length Monitor Single shot non-interceptive bunch length diagnostics Coherent edge radiation from chicane bend Broadband pyroelectric detector for far infrared Wavelengths 1 mm 2 μm Detector Signal (1 5 cts) Pyro-Detector Signal Fit Function Bunch Length (µm) Mesh Filter Paraboloid Beam Splitter Pyro Detector Beam Edge Radiation Detector calibration with absolute measurement from TCAV Empirical fit of signal to (σ z ) 4/3 Use fit to calculate peak current BIW Henrik Loos

19 X-Ray Diagnostics in FEE Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Courtesy R. Bionta, LLNL BIW Henrik Loos

20 Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM X-Ray Energy Measurements FEL Energy Loss (MeV) Energy Loss Gas Detector XCOR:UND1:18 (G-m) Determine X-ray beam energy from electron beam loss due to lasing Compare energy in main dump with energy upstream of undulator Also loss from wake fields in undulator vacuum chamber and spontaneous emission Kick orbit to suppress lasing as base line Absolute measurement to calibrate others BIW Henrik Loos

21 Gas Detectors Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Part of gas attenuator system located between differential pumping stations N 2 gas at.1 2 Torr Pressure depends on X- ray wavelength X-rays create Auger e -, trapped in magnetic field Generate secondary e -, and N 2 fluorescence, detect with PMTs GDET:FEE1:241:ENRC Energy Loss (MeV) slope= offset= MeV BPM Energy Loss (MeV) Signal saturates at too much pressure Calibrate with energy loss scan Routinely done when X- ray wavelength changed BIW Henrik Loos

22 X-Ray YAG Screens Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM y (mm) Dump area X-Ray YAG Screen Direct imager cooled 16 bit CCD Measure X-ray beam size Use intensity for FEL gain length x (mm).5 FEE Direct Imager Main X-ray beam with diffraction pattern from C-wire at last undulator Spontaneous background with shadow from undulator vacuum chamber Visible light CER ring from dump bend y (mm) x (mm) BIW Henrik Loos

23 Summary Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM Diagnostics meets all requirements necessary for successful FEL operation Highly integrated into EPICS control system High level Matlab applications to automate measurements COTR issue of profile monitors offset by use of wire scanners New 2D diagnostics needed for time resolved emittance measurements for compressed bunches Sub-micron bunch length in 2 pc mode poses diagnostics challenge, new methods being discussed Single shot X-ray spectrum measurement soon available X-ray pulse length measurement in development BIW Henrik Loos

24 Acknowledgements Editor's Note: PDF version of slides from Beam Instrumentation Workshop 21, Santa Fe, NM LCLS Commissioning Team R. Akre A. Brachmann R. Coffee F.-J. Decker Y. Ding D. Dowell S. Edstrom P. Emma A. Fisher J. Frisch S. Gilevich G. Hays Ph. Hering Z. Huang R. Iverson H. Loos M. Messerschmidt A. Miahnahri S. Moeller H.-D. Nuhn D. Ratner J. Rzepiela T. Smith P. Stephan H. Tompkins J. Turner J. Welch W. White J. Wu G. Yocky BIW Henrik Loos