LCLS Injector Diagnostics Henrik Loos Diagnostics overview Transverse

LCLS Injector Diagnostics Henrik Loos • Diagnostics overview • Transverse Beam Properties • Longitudinal Beam Properties 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

LCLS Diagnostics Tasks Charge Toroids (Gun, Inj, BC, Und) Faraday cups (Gun & Inj) Trajectory & energy Stripline BPMs (Gun, Inj, Linac) Cavity BPMs (Und) Profile monitors (Inj), compare position with alignment laser Transverse emittance & energy spread Wire scanners YAG screen (Gun, Inj) OTR screens (Inj, Linac) 4 December 2006 LCLS Injector Diagnostics Bunch length Transverse cavity + OTR (Inj, Linac) Coherent radiation power (BC) Slice measurements Horizontal emittance T-cavity + quad + OTR Vertical Emittance OTR in dispersive beam line + quad Energy spread T-cavity + OTR in dispersive beam line Henrik Loos loos@slac. stanford. edu

LCLS Injector Diagnostics YAG, FC YAG Toroid T-Cavity Phase Monitor Wire Scanner Toroid OTR YAG 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu Toroid

Diagnostics Through BC 1 RF Gun & Solenoid L 0 a&L 0 b S-Band Linacs T-Cav Sec 29 Transverse RF Cavity Bunch-Compressor-1 (BPM, OTR, collimator) OTR & Wire Scanners Gun Spectrometer L 1 S-Band Linac 135 Me. V Wire Scanners + OTR 250 Me. V X-Band RF Straight Ahead Spectrometer Bunch Length Diagnostics 40 m 4 December 2006 LCLS Injector Diagnostics TD-11 stopper Henrik Loos loos@slac. stanford. edu

Transverse Diagnostics YAG scintillator OTR Wire Scanners 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Requirements for YAG & OTR Monitors Name Location YAG 01 GTL Hor. Beam Size (mm) Ver. Beam Size (mm) Resol. (µm) 1. 400 [7. 0] 1. 400 [6. 0] 15 Name Location Hor. Beam Size (mm) Ver. Beam Size (mm) OTR 11 Resol. (µm) BC 1 3. 800 0. 100 30 OTR 12 BC 1 0. 040 1. 000 13 YAG 02 GTL 0. 460 15 OTR 21 BC 2 2. 600 0. 050 16 YAG 03 L 0 0. 410 15 OTRTCAV L 3 0. 050 16 YAGG 1 GTL 3. 340 [45. 0] 1. 500 [8. 0] 30 0. 070 [1. 0] OTR 30 DL 2 0. 010 [0. 2] 0. 025 3 OTR 33 DL 2 0. 040 1. 000 13 OTRDMP Dump 0. 075 0. 060 [0. 6] 20 YAGS 1 SAB 0. 030 0. 060 15 YAGS 2 SAB 0. 030 [10. 0] 0. 100 [12. 0] 15 OTRH 1 DL 1 0. 180 0. 380 40 OTRH 2 DL 1 0. 200 0. 280 40 OTR 1, 3 DL 1 0. 125 0. 130 30 OTR 2 DL 1 0. 065 [8. 0] 15 OTR 4 DL 1 0. 160 [1. 5] 0. 120 [14. 0] 25 OTRS 1 SAB 0. 030 [10. 0] 0. 100 [12. 0] 7 4 December 2006 LCLS Injector Diagnostics Large 50 mm crystal required for gun spectrometer. Zoom lens needed. Requires foil with and angle of 5 deg to the beam and a likewise tilted camera to keep the entire screen in focus. Henrik Loos loos@slac. stanford. edu

YAG Beam Profile Monitor Yellow scintillator crystal, emits green light when charged particle passes through Fluorescence decay time 70 ns High photon yield Nφ = 3. 5 /e- For 1 n. C charge: Nφ = 2 ~108 Photons at 5 p. C 1010 Mirror e- θ YAG Lens CCD Plenty of photons to detect with a CCD 100µm thickness to meet resolution Saturation at high charge densities Saturation limit 0. 04 p. C/µm 2 Equals 65 µm beam size at 1 n. C Combined with Faraday cup in GTL -> camera shielding Thin mirror (1 mm) at higher energies 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Transition Radiation of a charged particle at relativistic speed moving from one medium into another. Relativistic speeds -> Coulomb field is quasi-electromagnetic wave. Vacuum-metal boundary -> Field is reflected and emitted in 1/γ angle Light intensity linear to bunch charge Emission is instantaneous and free of saturation effects 4 December 2006 LCLS Injector Diagnostics θ 2 γ Electron Beam Metal Foil Henrik Loos loos@slac. stanford. edu

OTR Profile Monitor Small quantum efficiency About 1 photon/100 electrons OTR yield for 100 mrad angular acceptance Energy (Me. V) QE (%), 450 -650 nm 135 0. 44 4300 0. 98 13500 1. 17 Logarithmic dependence on energy and solid angle 4 December 2006 LCLS Injector Diagnostics Aluminum foil 1µm Mitigates radiation issue Foil damage is concern Limited z-space Foil at 45 degree Depth of field ~1 mm Match reflection direction with TCAV or dispersion direction Henrik Loos loos@slac. stanford. edu

Optics Layout CCD Used for all standard YAG/OTR screens Telecentric lens Stack of 2 insertable neutral density filters Beam splitter and reticule for in situ calibration Megapixel CCD with 12 bit and 4. 6µm pixel size Radiation shielding in gun region 4 December 2006 LCLS Injector Diagnostics Filters Lens 55 mm focal length >100 line pairs/mm Magnification up to 1: 1 with extender Mounting of camera enables field of view from 5 to 20 mm Vacuum OTR Beam splitter Reticule YAG e-beam Illumination Henrik Loos loos@slac. stanford. edu

OTR/YAG Optics Design Actuator Optics Box Screen CCD Lens Filters Beam Splitter Reticle 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

OTR Imager for 135 Me. V Spectrometer Need wide field of view in focus for measurements in spectrometer beam line Tilt OTR screen and CCD by 5 degrees in 1: 1 imaging 12 um resolution tested Device ready to install No actuator, rate limit required for beam into spectrometer line 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

CCD Camera and Lens Test Uniq Vision CCD Dark Image Test Periodic BG structure removed with background subtraction Background noise 2 bits rms Dynamic range > 100 4 December 2006 LCLS Injector Diagnostics TECM 55 lens with ruler (scale 1/64”) Resolution: B/W transition < 20 um Henrik Loos loos@slac. stanford. edu

Profile Monitor Controls y Rate limit electron beam Single bunch & burst mode Prevent foil damage and limit camera irradiation CCD Image x Profile monitor hardware control Chassis for actuator, filters, illumination EPICS driver ready Camera control (EPICS) Rows YAG Crystal Cameralink and EPICS IOC Buffered acquisition@10 Hz Screen update @1 Hz Image processing (Matlab) Different algorithms implemented Gaussian fit Baseline cut, etc. 4 December 2006 LCLS Injector Diagnostics up koc Beam size calculation M Flip image to match image coordinates with beam Background subtraction Automated image cropping Henrik Loos loos@slac. stanford. edu

Software Development Matlab EPICS 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Profile Monitor Commissioning Tasks Verify correct image polarity and calibration. Compare with alignment laser, BPMs and wire scanners. Find proper attenuation filter for YAG profile monitors. Determine beam center with alignment laser. 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Wire Scanner Status Requirements Step size 5 um Accuracy 2 um, reproducibility 10 um Tungsten wire 20 um to 60 um, matched to beam size Hardware status Wire scanners for injector tested to meet specs and calibrated Photomultipliers with charge integrating ADCs tested Software Low level EPICS Calibration tool Scan user interface to select 1 or more wires Buffered acquisition linked to timing system High level Matlab Software for normalization with toroid and jitter correction with BPM Profile analysis and emittance calculation same as for profile monitors 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Requirements Area IN 20 LI 21 LI 24 LI 27 LI 28 LTU Total Scanners 4 3 4 19 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Design - Mechanical Distance Measurement (LVDT or similar) Beam 4 December 2006 LCLS Injector Diagnostics Motor Limit Switches Henrik Loos loos@slac. stanford. edu

User Interface - Operations 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Bunch Length Monitoring Transverse Cavities are the Gold standard Provide single shot energy vs. time, with excellent resolution (<5 micron bunches measured at TTF 2/FLASH) Invasive – can only measure at a low repetition rate Used to calibrate other measurements Coherent mm-wave radiation power detectors Used a full rate for uncalibrated feedback measurement. Other systems may be used to reduce need for transverse cavity based calibration – but not baseline Electro-optical measurement Optical spectrum statistical measurement 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Transverse Cavity Bunch Length Measurement TCAV in injector @ 135 Me. V Low field of 1. 4 MV sufficient Invasive measurements on OTR 2, 4, S 1, YAGS 2 TCAV in sector 25 at 5. 9 Ge. V in ‘ 08 Max field of 25 MV Parasitic measurement with horizontal kicker and off-axis OTR Horizontal Kicker Vertical Deflecting Cavity Electron Beam 4 December 2006 LCLS Injector Diagnostics Off-axis Screen Henrik Loos loos@slac. stanford. edu

Injector TCAV tested successfully at full gradient in klystron lab 3 MW, 120 Hz, 3 us pulse 2 MW, 120 Hz, 3 us pulse was requirement 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Transverse Cavity Calibration p -u k oc up koc LCLS Injector Diagnostics M 4 December 2006 M Temporal resolution limited by beta function, RF power, screen size Calibration with TCAV phase scan Calibration accuracy limited by phase jitter TCAV injector: >>20 slices possible TCAV linac: <5 slices due to limited RF, nondedicated optics, screen resolution Henrik Loos loos@slac. stanford. edu

Software Development 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Bunch Length Monitor Relative bunch length measurement used for longitudinal feedback Non-intercepting, calibrated with interceptive TCAV measurement Based on integrated power from coherent radiation source (C*R) BC 1 Single electron radiation spectrum W 1(ω) depends on radiation source Bunch length determined by long wavelengths λ » 2πσrms BC 1: 1 cm – 1 mm BC 2: 1 mm -. 1 mm 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu BC 2

Millimeter Wave Gap Radiation Single Shot (assuming single shot spectrometer, or multiple detectors) Non-Invasive Simple high rate readout – can use signal from single detector Very simple, low cost Low noise readout <1% RMS demonstrated Diode detectors work to ~300 GHz -> ~200 micron bunch length Possibly can be extended to ~ 1 THz, ~70 micron bunch length Provides only relative measure of bunch length To be installed after BC 1. 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Layout of Gap Radiation Measurement 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Millimeter-wave gap monitor tests in End Station A Output of 100 GHz detectors as phase (bunch length) is adjusted M. Woods SLAC Comparison of 2, 100 GHz detectors for a range of operating conditions RMS difference 1. 4% for 10, 000 pulses 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Millimeter Wave Coherent Synchrotron Radiation Single Shot (assuming single shot spectrometer, or multiple detectors) Non-Invasive Measures from arbitrarily short to ~mm bunches (with appropriate filters). Simple high rate readout – can use signal from single detector with input filter Measures power spectrum (no phase information) – cannot reconstruct bunch shape Variations on spectral response must be calibrated using external bunch length measurement – not practical to provide a calibrated signal To be installed after BC 1 and BC 2. 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

BL 11 Millimeter-wave CER bunch length monitor Mirror with hole after bend to collect synchrotron radiation stripe Reflective optics (off-axis parabolas) to collect and transport light Beam splitting filter for high pass / low pass to 2 mm-wave detectors Different filters available Compare power on detectors for (uncalibrated) bunch length measurement Similar in concept to gap monitor, but bend and collecting optics give larger (>X 10) signal, at cost of increased complexity Need higher signal for short bunch measurements where diode detector do not work 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Layout of CER Bunch Length Monitor 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Detector Setup for BL 11 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Bunch Length Sensitivity of Detector Signal Detection efficiency includes diffraction, vacuum window, water absorption, pyroelectric detector response, and bunch form factor. Introduce high and low pass filters at 10 cm-1 and 20 cm-1. 4 December 2006 LCLS Injector Diagnostics Henrik Loos loos@slac. stanford. edu

Optical Synchrotron Radiation Noise Measurement RMS distribution measurement does not require calibration Non-invasive Not single shot Will test after BC 1 Can upgrade to (near? ) single shot measurement using optical spectrometer 4 December 2006 LCLS Injector Diagnostics 1. 5 ps 4. 5 ps 1. 5 ps. 200 -500 p. C, 44 Me. V beam using a spectrometer with a resolution of 0. 05 nm/pixel P. Catravas et al, Physical Review Letters 82 (1999) 5261 Henrik Loos loos@slac. stanford. edu