Linac Diagnostics Commissioning Experience LCLS DOE Review July 11, 2007 Henrik Loos, for the LCLS Commissioning Team Diagnostics overview BPMs, Toroids, FCs Wire Scanners YAG/OTR Profile Monitors Transverse Cavity Bunch Length Monitors

LCLS Diagnostics Tasks Charge Toroids (Gun, Inj, BC, Und) Faraday cups (Gun & Inj) Trajectory & energy Stripline BPMs (Gun, Inj, Linac) Profile monitors (Inj), compare position with alignment laser Transverse emittance & energy spread Wire scanners YAG screen (Gun, Inj) OTR screens (Inj, Linac) 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

Diagnostics Overview OTR screens (7) YAG screens (7) Wire scanners (7) Dipole magnets (8) Beam stoppers (2) S-band RF acc. sections (5) RF Gun Gun Solenoid Spectrometer RF Deflector X-band RF acc. section BC1

Beam Position and Charge Monitors 21 BPMs functional BPM polarity and scale checked with correctors and model 5 current monitors and 1 Faraday cup operational EPICS Displays

BPM Position and Charge Online Display

BPM Resolution Test Synchronous acquisition of all BPM positions Fit of one BPM position vs. position calculated from all others Specification < 10μm Typical < 5μm

Charge Calibration First toroid and FC after gun not functional Use FC in gun spectrometer to calibrate sum signal from first BPM

Wire Scanners 7 wire scanners installed 5 photo-multipliers and 4 ion chambers working EPICS Displays

Wire Scanner User Interface Raw Synchronized Data PMT, Toroid, BPM Selection Processed Profile

Wire Scanner Data Correction No Correction Charge Correction Charge & Jitter Correction

Wire Scanner Status All wire scanners are working WS orientation and calibration cross-checked with correctors, BPMs and OTRs Some wire cards rotated, fixed in software Charge and jitter correction commissioned PMT/Ion chambers need work Some WS give weak signals on PMTs Ion chambers close to TD11 dump saturate and have large background

YAG/OTR Profile Monitors 7 YAG and 7 OTR screens installed 14 optics boxes commissioned Control for screen insertion, 2 neutral density filters, screen and reticle illumination functional EPICS Displays

Profile Monitor Calibration Measure known diameter of YAG crystal on CCD image Verify calibration of reticle image Use reticle for calibration if screen edge outside FOV

OTR Screen Calibration Test Screen calibration agrees within 2.5% with prediction from corrector scan and model Best focus close to screen center Constant beam size within +- 1mm

OTR Screen vs. Wire Scanner Same beam size from WS and OTR Beam shape shows good agreement Gaussian Fits

Coherent Optical Transition Radiation Gaussian profile from WS Fluctuating profile from OTR with compressed beam OTR screen not usable for emittance measurement of highly compressed beam

Transverse Deflecting Cavity Software for automated time scale calibration and bunch length measurement

BL11 – Coherent Edge Radiation Bunch Length Monitors BL12 – Ceramic Gap BL11 – Coherent Edge Radiation Ceramic Gap Waveguide GHz Diode Detectors

Edge Radiation Monitor Bunch Length Monitors Both bunch length monitors installed Signal from wave guide diodes and pyroelectric detectors available All signals show strong correlation with accelerator phase and bunch compression Absolute calibration with TCAV in S29 to be done Edge Radiation Monitor Ceramic Gap Monitor 100 GHz Diode 300 GHz Diode

High Level Applications - Emittance Methods Multi screen Quad scan Devices OTR Wire scanner Features Scans automatic & manual Data & config files 1 button -> logbook Average & raw data Phase space plot Slice emittance

High Level Applications – Correlation Plot Purpose Measure accelerator parameters vs. settings Use EPICS and results from HLA Features Scans 1 or 2 control variables Reads any process variable plus OTR/YAG screens Wire scan Emittance Synchronous acquisition 2D data plots Different fit options

Summary Most of the diagnostics is installed and commissioned Diagnostics is integrated into control system and being used by high level applications Bunch length monitors need more commissioning Some diagnostics in gun region (YAG, FC, IM) needs work in next down time Observation of coherent phenomena on OTR for ultra-short bunches: Future problems for OTR beyond BC2?