LCLS Lehman Review February 7-9, 2005 X Ray Diagnostics LCLS Lehman Review February 7-9, 2005

FEE Contains Attenuators, Diagnostics, and FEL Offset Mirror System Be Mirrors 2 & 3 Slit Diagnostics Package Collimator 1 Solid Attenuator Fast close valve Gas Attenuator Ion Chamber Ion Chamber SiC Mirror 1 SiC Mirror 2

Raw LCLS Beam Contains FEL and Spontaneous Halo 3 mJ High energy core Eg > 400 keV 2-3 mJ (0.3 W) FEL 20 mJ (2.4 W) Spontaneous Spontaneous halo has rich spectral and spatial structure: 20 mm 0 < E < 10 keV 7.6 < E < 9.0 keV 10 < E < 20 keV 20 < E < 27 keV At entrance to Offset Mirrors, FEL tuned to 8261 eV Fundamental, 0.79 nC

Avoid Damage By Staying Below Melt Dose along the beam line for different materials (under normal illumination) Shown is the maximum dose (over Ephoton=827 to 8267eV) SiC melt Si melt (maximum over 827-8267eV) Dose (eV/atom) B4C melt Be melt SiC Mirror - 1/9 melt B4C PPS - 1/12 melt Be Solid Attenuator - 1/50 melt z (m from end of undulator)

15 single shots at each attenuator setting Experiment Executed at the TTF VUVFEL to Verify SiC and B4C Damage Threshold C Mirror Linac Undulator Gas Attenuator Gas Detector Focusing Mirror Sample Samples: Bulk SiC Bulk B4C Thin Film SiC Thin Film B4C Thin Film a-C Bulk Si Thin Foil Al TTF VUV Beamline 15 single shots at each attenuator setting The TTF photon energy of 39 eV is strongly absorbed in C resulting in extreme energy deposition in small volumes.

Measured crater depths scale with measured pulse energy Nomarski picture of ~ 30 micron diameter crater in SiC induced by FEL at 8 x melt Crater depths, if any, were measured by Zygo interferometry Pulse-energy measurement below Enominal=1mJ is very noisy. Therefore, we determined the single-shot pulse energy below 1mJ statistically from the pulse energy statistics at pulse energies ≥ 2mJ

Statistical analysis shows damage threshold 15 shot series shot-to-shot relative pulse energy measurements ordered in increasing energy / pulse Measured crater depths for 2 low fluence 15 shot series, ordered in increasing depth / pulse Data shows that the shot-to-shot pulse energy varies ~linearly between 0 and 200% Data shows a consistent damage threshold between 120 and 180 mJ/cm2 No evidence for surface damage below the melt threshold (~ 90 mJ/cm2 to reach Tmelt, ~130 mJ/cm2 to melt SiC)

Prioritized List of Desired FEL Measurements Total energy / pulse l1 Photon wavelength Dl/l1 Photon wavelength spread Pulse centroid Beam direction f(x,y) Spatial distribution su,sl1 Temporal variation in beam parameters t Pulse duration

Prioritized List of Desired Spontaneous Measurements f(x,y,l1) Spatial distribution around l1 l1 1st harmonic Photon wavelength Dl/l1 1st harmonic wavelength spread Beam direction u Total energy / pulse su,sl1 Temporal variation in beam parameters

FEE Schematic e- Start of Experimental Hutches Windowless Ion Chamber Diagnostic Package 5 mm diameter collimators Solid Attenuator Spectrometer / Indirect Imager mirror High-Energy Slit Total Energy Calorimeter FEL Offset mirror system e- Gas Attenuator WFOV Direct Imager Windowless Ion Chamber Muon Shield FEL Spectrometer and Direct Imager in NEH

Wide Field of View Direct Imager Photoelectrons generated by 0.01% FEL Single shot measurement of f(x,y), x, y ,u Camera Scintillators

Single shot measurement of f(x,y), x, y, u Multi shot measurement of l Indirect Imager B4C/SiC Test Multilayers Fabricated Single shot measurement of f(x,y), x, y, u Multi shot measurement of l Angle selects energy and attenuation

Total Energy Calorimeter Thermal diffusion calculations performed Single shot measurement of f(x,y), x, y, u t = 300 ms t = 100 ms Nd0.8Sr0.2MnO3 Cold Si substrate CMR Sensor array 100 pixels Xray Beam t = 0 T Cooling ring T, ms 5

Sensor Development: Nd0.8Sr0.2MnO3

Single shot, non destructive, measurement of Ion Chamber Single shot, non destructive, measurement of x’, y’, x, y ,u Segmented cathodes for position measurement 10 cm 1 torr Imaging of optical emission for position measurement

FEL Spectrometer Single shot, measurement of l with 8.26 keV Transmission Grating Specrometer Sputter-sliced SiC / B4C multilayer Interference Function P = 200 nm N = 500 D = 100 mm Single Slit Diffraction Pattern 33 mm thick Observed Intensity Beam 100 mm angle

Off-Axis Zone Plate Scintillator Image of 8.26 keV FEL Positive Positive Spectra (Unfocused) Negative Negative Spectra (Focused)

Spectrometer measures FEL central Wavelength to < 10-3 -4,000 -4,000 l = 0.149942 nm l = 0.151113 nm m = -4091 mm m = -4124 mm

Using FEL Spectrometer to measure Undulator K* On axis: Effect of changing K But etc. * One of several methods under study to measure K

Monte Carlo simulation of Transmission Grating in LCLS Beam Spontaneous Photons generated From Near-Field Spontaneous Radiation Calculations to energies up to 4 MeV FEL photons generated from Gaussian FEL Model Imager Horizontal Slit Scintillator Transmission Grating Vertical Slit photons All photons tracked through undulator and photon beamline to grating, then to scintillator Undulator

Scintillator Image using spontaneous radiation from First Undulator Segment with Nominal K Positive Spectra (Unfocused) Negative Spectra (Focused)

Measured Spectra of First Segment Nominal K K detuned by 10-3 Fitted Centroid: -4148.70 ± 0.06 mm Fitted Centroid: -4155.82 ± 0.06 mm 53,192 photons in Monte Carlo Simulation Scaled to Full Pulse: 135,799 ± 588 photons

Undulator Segment Spectral Measurements Summary Spectral Shift Relative Difference = (L-LastNom)/LastNom L = Data set Fit Centroid LastNom = Last Segment, nominal K, Fit Centroid DataSet Fit Centroid (mm) Relative Difference X 104 FirstDet-3 -4155.824 ± 0.062 16.9 ± 0.4 FirstDet-4 -4149.342 ± 0.062 1.3 ± 0.4 FirstNom -4148.695 ± 0.063 -0.3 ± 0.4 MidDet-3 -4156.090 ± 0.083 17.6 ± 0.4 MidDet-4 -4149.435 ± 0.083 1.5 ± 0.4 MidNom -4148.735 ± 0.083 -0.2 ± 0.4 LastDet-3 -4155.989 ± 0.137 17.3 ± 0.5 LastDet-4 -4149.462 ± 0.137 1.6 ± 0.5 LastNom -4148.803 ± 0.062 0.0

Diagnostics Summary Instrument Purpose Calibration and Physics risks Status Direct Imager SP f(x,y), look for FEL, measure FEL u, f(x,y), x,y Scintillator linearity, Attenuator linearity and background Prototype Indirect Imager Measure FEL u, f(x,y), spectral imaging of SP and FEL harmonics, attenuator calibration Mirror reflectivity, damage ESD Total Energy FEL u Energy to Heat, damage Ion Chamber FEL u, x,y,x',y' Signal strength Conceptual Spectrometers FEL, SP spectra Resolution, damage

Summary FEL Offset Mirror integrated into FEE layout TTF Damage Experiment confirms damage thresholds for SiC Conceptual designs for Imagers, Calorimeter, FEL Spectrometer, and Gas Detector We are confirming Conceptual designs with our detailed simulation FEL Spectrometer shows some utility for determining K of undulator segments to 10-4