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XTOD Diagnostics for Commissioning the LCLS*

XTOD Diagnostics for Commissioning the LCLS*. January 19-20, 2003 LCLS Undulator Diagnostics and Commissioning Workshop Richard M. Bionta.

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XTOD Diagnostics for Commissioning the LCLS*

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  1. XTOD Diagnostics for Commissioning the LCLS* January 19-20, 2003 LCLS Undulator Diagnostics and Commissioning Workshop Richard M. Bionta *This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48 and by Stanford University, Stanford Linear Accelerator Center under contract No. DE-AC03-76SF00515.

  2. Provides unobstructed vacuum path from end of undulator to end of FEH Flux densities in NEH will be the highest available Flux densities in FEH will be similar to synchrotron facilities WBS 1.5 X-Ray Transport, Optics, & Diagnostics (XTOD) FEH - Far Experimental Hall Tunnel NEH - Near Experimental Hall FEE Front End Enclosure LCLS X-Ray Beam R. M. Bionta

  3. X-ray Transport, Optics, and Diagnostics Layout Each 13 m long hutch has two vacuum tanks for experimental and facility hardware NEH FEH FEE Tunnel FEL Measurements & Experiments: Compression Spectra Coherence Pulse Length Experiments Optics Structual Bio Nano-scale Femtochem Front End Enclosure Diagnostics Slits Attenuators Low Energy Order Sorting Mirror Monochrometer Pulse-Split & Delay Diagnostics Experiments: Optics Warm Dense Matter Atomic Physics R. M. Bionta

  4. Beam Models

  5. FEL beam power levels Saturated power Plasma frequency FEL r parameter Gain length parameterization Correct definition of h parameters R. M. Bionta

  6. Spatial-temporal shape FEL can be modeled as a Gaussian beam in optics Phase curvature function Gaussian width Gaussian waist Origin is one Rayleigh length in front of undulator exit Amplitude is given in terms of saturated power level R. M. Bionta

  7. LCLS Fundamental Electric Field and Dose Equations Gaussian Electric Field: Phase Curvature waist With origin Waist at origin matches electron distribution gives Electric field intensity x duration Matches photon distribution with Peak photon density Dose R. M. Bionta

  8. FEL parameters at absorber exit, z = 65 meters And at other locations: R. M. Bionta

  9. 0 150 Ginger provides complex Electric Field envelope at undulator exit Data in the form of Each radial distribution has radial distributions of complex numbers representing the envelope of the Electric Field at the undulator exit. radial points. R, mm Electric Field Envelope Power Density vs time at R = 0 Samples are separated in time by wavelengths. watts/cm2 Time between samples is R. M. Bionta

  10. watts c m2 watts c m2 watts c m2 watts c m2 x 1015 x 1017 x 1017 x 1015 Power Density Time Domain Frequency Domain Power Density 1.94 Temporal Transform 1.73 0 0 w0-400/fs w0 w0+400/fs 2 4 0 6 Time, femtoseconds frequency 0 150 Spatial Transform Power Density Power Density 1.94 1.73 0 0 -325 -10 304 -150 0 150 Wavenumber, mm-1 Transverse position, microns Tools for manipulating GINGER output Viewer GINGER output: Tables of electric field values at undulator exit at different times viewer R, mm Transformation to Frequency Domain Propagation to arbitrary z R. M. Bionta

  11. FEL spatial FWHM downstream of undulator exit, l = 0.15 nm Transverse beam profile at undulator exit Ginger (points) Transverse beam profile 15 m downstream of undulator exit Gaussian Beam (line) R. M. Bionta

  12. Total power at undulator exit • 10 Ginger simulations were run at different electron energies but with fixed electron emittance through 100 meter LCLS undulator. Ginger simulations • The Ginger runs at the longer wavelengths were not optimized, resulting in significant post-saturation effects. Results at longer wavelengths carry greater uncertanty. Theoretical FEL saturation level R. M. Bionta

  13. watts c m2 x 1017 3 Power Density 0 w0 = 12558 /fs w0 + 50 /fs w0 - 50 / fs frequency RMS Bandwidth l= 0.15 nm Time Domain l= 0.15 nm Frequency Domain R. M. Bionta

  14. 300 meters 75 meters 0 meters FWHM vs. wavelength at 0, 75 and 300 meters R. M. Bionta

  15. We can confidently calculate the dose to transmissive optics. Transmissive Dose Model Reflective Dose Model Low Z materials for transmissive optics can be chosen to survive in the LCLS experimental halls in the simple dose model on the left. The survivability of common high Z reflectors depends on additional assumptions. R. M. Bionta

  16. Dose / Power Considerations Fluence to Melt Energy Density Reduction of a Reflector Be will melt at normal incidence at E < 3 KeV near undulator exit. Using Be as a grazing incidence reflector may gain x 10 in tolerance. R. M. Bionta

  17. Roman’s far Field spontaneous R. M. Bionta

  18. Detailed Spontaneous, in progress R. M. Bionta

  19. E > 400 KeV R. M. Bionta

  20. FEE Instrumentation R. M. Bionta

  21. Front End Enclosure Layout PPS Diagnostics Slits Solid Attenuator 40m WestFace Near Hall Gas Attenuator 33m WestFace Dump Windowless Ion Chamber Diagnostics 10.5 m Slits Slow valve Fast valve Fixed Mask Pump 16.226 m Eastface Last Dump Mag Westface front End Enclosure Valve Pump 0 m End of Undulator R. M. Bionta

  22. Adjustable High-Power Slits • Intended to intercept spontaneous beam, not FEL beam -- but will come very close, so peak power is an issue • Two concepts being pursued for slit jaws • Treat jaw as mirror (high-Z material) • Treat jaw as absorber (low-Z material • Either concept requires long jaws with precision motion • Mechanical design based on SLAC collimator for high-energy electron beam R. M. Bionta

  23. Front End Diagnostic Tank Solid Filter Wheel Assembly ION Chamber Be Isolation valve Space for calorimeter Direct Imager Indirect Imager Turbo pump R. M. Bionta

  24. Prototype LCLS X-Ray imaging camera CCD Camera Microscope Objective X-ray beam X-ray beam LSO or YAG:Ce crystal prism assembly R. M. Bionta

  25. Indirect Imager Be Mirror Be Mirror Reflectivity at 8 KeV 1 Be Mirror angle provides "gain" adjustment over several orders of magnitude 0.1 0.01 0.001 0.0001 R. M. Bionta

  26. Multilayer allows higher angle and higher transmision but high z layer gets high dose Be Mirror needs grazing incidence, camera close to beam Single high Z layer tamped by Be may hold together R. M. Bionta

  27. First check CCD by measuring Response Equation Coefficients Digitized gray level of pixel in row r, column c. Electronic gain in units grays/photo electron. Signal in units photo electrons. Pixel Sensitivity non-uniformity correction. Pixel Dark Current in units photo electrons/msec. Pixel fixed-pattern in units grays. Integration time in units msec. R. M. Bionta

  28. Photon Transfer Curve Temporal mean gray level of pixel r,c. Temporal gray level fluctuations of pixel r,c. R. M. Bionta

  29. Calibration Data for one pixel R. M. Bionta

  30. Calibration Coefficients for All Pixels R. M. Bionta

  31. LSO Monte Carlo Bend Photon Monte Carlo Simulations for predicting lens and camera performance Y, microns X, microns X Ray Photons SPEAR source simulation Visible photons R. M. Bionta

  32. Direct Imager Version 1 efficiency R. M. Bionta

  33. Camera Sensitivity Measurements at SPEAR 10-2 attenuator Ion chamber Imaging camera Ion Chamber Photon rate Sum of gray levels R. M. Bionta

  34. Measured and predicted sensitivities in fair agreement R. M. Bionta

  35. Camera Resolution Model R. M. Bionta

  36. Camera Resolution in qualitative agreement with models 1.1 mm R. M. Bionta 1.5 mm 1.5 mm

  37. Camera Resolution Quantitative Data Analysis in progress R. M. Bionta

  38. Micro Strip Ion Chamber Cathodes Isolation valve with Be window Windowless FEL entry Segmented horizontal and vertical anodes Differential pump Differential pump R. M. Bionta

  39. Gas Attenuator • For use when solid absorber risks damage (low-E FEL, front end) • Windowless, adjustable attenuation • Can provide up to 4 orders of magnitude attenuation R. M. Bionta

  40. Solid Attenuator • B4C attenuators can tolerate FEL beam at E > 4 keV in FEE, and at all energies in experimental hutches • Linear/log configurations • Can be wedged in 2 dimensions for continuously variable attenuation • Translation stages provide precision X and Y motion R. M. Bionta

  41. Missing • Predicted performance of direct and indirect imager for Spontanous vs. I, and FEL vs. Power • Calculations of linearity and signal levels in Ion chamber • Integration with FEE + Beam Dump floor plan R. M. Bionta

  42. Commissioning Diagnostic Tank R. M. Bionta

  43. Commissioning Diagnostics Measurements • Total energy • Pulse length • Photon energy spectra • Spatial coherence • Spatial shape and centroid • Divergence R. M. Bionta

  44. Commissioning diagnostic tank Detector and attenuator Stage Aperture Stage “Optic” Stage Rail alignment Stages Rail R. M. Bionta

  45. Costing based on SSRL 2-3 set up R. M. Bionta

  46. Total Energy Temperature sensor Poor Thermal Conductor absorber Heat Sink Crossed apertures On positioning stages Attenuator Scintillator R. M. Bionta

  47. Photon Spectra Measurement Detector and attenuator Stage Aperture Stage Crystal (8KeV) Grating (0.8 KeV) Stage X ray enhanced linear array and stage R. M. Bionta

  48. Spatial Coherence Measurement Detector and attenuator Stage Slits Stage Array of double slits R. M. Bionta

  49. Spatial shape, centroid , and divergence • A1 • A2 • A4 • FEE: HALL A FFTB Diagnostic Tanks FEE 1 & 3: Commissioning Diagnostic Tank A4-1 Diagnostic Tank A1-1 Spatial shape, centroid , and divergence measured by combining data from the imagers in these tanks. R. M. Bionta

  50. Rad Sensor - a candidate technology for LCLS pulse length measurement and pump probe synchronization Rad sensor is an InGaAs optical wave guide with a band gap near the 1550 nm. X-Rays strike the rad sensor disturbing the waveguide’s electronic structure. This causes a phase change in the interferometer. The process is believed to occur with timescales < 100 fs. SPEAR Single electron bunch mode 1550 nm optical carrier X-Ray Photons X-Ray measurements of the time structure of the SPEAR beam in January and March 2003 confirmed the devices x-ray sensitivity for LCLS applications. Rad sensor is inserted into one leg of a fiber-optic interferometer. phase 1550 nm optical carrier beam splitter Reference leg Detector time Point of interference X-Ray induced phase change observed as an intensity modulation at point of interference Fiber Optic Interferometer Mark Lowry, R. M. Bionta

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