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X-Ray Transport, Diagnostic, & Commissioning Plans

X-Ray Transport, Diagnostic, & Commissioning Plans. LCLS Diagnostics and Commissioning Workshop.

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X-Ray Transport, Diagnostic, & Commissioning Plans

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  1. X-Ray Transport, Diagnostic, & Commissioning Plans LCLS Diagnostics and Commissioning Workshop *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. Outline • XTOD Layout • FEL parameters along Beam line • XTOD Diagnostics and Front-End Optics • Spontaneous Radiation Model • Spontaneous and FEL signals in Direct Imager Diagnostic • Spontaneous Reflection in Undulator Vacuum Chamber • Conclusions

  3. Diagnostics and Front-End Layout

  4. PPS 1.5 Scope: Front End Enclosure/ Near Experimental Hall 4' Muon shield NEH PPS Flipper Mirror Front End Enclosure Comissioning: Spectrometer, Total Energy Solid Attenuator Slit A 112 m Photon Beam Direct Imager Indirect Imager 83 m Slit B Gas Attenuator 13' Muon shield Fast close valve Electron Beam Electron Dump

  5. Diagnostics for Commissioning 112 m from end of undulator 83 m from end of undulator Front End Enclosure Near Hall Hutch 1 Calorimeter or spectrometer Gas Attenuator Imaging Systems Slits Slits Solid Attenuator Muon Shield Muon Shield

  6. FEL parameters along Beam line

  7. FEL Parameters at 8.261 KeV

  8. Dose to melt for various materials Melt dose ev/atom Dose in NEH Hutch 1 Z 8 keV 1 keV Beryllium 4 0.58 0.013 0.000 Diamond 6 2.13 0.062 0.002 Aluminum 13 0.20 0.072 0.058 Silicon 14 0.91 0.100 0.078 Copper 29 0.44 0.183 0.142 Molybdenum 42 1.24 0.993 0.649 Tin 50 0.14 1.873 1.292 Tungsten 74 1.06 1.316 1.341 Lead 82 0.14 2.016 2.042 Doses should be compared to dose needed to melt

  9. FEL Parameters at 4.000 KeV

  10. FEL Parameters at 0.826 KeV

  11. Material suitability a strong function of photon energy Low Z materials such as Be, C, B4C and Si will survive at least > 1 shot in the NEH NEH Peak Fluence at entrance Fluence to Melt Melts in NEH

  12. Diagnostics and Front-End Optics

  13. Gas and Solid Attenuators Gas Attenuator stage 2 Gas Attenuator stage 1 Gas Attenuator high pressure vesssel Slit B Autocad Solid Attenuator

  14. Solid Be likely to survive at 88 m Be < 0.1 eV/atom for all photon energies

  15. Pressure or thickness for 10-4 attenuation Use Gas Use Solids * 6 m of gas at pressure

  16. Conductance – Intermediate Flow Modeled + Gas Attenuator Prototype Design and Analyses Will Validate Concepts

  17. NEH Hutch 1 Diagnostic systems Direct Imager Indirect Imager Comissioning Tank

  18. Imaging Detector Tank Be Isolation valve Indirect Imager (Sees only a low intensity reflection) Direct Imager (Placed directly in beam) Turbo pump

  19. Imaging detector head prototype CCD Camera Microscope Objective X-ray beam LSO or YAG:Ce crystal prism assembly

  20. Direct imager issues • Vacuum Operation • Low Photon Energy Performance • 120 Hz Readout • Afterglow in LSO • High Energy Spontaneous Background • Damage threshold

  21. Indirect Imager reflects small amount of FEL into camera, avoiding damage Be Mirror Reflectivity at 8 KeV Be Mirror 1 0.1 0.01 0.001 Be Mirror angle provides "gain" adjustment over several orders of magnitude and discriminates against high energy spontaneous background 0.0001

  22. Minimum mirror reflectivity needed to fill CCD well

  23. Indirect imager issues • Calibration • Mirror roughness • Tight camera geometry • Compton background • Vacuum q-2q mechanics • Making mirror thin enough for maximum transmission • Ceramic multilayers? • Use as an Imaging Monochrometer

  24. Commissioning strategy • Start with Low Power Spontaneous • Saturate Direct Imagers, measure linearity with solid attenuators • Raise power, Measure linearity of Calorimeter and Indirect imager. Cross calibrate • Test Gas Attenuator • Raise Power, Look for FEL • in Direct Imager • Verify linearity with attenuators • switch to Indirect Imager if scintilator damages

  25. Spontaneous Radiation Model

  26. y E x Spontaneous Data Chain • UCLA Near-Field Calculator • ~2 Gbyte HDF5 • HDF5 to Paradox Converter • (x,y,E,P) Paradox format, 4 X 1 GByte • ReBinner – Coarser Energy Bins (159) • (x,y,E,P) Paradox format, 350 MByte • Blob DB Converter – faster to read • (E,P[x,y]) Paradox, 50 MBytes • Viewer

  27. Spontaneous Fluence at NEH Hutch 1 Te = 4.5 GeV Z = 243 m Dx = 1.0 mm Dy = 0.3 mm 1.85 mJ Te = 14.5 GeV Z = 243 m Dx = 0.3 mm Dy = 0.1 mm 18.2 mJ 2” 4”

  28. Energy Slices Near-Field calculation 88 m from End-of-Undulator, Sven Richie, UCLA 20 mm 20 mm Far-Field calculation 400 m from Center-of-Undulator, Roman Tatchyn, SSRL 0 < E < 10 keV 7.6 < E < 9.0 keV 10 < E < 20 keV 20 < E < 27 keV

  29. LCLS beam footprint Expected LCLS beam profile contains FEL and Spontaneous halo 2-3 mJ FEL 3 mJ High energy core Eg > 400 keV 20 mJ Spontaneous At entrance to NEH, FEL tuned to 8261 eV Fundamental

  30. Spontaneous and FEL signals in the Direct Imager Diagnostic

  31. y E x Camera Image Calculator Chain Spontaneous DB Photoelectrons in Camera (2.5 x Zeiss + SITEC CCD) Spontaneous + e x FEL Absorbed in 25 mm LSO (E,P[x,y]) x e FEL Transmitted by Material

  32. 14.5 GeV Spontaneous, NEH H1 All photons Stops in 25 mm LSO

  33. 14.5 GeV Spontaneous Direct Imager Signal Photons Energy All photons Stops in 25 mm LSO Photoelectrons/Pixel CCD photoelectron levels < 150K e- Full well (16 bit) 327K e- so this is ½ scale on CCD readout (X-Ray resolution 300 x 100 mm)

  34. 14.5 GeV Spontaneous + FEL Photons Energy All photons Stops in 25 mm LSO Need attenuation of 2.4 x 10-4 for CCD full well Photoelectrons/Pixel (X-Ray resolution 300 x 100 mm)

  35. Use of 16.9 mm B4C Attenuator Raw photon spectra of FEL + Spontaneous Spectra of FEL + Spontaneous after B4C Photons/keV Spectra of photons stopping in LSO

  36. Direct Imager Image 14.5 GeV 100% FEL + Spontaneous through 16.8 mm B4C into 25 mm LSO Good FEL signal at ½ CCD Full Scale but increased background in image (X-Ray resolution 300 x 100 mm)

  37. How faint can FEL be? (X-Ray resolution 300 x 100 mm) 14.5 GeV 1% FEL + Spontaneous directly into 25 mm LSO 0.01% FEL + Spontaneous into 25 mm LSO

  38. 4.5 GeV Spontaneous, NEH H1 All photons 1.852 mJ Direct Imager Photoelectrons 8 x 1011 Photons / keV 0 Stops in 25 mm LSO 1.205 mJ Direct Imager Photoelectrons (X-Ray resolution 1000 x 300 mm)

  39. 4.5 GeV Spontaneous + e x FEL Direct Imager Image Direct Imager Photoelectrons 1 % FEL 0.01 % FEL (X-Ray resolution 1000 x 300 mm)

  40. Commissioning with Direct Imager • Direct Imager will see spontaneous on a single shot at 4.5-24.5 GeV • Direct Imager will need 10-4 attenuation for on scale operation at full FEL power, which increases background. These calculations show a factor of ~5-10 margin. • Without attenuator, Direct Imager will see FEL at 0.01% power at 4.5 GeV and significantly < 0.01% at 14.5 GeV

  41. Spontaneous Reflection in Undulator Vacuum Chamber

  42. Spontaneous Monte Carlo Chain • Spontaneous Blob DB • (E,P[x,y]) Paradox, 50 Mbytes • Inject FEL • (E,P[x,y]) Paradox, 50 Mbytes • Cumulative DB • (x,y,F[E]) Paradox, 50 Mbytes • Photon MC Generator – creates random photons according to cumulative distribution • (x,y,z,vx,vy,vz,E) of individual photons

  43. Spontaneous Monte Carlo Simulation Photon starting angles generated to give calculated spontaneous spatial distribution Photon starting x, y matches electron distribution, a Gaussian with s = 30 mm Photon starting z is uniform along undulator (from 0 < z < 130 m)

  44. y E x Each photon final x, y has its own cumulative energy distribution Calculated far-field energy spectrum Monte Carlo Energy Distribution

  45. Simulated spatial distributions agree with far-field calculation All Photons Monte Carlo 465 m from beginning of undulator Far-Field Calculation 400 m from center of undulator

  46. Simulated spatial distributions agree with far-field calculation – higher orders

  47. Spontaneous Emission Angle Below Critical Angle 243 m 130 m 60-200 mm Qmin = 0.2 – 0.8 mRad Qmax = 0.5 – 1.8 mRad

  48. Vacuum Pipe Simulation 14.5 GeV Without pipe With pipe

  49. Line outs through center Without pipe With pipe

  50. Reflection at higher orders UCLA Calculation, without pipe Monte Carlo, without pipe Monte Carlo, with pipe 0 < E < 10 keV 10 < E < 20 keV 20 < E < 30 keV

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