X Ray Beam Characterization Richard M. Bionta Facility Advisory Committee Meeting April 30, 2004 Richard M. Bionta Facility Advisory Committee Meeting April 30, 2004

Richard M. Bionta X-Ray Beam April 29, 2004 LCLS Commissioning Measuring Gain vs z. Kick beam at z to stop FEL gain Measure at end of undulator Measure Spectra with resolution <  = 5-15x10 -4 But with bandwidth of 0.5% Pulse length …

Richard M. Bionta X-Ray Beam April 29, 2004 FEL beam power level calculations Saturated power FEL r parameter Plasma frequency Gain length parameterization

Richard M. Bionta X-Ray Beam April 29, 2004 LCLS Spectral Output

Richard M. Bionta X-Ray Beam April 29, 2004 Model FEL beam propagation as a single- mode gaussian FEL 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

Richard M. Bionta X-Ray Beam April 29, 2004 Check Gaussian with Ginger: A numerical FEL simulation Data in the form of radial distributions of complex numbers representing the envelope of the Electric Field at the undulator exit. Samples are separated in time by wavelengths. Time between samples is R, mm 0150 Each radial distribution has radial points. Electric Field Envelope Power Density vs time at R = 0 watts/cm 2

Richard M. Bionta X-Ray Beam April 29, 2004 FEL Photon Spectra 0 w 0 = /fs w / fs 3 x watts c m 2 w /fs frequency Power Density l= 0.15 nm Time Domain l= 0.15 nm Frequency Domain 0.8%  E/E

Richard M. Bionta X-Ray Beam April 29, 2004 FEL spatial FWHM downstream of undulator exit, l = 0.15 nm Transverse beam profile at undulator exit Transverse beam profile 15 m downstream of undulator exit Ginger (points) Gaussian Beam (line)

Richard M. Bionta X-Ray Beam April 29, 2004 Ultimate output power uncertain Ginger simulations Theoretical FEL saturation level 10 Ginger simulations were run at different electron energies but with fixed electron emittance through 100 meter LCLS undulator. The Ginger runs at the longer wavelengths were not optimized, resulting in significant post- saturation effects. Results at longer wavelengths carry greater uncertanty.

Richard M. Bionta X-Ray Beam April 29, 2004 Fast close valve Slit A PPS 13' Muon shield Gas Attenuator Solid Attenuator Slit B PPS 4' Muon shield Windowless Ion Chamber Direct Imager Indirect Imager Spectrometer, Total Energy PPS Access Shaft Access Shaft Electron Beam Photon Beam Electron Dump Front End Enclosure NEH Hutch 1 Front End Enclosure/ Hutch 1 Layout

Richard M. Bionta X-Ray Beam April 29, 2004 Diagnostics Commissioning Start with Low Power Spontaneous Saturate DI, 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 DI, switch to Indirect Imager when attenuator burns Solid Attenuator Slits Ion Chamber Direct Imager Indirect Imager Total energy Gas Attenuator Slits

Richard M. Bionta X-Ray Beam April 29, 2004 Spontaneous radiation is a big background 0 < E photon < 1.2 MeV 400 keV < E photon < 1.2 MeV Far-field radiation pattern calculated by R. Tatchyn 400 m from undulator exit.

Richard M. Bionta X-Ray Beam April 29, 2004 FEE Layout Gas Attenuator Solid Attenuator Slit B PPS

Richard M. Bionta X-Ray Beam April 29, 2004 Windowless Gas Attenuator – 10 m system Region of highest pressure Gas Inlet Window Vacuum pumps Photon Energy eV GasPressure, torrTransmission 800N Ar100.2

Richard M. Bionta X-Ray Beam April 29, 2004 Gas Attenuator – Windows Open, tilted, nozzle High gas flow Rotating slots Synchronization Plasma Window Gas flow Photon Energy eVFEL FWHM mm Z = 90 m

Richard M. Bionta X-Ray Beam April 29, 2004 Gaussian Model Layout Code

Richard M. Bionta X-Ray Beam April 29, 2004 Gas Attenuator Issues Beam size Window Blocking Spontaneous Gas delivery and recovery in FEE tunnel Physics instrumentation ( 1 st experiment)

Richard M. Bionta X-Ray Beam April 29, 2004 Solid Attenuator Be, Li, and B 4 C attenuators can tolerate FEL beam at E > 2- 3 keV Linear/log configurations Multiple wheels allowing multiple configurations

Richard M. Bionta X-Ray Beam April 29, 2004 Solid Attenuator - Issues Contamination of low Z attenuators Damage and ES&H from damaged Be Bleaching

Richard M. Bionta X-Ray Beam April 29, 2004 NEH Hutch 1 Diagnostic systems Windowless Ion Chamber Imaging Detector Tank Comissioning Tank

Richard M. Bionta X-Ray Beam April 29, 2004 Imaging Detector Tank Direct Imager Indirect Imager Turbo pump Space for calorimeter Be Isolation valve

Richard M. Bionta X-Ray Beam April 29, 2004 Prototype Low Power imaging camera CCD Camera Microscope Objective LSO or YAG:Ce crystal prism assembly X-ray beam

Richard M. Bionta X-Ray Beam April 29, 2004 Photon Monte Carlo Simulations for predicting backgrounds and detector performance (at SPEAR) SPEAR source simulation Visible photons X, microns Y, microns Monte Carlo Bend LSO X Ray Photons

Richard M. Bionta X-Ray Beam April 29, 2004 Simulation to predict performance at LCLS Far-field Spontanious Distribution Undulator Optics Predict spectrum and spatial distribution in plane of camera

Richard M. Bionta X-Ray Beam April 29, 2004 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.

Richard M. Bionta X-Ray Beam April 29, 2004 Photon Transfer Curve Temporal mean gray level of pixel r,c. Temporal gray level fluctuations of pixel r,c.

Richard M. Bionta X-Ray Beam April 29, 2004 Calibration Data for one pixel

Richard M. Bionta X-Ray Beam April 29, 2004 Calibration Coefficients for All Pixels

Richard M. Bionta X-Ray Beam April 29, 2004 Direct Imager Version 1 efficiency

Richard M. Bionta X-Ray Beam April 29, 2004 Camera Sensitivity Measurements at SPEAR 10-2 Sum of gray levels Ion Chamber Photon rate attenuator Imaging camera Ion chamber

Richard M. Bionta X-Ray Beam April 29, 2004 Measured and predicted sensitivities in fair agreement

Richard M. Bionta X-Ray Beam April 29, 2004 Camera Resolution Model

Richard M. Bionta X-Ray Beam April 29, 2004 Camera Resolution in qualitative agreement with models 1.5 mm 1.1 mm 1.5 mm

Richard M. Bionta X-Ray Beam April 29, 2004 Issues Vacuum Operation Low Photon Energy Performance Noise levels and Format of 120 Hz Readout CCDs Afterglow in LSO High Energy Spontaneous Background

Richard M. Bionta X-Ray Beam April 29, 2004 Indirect, high power imaging system Be Mirror Be Mirror angle provides "gain" adjustment over several orders of magnitude. Cuts off high energy spontaneous

Richard M. Bionta X-Ray Beam April 29, 2004 Multilayer allows higher angle, higher transmission and energy selection, 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

Richard M. Bionta X-Ray Beam April 29, 2004 Indirect Imager Mirror sizes Photon Energy eV FEL FWHM mm Mirror Length mm Normal Incidence dose to Be, eV/atom  = 1.0 deg Z = 105 m

Richard M. Bionta X-Ray Beam April 29, 2004 Indirect imager issues Calibration Mirror roughness Tight camera geometry Compton background Vacuum  mechanics Making mirror thin enough for maximum transmission Ceramic multilayers? Use as an Imaging Monochrometer

Richard M. Bionta X-Ray Beam April 29, 2004 Windowless Ion Chamber for monitoring position and intensity Measures intensity using x-ray gas interactions Windowless for operation at low photon energies Open nozzel Rotating slots Plasma window Crude imaging may be possible As a drift chamber As a Quad cell As a Fluorescent Imager

Richard M. Bionta X-Ray Beam April 29, 2004 Micro Strip version Differential pump Differential pump Cathodes Segmented horizontal and vertical anodes Isolation valve with Be window Windowless FEL entry

Richard M. Bionta X-Ray Beam April 29, 2004 Windowless ion chamber issues Windowless operation issues (gas attenuator) Beam size Window Blocking Spontaneous Gas delivery and recovery in Hutch Choice of readout Pulsed operation

Richard M. Bionta X-Ray Beam April 29, 2004 Commissioning Diagnostics Tank Intrusive measurements behind attenuator Measurements Photon energy spectra Total energy Spatial coherence Spatial shape and centroid Divergence R&D Pulse length

Richard M. Bionta X-Ray Beam April 29, 2004 Commissioning diagnostic tank Aperture Stage “Optic” Stage Detector and attenuator Stage Rail alignment Stages Rail

Richard M. Bionta X-Ray Beam April 29, 2004 Total Energy Crossed apertures On positioning stages absorber Temperature sensor Attenuator Scintillator Poor Thermal Conductor Heat Sink

Richard M. Bionta X-Ray Beam April 29, 2004 Total energy issues 120 Hz operation Segmentation Non-standard materials (Be)

Richard M. Bionta X-Ray Beam April 29, 2004 Photon Spectra Measurement Aperture Stage Crystals or gratings for 3 Photon energies Detector and attenuator Stage X ray enhanced linear array and stage

Richard M. Bionta X-Ray Beam April 29, 2004 Sputtered-sliced multilayer gratings as high bw spectrometers 5-  m-thick Mo/Si multilayer (d=200 Å) on Si wafer substrate. Thinned and polished to a 10-  m-thick slice SEM image of Mo/Si multilayer

Richard M. Bionta X-Ray Beam April 29, 2004 Spectrometer Issues How to achieve resolution over a 0.5% bandwidth shot-to-shot? Dynamic range Designs for low divergence beam

Richard M. Bionta X-Ray Beam April 29, 2004 Pulse length measurement fsec! Rad sensor is an InGaAs optical wave guide with a band gap near the 1550 nm nm optical carrier Reference leg Detector beam splitter 1550 nm optical carrier Fiber Optic Interferometer Rad sensor is inserted into one leg of a fiber-optic interferometer. 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. X-Ray Photons Point of interference X-Ray induced phase change observed as an intensity modulation at point of interference 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. time phase SPEAR Single electron bunch mode Mark Lowry,

Richard M. Bionta X-Ray Beam April 29, 2004 NIF Rad-Sensor Experimental Layout at SLAC Ion chamber attenuator Imaging camera Diamond PCD RadSensor slit

Richard M. Bionta X-Ray Beam April 29, 2004 RadSensor Response to single-bucket fill pattern Fast rise Long fall-time will be improved Complementary outputs => index modulation Xray pulse history (conventional) 781 ns Mark Lowry

Richard M. Bionta X-Ray Beam April 29, 2004 Significant Improvements in sensitivity are realized near the band edge Systematic spectral measurements of both index and absorption under xray illumination must be made to get a clear understanding of the sensitivity available Absorption width = 0.01 nm Absorption width = 1 nm Adding in x4 for QC enhancement we should detect a single xray photon at least 8x10 -4 fringe fractions. If we allow for a cavity with finesse , this allow the development of a useful instrument Data to date = exciton abs peak width From Gibbs, pg 137 Absorption edge at 1214 nm Mark Lowry

Richard M. Bionta X-Ray Beam April 29, 2004 Pulse length sensor issues Significant R&D needed in "magic material" that converts between x-ray and optical laser light Acquisition and recording systems with fs resolution

Richard M. Bionta X-Ray Beam April 29, 2004 XRTOD Diagnostics Timeline FY04 – PED year 4 Complete simulations of camera response to FEL and Spontanous R&D on Ion Chamber, gas attenuator, and spectrometer FY05 – PED year 3 FEE Detailed design FY06 - Start of Construction FEE Build and test NEH Design FY07 FEE Install NEH Build and Test FEH Design FY08 NEH Install FEH Build and Test FY09 - Start of Operation

Richard M. Bionta X-Ray Beam April 29, 2004 Diagnostics Issues Large number of independent deliverables Source for testing damage issues does not exist Funding Profile means considerable design work still ahead But, the resources are available for success.