Slide1: 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.
WBS 1.5 X-Ray Transport, Optics, & Diagnostics (XTOD) : WBS 1.5 X-Ray Transport, Optics, & Diagnostics (XTOD) Provides unobstructed vacuum path from end of undulator to end of FEH
LCLS X-Ray Beam Tunnel NEH - Near
Experimental
Hall Flux densities in NEH will be the highest available
Flux densities in FEH will be similar to synchrotron facilities FEE
Front End Enclosure FEH - Far
Experimental
Hall
X-ray Transport, Optics, and Diagnostics Layout: X-ray Transport, Optics, and Diagnostics Layout Front End
Enclosure
Diagnostics
Slits
Attenuators Low Energy
Order Sorting
Mirror FEL Measurements
& Experiments:
Compression
Spectra
Coherence
Pulse Length
Monochrometer
Pulse-Split & Delay
Diagnostics Experiments
Optics
Structual Bio
Nano-scale
Femtochem FEE NEH FEH Tunnel Experiments:
Optics
Warm Dense Matter
Atomic Physics Each 13 m long hutch has two vacuum tanks for experimental and facility hardware
Slide4: Beam Models
FEL beam power levels: FEL beam power levels Saturated
power FEL r parameter Plasma
frequency Gain length parameterization Correct definition of h parameters
Spatial-temporal shape: 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
LCLS Fundamental Electric Field and Dose Equations: LCLS Fundamental Electric Field and Dose Equations Gaussian Electric Field: With origin waist Phase
Curvature Waist at origin matches electron distribution gives Electric field intensity x duration Matches photon distribution with Peak photon density Dose
FEL parameters at absorber exit, z = 65 meters: FEL parameters at absorber exit, z = 65 meters And at other locations:
Slide9: Ginger provides complex Electric Field envelope at undulator exit 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 Each radial distribution has radial points. Electric Field Envelope Power Density vs time
at R = 0 watts/cm2
Tools for manipulating GINGER output: Tools for manipulating GINGER output GINGER output: Tables of electric field values
at undulator exit
at different times viewer Viewer Transformation to
Frequency Domain Propagation
to arbitrary
z R, mm
FEL spatial FWHM downstream of undulator exit, l = 0.15 nm: 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)
Total power at undulator exit: Total power at undulator exit 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.
RMS Bandwidth: RMS Bandwidth l= 0.15 nm
Time Domain l= 0.15 nm
Frequency Domain
FWHM vs. wavelength at 0, 75 and 300 meters: FWHM vs. wavelength at 0, 75 and 300 meters
We can confidently calculate the dose to transmissive optics.: We can confidently calculate the dose to transmissive optics. 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. Transmissive Dose Model Reflective Dose Model
Dose / Power Considerations: 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.
Roman’s far Field spontaneous: Roman’s far Field spontaneous
Detailed Spontaneous, in progress: Detailed Spontaneous, in progress
E > 400 KeV: E > 400 KeV
FEE Instrumentation: FEE Instrumentation
Front End Enclosure Layout: Front End Enclosure Layout Valve
Pump Pump Slow valve
Fast valve
Fixed Mask Slits Diagnostics Windowless
Ion Chamber Gas Attenuator Solid Attenuator Slits Diagnostics PPS 40m
WestFace Near Hall 33m
WestFace Dump 16.226 m
Eastface Last Dump Mag
Westface front End Enclosure 10.5 m 0 m
End of Undulator
Slide22: 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
Front End Diagnostic Tank: Front End Diagnostic Tank Direct Imager Indirect
Imager ION Chamber Turbo pump Space
for
calorimeter Be
Isolation
valve Solid Filter Wheel Assembly
Prototype LCLS X-Ray imaging camera: Prototype LCLS X-Ray imaging camera CCD
Camera Microscope
Objective LSO or YAG:Ce crystal prism assembly X-ray beam X-ray beam
Indirect Imager: Indirect Imager Be Mirror Reflectivity at 8 KeV 1 0.1 0.01 0.001 0.0001 Be Mirror Be Mirror angle provides "gain" adjustment over several orders of magnitude
Multilayer allows higher angle and higher transmision but high z layer gets high dose: 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
First check CCD by measuring Response Equation Coefficients: 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.
Photon Transfer Curve: Photon Transfer Curve Temporal mean gray level of pixel r,c. Temporal gray level fluctuations of pixel r,c.
Calibration Data for one pixel: Calibration Data for one pixel
Calibration Coefficients for All Pixels: Calibration Coefficients for All Pixels
Photon Monte Carlo Simulations for predicting lens and camera performance: Photon Monte Carlo Simulations for predicting lens and camera performance SPEAR source simulation Visible photons X, microns Y, microns X Ray Photons
Direct Imager Version 1 efficiency: Direct Imager Version 1 efficiency
Camera Sensitivity Measurements at SPEAR 10-2: Camera Sensitivity Measurements at SPEAR 10-2 Sum of gray levels Ion Chamber
Photon rate attenuator Imaging camera Ion chamber
Measured and predicted sensitivities in fair agreement: Measured and predicted sensitivities in fair agreement
Camera Resolution Model: Camera Resolution Model
Camera Resolution in qualitative agreement with models: Camera Resolution in qualitative agreement with models 1.5 mm 1.1 mm 1.5 mm
Camera Resolution Quantitative Data Analysis in progress: Camera Resolution Quantitative Data Analysis in progress
Micro Strip Ion Chamber: Micro Strip Ion Chamber Differential
pump Differential
pump Cathodes Segmented
horizontal
and
vertical
anodes Isolation valve
with
Be window Windowless
FEL entry
Slide39: For use when solid absorber risks damage (low-E FEL, front end)
Windowless, adjustable attenuation
Can provide up to 4 orders of magnitude attenuation
Slide40: 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
Missing: 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
Commissioning Diagnostic Tank: Commissioning Diagnostic Tank
Commissioning Diagnostics: Commissioning Diagnostics Measurements
Total energy
Pulse length
Photon energy spectra
Spatial coherence
Spatial shape and centroid
Divergence
Commissioning diagnostic tank: Commissioning diagnostic tank Aperture
Stage “Optic”
Stage Detector and attenuator
Stage Rail alignment
Stages Rail
Costing based on SSRL 2-3 set up: Costing based on SSRL 2-3 set up
Total Energy: Total Energy Crossed apertures
On positioning stages absorber Temperature
sensor Attenuator
Scintillator Poor Thermal
Conductor Heat
Sink
Photon Spectra Measurement: Photon Spectra Measurement Aperture
Stage Crystal (8KeV)
Grating (0.8 KeV)
Stage Detector and attenuator
Stage X ray enhanced linear array and stage
Spatial Coherence Measurement: Spatial Coherence Measurement Slits
Stage Detector and attenuator
Stage Array of double slits
Spatial shape, centroid , and divergence: Spatial shape, centroid , and divergence FEE: A1 A2 A4 FFTB HALL A Diagnostic
Tanks
FEE 1 & 3: Diagnostic
Tank
A1-1 Commissioning
Diagnostic
Tank
A4-1 Spatial shape, centroid , and divergence measured by combining data from the imagers in these tanks.
Rad Sensor - a candidate technology for LCLS pulse length measurement and pump probe synchronization: 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. 1550 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,
NIF Rad-Sensor Experimental Layout at SLAC: NIF Rad-Sensor Experimental Layout at SLAC Ion chamber attenuator Imaging camera Diamond
PCD RadSensor slit
Slide52: 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
Slide53: 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 10-100, 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
XRTOD Diagnostics Timeline: XRTOD Diagnostics Timeline FY04 – PED year 4
PCMS certification - Jan 2004
Baseline Review - Aug 2003
Complete simulations of camera response to FEL and Spontanous
Prototype Windowless Ion Chamber / gas attenuator
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
Startup Procedure: Startup Procedure
FEE Diagnostics Comissioning: FEE Diagnostics Comissioning Start with Low Power Spontaneous
Saturate DI, measure linearity with solid attenuators
Test Gas Attenuator
Raise Power, Look for FEL
in DI, switch to Indirect Imager when attenuator burns
Move behind Gas Attenuator
Move to Comissioning Diagnostic Tank Attenuator Direct
Imager Indirect
Imager Ion
Chamber Attenuator Direct
Imager Indirect
Imager Ion
Chamber Gas Attenuator
Summary: Summary 3 detector designs for flexibility
Move back if necessary
Bring on the beam!