WBS%201.3.1:%20PED%20Plans%20for%20FY

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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.
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WBS 1.5 X-Ray Transport, Optics, Diagnostics
(XTOD)
FEH - Far Experimental Hall

• Provides unobstructed vacuum path from end of
  undulator to end of FEH

Tunnel

• Flux densities in NEH will be the highest
  available
• Flux densities in FEH will be similar to
  synchrotron facilities

NEH - Near Experimental Hall
FEE Front End Enclosure
LCLS X-Ray Beam
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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 Spect
ra Coherence Pulse Length
Experiments Optics Structual Bio Nano-scale Femtoc
hem
Front End Enclosure Diagnostics Slits
Attenuators
Low Energy Order Sorting Mirror
Monochrometer Pulse-Split Delay Diagnostics
Experiments Optics Warm Dense Matter Atomic
Physics
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Beam Models
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FEL beam power levels
Saturated power
Plasma frequency
FEL r parameter
Gain length parameterization
Correct definition of h parameters
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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
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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
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FEL parameters at absorber exit, z 65 meters
And at other locations
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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
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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
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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)
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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
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RMS Bandwidth
l 0.15 nm Time Domain
l 0.15 nm Frequency Domain
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FWHM vs. wavelength at 0, 75 and 300 meters
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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.
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Dose / Power Considerations
Fluence to Melt
Energy Density Reduction of a Reflector
Be will melt at normal incidence at E lt 3 KeV
near undulator exit. Using Be as a grazing
incidence reflector may gain x 10 in tolerance.
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Romans far Field spontaneous
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Detailed Spontaneous, in progress
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E gt 400 KeV
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FEE Instrumentation
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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
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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

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Front End Diagnostic Tank
Solid Filter Wheel Assembly
ION Chamber
Be Isolation valve
Space for calorimeter
Direct Imager
Indirect Imager
Turbo pump
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Prototype LCLS X-Ray imaging camera
CCD Camera
Microscope Objective
X-ray beam
X-ray beam
LSO or YAGCe crystal prism assembly
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Indirect Imager
Be Mirror
Be Mirror Reflectivity at 8 KeV
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Be Mirror angle provides "gain" adjustment over
several orders of magnitude
0.1
0.01
0.001
0.0001
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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
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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.
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Photon Transfer Curve
Temporal mean gray level of pixel r,c.
Temporal gray level fluctuations of pixel r,c.
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Calibration Data for one pixel
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Calibration Coefficients for All Pixels
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Photon Monte Carlo Simulations for predicting
lens and camera performance
Y, microns
X, microns
X Ray Photons
SPEAR source simulation
Visible photons
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Direct Imager Version 1 efficiency
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Camera Sensitivity Measurements at SPEAR 10-2
attenuator
Ion chamber
Imaging camera
Ion Chamber Photon rate
Sum of gray levels
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Measured and predicted sensitivities in fair
agreement
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Camera Resolution Model
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Camera Resolution in qualitative agreement with
models
1.1 mm
1.5 mm
1.5 mm
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Camera Resolution Quantitative Data Analysis in
progress
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Micro Strip Ion Chamber
Cathodes
Isolation valve with Be window
Windowless FEL entry
Segmented horizontal and vertical anodes
Differential pump
Differential pump
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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

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Solid Attenuator

• B4C attenuators can tolerate FEL beam at E gt 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

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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

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Commissioning Diagnostic Tank
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Commissioning Diagnostics

• Measurements
• Total energy
• Pulse length
• Photon energy spectra
• Spatial coherence
• Spatial shape and centroid
• Divergence

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Commissioning diagnostic tank
Detector and attenuator Stage
Aperture Stage
Optic Stage
Rail alignment Stages
Rail
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Costing based on SSRL 2-3 set up
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Total Energy
Temperature sensor
Poor Thermal Conductor
absorber
Heat Sink
Crossed apertures On positioning stages
Attenuator Scintillator
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Photon Spectra Measurement
Detector and attenuator Stage
Aperture Stage
Crystal (8KeV) Grating (0.8 KeV) Stage
X ray enhanced linear array and stage
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Spatial Coherence Measurement
Detector and attenuator Stage
Slits Stage
Array of double slits
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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.
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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
waveguides electronic structure. This causes a
phase change in the interferometer. The process
is believed to occur with timescales lt 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
Reference leg
beam splitter
Detector
time
Point of interference
X-Ray induced phase change observed as an
intensity modulation at point of interference
Fiber Optic Interferometer
Mark Lowry,
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NIF Rad-Sensor Experimental Layout at SLAC
Ion chamber
slit
Diamond PCD
RadSensor
Imaging camera
attenuator
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RadSensor Response to single-bucket fill pattern
Xray pulse history (conventional)

• Fast rise
• Long fall-time will be improved
• Complementary outputs gt
• index modulation

781 ns
Mark Lowry
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Significant Improvements in sensitivity are
realized near the band edge
exciton abs peak width
Absorption width 0.01 nm
From Gibbs, pg 137

• 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

Absorption width 1 nm
Data to date
Absorption edge at 1214 nm
Systematic spectral measurements of both index
and absorption under xray illumination must be
made to get a clear understanding of the
sensitivity available
Mark Lowry
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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

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Startup Procedure
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FEE Diagnostics Comissioning
Ion Chamber
Ion Chamber
Attenuator
Attenuator
Gas Attenuator
Direct Imager
Direct Imager
Indirect Imager
Indirect Imager

• 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

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Summary

• 3 detector designs for flexibility
• Move back if necessary
• Bring on the beam!