LUSI Diagnostics & Common Optics
Facility Advisory Committee
XTOD/XES/LUSI Breakout
June 16-17 2008
Overview
Intensity-Position Monitor
Wavefront Monitor
Slits
June 16-17 2008
LUSI Diagnostics & Common Optics
1
Yiping Feng
YFENG@SLAC.Stanford.edu
Diagnostics Overview
X-ray Free-Electron Laser (FEL) is of fundamental differences from
storage-ring based synchrotron sources
At LCLS, it is Linac-based, single-pass, operating at 120 Hz
Feedback is limited by low repetition rate
Each macro electron bunch is different in timing, length, density, energy
(velocity), orbit, emittance, etc.
At LCLS, the self-seeding SASE is responsible for X-ray amplification
process
Lasing starts from a random electron density distribution
Each X-ray pulse consists of a random time sequence of spikes of varying
degrees of saturation
LCLS X-ray FEL exhibits inherent intensity, spatial/modal,
temporal/spectral, & timing fluctuations on pulse by pulse
basis
June 16-17 2008
LUSI Diagnostics & Common Optics
2
Yiping Feng
YFENG@SLAC.Stanford.edu
Expected Fluctuations of LCLS FEL
Parameter
Value
~ 30 %
Origin
(in contrast to synchrotron where
fluctuation is Poisson limited)
Varying # of FEL producing SASE
spikes; 100% intensity fluctuation/perspike; variation in bunch charge.
Position & pointing jitter (x, y,
a, b)
~ 25 % of beam diameter
~ 25 % of beam divergence
Varying trajectory per pulse; Saturation
at different locations of b-tron
curvature
Source point jitter (z)
~5m
SASE process reaching saturation at
different z-points in undulator
X-ray pulse timing (arrival
time) jitter
~ 1 ps FWHM
Pulse intensity fluctuation
(peculiar to FEL)
(in addition to limit to phase lock
probe/excitation laser)
X-ray pulse width variation
~ 15 %
Center wavelength variation
~ 0.2 %
June 16-17 2008
LUSI Diagnostics & Common Optics
Timing jitter btw injection laser and RF;
Varying e-energy per-pulse
Varying e-energy leading to varying
path (compression) in bunch
compressors
(comparable to FEL bandwidth)
3
Varying e-energy leading to varying
FEL fundamental wavelength and
higher order
Yiping Feng
YFENG@SLAC.Stanford.edu
Diagnostics Objectives
X-ray diagnostics are required to measure these fluctuations
Integral parts of Instruments
High-resolution intensity measurements for XPP experiments
Wavefront characterization for CXI/XCS experiments
Measurements made on pulse-by-pulse basis
Requiring sophisticated data acquisition system
Commonalities in needs & specs
Standardized and used for all applicable instruments
Modularized for greater flexibilities
All diagnostics must be performed and measurement data
made available on pulse-by-pulse basis if needed
June 16-17 2008
LUSI Diagnostics & Common Optics
4
Yiping Feng
YFENG@SLAC.Stanford.edu
X-ray Diagnostics Suite
(consisting of 4 Monitors/Devices)
Diagnostics/Measurement
Monitors/Devices
Alignment/Beam Quality
Pop-in Profile Monitor
Alignment/Intensity
Pop-in Intensity Monitor
- Direct X-ray Scintillation w/ optical detection
- Direct X-ray detection
Intensity-Position Monitor
Intensity/Beam Position & Pointing
Wavefront
June 16-17 2008
LUSI Diagnostics & Common Optics
- Concurrent w/ experiment
- Measure signal from scattering/photoelectric
processes
Wavefront Monitor
- Direct X-ray Scintillation w/ optical detection
- Mathematical reconstruction of wavefront
5
Yiping Feng
YFENG@SLAC.Stanford.edu
Common Optics Overview
Driven by Common Experimental Needs & Performance
Requirements
X-ray optics to manipulate pulses delivered to sample
Shaping & cleaning
Attenuation
Pulse pattern alteration or repetition rate reduction
High harmonic rejection
Focusing
Common requirements
Must sustain peak power when used in pink beam
Average thermal load is small (< 1 W, i.e. no cryogenic cooling)
Preserve coherence to the extent possible
X-ray Common Optics needs and requirements are shared by
all LUSI instruments, leading to common design, and
implementation
June 16-17 2008
LUSI Diagnostics & Common Optics
6
Yiping Feng
YFENG@SLAC.Stanford.edu
X-ray Common Optics Suite
(consisting of 5 Optics/Devices)
Beam Manipulation
Common Optics/Device
Coarse focusing
Be Refractive Focusing Lens
Shaping & Cleaning
X-ray Slits
Attenuation
X-ray Attenuators
Pulse pattern alteration/
repetition reduction
Pulse Picker
High harmonics rejection
Harmonic Rejection Mirrors
June 16-17 2008
LUSI Diagnostics & Common Optics
- Chromatic, long focal length
- primary, guard, mono, coarse/precision
- Capable of selecting random pulse sequence
7
Yiping Feng
YFENG@SLAC.Stanford.edu
LCLS
Front End Enclosure
Near Experimental Hall
(XPP)
X-ray Transport Tunnel
(CXI, XCS)
Far Experimental Hall
(CXI, XCS)
June 16-17 2008
LUSI Diagnostics & Common Optics
8
Yiping Feng
YFENG@SLAC.Stanford.edu
X-ray Optics and Diagnostics in FEE
•Designed primarily for FEL beam conditioning,
commissioning, and global measurements
June 16-17 2008
LUSI Diagnostics & Common Optics
9
Yiping Feng
YFENG@SLAC.Stanford.edu
Diagnostics/Optics Scope
Far Experimental Hall
•Diagnostics/Common Optics
•Scope include:
• XPP Instrument
• CXI Instrument
• XCS Instrument
• X-ray Transport Tunnel
CXI
Endstation
XCS
Endstation
Near Experimental Hall
XPP
Endstation
AMO
(LCLS)
•Designed primarily to meet instrument specific (local)
FEE
needs for beam manipulations and experimental
measurements
•Use FEE optics and diagnostics when appropriate
June 16-17 2008
LUSI Diagnostics & Common Optics
10
Yiping Feng
YFENG@SLAC.Stanford.edu
Diagnostics/Optics Status
Diagnostics/Optics
XPP
CXI
XCS
Total
PRD
ESD
Design
Pop-in Profiler Monitor
3
4
5(6)
12(13)
√
review
prelim
Pop-in Intensity Monitor
2
2
5(6)
9(10)
√
review
prelim
Intensity-Position Monitor
3
3
5
11
√
draft
prelim
1
√
review
prelim
Wavefront Monitor
EO Monitor (LCLS AIP)
1
1
1
Monochromator (BCR)
0(1)
0(1)
1
2
√
draft
prelim
X-Ray Focusing Lenses
1
Slit System
3
4
7
14
√
review
prelim
Attenuator-Filters
1
1
1
3
√
review
prelim
Pulse Picker
1
0(1)
0(1)
1(3)
√
draft
prelim
Harmonic Rejection Mirrors
1
1
2
√
draft
prelim
•Numbers in parentheses are for when mono is in scope by BCR
June 16-17 2008
LUSI Diagnostics & Common Optics
11
Yiping Feng
YFENG@SLAC.Stanford.edu
Diagnostics Summary Specifications
Diagnostic Item
Pop-in
profile monitor
(moderate position resolution,
coarse/fine spatial resolution)
Pop-in
intensity monitor
(moderate intensity resolution)
(Leave-in)
intensity-position monitor
(high intensity/position resolution)
Wavefront monitor
(in-situ but after sample, destructive
after detection)
Purposes
Specifications*
Coarse beam alignment/monitoring;
Coarse/fine beam profile
Destructive; Retractable;
At 100 mm resolution
- 24x24 mm2 field of view;
At 8 mm resolution
- 2x2 mm2 field of view;
Capable of per-pulse op. @ 120 Hz
Coarse beam alignment/monitoring;
Simple point detector
Destructive; Retractable;
Relative accuracy < 1%;
Dynamic range 100;
Capable of per-pulse op. @ 120 Hz
Per-pulse normalization of
experimental signals;
High-resolution beam position
monitoring
Highly transmissive (< 5% loss);
Relative accuracy < 0.1%;
Dynamic range 1000;
Per-pulse op. at 120 Hz;
Per pulse characterization of wavefront;
Locating focal point of focused beam
Destructive but after sample;
At 51 mm resolution
- 12.3x12.3 mm2 field of view;
At 4.3 mm resolution
- 1.03x1.03 mm2 field of view;
Per-pulse op. @ 120 Hz
* Must have high damage threshold
June 16-17 2008
LUSI Diagnostics & Common Optics
12
Yiping Feng
YFENG@SLAC.Stanford.edu
Device Concepts/Implementations
Needing FAC feedbacks/recommendations
Intensity-position monitor
Validation of concept
Risk assessment & mitigation
Wavefront monitor
Validation of concept
In lieu of Hartmann wavefront monitor
Performance expectations
Slits
Validation of concept
Material selection
Risk assessment & mitigation
June 16-17 2008
LUSI Diagnostics & Common Optics
13
Yiping Feng
YFENG@SLAC.Stanford.edu
Intensity-Position Monitor
Physics Requirements
Primary Purpose
Intensity measurement of incident X-ray
In-situ, non-destructive
If in transmission geometry, transmissivity > 95%
Energy range from 2 to 25 keV
0.1% accuracy if permitted by Poisson counting statistics
Dynamic range of > 1000
Per pulse operation
2x2 mm2 working range
Secondary Purpose
Beam position monitoring w/ use of array detectors
x,y positions to < 5 mm
Pointing in x,y to < 5/L mrad w/ two monitors separated by L meters.
June 16-17 2008
LUSI Diagnostics & Common Optics
14
Yiping Feng
YFENG@SLAC.Stanford.edu
Intensity-Position Monitor
System concept
Incident intensity measurement
Scattering from target material
Ability to withstand the peak fluence of an unfocused X-ray FEL beam.
Highly transmissive in the operating range of 2 keV to 8.3 keV (w/ 3rd harmonic
from 6 to 25 keV).
High Compton scattering cross-section to enhance back scattering.
Low photoelectric cross-section, but high scattering cross-section.
Availability in thin free-standing foil form with sufficient mechanical rigidity.
High density uniformity and small surface roughness so it will not become a
phase object and relatively free of absorption edges.
Preferably in amorphous state
Position/pointing measurement
Use array detectors (at least 4 in quadrature configuration).
Normal incidence preferred by resolution considerations
Use large separation between monitors for high angular resolution.
June 16-17 2008
LUSI Diagnostics & Common Optics
15
Yiping Feng
YFENG@SLAC.Stanford.edu
Conceptual Design
- Back Scattering Geometry
Quad-Detector
R2
q1
q2
R1
Target
L
•Monolithic design
•Expensive fabrication
•High collection efficiency
June 16-17 2008
LUSI Diagnostics & Common Optics
•Four-diode design
•Readily available/easy assembly
•Less collection efficiency/difficult to model
16
Yiping Feng
YFENG@SLAC.Stanford.edu
X-ray energy
Peak Intensity
Material vs. Energy & Peak Intensity
actual
intensity
operating
energy
Effective
atomic number Z
Effective
atomic number Z
• the smaller the Z, the safer
• the higher the energy, the safer
• the FEH is safer if no additional focusing
June 16-17 2008
LUSI Diagnostics & Common Optics
• the smaller the Z, the safer
• the lower the peak intensity, the safer
• the FEH is safer if no additional focusing
17
Yiping Feng
YFENG@SLAC.Stanford.edu
Option 1: Beryllium
Peak Dose at 8.265 keV for Beryllium
at normal incidence
FEH
NEH
1.E+02
1.E+02
1.E+01
1.E+01
Peak Fluence (eV/atom)
Peak Fluence (eV/atom)
NEH
Peak Dose at 2.000 keV for Beryllium
at normal incidence
1.E+00
1.E-01
1.E-02
Dose
1.E-03
NEH-3
1.E+00
1.E-01
1.E-02
Dose
1.E-03
FEH-4
1.E-04
1.E-04
1.E-05
1.E+00
1.E+02
1.E-05
1.E+01
1.E+03
Beam Waist (mm)
L
pe
n

h
I
0
T


 0 
 2 


2
FEH-5
Fluence for melt
1.E+01
F
NEH-3
FEH-4
FEH-5
Fluence for Melt

FEH
L
pe
n
E
1.E+02
1.E+03
1.E+04
Beam Waist (mm)
pulse


 0 
 2 


June 16-17 2008
LUSI Diagnostics & Common Optics
2
L
pe
n
E

pulse

 0 
 2 


2
18
pe
• Assuming 2 mJ/pulse for all energies
• Gaussian beam, 0 is waist at z
• Source point at 1 Rayleigh length upstream
of down stream end of undulator
Yiping Feng
YFENG@SLAC.Stanford.edu
Scattering Processes
Scattering signals
Compton scattering
Higher cross-section in back scattering geometry
The lower the Z, the higher the cross-section
Thomson scattering
Mostly in the forward direction
Proportional to Z2
y
x
K-fluorescence
Negligible at low Z
ê
ê||
┴
ê0
Photoelectrons
k0
Primary electrons
Auger electrons
June 16-17 2008
LUSI Diagnostics & Common Optics
k
z
q
19
f
Yiping Feng
YFENG@SLAC.Stanford.edu
Calculated Performance
1st order
1st order w/ mono
@ 2%
3rd order
@ 1%
3rd order w/ mono
@ 2%
FEL
1.50E+12
3.00E+10
1.50E+10
3.00E+08
spontaneous only
@ 10-4
1.50E+08
3.00E+06
1.50E+06
3.00E+04
1st order @ 2.000keV,
3rd order @ 6.000 keV
1st order @ 8.265 keV,
3rd order @ 24.797 keV
Parameters
Incident
(photons/pulse)
297
Beryllium foil thickness (mm)
3.27E+09
6.55E+07
1.38E+08
2.76E+06
0.002%
0.012%
0.009%
0.060%
3.27E+05
6.55E+03
1.38E+04
2.76E+02
0.17%
1.24%
0.85%
6.02%
FEL
6.20E+12
1.24E+11
6.20E+10
1.24E+09
spontaneous only
@ 10-4
6.20E+08
1.24E+07
6.20E+06
1.24E+05
Scattered
(photons/pulse)
w/ FEL
Scattered
(photons/pulse)
w/ Spontaneous
Incident
(photons/pulse)
1622
25
Beryllium foil thickness (mm)
Scattered
(photons/pulse)
w/ FEL
Scattered
(photons/pulse)
w/ Spontaneous
115
1.72E+09
3.45E+07
5.78E+07
1.16E+06
0.0024%
0.0170%
0.0132%
0.0930%
1.72E+05
1.72E+05
1.72E+05
1.72E+05
0.24%
1.70%
1.32%
9.30%
•At 25 mm for 2keV, the transmission is only 71%
June 16-17 2008
LUSI Diagnostics & Common Optics
20
Yiping Feng
YFENG@SLAC.Stanford.edu
Risks/Mitigations
Beryllium is all most ideal, but
Glitches from diffractions (power rings, Bragg/Laue)
Affect intensity/position measurement accuracies
Use amorphous materials
Si3N4, but damage issues below 4 keV
Smaller signal
Capability loss
Use diamond single crystal
Expensive
Sub-mm at 2 keV for 95% transmission
Somewhat smaller signal
June 16-17 2008
LUSI Diagnostics & Common Optics
21
Yiping Feng
YFENG@SLAC.Stanford.edu
Foil Thickness
Com pton Scattering Cross-Section
Be, B4C, Diam ond, Si, Si3N4, YAG
X-ray Attenuation Length @ 5%
Be, B4C, Diamond, Si, Si3N4
1.00E-03
10000
8.265 keV
Compton Scattering Cross-Section (A.U.)
Attenuation Length ( m m)
8.265 keV
Be
1000
100
10
1
Be
B4C
0.1
B4C
1.00E-04
C
YAG
1.00E-05
Si3N4
Si
Diamond
Si
Si3N4
0.01
1.00E-06
0
5000
10000
15000
20000
25000
0
2
4
Energy (eV)
LUSI Diagnostics & Common Optics
8
10
12
14
16
Effective Atom ic Num ber
I
June 16-17 2008
6
22
Compton
0
q  90  I inc
Z  L5%
Yiping Feng
YFENG@SLAC.Stanford.edu
Alternative Concepts
Commercial fluorescence monitor*
using similar design provides equal resolution
but not viable due to damage considerations
Must use material w/ Z > 20
CVD diamond BPM**
Good from damage point of view
Based on photoconduction
Large band gap, somewhat smaller signal
design more complex in fabrication
Electrodes on diamond, must be in direct path of FEL
Prone to damage
Small working range ~ order of beam size
Expensive
*R.W.Alkire et al J. Synch. Rad. (2000), 7 (61-68);
Oxford-Danfysik, QBMP
June 16-17 2008
LUSI Diagnostics & Common Optics
**P. Bergonzo, et al J. Synch. Rad. (2006), 13 (151-158)
23
Yiping Feng
YFENG@SLAC.Stanford.edu
Wavefront Characterization
plane wave assumed
Characterization of wavefront of a focused X-ray FEL is a
challenge
Critical to CXI experiments if atomic resolution is ultimately to be
achieved
Wavefront distortion must be backed out in phase retrieval algorithm
Common scanning or direct imaging techniques made at focus not
viable due to FEL high peak power
June 16-17 2008
LUSI Diagnostics & Common Optics
24
Yiping Feng
YFENG@SLAC.Stanford.edu
Hartmann Wavefront Sensor
Hartmann wavefront sensor technique was considered viable
Measurement made far from focus
Focal point determination calculated from radius of curvature
measurement
Wavefront distortion obtained by back-propagation of diffracted wavefront determined at mask plane
Commercial Hartmann wavefront for long wavelength
Successful in optical applications (adaptive optics, etc.)
For X-ray applications
X-EUV sensor for energy up to 4 keV
Prototype for hard X-rays up to 10 keV
Image acquisition < 120 Hz
June 16-17 2008
LUSI Diagnostics & Common Optics
25
Yiping Feng
YFENG@SLAC.Stanford.edu
Hartmann Wavefront Sensor (con’t)
Challenges
Working at > 8 keV
Tighter technical specs at shorter wavelength
Holes on mask must not work as waveguides
Could use grids instead
Mask materials must withstand FEL peak fluence
120 Hz operation
Algorithm
Image obtained from
Imagine Optics, Ltd
modal/zonal reconstruction algorithms
June 16-17 2008
LUSI Diagnostics & Common Optics
26
Yiping Feng
YFENG@SLAC.Stanford.edu
Diffractive Wavefront Reconstruction
The oversampled diffraction pattern of the focus is measured.
The focal spot is iteratively reconstructed using phase retrieval methods
by propagating the wave from the optic to the focus and then to the
detector plane.
The constraints are applied at the optic and detector planes.
Focal Plane
Focusing
Optic
FEL Beam
w0
f
2D Detector
Attenuator
Detector
W
L
H. M. Quiney et al. Nature Physics 2, 101 - 104 (2006)
June 16-17 2008
LUSI Diagnostics & Common Optics
27
Yiping Feng
YFENG@SLAC.Stanford.edu
Wavefront Monitor
Physics Requirements
Primary Purpose
Characterizing 2D intensity profile of a focused FEL beam
Capturing 2D beam profile far away from focal point
Large FOV of 40x40 mm2, 165 mm
Medium FOV of 8x8 mm2, 33 mm
Small FOV of 1.2x1.2 mm2 , 5 mm
Intensity levels, 1024 or 10 bits, w/ goal of 4096 or 12 bits
Per-pulse operation
Attenuation whenever appropriate in high fluence
Secondary Purpose
Measurement of complimentary low-Q data for diffraction
experiments
Large dynamic range desired
June 16-17 2008
LUSI Diagnostics & Common Optics
28
Yiping Feng
YFENG@SLAC.Stanford.edu
Wavefront Monitor
45º
mirror
YAG:Ce
screen
June 16-17 2008
LUSI Diagnostics & Common Optics
Zoom
lens
working distance
120 Hz CCD
camera
29
Yiping Feng
YFENG@SLAC.Stanford.edu
Imaging System
45º geometry
Optical
CCD
Camera w/
zoom lens
x
q
f
Working
distance
x = tsin(f)/cos(q)
X-ray
pulses
Scintillator
Virtual image
June 16-17 2008
LUSI Diagnostics & Common Optics
30
Yiping Feng
YFENG@SLAC.Stanford.edu
Key Components
YAG:Ce scintillation screen
Summary characteristics
High radiation hardness
YAG:Ce
High melting temperature
High thermal conductivity
In NEH & FEH, capable of
sustain full unfocused X-ray FEL
beam at normal incidence
Fast scintillator
moderate optical fluorescence
yield
Peak response (550 nm)
matches optical CCD QE curve
High spatial resolution
Capable of normal incidence
Clear, not diffuse as phosphor
Chemical formula
Y3Al5O12:Ce
Ce doping
0.1 mol%
Melting point
1970 C˚
Fluorescence spectral peak
550 nm
Light yield (Ce doping
dependent)
80 /10 keV X-ray
Decay constant
70 ns
After glow (at 6 ms)
< 0.005 %
X-ray attenuation length
5 - 35 mm @ 4 - 8.3 keV
Size (diameter/side)
10 - 50 mm
Thickness
50 - 100 mm
Vacuum compatible
June 16-17 2008
LUSI Diagnostics & Common Optics
31
Yiping Feng
YFENG@SLAC.Stanford.edu
YAG:Ce Selection
Size
The bigger, the thicker
25x25 mm2 , 75 mm
12x12mm2 , 50 mm
YAG:Ce
crystal
Thickness
Affect resolution achievable
< Depth of field
Requiring telecentric lens if too
thick
Thickness limited for free
standing crystals
YAG
crystal
>= 50 mm
Thinner sample will be based on
epitaxial YAG:Ce on YAG
substrate
5 mm
YAG:Ce
epitaxial
layer
~ 5 mm possible
But YAG glows as well
June 16-17 2008
LUSI Diagnostics & Common Optics
32
Yiping Feng
YFENG@SLAC.Stanford.edu
YAG:Ce Resolution
Parallaxial distortion
Diffusive broadening
r
t
t
Z1
f
diff
para
diff = at
para = -Mtr/(z1-f)
June 16-17 2008
LUSI Diagnostics & Common Optics
33
Yiping Feng
YFENG@SLAC.Stanford.edu
Transmission & QE
YAG Quantum Efficiency
= 1-Transmission
= 70% @ 10 keV @ 75 mm
June 16-17 2008
LUSI Diagnostics & Common Optics
34
Yiping Feng
YFENG@SLAC.Stanford.edu
Damage Consideration
Peak Fluence at 2.000 keV for YAG:Ce
at normal incidence
Peak Fluence at 8.265 keV for YAG:Ce
at normal incidence
10000
1000
Peak Dose
Peak Dose
NEH-3 Dose
1000
NEH-3 Dose
100
FEH-4 Dose
FEH-4 Dose
FEH-5 Dose
Melt Dose
10
Peak Fluence (eV/atom)
100
Peak Fluence (eV/atom)
FEH-5 Dose
Melt Dose
10
1
0.1
1
0.1
0.01
0.01
0.001
0.001
1
10
100
0.0001
1000
10
Beam Waist (mm )
100
1000
10000
Beam Waist (mm )
•Attenuation needed for low energies in NEH-3
June 16-17 2008
LUSI Diagnostics & Common Optics
35
Yiping Feng
YFENG@SLAC.Stanford.edu
Zoom Lens System
Motorized
Zoom Lens
Zoom Lens
Navitar Large Zoom lens
Modular design
Attachment+zoom+adapter
Flexible to achieve diverse
requirements
adapter
Large range of FOV
12x
Maintaining focus while zooming
Fixed working distance
165 mm
Sufficient numerical aperture for
good resolution
zoom
NA ~ 0.05 – 0.2
Readily Motorized
Focus or zoom or focus&zoom
attachment
June 16-17 2008
LUSI Diagnostics & Common Optics
36
Yiping Feng
YFENG@SLAC.Stanford.edu
Digital Camera
Imaging
½ inch optical CCD - Pulnix
TM-6710CL
Optimal response at 600 nm
w/ QE ~ 30%
648x484 pixels
Progressive scan @ 120 Hz
9.9 mm square pixels
8 bits
Cameralink
Frame grabber supported on
Linux OS
June 16-17 2008
LUSI Diagnostics & Common Optics
37
Yiping Feng
YFENG@SLAC.Stanford.edu
Expected Performance
Beam size in
vertical (FWHM/
waist in mm)
2672/2270
(0.1 mm focus)
624/530
(1.0 mm focus)
63/54
(10 mm focus &
high resolution
configuration)
Field of View
(mmxmm)/
[resolution (mm)]
Image size on ½
CCD sensor
(# of pixels)
# of e- per pixel
@ 1.5x1012
photons @ 8 keV
& 50 mm YAG
Attenuation
needed to match
full well (20k e-)
Note
40x40
[165]
27x50
2.4x105
12
FEL only
10x10
[41.3]
110x198
1.1x105
6
FEL only
8x8
[33]
32x34
1.7x106
84
2x2
[8.3]
128x135
2.2x105
11
1.2x1.2
[5]
22x22
5.0x106
251
0.8x0.8
[3.3]
33x33
2.8x106
139
June 16-17 2008
LUSI Diagnostics & Common Optics
38
FEL only
Yiping Feng
YFENG@SLAC.Stanford.edu
Expected Performance
Wavefront measurement in FEH-5 – 0.1 mm KB (in Q space)
40 mm FOV, waist = 27x50 pixels
(0.1 mm focusing @ FEH-5 @ 5 m from focus)
10 mm FOV, waist = 110x198 pixels
(0.1 mm focusing @ FEH-5 @ 5 m from focus)
•188 Å resolution, 4.5 mm FOV, 242 resolving power
June 16-17 2008
LUSI Diagnostics & Common Optics
•Revealing features outside of focal region
39
Yiping Feng
YFENG@SLAC.Stanford.edu
Expected Performance
Wavefront measurement in FEH-5 – 1.0 mm KB (in Q space)
8 mm FOV, waist = 32x34 pixels
(1.0 mm focusing @ FEH-5 @ 11 m from focus)
2 mm FOV, waist = 128x135 pixels
(1.0 mm focusing @ FEH-5 @ 11 m from focus)
•2063 Å resolution, 50 mm FOV, 242 resolving power
June 16-17 2008
LUSI Diagnostics & Common Optics
•Revealing features outside of focal region
40
Yiping Feng
YFENG@SLAC.Stanford.edu
Expected Performance
Wavefront measurement in FEH-5 – 10 mm Be Lens (in Q space)
800 mm FOV, waist = 33x33 pixels
(10 mm focusing @ FEH-5 @ 11 m from focus)
1.2 mm FOV, waist = 22x22 pixels
(10 mm focusing @ FEH-5 @ 11 m from focus)
•1.38 mm resolution, 333 mm FOV, 242 resolving power
June 16-17 2008
LUSI Diagnostics & Common Optics
41
•Revealing features outside of focal region
Yiping Feng
YFENG@SLAC.Stanford.edu
Slit System
Slit systems requirements
Variable horizontal and vertical gap from -.1 μm – 10 mm
Can withstand full LCLS flux – unfocused
Minimize background scatter from blades
Name
Transmission
at 25 keV
Transmission
in 2-8.3 keV
range
Positioning
Accuracy &
Repeat. (µm)
Radiation
Protection
Precise
Primary
<10-8
<10-11
0.5
White beam
Precise
Guard
N/A
<10-9
0.5
White beam
Precise
Monochromatic
<10-8
<10-9
0.5
Monochromatic
beam
Coarse
Primary
<10-8
<10-11
5
Full
white beam
Coarse
Guard
N/A
<10-9
5
White beam
Coarse
Monochromatic
<10-8
<10-9
5
Monochromatic
beam
June 16-17 2008
LUSI Diagnostics & Common Optics
42
Yiping Feng
YFENG@SLAC.Stanford.edu
Slits System Design
D. Le Bolloc’h et al., J. Synchrotron Rad., 9, 258-265 (2002).
Offset in Z to fully close
But asymmetry in near field
Pink beam
Low-Z High-Z
Mono beam
D=3 mm
Slit-round
blades
June 16-17 2008
LUSI Diagnostics & Common Optics
High-Z
43
Yiping Feng
YFENG@SLAC.Stanford.edu
Wavefront Simulation
for XPP by S. Boutet
Distance
depends
on photon
energy
105.8 m
32.4 m
Undulator Exit
0.597 m
2.613 m
1.487 m
June 16-17 2008
LUSI Diagnostics & Common Optics
44
Yiping Feng
YFENG@SLAC.Stanford.edu
2 keV Through 20 micron Ta 1st Slit
Through 3 Lenses, Through 30 micron Ta 2nd Slit
June 16-17 2008
LUSI Diagnostics & Common Optics
45
Yiping Feng
YFENG@SLAC.Stanford.edu
Material Selection
Only materials that survive the beam at 2 keV
B, Be, BN, Diamond and Li
No good options
Only materials that survive the beam at 4 keV
Al, B4C, B, Be, BN, Diamond, Li, Mg, Si3N4, YAG, ZnO
Si3N4 looks good
Double blades only useful if placed very close to the
sample (<< 1 m)
June 16-17 2008
LUSI Diagnostics & Common Optics
46
Yiping Feng
YFENG@SLAC.Stanford.edu
Proposed Solutions
Use Si3N4 for Guard slits
Always safe in FEH
Only above 4 keV in NEH without attenuation
Use Ta for Mono slits
Since Si crystals for the monochromators will not survive the
beam in the NEH, we will have to use diamond
Ta is safe above 3keV for mono beam with Diamond (220)
Use Si3N4 as 1st blade for Primary slits
Ta for 2nd blade
Requires a 4±1 micron offset of the 2nd blade
June 16-17 2008
LUSI Diagnostics & Common Optics
47
Yiping Feng
YFENG@SLAC.Stanford.edu
Summary
Diagnostics
Focused on key FEL attributes that impact the success of LCLS
scientific programs
Characterizing inherent LCLS fluctuations
Common mechanical interface allows flexibilities
X-ray common optics
Enabling users to manipulate/shape FEL beam to maximize
scientific output
Designed to preserve FEL characteristics
Transverse coherence
Common design & implementation
June 16-17 2008
LUSI Diagnostics & Common Optics
48
Yiping Feng
YFENG@SLAC.Stanford.edu
Contributors
Physics
Engineering
Instrument
System
Jerry Hastings
David Fritz
Aymeric Robert
Sébastien Boutet
Marc Messerschmidt
Niels van Bakel
John Bozek
Nadine Kurita
Eliazar Ortiz
Paul Montanez
J. Brian Langton
Donald Arnett
Jean-Charles Castagna
Jim Defever
Jim Delor
Rick Jackson
Nicolas Reeck
Accelerator, XTOD, and FEL
Physics
John Arthur
Paul Emma
Zhirong Huang
Peter Steffen
XTOD team
June 16-17 2008
LUSI Diagnostics & Common Optics
Controls/Data Systems
Gunther Haller
Dieter Freytag
Steffen Luitz
David Nelson
Amedeo Perazzo
Raymond Rodriguez
49
Yiping Feng
YFENG@SLAC.Stanford.edu
End of Presentation
June 16-17 2008
LUSI Diagnostics & Common Optics
50
Yiping Feng
YFENG@SLAC.Stanford.edu
Diagnostics/Common Optics
on XPP, CXI, XCS Instruments
XPP
June 16-17 2008
LUSI Diagnostics & Common Optics
51
Yiping Feng
YFENG@SLAC.Stanford.edu
CXI
June 16-17 2008
LUSI Diagnostics & Common Optics
52
Yiping Feng
YFENG@SLAC.Stanford.edu
XCS
June 16-17 2008
LUSI Diagnostics & Common Optics
53
Yiping Feng
YFENG@SLAC.Stanford.edu
XCS
June 16-17 2008
LUSI Diagnostics & Common Optics
54
Yiping Feng
YFENG@SLAC.Stanford.edu
WBS Structure (Level 3-4)
1.5 Diagnostics & Common Optics
1.5.1 Diagnostics & Common Optics Integration & Design
1.5.2 Diagnostics
1.5.2.1 Pop-in Profile/Wavefront Monitor
1.5.2.2 Pop-in Intensity Monitor
1.5.2.3 Intensity-Position Monitor
1.5.2.4 Wavefront Sensor (removed from scope)
1.5.2.5 EO Sampling Monitor (LCLS AIP)
1.5.3 Common Optics
1.5.3.1 Monochromator (BCR in progress, will be in XCS scope)
1.5.3.2 X-ray Focusing Lens
1.5.3.3 Slit System
1.5.3.4 Attenuators-Filters
1.5.3.5 Pulse Picker
1.5.3.6 Harmonic Rejection Mirrors
June 16-17 2008
LUSI Diagnostics & Common Optics
55
Yiping Feng
YFENG@SLAC.Stanford.edu
Compton Scattering
Differential cross-section

 d 


d
W


Inelastic
8.266 keV

 d 


d
W


S q, Z 
337.5
Inelastic Scattering
(d/dW )KNS(q ,Z)
0
4.0
q 0
q  45
q  90
q  135
q  180
22.5
3.5
Klein Nishina
3.0
315.0
45.0
2.5
 d 


d
W


||
 d 

d
W


2.0
||
S q, Z 

Inelastic
292.5
1.0
Klein Nishina
0.5
270.0
 d 


 dW 
Total

 d 

 dW 

Inelastic
67.5
1.5
 d 

 dW 
0.0
90.0
||

Inelastic
247.5
Inelastic
112.5

 d 


 dW 
2

1 2  0 
 re 2  
 2  dW
4    0

0 
Klein Nishina
225.0
135.0
202.5
157.5
180.0
 d 


d
W


||

Klein Nishina
2
1 2  0 
2
2
 2  4 1  sin q cos f
 
r
2
e
4    0
0 
June 16-17 2008
LUSI Diagnostics & Common Optics

dW

56
Yiping Feng
YFENG@SLAC.Stanford.edu
Thomson Scattering
Differential cross-section
8.266 keV

 d 


 dW 
337.5
0
Elastic Scattering
(d/dW )Thomson[F(q ,Z)] 2
0
16.0
q 0
q  45
q  90
q  135
q  180
22.5
14.0
12.0
315.0
Elastic
45.0
10.0
 d 


d
W


8.0
 d 

d
W


||
||
F q, Z 

Elastic
292.5
2
4.0
T hom son
2.0
270.0
 d 


 dW 
Total
 d 

 dW 
67.5
6.0
0.0
90.0
||

Elastic
247.5
Elastic
112.5

 d 


 dW 
225.0
0
135.0
202.5
T hom son
157.5
180.0
 d 


d
W


||


 r e 1  sin q cos f dW
2
2
2
T hom son
June 16-17 2008
LUSI Diagnostics & Common Optics
57
Yiping Feng
YFENG@SLAC.Stanford.edu
Scattering Intensity
2 keV
Total intensity
total
0.80
 d  f ,q dz

I e L  sin qdq  df 
q
 dW 

q
 d  f ,q  1  
 I  sin qdq  df 

 e L L


q
 dW 

q
 d  f ,q    L for L
 I  sin qdq  df 


for L
 L
q
 dW 

L
0
0
inc

total
2
2
0.60
0
0
1
total
2
2

L
0
inc
0
total
0
2
2
inc
1
0
0
S f (d/dW )dfsin( q )dq
24.797 keV
Total
0.50
0.40
Elastic
0.30
0.20
0
1
Inelastic
0.10
 L0
 L0
0.00
0
15
30
45
8.266 keV
[Inelatic+Elastic] Scattering
0.80
0.80
0.70
0.70
0.60
0.60
0.50
0.40
0.30
60
75
90
105
120
135
150
165
180
150
165
180
Scattering Angle (q )
S f (d/dW )dfsin( q )dq
0
Integration in q
0.70
S f (d/dW )dfsin( q )dq
I
q
t
[Inelatic+Elastic] Scattering
Total
[Inelatic+Elastic] Scattering
0.50
0.40
Total
0.30
0.20
0.20
Inelastic
Inelastic
0.10
0.10
Elastic
Elastic
0.00
0.00
0
15
30
45
60
75
90
105
120
135
150
165
June 16-17 2008
LUSI Diagnostics & Common Optics
180
0
15
30
45
60
75
90
105
120
135
Scattering Angle (q )
Scattering Angle (q )
58
Yiping Feng
YFENG@SLAC.Stanford.edu
K-Fluorescence
Total k-fluorescence intensity
Be K-Fluorescence
Assuming isotropic
L
0

0
I e
inc
q
q
2
q
1

L0  sin qdq  df K dz
4
0
2
2
 I inc  sin qdq  df
0
q
 I inc cosq 1
K

pe K
4
0
1
0

1.0E+09
2

 cosq 

pe K
2
K

2


Compton/Thomson
signal
1.0E+08

L


 1  e L  L0
K

  L
 L0
  pe K  K
0
for L  L0
for L  L0
IK-fluorescence (photon/pulse)
IK  
t

K
 3.23  104
 2
pe K
d


0 0
pe K
dW
d
1.0E+06
25mm foil
1.0E+05
1.0E+04
ln 1  K  1  3.94 ln Z   13.5

1.0E+07
pe K
dW
1.0E+03
for Z  4
8.265 keV
1.0E+02
sin qdqdf
 
 r e2 Z 5 a 4 25 2 me c
h
2 72
1
10
100
Photon Energy (keV)
2
2
sin q cos f
June 16-17 2008
LUSI Diagnostics & Common Optics
• Be Ka ~ 109 eV
• Attenuation at 109 eV ~ 1 mm, making fluorescence even lower
• Negligible compared to scattering signals
59
Yiping Feng
YFENG@SLAC.Stanford.edu
Photoelectrons
Primary photoelectrons
dW
I
K

e

L
0
 
 r e2 Z 5 a 4 25 2 me c
h
0
I e
inc
q
2

q
Be Primary Photoelectrons
2
2
sin q cos f
1.0E+10
 d pe K 
q , f  dz
L0  sin qdq  df 

d
W
0


q1
t
1.0E+09
2
2
2
 

 

 
0
 I inc  sin qdq  df r e2 Z 5 a 4 25 2 me c
h
0
q


1
2 72
1.0E+08



2
2
sin q cos f  1  e L0  L0


2
q1
0
1
 I inc  cos q  cos3q r e2 Z 5 a 4 25 2 me c
3
h
q2
2
q1
0
1
 I inc  cos q  cos3q r e2 Z 5 a 4 25 2 me c
3
h
q2
72
72
L

 L0
  L
for L  L0
for L  L0
  escape
Npe (#/pulse)
d  pe K
2 72
1.0E+07
1.0E+06
1.0E+05
1.0E+04
1.0E+03
1
10
100
Photon Energy (keV)
June 16-17 2008
LUSI Diagnostics & Common Optics
60
Yiping Feng
YFENG@SLAC.Stanford.edu
Auger Electrons
Secondary electrons
  1
   
A
pe K

L
0
A

q
t
pe K
1 
K

2
2
1.0E+09
I e L  sin qdq  df 4 dz
0
0
inc
q
q
2
q
1
2

pe K
0
 I inc cos q 1  cos q 2 
0
 I inc cos q 1  cos q 2 
0
1.0E+08
0
1
 I inc  sin qdq  df
0
A


1   
K
4
pe K


L
0
1   
K
2
pe K

 1  e L  L0


1   
K
2

 L0
  L
for L  L0
for L  L0
NAuger (#/pulse)
A
1.0E+10
K
A
I
Be Auger Electrons
1.0E+07
1.0E+06
1.0E+05
  escape
1.0E+04
1.0E+03
1
10
100
Photon Energy (keV)
June 16-17 2008
LUSI Diagnostics & Common Optics
61
Yiping Feng
YFENG@SLAC.Stanford.edu
Pop-In Profile Monitor
(WBS 1.5.2.1)
Translation
stage
45º
mirror
75 mm
YAG:Ce
screen
June 16-17 2008
LUSI Diagnostics & Common Optics
12x Zoom
lens
working distance ~ 165 mm
120 Hz CCD
camera
62
Yiping Feng
YFENG@SLAC.Stanford.edu
Pop-In Intensity Monitor (WBS 1.5.2.2)
Pneumatic
Drive
Si Diode Used at SPPS
Si Diode
June 16-17 2008
LUSI Diagnostics & Common Optics
Analog/Digital Circuitry for readout
63
Yiping Feng
YFENG@SLAC.Stanford.edu
Offset Monochromator System (WBS 1.5.3.1)
LUSI Offset Monochromator Purpose
Narrow X-ray spectrum
Mitigates spectral fluctuations of the LCLS
Increase longitudinal coherence length
Multiplex incident beam
Monochromatic beam line (750 mm offset)
Diagnostics beamline
June 16-17 2008
LUSI Diagnostics & Common Optics
64
Yiping Feng
YFENG@SLAC.Stanford.edu
X-ray Focusing Lens System (WBS 1.5.3.2)
B. Lengeler et al., J. Synchrotron Rad., 6,
1153-1167 (1999).
LUSI X-ray Focusing Lens Purpose
Increase the X-ray fluence at the sample
Simpler than KB systems, no diff. orders as in Fresnel lens
Chromatic, some attenuation at low energies
LUSI X-ray Focusing Lens Requirements
Produce a variable spot size between 2 – 10 micron and 40 – 60 microns
(out of focus)
Preserve coherence
Withstand full flux
June 16-17 2008
LUSI Diagnostics & Common Optics
65
Yiping Feng
YFENG@SLAC.Stanford.edu
Be Refractive Lens Design
Be lens stack
Be Lens
stack
Be Lens
stack holder
System built by B. Lengeler
RWTH AACHEN University
June 16-17 2008
LUSI Diagnostics & Common Optics
66
Yiping Feng
YFENG@SLAC.Stanford.edu
Attenuator System (WBS 1.5.3.4)
LUSI Attenuator Purpose
Reduce incident X-ray flux
Sample damage
Detector saturation
Diagnostic saturation
Alignment of optics and
diagnostics
LUSI Attenuator Requirements
Preserve coherence
Spatial/temporal/spectral jitters
would reduce coherence
Withstand unfocused flux
108 attenuation at 8.3 keV
105 attenuation at 24.9 keV
3 steps per decade
June 16-17 2008
LUSI Diagnostics & Common Optics
67
Yiping Feng
YFENG@SLAC.Stanford.edu
Pulse Picker (WBS 1.5.3.5)
Pulse Picker Requirements
Millisecond shutter speed
Allows any pattern of pulses to be selected.
Withstand full LCLS flux - unfocused
Requires 1 mm B4C to protect the steel blade
Pulse Picker Purpose
Reduce LCLS repetition rate
Important if longer sample recover time is needed
Damage experiments - sample needs to be translated
FEL beam
Steel
blade
pivot
magnet
http://www.azsol.ch/
June 16-17 2008
LUSI Diagnostics & Common Optics
68
Yiping Feng
YFENG@SLAC.Stanford.edu
Pulse Picker Design
B4C coating on blade
to reduce damage
http://www.azsol.ch/
June 16-17 2008
LUSI Diagnostics & Common Optics
69
Yiping Feng
YFENG@SLAC.Stanford.edu
Harmonic Rejection Mirror System (WBS 1.5.3.6)
A
B
LUSI Harmonic Rejection Mirror Purpose
Isolate fundamental radiation from 3rd harmonic
Angle beam downward (liquid interface experiments)
LUSI Harmonic Rejection Mirror Requirements
> 80% system throughput
Preserve coherence
Withstand full flux
> 10 5 contrast (10 7 overall)
June 16-17 2008
LUSI Diagnostics & Common Optics
70
C
Yiping Feng
YFENG@SLAC.Stanford.edu
HRMS Design
Harmonic Rejection Mirrors
3.5 mrad incidence
Si single crystal
300 mm long
No pre-figure
No bender
Specs
250 nrad slope error
1 mm to 300 mm
0.5 nm surface roughness
20 nm to 1 mm
June 16-17 2008
LUSI Diagnostics & Common Optics
71
Yiping Feng
YFENG@SLAC.Stanford.edu
Wavefront Sensor Design
Direct Sensing
1 mm – 5 mm spot size
Mask
X-ray Mpixel sensor
Limited to 20 mm
spacing
Attenuator
X-ray Mpixel sensor
Wavefront standard
algorithms
Optically coupled
Visible Mpixel sensor
Zoom lens
mask
YAG:Ce
attenuator
June 16-17 2008
LUSI Diagnostics & Common Optics
72
Indirect sensing
0.1 – 5 mm spot size
Mask not used for 0.1
mm
Attenuator
YAG:Ce scintillator
Zoom lens
Optical Mpixel sensor
Use diffractive imaging
iterative algorithm for
maskless operation
Yiping Feng
YFENG@SLAC.Stanford.edu