X Ray Diagnostics Overview
FAC X-TOD Breakout
October 12, 2006
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
LCLS Layout at SLAC
Linac-toUndulator
(227m
e- beam)
Undulator
Hall (175m
e- and g
beam)
eBeam
Dump
(40M eand g
beam)
Near
Expt.
Hall
Far
Expt.
Hall
Linac ebeam
(FEE) Front
End
Enclosure
(29m g
beam)
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
X-ray Vacuum
Transport
(250m g beam)
Richard M. Bionta
bionta1@llnl.gov
Raw LCLS Beam Contains FEL and
Spontaneous Halo
3 mJ High
energy core
Eg > 400 keV
2-3 mJ
(0.3 W)
FEL
Pulse
duration
< 250 fs
20 mJ (2.4 W)
Spontaneous
20 mm
Spontaneous halo has rich spectral and spatial structure:
0 < E < 10 keV
7.6 < E < 9.0 keV
10 < E < 20 keV
20 < E < 27 keV
At midpoint of FEE, FEL tuned to 8261 eV Fundamental, 0.79 nC
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Prioritized List of Desired FEL Measurements
(to be measured after finding the FEL)
u
l1
Dl/l1
x, y
x , y 
f(x,y)
s u,s l 1
s x ,s y ,s x ,s y 
t
October 12, 2006
X-TOD Diagnostics
Total energy / pulse
Photon wavelength
Photon wavelength spread
Pulse centroid
Beam direction
Spatial distribution
Temporal variation in beam
parameters
Pulse duration
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Prioritized List of Desired Spontaneous
Measurements
l1i/l1j
Relative 1st harmonic wavelength
of undulator i and j
f(x,y,l1)
Spatial distribution around l1
1st harmonic Photon wavelength
1st harmonic wavelength spread
Beam direction
Total energy / pulse
Temporal variation in beam
parameters
l1
Dl/l1
x , y 
u
s u,s l 1
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Codes indicate that damage occurs above melt so
choose materials whose doses are a fraction of melt
Maximum dose along the beam line for different materials
(under normal illumination assuming fully saturated FEL a la M. Xie)
Dose (eV/atom)
(maximum over 827-8267eV)
Shown is the maximum dose (over Ephoton=827 to 8267eV)
edump
FEE
SiC melted
Si melted
B4C melted
Be melted
Si - 5/9 melt
SiC - 1/9 melt
B4C - 1/12 melt
Be - 1/50 melt
meters from end of undulator
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Candidate detectors pros and cons
Element
Technology
Attenuator
Problems
Signal reduced, background remains the same
Differential pumped N2 gas
Space charge, aperture size
Low Z solids
Damage, scattering
CCD
Deep depletion
Damage, Effect of High E spontaneous, dynamic range
CZT imagers
Dental X-ray
Damage, Effect of High E spontaneous, dynamic range,
resolution
Phosphor coated imagers
Phase plate coupled to CCD
Damage, Effect of High E spontaneous, dynamic range,
resolution, phosphor saturation
Optical coupled Scintillator
screen
Camera not in beam
Damage, dynamic range, saturation
Indirect Imager
Multilayer mirror reflects
fraction of beam into camera
Damage, Calibration depends on alignment
Photodiodes, PC diamond
Damage, Effect of High E spontaneous, spatial resolution
Florescence
Be doped with high z
Damage, contamination and background, signal level
Photoelectric
Be grid with MCP
Calibration, geometry, Effect of High E spontaneous
Thermal
Energy to heat
Damage, sensitivity
Ion chamber
Count ions
sensitivity
N2 Photoluminescence
Count photons
Non-linear space charge, calibration
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
“Direct Imager” x-ray cameras
X-ray sensitive CCD
or photodiode array
X-Ray Beam
www.ajat.fi
Optical Fiber
Scintillator
X-Ray Beam
Visible Imager
X-ray scintilator with
fiber coupled imager
X-Ray Beam
Scintillator
Lens
Visible Imager
X-ray scintilator with
lense coupled imager
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
YAG:Ce Light Output
Short FEL pulse reveals scintillator
saturation
FEL energy
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Candidate detectors pros and cons
Element
Technology
Attenuator
Problems
Signal reduced, background remains the same
Differential pumped N2 gas
Space charge, aperture size
Low Z solids
Damage, scattering
CCD
Deep depletion
Damage, Effect of High E spontaneous, dynamic range
CZT imagers
Dental X-ray
Damage, Effect of High E spontaneous, dynamic range,
resolution
Phosphor coated imagers
Phase plate coupled to CCD
Damage, Effect of High E spontaneous, dynamic range,
resolution, phosphor saturation
Optical coupled Scintillator
screen
Camera not in beam
Damage, dynamic range, scintillator saturation
Indirect Imager
Multilayer mirror reflects
fraction of beam into camera
Damage, Calibration depends on alignment
Photodiodes, PC diamond
Damage, Effect of High E spontaneous, spatial resolution
Florescence
Be doped with high z
Damage, contamination and background, signal level
Photoelectric
Be grid with MCP
Calibration, geometry, Effect of High E spontaneous
Thermal
Energy to heat
Damage, sensitivity
Ion chamber
Count ions
sensitivity
N2 Photoluminescence
Count photons
Non-linear space charge, calibration
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Diagnostics Occupy Upstream End of the
Front End Enclosure (FEE)
Slit
Spectrometer
Package
Solid
Attenuators
Collimator 1
Total Energy
Fixed
Mask
Gas
Detector
October 12, 2006
X-TOD Diagnostics
Gas Attenuator
Gas
Detector
Direct Imager
(Scintillator)
UCRL-PRES-xxxxxxx
FEL Offset Mirror System
Richard M. Bionta
bionta1@llnl.gov
FEE Schematic
5 mm
diameter
collimators
Windowless
Gas
Detector
Start of
Experimental
Hutches
K Spectrometer Direct Imager
Solid
Attenuator
e-
High-Energy
Slit
Gas
Attenuator
Muon
Shield
October 12, 2006
X-TOD Diagnostics
NFOV
Grating
Total
Energy
Thermal
Detector
WFOV
FEL Offset
mirror
system
Windowless
Gas
Detector
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Slit and Fixed Mask Define Maximum Beam
Spatial Extent
Slit
Fixed Mask
Status:
PRD done
SCR done
PDR done
ESD in signature
FDR in preparation
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Gas Detector / Attenuator Conceptual
Configuration
N boil-off
2
(surface)
Gas detector
Flow restrictor
4.5 meter long,
Differential
high pressure N2 pumping sections
section
separated by 3
mm apertures
3 mm diameter
Solid
holes in Be disks attenuators
N2 Gas inlet
allow 880 mm
(FWHM), 827 eV
Status Attenuator:
FEL to pass
PRD done
unobstructed
SCR done
Prototype done
ESD draft
PDR in preparation
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Gas detector
Green line
carries
exhaust to
surface
Richard M. Bionta
bionta1@llnl.gov
Prototype Gas Attenuator runs well at 0-20 Torr
Gas Attenuator prototype pressure control tests
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Gas detectors share differential pumping with the Gas Attenuator
Gas
Attenuator
high
pressure
section
20 Torr
Optical
band pass
filter
Photo
diode
Gas
detector
~1
Torr
~10-3
Torr
~0.1 to 2
Torr N2
~10-3
Torr
~10-6
Torr
~20 cm
inner
diameter
Single shot, non destructive,
measurement of u
2m
Photo tube
non-specular reflective
surface (e.g. treated Al)
Optical ND
filters
LCLS X rays cause N2 molecules to fluoresce in the near UV
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Gas Detector pressure can be adjusted
independently of Gas Attenuator pressure
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Schematic of the gas detector from the ESD
Data Acquisition System
APD
Electronics
Photodiode
Electronics
Avalanche Photo Diode
Coating
Photodiode
Bandpass and ND Filters
Differential Pumping
Section
3 mm apertures
along beam path
Magnet Coils
Magnet
Power
Supply and
Controller
October 12, 2006
X-TOD Diagnostics
Beam / Gas
Interaction
Region
(~0.1 – 2 Torr N2)
Cylindrical Vessel
UCRL-PRES-xxxxxxx
Gas Feed
And
Pressure Control
Richard M. Bionta
bionta1@llnl.gov
Overview of physical processes
Auger e-
photo eH.K. Tseng et al.,
Phys. Rev. A 17,
1061 (1978)
x-rays
r
N2 gas
B
q
• N2 molecules absorb a fraction of the x-rays by K-shell photoionization,
emitting photoelectrons of energy Ex-ray − 0.4 keV
• Ionized nitrogen relaxes by Auger decay, emitting
Auger electrons of energy ~ 0.4 keV
• High-energy electrons deposit their energy into the N2 gas until they are
thermalized or reach the detector walls
• Excited gas relaxes under the emission of near-UV photons
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Photoluminescence of N2
A.N. Brunner
Cornell University (1967).
• N2 has strongest lines in the near UV (between 300 and 430 nm)
• Backgrounds in the near-UV are difficult to estimate:
• Effect of recombination of ions at chamber walls?
• Effect of electrons hitting the chamber walls?
• We use existing experimental data to estimate the near UV signal:
•e.g. measurements made for the Fly’s Eye cosmic ray detector
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
The fluorescence yield per deposited energy
depends only weakly
on the energy of the exciting electron
Fluorescence Yield
per deposited
energy
(a.u.)
1.5 Torr
15 Torr
150 Torr
760 Torr
0.85 MeV
400 eV
(F. Arqueros et al.,
submitted)
8 keV
Electron energy (eV)
Dependence of the photoluminescence yield on the energy of the incoming electron
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Small magnetic field keeps primary
photoelectrons away from walls
Electron trajectories and energy deposition in N2 at 8.3 keV
B = 250 Gauss
without magnetic field
3.0
3.0
2.5
2.5
2.0
2.0
r (cm) 1.5
r (cm) 1.5
1.0
1.0
0.5
0.5
0.0
0
October 12, 2006
X-TOD Diagnostics
5
10
15
z (cm)
20
25
30
UCRL-PRES-xxxxxxx
0.0
0
5
10
15
20
z (cm)
25
Richard M. Bionta
bionta1@llnl.gov
30
Expected near-UV signal at FEL saturation
8.3 keV, 2 Torr,
2.3 mJ, 250 Gauss
0.83 keV, 0.1 Torr,
2.3 mJ, 60 Gauss
Lambertian
Lambertian
reflector
8x10
1.2x10
8
Number
Number
of
of
specular
Photons
4x10
reflector
8
8.0x10
specular
Photons
reflector
reflector
8
absorber
4.0x10
X-TOD Diagnostics
7
absorber
0.0
0
October 12, 2006
7
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Expected near-UV signal for low intensities
0.83 keV, 0.1 Torr,
0.1 mJ, 60 Gauss
3
6.0x10
Lambertian
4.0x10
Lambertian
reflector
4
reflector
3
Number 4.0x10
Number
of
Photons
8.3 keV, 2 Torr,
1 mJ, 250 Gauss
2.0x10
specular
4
reflector
of
specular
Photons
reflector
3
2.0x10
absorber
0.0
absorber
0.0
1 cm recess
x-rays
2.5”
30 cm
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Total Energy (Thermal) Sensor Concept
Thin low-Z high-G substrate for FEL absorption, thermistor deposited on back side.
Temperature rise is proportional to FEL energy, heat flow to cold bath through substrate
• Radiation-hard absorber
• High E halo transmitted
• Sensor protected from beam
• Low T operation for high diffusivity ( Speed) and low heat capacity C ( Sensitivity)
0.5 mm Si substrate
(sets absorption,
C and G)
15
Nd
Thermistor
(sets operating Top,
sensitivity R/T)
Resistance [k½]
FEL pulse
60
50
Sr
0.67
MnO
0.33
3
sensor on STObufffered Si 10
40
30
5
20
0
10
0
1/R dR/dT [%/K]
Cu heat
sink
(sets Tbath)
-5
90
120 150 180 210 240
Temperature [K]
Sensor implementation: Nd0.66Sr0.33MnO3 (CMR material) on buffered Si substrate.
Cooling in mechanical low-vibration pulse-tube cryocooler
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
t=0
t = 0.1 ms
t = 0.25 ms
Sensor
FEL
0.5mm Si
Delta Temperature at Chip [K]
FEL induced Temperature pulse quickly diffuses to
sensor side, then dissipates
5
Tc200
Tc150
Tc100
4
3
2
1
0
0
0.05
0.1
0.15
0.2
0.25
Time [ms]
Peak signals are ~1K per mJ of FEL pulse energy as expected for ~mm3 of Si at ~150K.
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
0.3
Sensor temperature maintained by Pulse tube cryocooler
Considerations:
1) No liquid cryogens in tunnel
2) Low vibrations to reduce microphonic noise and fluctuations in sensor position
Low vibrations (SEM compatible)
4 1/2” flange
Pulse tube
Cold head
He gas compressor and rotary valve separated
acceleration [µg/rtHz]
103
102
101
100
0
10
20
30
frequency [Hz]
VeriCold PT: ~5W cooling power at 80K, low vibrations by separating rotary valve.
Sensor position should fluctuate less than ~25 µm beam jitter.
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
40
Calibration of Total Energy Sensor will be maintained through in
situ Laser system
Sensor on Si
Attenuator:
Filter wheel
Beam focus
Beam splitter
on
Gimbal mount
Minilite pulsed
Nd-YAG laser,
532 nm
Sources of error (according to specs):
Variations in laser output E:
Absolute accuracy of laser output:
Variations in optical components:
Absolute accuracy of pulse meters:
Reflection at Si:
October 12, 2006
X-TOD Diagnostics
Ophir PE-10
Pulse meters:
3% accuracy
Incident beam
calibration
Reflected beam
monitoring to assess
radiation damage
±1% rms
Not calibrated
Negligible (below damage threshold)
±5% at 532 nm
37% at 532 nm (flat surface)  roughen, calibrate
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Total Energy Error Budget Summary
Calibration errors:
<5% (limited by accuracy of pulse meter)
Electronic noise error:
<0.1% at saturation
<10% at low energies
(depends on excess 1/f noise)
Energy loss error:
<2% (limited by electron escape)
Jitter error:
<3% (if jitter is as low as specified)
Total error:
< 7% at saturation (2 mJ/ pulse)
< 7% at 0.2 mJ
< 12% at low energies (10 µJ/pulse)
Status Total Energy:
PRD done
SCR done
Prototype in preparation
ESD in preparation
PDR in preparation
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Total Energy Monitor Prototype
Vacuum chamber: Based on 6-way cross
Refrigeration: Pulse-tube cryocooler
To pulse tube
and xy-stage
Weak link
Heater
No xy-motion in prototype (yet)
XYZ-stage with 5µm steps in z, 3µm in xy
Sensor: Nd0.67Sr0.33MnO3 on Si chip
Cu chip mount
Surface mount resistor as test heat source, laser
soon
Multiple sensors for different FEL conditions
can be operated in final design.
Cu-capton-Cu
wiring traces
Sensor
Cu clamps
Sensor mount on xy-stage allows ±5 mm field of regard and 40  35 mm2 stay-clear area.
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Thermal Detector and Direct Imager
Direct Imager
Thermal Detector
Calibration Laser
Laser Energy Meter
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Wide Field of View Direct Imager
Single shot measurement of
f(x,y), x, y ,u
Camera
Scintillators
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Photometrics Cascade:512B
The Cascade:512B utilizes a back-illuminated EMCCD with on-chip
multiplication gain. This 16-bit microscopy camera’s "e2v CCD97" device
features square, 16-µm pixels in a 512 x 512, frame-transfer format.
Thermoelectric cooling and state-of-the-art electronics help suppress
system noise.
Dual amplifiers ensure optimal performance not only for applications that
demand the highest available sensitivity (e.g., GFP-based single-molecule
fluorescence) but also for those requiring a combination of high quantum
efficiency and wide dynamic range (e.g., calcium ratio imaging).
The Cascade:512B can be operated at 10 MHz for high-speed image
visualization or more slowly for high-precision photometry. Supravideo
frame rates are achievable via subregion readout or binning.
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Run027: Low Energy, All undulator modules, Spontaneous
Absorbed in 5 um YAG,
Maximum ~ 20,000 photoelectrons/pixel
Full Well: 200,000
Camera: Photometrics 512B
Objective: Navitar Platinum 50
Power: 0.1365
NA:
0.060
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Run030: Low Energy, All undulator modules, FEL
Absorbed in 5 um YAG,
Maximum ~ 3.7e+8 photoelectrons/pixel
Full Well: 200,000
Camera: Photometrics 512B
Objective: Navitar Platinum 50
Power: 0.1365
NA:
0.060
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Run030: Low Energy, All undulator modules, FEL
Absorbed in 5 um YAG,
Maximum ~ 3.7e+8 photoelectrons/pixel
Full Well: 200,000
Camera: Photometrics 512B
Objective: Navitar Platinum 50
Power: 0.1365
Zoomed
NA:
0.060
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Run025: High Energy, All undulator modules, Spontaneous
Absorbed in 50 um YAG,
Maximum ~ 10,000 photoelectrons/pixel
Full Well: 200,000
Camera: Photometrics 512B
Objective: Linos/Rodenstock Apo-Rodagon-D
Power: 0.8
NA:
0.055
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Run026: High Energy, All undulator modules FEL
Absorbed in 50 um YAG,
Maximum ~ 5.0e+7 photoelectrons/pixel
Full Well: 200,000
Camera: Photometrics 512B
Objective: Linos/Rodenstock Apo-Rodagon-D
Power: 0.8
NA:
0.055
Zoomed
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Run036: Low Energy, First undulator module, Spontaneous
Absorbed in 1 mm YAG,
Maximum ~ 1,800 photoelectrons/pixel
Full Well: 200,000
Camera: Photometrics 512B
Objective: Navitar Platinum 50
Power: 0.1365
NA:
0.060
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Experiments Executed at the FLASH
VUVFEL to Verify melt Thresholds
Linac
Undulator
Gas
Attenuator
C Mirror
Gas
Detector
Focusing
Mirror
Sample
Samples:
Bulk SiC
Bulk B4C
Thin Film SiC
Thin Film B4C
Thin Film a-C
Bulk Si
Thin Foil Al
Diamond
FLASH VUV Beamline
YAG
15 single shots at each attenuator setting
The FLASH photon energy of 39 eV is strongly absorbed in C resulting in extreme energy
deposition in small volumes yet multipulse effects in mirrors not yet a problem.
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Measured crater depths scale with
measured pulse energy
Nomarski picture of ~ 30
micron diameter crater in SiC
induced by FEL at 8 x melt
Crater depths, if any, were
measured by Zygo interferometry
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Statistical analysis shows damage threshold
Measured crater depths for 2 low fluence 15
shot series, ordered in increasing depth / pulse
15 shot series shot-to-shot relative pulse energy
measurements ordered in increasing energy / pulse
40
closed symbols: SiC
open symbols: B4C
Enominal =
30
0.010
Peak Depth (nm)
GMD
e-
/ E nominal (V/uJ)
0.012
2uJ
0.008
5uJ
0.006
0.004
0.002
0.4uJ
0.8 mJ
20
10
no damage up to
27-33% (0.59-0.66uJ)
no damage up to
73-80% (0.43-0.64uJ)
0
0.000
-0.002
0
0.4 mJ
0.8uJ
20
40
60
80
100
0
Cumulative Percentage
Data shows that the shot-to-shot pulse
energy varies ~linearly between 0 and
200%
20
40
60
80
100
Cumulative Percentage
Data shows a consistent damage
threshold between 120 and 180 mJ/cm2
•No evidence for surface damage below the melt threshold
(~ 90 mJ/cm2 to reach Tmelt, ~130 mJ/cm2 to melt SiC)
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
S. Hau-Reige and D. Rutyov postulate multipulse
thermal fatigue thresholds ~ 1/10 of melt
Calculate doses for onset of thermal fatigue (D3), to reach melting T (D1), to melt (D2)
Doses below melt
but above D3will not
visibly damage
surface in one shot
but material may
breakdown after an
unknown number of
repeated shots in the
same place.
Multipulse
exposures with
eximer laser was
inconclusive for Si
but data still under
analysis
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Channel-cut Si Monochrometer (KSpectrometer)
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Diagnostics Summary
Instrument
Name
Method
Purpose
Calibration and
Physics risks
Direct Imager
Scintillator in beam
SP f(x,y), look
for FEL,
measure FEL u,
f(x,y), x,y
Scintillator linearity,
Scintillator damage,
Must be used with
Attenuator,
Attenuator linearity
and background
Total Energy
Energy to Heat
FEL u
damage
Gas Detector
N2 Photolumenescence
FEL u
Signal strength,
Nonlinearities
Soft x-ray
Spectrometer
Be Reflection grating
FEL l, FEL u
Energy Resolution
K Spectrometer
Channel-cut Si
monochrometer
Measure
undulator
relative K
Damage,
Signal Strength
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov
Conclusions
Uncertanties constrain detector technology
FEL size, shape, and pulse energy
Damage thresholds & mechanisms – melted, melt, fatigue
Short pulse effects – saturation
High energy spontaneous background
Avoid placing active detector electronics in beam
Single shot damage thresholds at melt verified at
FLASH FEL
Three technologies chosen for LCLS
YAG Scintillator / camera / attenuator – faint FEL
Gas photoluminescence – indestructible
Thermal – least unknowns
October 12, 2006
X-TOD Diagnostics
UCRL-PRES-xxxxxxx
Richard M. Bionta
bionta1@llnl.gov