X%20Ray%20Diagnostics

1
X Ray Diagnostics

• LCLS FAC Meeting
• Oct. 27, 2005

2
FEE Layout
Slit
Be Mirrors 2 3
Diagnostics Package
Solid Attenuator
Collimator 1
Fast close valve
Gas Attenuator
Ion Chamber
SiC Mirror 1
Ion Chamber
Diagnostics Package
SiC Mirror 2
3
Damage Considerations
Dose along the beam line for different materials
at Gaussian peak (under normal illumination)
Shown is the maximum dose (over Ephoton827 to
8267eV)
SiC melt
Si melt
Dose (eV/atom) (maximum over 827-8267eV)
B4C melt
Be melt
z (m from end of undulator)
4
Dose obtained at TTF
5
TTF VUV Beamline
6
Damage experiment chamber
TOF ion spectrometer
Sample holder
Visible spectrometer
Microscope
7
SiC thin film, 1 shot, 8 x melt
8
SiC thin film, 10000 shots, 1 x melt
Emission spectra shows plasma was formed
9
SiC thin film, 10000 shots, 10 melt
No spectra can be distinguished above background
10
Si/C mirror reflects for one shot
First shot
Second shot
11
Desired FEL Measurements
u Total energy / pulse
l1 Photon wavelength
Dl/l1 Photon wavelength spread
Pulse centroid
Beam direction
f(x,y) Spatial distribution
su,sl1 Temporal variation in beam parameters
t Pulse duration
12
Desired Spontaneous Measurements
f(x,y,l1) Spatial distribution around l1
l1 1st harmonic Photon wavelength
Dl/l1 1st harmonic wavelength spread
Beam direction
u Total energy / pulse
su,sl1 Temporal variation in beam parameters
13
FEE Cartoon
Start of Experimental Hutches
5 mm diameter collimators
Windowless Ion Chamber
Diagnostic Package
Spectrometer / Indirect Imager mirror
Solid Attenuator
High-Energy Slit
Total Energy Calorimeter
e-
WFOV Direct Imager
Gas Attenuator
FEL Offset mirror system
Spectrometer camera
Windowless Ion Chamber
Muon Shield
14
Redundant Commissioning Instrumentation
Instrument Purpose Adjustment Calibration and Physics risks
Direct Imager SP f(x,y), look for FEL, measure FEL u, f(x,y), x,y ND filter, Attenuators Scintillator linearity, Attenuator linearity and background
Indirect Imager Measure FEL u, f(x,y), spectral imaging of SP and FEL harmonics, attenuator calibration Mirror Angle Mirror reflectivity, damage
Total Energy FEL u Attenuators Energy to Heat, damage
Ion Chamber FEL u, x,y,x',y' Pressure Signal strength
Spectrometers FEL, SP spectra Attenuators Resolution, damage
15
Wide Field of View Direct Imager
Photoelectrons generated by 0.01 FEL
Single shot measurement of f(x,y), x, y ,u
Camera
Scintillators
16
Indirect Imager
Single shot measurement of f(x,y), x, y, u Multi
shot measurement of l
Angle selects energy and attenuation
17
B4C/SiC Test Multilayers Fabricated

• 40 layer pairs
• G 0.7
• P 6 nm

Data at Cu Ka, 8 keV
18
Total Energy Calorimeter
Thermal diffusion calculations performed
Single shot measurement of f(x,y), x, y, u
t 300 ms
t 100 ms
Nd0.8Sr0.2MnO3
Cold Si substrate
CMR Sensor array 100 pixels
t 0
Xray Beam
T
Cooling ring
T, ms
5
0
Sample CMR at LLNL for etching and R(T)
measurements
19
Sensor Development Nd0.8Sr0.2MnO3
20
Ion Chamber
Single shot, non destructive, measurement of x,
y, x, y ,u
Segmented cathodes for position measurement
1 torr
Imaging of optical emission for position
measurement
21
Measuring K with photons
On axis
But
Effect of changing K
22
Near-Field calculations of detuned single
undulator segments
Mean, keV
Photons/pulse/20 eV
First and Last 2mm x 2mm
First 8.2658 Last 8.2362
First 2 x 2 mm Last 1 x 1mm
First 8.2658 Last 8.2651
Last has K(110-4)
First 2 x 2 mm Last 1 x 1mm
First 8.2658 Last 8.2645
Photon Energy, keV
23
Single Shot 8 keV Spectrometer
Single shot measurement of l
20 m downstream
1.4991 Å
Sputter-sliced SiC / B4C multilayer
P 20 nm N 1x104 D 200 mm
1.4994 Å
33 mm thick
200 mm
Problems Don't have 20 m. Signal degradation due
to grating thickness (coupled waveguides.) Only
possible at high photon energies.
Beam
24
Other candidates for Single-Shot Spectrometers
Mosaic Graphite crystal
Asymmetric cut multilayer
25
Summary

• X-ray characterization for LCLS is challenging
• Dose limits materials choice
• Large range of signal levels
• Some measurements require precision near r 10-4
• Redundant diagnostics techniques will be used to
  measure pulse energy
• Total energy calorimeter
• Direct Imager
• Indirect Imager
• Ion chamber
• Much work needed on single-shot spectral
  measurements
• TTF damage experiment to be analyzed