1. In collaboration with Winthrop Brown, T.Y. Fan, Franz Kaertner,
Integrating Laser and Linac Technology for Next Generation X-ray Sources
William S. Graves
MIT
September 11, 2008
Alghero, Sardinia
In collaboration with Winthrop Brown, T.Y. Fan, Franz Kaertner,
and David Moncton

2. MIT Inverse Compton Source Concept
Yb:YAG Pre amp
Yb:YAG Osc
pump diode
SESAM
Multi-passYb:YAG Amplifier
4 m
Superconducting linac operating at 325 MHz and 4K
Diodes
¼-wave SRF injector
RF amp
RF amp
RF amp
≤50 MeV electron beam
x-ray detectors
Pulse shaping
4th harmonic generation
Collimating chicane
Tunable x-ray optics
RF IOT
Yb:YLF Amplifier
8 m

3. Laser Technology Oscillator or Osc./Amp. combination Electron beam
X-ray beam
Continuous 10mJ operation
Cryo-cooled Yb:YAG
multi-pass amplifier
1ps, 100mJ, 10 MHz
1kW
1 m Yb:YAG
1 ps, 1mJ, 10 MHz, 10W
Oscillator or
Osc./Amp. combination

4. 200 W cryo-cooled Yb:YAG T.Y. Fan group at Lincoln Lab Polarizers
L N2 dewar
Multi-pass cell
Output coupler & AOM
Polarizers
Fiber head for diode pump
Photodiode
T.Y. Fan group at Lincoln Lab

5. Brightness and Flux scale dramatically with the electron beam quality:
ICS Optimization
Brightness and Flux scale dramatically with the electron beam quality:
Flux
Peak Brightness
Avg Brightness

6. Dependence on Electron Beam Focus Electron Beam Parameters (25 MeV)
Emittance = 0.7 mm-mrad
Q = 0.1 nC (S2E Case)
Rms Duration = 2.1 ps
Laser Parameters
l = 1 mm
W = 10 mJ
Rms Duration = 0.5 ps
Performance vs. Laser Spot Size for Different Electron Beam Focus Sizes 10 20 30 40 2 4 6 8
x 10
Rms Laser Spot Size (microns)
Total X-ray Dose
2.175 microns
4.35 microns
6.525 microns
8.7 microns
microns 10 20 30 40 5 15
x 10
Rms Laser Spot Size (microns)
Avg. Brightness/Rep. Rate
2.175 microns
4.35 microns
6.525 microns
8.7 microns
microns

7. Full Calculations of the Photon Spectrum
Time dependent, 3D code developed at LLNL for linear regime
Normalized emittance = 0.3 mm
Normalized emittance = 1.0 mm 10
0.1
0.01
100
photons/mrad2/eV 1
photons/mrad2/eV 10
0.1
0.01 1
Note: Plane Perpendicular to Laser Polarization

8. Dependence on Electron Bunch Duration Electron Beam Parameters
en = 0.7 mm-mrad (25 MeV)
Rms spot size = 4.3 mm
Q = 0.1 nC
Laser Parameters
l = 1 mm
W = 10 mJ
Pulse duration = 0.5 ps 5 10 15 20 2 4 6 8 12
x 10
Rms Laser Spot Size (microns)
Total X-ray Dose
0.125 ps
0.25 ps
0.5 ps
1 ps
2 ps
5 ps
10 ps 5 10 15 20 2 4 6 8
x 10
Rms Laser Spot Size (microns)
Avg. Brightness/Rep. Rate
0.125 ps
0.25 ps
0.5 ps
1 ps
2 ps
5 ps
10 ps

9. Intensity Profile of 12 keV X-rays with 0.1% bw
Emittance = 0.7 mm-mrad
Photons/sec = 8 x MHz

10. X-ray Source Performance Comparison
Peak Brilliance
Brilliance
Flux
‘Ideal’ XFEL x x x 1016
APS x x x 1014
SRF Linac ICS x x x 1010
SR ICS x x x 1010
NC Linac ICS x x x 108
Rotating Anode x x x 109
Note: All numbers are in units of 0.1%BW

11. Summary
ICS flux and brightness depend on electron beam current and emittance (just like a synchrotron source!)
SRF accelerator combined with high average power laser can generate optimal beam parameters for best flux, peak and average brightness
ICS parameters much better than existing home sources but still less than big synchrotrons
ICS outperforms big synchrotrons in ultrafast x-ray performance, and is competitive in level of coherence
Cost of ICS source similar to 3rd gen beamline: ~$10M