1. USPAS Course on 4th Generation Light Sources II
ERLs and Thomson Scattering
G. A. Krafft and I. V. Bazarov
Jefferson Lab and Cornell University
Thomson Scattering Sources

2. Thomson Scatter Sources & Related Proposals
Thomson Scattering vs. Undulator Radiation
Thomson Scattering Sources (TSS):
JLAB
BNL
Duke
Berkeley
Idaho Accelerator Center
Naval Research Lab
Other proposals:
Small-Angle Geometry
Laser Electron Storage Ring
Sir J.J. Thomson

3. Thomson Scattering vs. Undulator Radiationp
Undulator radiation can be looked as Thomson scattering (and vice versa)
Same signature: polarization, harmonic content when a0, K  1

4. Thomson Scattering Same as Short Undulator Radiation
For K  1:
useful fraction
~ (/)(/ph)2
Scaling with undulator period of the formulas above:
to keep radiation wavelength the same:
to keep the number of photons the same
if undulator length is kept the same:
if number of periods is kept the same:
B0 in undulator is limited to ~ Tesla, thus, electron energy is constrained to some multi-GeV, and undulator period to ~ cm for hard x-ray production.

5. Different Thomson Scattering Geometries
mbarn
possible advantages include compact design (small ), fs x-ray pulses
we’ll look at different examples of TSS:  = /2,  =  and  << 1

6. Photons Wanted

7. Reality Check Against Photon “Starvation”
From undulator:
mostly
incoherent
photons 
Thomson scattered x-rays:
Laser pulse needed: 1 ~
or:
or ~ 10 J / pulse (TW laser)
for
can be tough to match laser and electron beams in space-time, i.e. only a fraction of electrons or photons will participate in scattering
rep rate is limited to ~ kHz (don’t need more for pump probe exp.)

8. Outline Thomson Scattering vs. Undulator Radiation
Thomson Scattering Sources (TSS):
JLAB
BNL
Duke
Berkeley
Idaho Accelerator Center
Japanese Tohuku Group
Other proposals:
Small-Angle Geometry
Laser Electron Storage Ring

9. … …

10. …
peak
0.1 % bw
peak

11. Outline Thomson Scattering vs. Undulator Radiation
Thomson Scattering Sources (TSS):
JLAB
BNL
Duke
Berkeley
Idaho Accelerator Center
Japanese Tohuku Group
Other proposals:
Small-Angle Geometry
Laser Electron Storage Ring

12. Duke FEL-production

13. Machine Description

14. Measured -rays
Note: -ray polarization is ~ 100 %

15. Future Plans

16. Outline Thomson Scattering vs. Undulator Radiation
Thomson Scattering Sources (TSS):
JLAB
BNL
Duke
Berkeley
Idaho Accelerator Center
Japanese Tohuku Group
Other proposals:
Small-Angle Geometry
Laser Electron Storage Ring

21. Experimental Results

22. Outline Thomson Scattering vs. Undulator Radiation
Thomson Scattering Sources (TSS):
JLAB
BNL
Duke
Berkeley
Idaho Accelerator Center
Naval Research Lab
Other proposals:
Small-Angle Geometry
Laser Electron Storage Ring

24. The Layout

25. Interaction Region

26. Indirect Laser Pulse Measurements

27. X-ray Measurements

28. Outline Thomson Scattering vs. Undulator Radiation
Thomson Scattering Sources (TSS):
JLAB
BNL
Duke
Berkeley
Idaho Accelerator Center
Naval Research Lab
Other proposals:
Small-Angle Geometry
Laser Electron Storage Ring

30. Outline Thomson Scattering vs. Undulator Radiation
Thomson Scattering Sources (TSS):
JLAB
BNL
Duke
Berkeley
Idaho Accelerator Center
Naval Research Lab
Other proposals:
Small-Angle Geometry
Laser Electron Storage Ring

31. … …
 3°

32. 6° 3°

33. … … … …
x, y = 4 mm?
Note: state-of-the-art peak brightness from 3rd generation light sources approaches 1024 photons s-1 mm-2 mrad-2 per 0.1% bw, and average flux is 1015 photons s-1 per 0.1% bw.

34. f
104 per 0.1% bw
per pulse
should be 1018
Note: different laser parameters were used for different Thomson scattering sources

35. Peak brightness alone can be misleading
Single photon peak brightness:
or in conventional units:
peak 1 Å when photon degeneracy is 1
Summary
Thomson scattering sources can provide ~ shorter pulses than that of 3rd generation light sources, with peak brightness lower by at least ~ and average flux lower by at least assuming state-of-the-art rep rate for laser. Even if the rep rate of Thomson scattering event were somehow improved to some sub-GHz (c.f. next project), average flux would still be ~ when compared to a 3rd generation light sources.

36. Outline Thomson Scattering vs. Undulator Radiation
Thomson Scattering Sources (TSS):
JLAB
BNL
Duke
Berkeley
Idaho Accelerator Center
Naval Research Lab
Other proposals:
Small-Angle Geometry
Laser Electron Storage Ring

38. General Idea phase space damping rate: due to bends alone, i.e. small
phase space excitation rate:
due to bends alone, i.e. small

39. Damping From Thomson “Undulator”

40. Theoretical emittance & energy spread
Note: large initial emittance
can hinder the damping

41. Fabry-Perot resonator & Projected performance
laser peak power: 0.2 TW (transient)
6 GW (steady)
rep rate: 0.1 GHz (steady)
laser power req.d: 200 W