uspas course on 4th generation light sources ii erls and...
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USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
USPAS Course on4th Generation Light Sources IIERLs and Thomson Scattering
G. A. Krafft and I. V. BazarovJefferson Lab and Cornell University
Thomson Scattering Sources
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Thomson Scatter Sources & Related Proposals
1. Thomson Scattering vs. Undulator Radiation2. Thomson Scattering Sources (TSS):
1. JLAB2. BNL3. Duke4. Berkeley5. Idaho Accelerator Center6. Naval Research Lab
3. Other proposals:1. Small-Angle Geometry2. Laser Electron Storage Ring
Sir J.J. Thomson
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Thomson Scattering vs. Undulator Radiation
λp
N N
N
S
SS
γ/K θ
λ
Lλ
λe–
• Undulator radiation can be looked as Thomson scattering (and vice versa)
• Same signature: polarization, harmonic content when a0, K ≥ 1
cmkeBK
ep
0=20
0 cmeAa
e
=
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Thomson Scattering Same as Short Undulator Radiation
)1(2
222 θγ
γλ
λ +≈ peptotph NNKN 2
, α≈For K ≤ 1:
1371
=e
erD
Scaling with undulator period of the formulas above:2~ γλp• to keep radiation wavelength the same:
• to keep the number of photons the sameif undulator length is kept the same: γ/1~0Bif number of periods is kept the same: 2
0 /1~ γB
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.
~ (∆ω/ω)×(ε⊥/εph)2
useful fraction
πλ 4/
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Different Thomson Scattering Geometries
Lλ
λ
e–
φθ
φθγ
γλλ
cos11)1(
222
2 −+≈ L
Θ′=Ω′
22 sineT r
ddσ
66538 2 == eT rπσ mbarn
• possible advantages include compact design (small γ), fs x-ray pulses
• we’ll look at different examples of TSS: φ = π/2, φ = π and φ << 1
φ ′φ
S S′
φcoskk z =yk yy kk =′
)cos( φβγ −−=′ kk z
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Photons Wanted
kTh /~
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Reality Check Against Photon “Starvation”From undulator:
Thomson scattered x-rays: eLphT
totph NNN ,, areaspot focused~ σ
mostlyincoherent
photons
204)µm 100(
2, 10~
mbarn 665~areaspot focused~
2
πσ
αT
pLph NKN
Laser pulse needed:
≈
~1
or ~ 10 J / pulse (TW laser)or:
)W/cm()µm(1085.0/ 29200 LLe IcmeAa λ−×≈=
218 W/cm102.2 ×≈LI1~0a 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.)
eptotph NNKN 2, α≈
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Outline
1. Thomson Scattering vs. Undulator Radiation2. Thomson Scattering Sources (TSS):
1. JLAB2. BNL3. Duke4. Berkeley5. Idaho Accelerator Center6. Japanese Tohuku Group
3. Other proposals:1. Small-Angle Geometry2. Laser Electron Storage Ring
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
… …
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
…
peak
peak
0.1 % bw
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Outline
1. Thomson Scattering vs. Undulator Radiation2. Thomson Scattering Sources (TSS):
1. JLAB2. BNL3. Duke4. Berkeley5. Idaho Accelerator Center6. Japanese Tohuku Group
3. Other proposals:1. Small-Angle Geometry2. Laser Electron Storage Ring
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Duke FEL γ-production
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Machine Description
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Measured γ-rays
Note: γ-ray polarization is ~ 100 %
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Future Plans
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Outline
1. Thomson Scattering vs. Undulator Radiation2. Thomson Scattering Sources (TSS):
1. JLAB2. BNL3. Duke4. Berkeley5. Idaho Accelerator Center6. Japanese Tohuku Group
3. Other proposals:1. Small-Angle Geometry2. Laser Electron Storage Ring
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
…
…
h ≈ 4 eV·fskT ≈ 1/40 eV
?
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
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USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
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USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Experimental ResultsR.W. Shoenlein et. al, Nature (274) 5285
e– beam50 MeV, 1.3 nC, 90 µm, 20 pslaser beam800 nm, 100 fs, 60 mJ, 30 µm
x-ray beam produced2 × 105 ph mm–2 mrad–2 s–1 in a 15% bandwidth
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Outline
1. Thomson Scattering vs. Undulator Radiation2. Thomson Scattering Sources (TSS):
1. JLAB2. BNL3. Duke4. Berkeley5. Idaho Accelerator Center6. Naval Research Lab
3. Other proposals:1. Small-Angle Geometry2. Laser Electron Storage Ring
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
The Layout
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Interaction Region
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Indirect Laser Pulse Measurements
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
X-ray Measurements
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Outline
1. Thomson Scattering vs. Undulator Radiation2. Thomson Scattering Sources (TSS):
1. JLAB2. BNL3. Duke4. Berkeley5. Idaho Accelerator Center6. Naval Research Lab
3. Other proposals:1. Small-Angle Geometry2. Laser Electron Storage Ring
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Outline
1. Thomson Scattering vs. Undulator Radiation2. Thomson Scattering Sources (TSS):
1. JLAB2. BNL3. Duke4. Berkeley5. Idaho Accelerator Center6. Naval Research Lab
3. Other proposals:1. Small-Angle Geometry2. Laser Electron Storage Ring
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
…
… ≈ 3°
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
3°
6°
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
…
…
…
…
βx, 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 fluxis 1015 photons s-1 per 0.1% bw.
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
f104 per 0.1% bw
per pulse
should be 1018
Note: different laser parameters were used for different Thomson scattering sources
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Peak brightness alone can be misleading
Single photon peak brightness: 33 )2/()2(1hπ
=peakB
3o
24221 ))A(/(104.2bw) 0.1%per mradmmsphoton ( λ×=---peakB
or in conventional units:
peak brightness @ 1 Å when photon degeneracy is 1
SummaryThomson scattering sources can provide ~ 103-4 shorter pulses than that of 3rd
generation light sources, with peak brightness lower by at least ~ 103-4 and average flux lower by at least 109-10 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 ~ 103-4 when compared to a 3rd generation light sources.
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Outline
1. Thomson Scattering vs. Undulator Radiation2. Thomson Scattering Sources (TSS):
1. JLAB2. BNL3. Duke4. Berkeley5. Idaho Accelerator Center6. Naval Research Lab
3. Other proposals:1. Small-Angle Geometry2. Laser Electron Storage Ring
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
General Idea
phase space damping rate:
phase space excitation rate:
EPphε∝ 2
4
ρEPph ∝ due to bends alone, i.e. small
ringphph HENE
22
1 &∝
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Damping From Thomson “Undulator”
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
Theoretical emittance & energy spread
Note: large initial emittancecan hinder the damping
USPAS 4th Generation Light Sources II Krafft/Bazarov 20 October 2002CHESS / LEPPCHESS / LEPP
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