Transcript Tutorial on FEL

Tutorial on FEL
by: Sverker Werin
FEL = Free Electron Laser
As opposed to bound electrons
?
Light Amplification by
Synchronised Electron
Retardation
Energy exchange: light  e-
Basics
Bunching
Radiation
Amplification
Cavity
FEL
CHG
Coherent Harmonic
Generation
Concepts
SASE
HGHG
High Gain Harmonic
Generation
Seeding
Self Amplified
Stimulated Emission
Light interacting with an electron beam
d
 dt mv   qE  v  B 

d


m c2   qE v
 dt
Making E and v parallell
Undulator
(or wiggler)
5 cm
Flux (ph/[s*100mA*0.%BW])
1E+14
* SR in harmonics
1E+13
* Velocity  s
1E+12
1E+11
0
50
100
150
200
Photon energy (eV)
250
300
Mixing light, e- and undulator
Ex
vx
vs
v


d
mc 2  ev x E x  0
dt
Undulator radiation
t1
t2
t3
l0
l0/2
Energy exchange
E-field
evx
lg
Some e- gain energy
Some e- loose energy
S=0
Bunching
-DE
Detour & lower v
+DE
Shortcut & higher v
e-
lg
Bunched e- with
distance of light
wavelength
Radiator
•Light generated in an undulator
lg
•Coherent
•With harmonics
lg/3
Amplification
E-field
Phase shift
vx
lg
• All e- loose energy
• E-field gains energy
• S0
Saturation
E-field
vx
lg
•Overbunching
•Amplification dies off
CHG - Coherent Harmonic Generation
laser
lO
l= lO /i
• i = 1, 3, 5, ?
• l  100 nm
• coherent
Resonator FEL
• IR 5-250 mm
• UV  200 nm
• Tunable: magnet /
e- energy
• Mirrors limit
• Storage ring: high
rep. Rate, ”stable”
• Linac: high peak
power, ”unstable”
SASE
(Self Amplified Stimulated Emission)
• From noice
P
• No mirrors ( X-rays)
• Tunable
L
• ”Spiky” (t and l)
SEEDING
laser
• Remove instabilities
• CHG with gain HGHG
Monochromator
FELIX
Resonator IR- FEL
FOM, Holland
ELETTRA, Italy
Storage ring FEL
l >= 190 nm
e- energy 1 GeV
TTF, Hamburg
Tesla Test Facility
l = 109 nm
SASE FEL
LCLS, Stanford
Linac Coherent Light Source
l = 1-15 Å
15 GeV
SASE FEL
MAX-lab
?
VUV FEL
Seeded SASE FEL
l = 100-400 nm
500 MeV
300-400 undulator periods
TESLA, Hamburg