Transcript Slide 1

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FEL2004
Beam Stability Issues
René Bakker
[email protected]
[email protected] / 10-Dec-2004
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•
Proceedings will become available through JACoW:
http://www.jacow.org
•
Preliminary proceedings available on conference web-site:
http://www.elettra.trieste.it/fel2004/proceedings.html
(papers & slides of oral presentations)
•
The abstract booklet, author and affiliation index is available at:
http://www.elettra.trieste.it/fel2004/abook.html
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[email protected] / 10-Dec-2004
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Types of free-electron lasers:
•
Single-pass devices
•
Storage-ring FELs
•
High average-power
devices
I will just discuss some examples, for an extensive view, please visit:
• the FEL2004 web-site:
http://www.elettra.trieste.it/fel2004
• FEL virtual library:
http://sbfel3.ucsb.edu/www/vl_fel.html
[email protected] / 10-Dec-2004
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Types of free-electron lasers:
•
Single-pass devices
undulator
•
Storage-ring FELs
S
S
•
High average-power
devices
accelerator
Accelerator
N
N
N
S
N
S
S
N
N
electron beam
S
bunch compressor
High-brighness
electron source
[email protected] / 10-Dec-2004
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Types of free-electron lasers:
•
Single-pass devices
•
Storage-ring FELs
electron bunch
•
High average-power
devices
mirror
undulator
laser micropulse
[email protected] / 10-Dec-2004
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Types of free-electron lasers:
•
Single-pass devices
•
Storage-ring FELs
•
High average-power
devices
acceleration
FEL + ERL:
Energy Recovery Linac Concept
Injector
Accelerators
Dump
Undulator
JLAB recirculating FEL
deceleration
FEL resonator
[email protected] / 10-Dec-2004
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Types of free-electron lasers:
•
Single-pass devices: high power / short wavelengths
VUV  X-ray
•
Storage-ring FELs:
optical properties / spectrum
visible  VUV
•
High average-power: IR
devices
[email protected] / 10-Dec-2004
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Single Pass FEL Activity
TTF / XFEL
4GLS
LEUTL
MIT / Bates
PAL – FEL
LUX
BESSY FEL
SCSS
LCLS
LEG
VISA / DUV
FERMI
SPARC / SPARX
SC technology / NC technology
[email protected] / 10-Dec-2004
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Storage Ring & High Average Power FELs
BINP / VEPP3
4GLS
UVSOR
JAERI FEL
New SUBARU
DFEL
SACO
IR-FEL
EUFELE
No longer operational
[email protected] / 10-Dec-2004
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Existing FELs
EXISTING FELs
FEL-CAT
UCSB mm FEL
Novosibirsk (RTM)
Korea (KAERI-FEL)
Himeji (LEENA)
UCSB (FIR FEL)
Osaka (ILE/ILT)
Osaka (ISIR)
Tokai (JAERI-FEL)
Bruyeres (ELSA)
Osaka (FELI4)
UCLA-Kurchatov
LANL (RAFEL)
Stanford (FIREFLY)
UCLA-Kurchatov-LANL
Maryland (MIRFEL)
Beijing (BFEL)
Dresden (ELBE1)
Korea (KAERI HP FEL)
Newport News (IR demo)
Darmstadt (FEL)
BNL (HGHG)
Osaka (iFEL1)
Tokyo (KHI-FEL)
Nieuwegein (FELIX)
Duke (MARKIII)
Stanford (SCAFEL)
Orsay (CLIO)
Vanderbilt (FELI)
Osaka (iFEL2)
Nihon (LEBRA)
UCLA-BNL (VISA)
BNL (ATF)
Dortmund (FELICITAI)
BNL NSLS (DUVFEL)
Orsay (Super-ACO)
Osaka (iFEL3)
Okazaki (UVSOR)
Tsukuba (NIJI-IV)
Italy (ELETTRA)
Duke (OK-4)
ANL (APSFEL)
DESY (TTF1)

(m)
760
340
120-180
97-1200
65-75
60
47
40
22
20
18-40
16
15.5
15-80
12
12-21
5-20
3-22
3-20
3, 6, 10
6-8
5.3
5.5
4-16
3-250
2.7-6.5
3-13
3-53
2.0-9.8
1.88
0.9-6.5
0.8
0.6
0.42
0.1
0.3-0.6
0.3-0.7
0.2-0.6
0.2-0.6
0.2-0.4
0.193-2.1
0.13
0.08-012
z
(ps)
15-20
25000
70
25
10
25000
3
30
2.5-5
30
10
3
15
1-5
5
5
4
10
10-20
0.2
2
6
10
2
1
3
0.5-12
0.1-3
0.7
10
<1
0.5
6
50
0.7
15
5
6
14
28
0.1-10
0.3
0.04
E
(MeV)
1.8
6
12
4.3-6.5
5.4
6
8
17
17
18
33
13.5
17
15-32
18
9-14
30
40
20-40
160
25-50
40
33.2
32-40
50
31-41.5
22-45
21-50
43
68
58-100
70.9
50
450
300
800
155
607
310
1000
1200
399
250
I
(A)
N
5
2
10
0.5
10
2
50
50
200
100
40
80
300
14
170
100
15-20
8
30
270
2.7
120
42
30
50
20
10
80
50
42
10-20
250
100
90
500
0.1
60
10
10
150
35
400
3000
16
42
2×33
80
50
150
50
32
52
30
30
40
200
25
100
73
50
2×34
30×2
25
80
60
58
43
38
47
72
38
52
78
50
220
70
17
256
2×10
67
2×9
2×42
2×19
2×33
648
492
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Proposed FELs
0
(cm)
2.5
7.1
12
2.5
1.6
2
2
6
3.3
3
8
1.5
2
6
2
1.4
3
2.73
3.5
20
3.2
3.3
3.4
3.2
6.5
2.3
3.1
5
2.3
3.8
4.8
1.8
0.88
25
3.9
13
4
11
7.2
10
10
3.3
2.73
K
(rms)
0.75
0.7
0.71
1.0-1.6
0.5
0.1
0.5
1
0.7
0.8
1.3-1.7
1
0.9
1
0.7
0.2
1
0.3-0.8
0.5-0.8
4.5
1
1.44
1
0.7-1.8
1.8
1
0.8
1.4
1.3
1
0.7-1.4
1.2
0.4
2
0.7
4.5
1.4
2
2
4.2
0-4.75
2.2
0.81
Table 2: Proposed Free Electron Lasers (2004)
RF,O
EA,O
RF,O
MA,O
RF,O
EA,O
RF,O
RF,O
RF,O
RF,O
RF,O
RF,A
RF,O
RF,O
RF,A
RF,O
RF,O
RF,O
RF,O
RF,O
RF,O
RF,A
RF,O
RF,O
RF,O
RF,O
RF,O
RF,O
RF,O
RF,O
RF,O
RF,S
RF,O
SR,O
RF,SH
SR,O
RF,O
SR,O
SR,O
SR,O
SR,O
RF,S
RF,S
PROPOSED FELs
Tokyo (FIR-FEL)
Netherlands (TEUFEL)
Rutgers (IRFEL)
Novosibirsk (RTM1)
Dresden (ELBE)
Daresbury (4GLS-IRFEL)
Novosibirsk (RTM)
Frascati (SPARC)
TJNAF (UVFEL)
Hawaii (FEL)
Harima (SUBARU)
Shanghai (SDUV-FEL)
Frascati (COSA)
Daresbury (4GLS-VUV)
Daresbury (4GLS-XUV)
Duke (OK-5,VUV)
DESY (TTF2)
Italy (SPARX)
BESSY (Soft X-ray)
Trieste (FERMI)
RIKEN (SPring8 SCSS)
MIT (Bates X-Ray FEL)
SLAC (LCLS)
DESY (TESLA)
Pohang (PAL X-FEL)

(m)
300-1000
180
140
3-20
30-750
5-100
2-11
0.533
0.25-1
0.3-3
0.2-10
0.5-0.088
0.08
0.4-0.1
0.1-0.01
0.03-1
0.006
0.0015
0.0012
0.001-0.1
0.00036
0.0003
0.00015
0.0001
0.0003
z
(ps)
5
20
25
10
1-5
0.2-1
20
0.1
0.2
2
26
1
10
0.1-1
0.1-1
0.1-10
0.17
0.1
0.08
0.1
0.5
0.05
0.07
0.08
0.1
E
(MeV)
10
6
38
50
10-40
50
98
142
160
100
1500
300
215
600
600
1200
1000
2500
2300
3000
1000
4000
14350
30000
3000
I
(A)
30
350
1.4
20-100
30
100
100
500
270
500
50
400
200
300
2000
50
2500
2500
3500
2500
2000
1000
3400
5000
4000
N
25
50
50
3×33
45
100
4×36
6×71
60
84
33,65
400
400
150
1000
4×32
981
1000
1450
570-1140
1500
1500
3328
4500
6000
0
(cm)
7
2.5
20
6
5
4
9
3
3.3
2.4
16,32
2.5
1.4
5
2
12
2.73
3
2.75
3.5
1.5
1.8
3
6
1.5
K
(rms)
1.5-3.4
1
1
2
0.4-1.6
2
1.6
1.3
1.3
1.2
8
1.025
1
2
1
3
0.9
1.2
0.9
1.2
1.3
2
3.7
3.2
1.1
RF,O
RF,O
MA,O
RF,O
RF,O
RF,O
RF,O
RF,S
RF,O
RF,O
SR,O
RF,O
RF,O
RF,O
RF,S
SR,O
RF,S
RF,S
RF,S
RF,S
RF,S
RF,S
RF,S
RF,S
RF,S
W.B. Colson - THPOS58
[email protected] / 10-Dec-2004
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Storage-Ring FELs
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The ELETTRA Storage Ring FEL
optical cavity length 32.4 m
4.5 m helical undulator
beamline
FEL beam
intensity (a.u.)
-e
Storage ring operation*
Tunability range
= 189.95 nm
 = 0.06 nm
 = 0.03 %
189.0
189.5
190.0
190.5
wavelength (nm)
191.0
1.0 GeV
350 – 190 nm
3.5 – 6.5 eV
1 W
~ 5 ps
 40 kW
 0.2 mJ
 1018 photons/s
circular (linear may also be possible)
4.6 MHz
1:1
Average power
Pulse length (FWHM)
Peak power
Pulse energy
Photon flux**
Polarization
Repetition rate
Synchronization with
synchrotron radiation
*
4-bunch operation, **within the laser bandwidth
[email protected] / 10-Dec-2004
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Storage-Ring FELs
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Critical Issues:
•
Longitudinal stability of electron beam:
rountrip time of
the optical cavity
must match the
bunch-spacing
electron bunch
M. Trovò
THPOS09
mirror
undulator
laser micropulse
[email protected] / 10-Dec-2004
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Critical Issues:
•
Longitudinal stability:
rountrip time of the optical cavity must match the bunch-spacing
(stability of RF frequency and longitudinal modes)
•
Transverse stability:
wavelength
2
  2 1  K rms
 ( ) 2 
Gain
g  1/ 
u
2
typically micron accuricy required
2
mirror
electron bunch
undulator
laser micropulse
[email protected] / 10-Dec-2004
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Critical Issues:
•
Longitudinal stability:
rountrip time of the optical cavity must match the bunch-spacing
S-ACO:
•
Transverse stability:
wavelength
TEM00
TEMnn
more
stability
Gain
more
gain
L
Transverse Cavity Stability!
R2
z
heat-load
R1
w0
M2
M1
[email protected] / 10-Dec-2004
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Cavity Stability
•
Storage-ring FEL
Important issue:
e.g., 1 W of average output power  200 W of intra-cavity power
•
High average-power IR FEL
e.g., JLAB FEL: > 10 kW average output power, i.e., more than
100 kW average intra-cavity power.
ref: TUCOS02, TUBOS03
[email protected] / 10-Dec-2004
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High average-power lasers: FEL challenge (JLAB)
•
FELs need a high peak current.
–
a factor of 4 growth in the longitudinal emittance due to space charge.
–
longer electron bunches in the injector can reduce space charge effects but reduces
the machine acceptance.
–
•
Halo loss initially limited the average current.
Resonator FELs need a high average current
–
Bunch spacing must match the cavity length.
Injector
acceleration Accelerators
Dump
Beam break-up limits avarege current
3 mA  8 mA Undulator deceleration
JLAB recirculating FEL
FEL resonator
[email protected] / 10-Dec-2004
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High average-power lasers: FEL challenge (JLAB)
•
Beam break-up
– Cavity design: suppression of HOMs
– Clever optics (damping of transverse motion)
•
Nice presentation by T.I. Smith: WEBOS03
Injector
Accelerators
Dump
Beam break-up limits avarege current
Undulator
JLAB recirculating FEL
FEL resonator
[email protected] / 10-Dec-2004
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High average-power lasers: FEL challenge (JLAB)
•
Challenges of recovering the beam
– RF kicks reversed for recovered beam
– No two pass BPMs
– Chromatic effects lead to betatron mismatch, causing beam loss.
– Need energy/phase correction to third order (octupoles are required)
– Operating close to crest does not provide enough footroom.
Injector
Accelerators
Dump
Undulator
JLAB recirculating FEL
FEL resonator
[email protected] / 10-Dec-2004
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Single Pass Devices
undulator
S
S
accelerator
Accelerator
N
N
N
S
N
S
S
N
N
electron beam
S
bunch compressor
High-brighness
electron source
Start-Up from Noise (SASE)
[email protected] / 10-Dec-2004
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Single Pass Devices
undulator
S
S
accelerator
N
N
N
S
N
S
S
N
N
electron beam
S
SEED
Accelerator
bunch compressor
High-brighness
electron source
Controlled Startup (SEED)
[email protected] / 10-Dec-2004
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Single-Pass Devices
• Startup from noise (auto-start): SASE
–
–
–
–
Relatively easy
Flexible for wavelength tuning
High output power
Spiky
• Seeded startup
–
–
–
–
Improved spectral purity
Suppression of spiking
Control over the μ-pulse duration
(Longitudinal jitter defined by seed)
[email protected] / 10-Dec-2004
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Seeded FEL: HGHG (BNL)
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Intensity (a.u.)
HGHG
Courtesy Li Hua Yu (BNL)
0.23 nm FWHM
SASE x105
wavelength (nm)
[email protected] / 10-Dec-2004
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Single-Pass Devices
• Startup from noise (auto-start): SASE
–
–
–
–
Relatively easy
Flexible for wavelength tuning
High output power
Spiky
LCLS, TTF, X-FEL, SPARC, …..
• Seeded startup
–
–
–
–
Improved spectral purity
Suppression of spiking
Control over the μ-pulse duration
(Longitudinal jitter defined by seed)
BESSY, FERMI, TTF, LUX,
MIT, ……. LCLS, X-FEL, ……
[email protected] / 10-Dec-2004
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Single-Pass Devices
Courtesy T. Shintake, RIKEN/SPring8, MOBIS01
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[email protected] / 10-Dec-2004
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Single-Pass Devices
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Storage Ring vs. LINAC
Storage Ring
LINAC
Machine condition
Steady state
Transient / Pulsed
Trajectory
Closed orbit
(eigen-vector)
Open trajectory
(no eigen-vector)
Damping
Synchrotron damping
No damping
Dynamic aperture of
machine
~1 kHz
(narrow tune resonance)
No clearing  dark
currents may propagate
~GHz
(no resonance)
Beam clearing
Noise bandwidth
Energy and intensity
10-5 – 10-6
stability
Courtesy T. Shintake, RIKEN/SPring8, MOBIS01 - MODIFIED
10-2 – 10-3
[email protected] / 10-Dec-2004
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Beam Energy Stability
u


2


1

K


2
rms
2 2


  
4

  10
   FEL

Courtesy T. Shintake, RIKEN/SPring8, MOBIS01
[email protected] / 10-Dec-2004
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Single-Pass Devices
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Sources of jitter
• AC line fluctuations
power supply fluctuations: gun, RF, orbit, …..
• Switch-tune pulse-to-pulse jitter
• Switching noise fluctuations
• AD/DA digitizing noise
• Temperature fluctuations
LINAC, electrical circuits ….
• Ground motion
natural, human activity
Feed-back is mostly not possible
Feed-forward:
• between micro-pulses
• between macro-pulses
[email protected] / 10-Dec-2004
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Electron-Beam Stability
•
Transverse stability
– Low energy (injector): transverse emittance dilution
(depends on the RF-frequency: X-band more sensitive than L-band)
– Beam break-up at high average current operation
– High energy (undulator): gain reduction and wavelength jitter
typically a (few) micron
orbit accuracy
•
Longitudinal stability (bunch / RF phase)
– Energy fluctuations
– Current fluctuations  FEL gain fluctuations
– Temporal jitter with synchronized sources
locked to seed laser
Talking about femto-second and
atto-second sources
[email protected] / 10-Dec-2004
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Transverse Orbit / Undulator
•
General guideline (not necessarily correct):
– Control orbit up to 10 % of the beam diameter
εn = 10-6 m rad, E = 2.5 GeV,
β = 10 m  Δx,y = 4.5 μm
εn = 10-6 m rad, E = 20 GeV,
β = 10 m  Δx,y = 1.6 μm
εn = 10-7 m rad, E = 6.0 GeV,
β=7m
 Δx,y = 0.8 μm
•
(BESSY)
(XFEL)
(LEG)
Sextupole fields of undulator may cause tougher constraints,
specifically for short-period, small-gap undulators.
N.B. CSR in magnetic bunch-compressors may kick parts of the
electron bunch off-axis in the horizontal plate.
[email protected] / 10-Dec-2004
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[email protected]
/ 10-Dec-2004
Courtesy T. Shintake, RIKEN/SPring8,
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SCSS undulator concept
Courtesy T. Shintake, RIKEN/SPring8, MOBIS01
[email protected] / 10-Dec-2004
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Gain Length
electron beam
undulator
photon beam
spontaneous
emission
radiated
log( power )
energy
modulation / bunching
beam
dump
λ
coherent emission
saturation
Lsat ≈ 15 – 20 Lg
106 - 109
z1
Lg
z2
z
Lg = z2 – z1, P(z2)/P(z1) = e
[email protected] / 10-Dec-2004
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Transverse Orbit / Undulator
•
•
Electron beam orbit must be controlled over a few gain-lengths.
Within this distance: gain reduction
L'g  Lg /(1  x 2 )
x   /  c ,  c   / Lg
Y.-C. Chae et al (APS) MOBOS03
 T. Tanaka, et al., FEL 2003
•
Over larger distances the overlap between optical field and the
electron beam may disappear. In such a case, the microbunching will re-initiate the FEL process over a few undulator
periods only.
[email protected] / 10-Dec-2004
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•
•
•
•
Alignment tolerances for single undulators
ħω
Isochronous bend: λ < 50 nm
Stable saturation
Beam break-up in linac
G1 roundtrip > 1
dump
linac
gun
bunching
undulator
Problems, e.g.,:
isochronous
bend
radiation
High-Gain Ring FEL
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High-Gain Ring FEL
N.A. Vinokurov, A.N. Matveenko – THPOS45
[email protected] / 10-Dec-2004