operation modes and longitudinal dynamics of the swissfel ... · soft limit 14.8 mv/m 25 mv/m 27...
TRANSCRIPT
+ SwissFEL
Operation Modes and Longitudinal Dynamics of the
SwissFEL Hard X-Ray Facility
Bolko Beutner - PSI
Microbunching Workshop 11.4.2012
+ SwissFEL + SwissFEL
• Introduction
• SwissFEL
• SwissFEL Injector Test Facility
• Operation Modes
• Stability Studies
• Summary
Contents
11.04.2012 2 Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL SwissFEL
11.04.2012 3
SwissFEL at PSI between Basel and Zuerich in northern Switzerland
• Phase I:Hard X-ray SASE line (Aramis) down to 0.1 nm at 5.8 GeV
• Phase II: Soft X-ray seeded FEL line (Athos) about 10-1 nm at 2.1-3.4 GeV
Different seeding options like Self-seeding, HHG,
EEHG and combinations of them
are presently under study
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL SwissFEL
11.04.2012 4
WLHA 250 MeV Injector
SwissFEL
assembly hall
OBLA C-band
test stand
PSI-West
PSI-East
Bolko Beutner - Paul Scherrer Institute
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11.04.2012 5
Injector
BC 1
Linac 1
BC 2
Linac 2 Linac 3 Collimator
Athos
Aramis
S-Band C-Band
• S-Band 2.5 cell RF gun (100 MV/m)
• S-Band Booster 1/2 (20 / 16 MV/m)
• X-Band Linearizer (20 MV/m)
• C-Band Main Linac (26-28.5 MV/m)
• Bunch Compressor with movable
girder system 0 – 5 deg
with R56 of -55mm at 3.8deg in BC1
and -20mm at 2.1 deg in BC2
Bolko Beutner - Paul Scherrer Institute
Aramis
Collimator
Linac 3
Linac 2 Linac 1
BC 1
BC 2
Booster 1/2
+ SwissFEL + SwissFEL SwissFEL Overview
11.04.2012 Bolko Beutner - Paul Scherrer Institute 6
0.7- 7 nm, 100 Hz
> 1 nm: transform limited
Athos Undulators 12 x 4 m; gap 24 - 6.5 mm
λu = 40 mm; K= 1 - 3.2; LU= 58 m
BC 2
Linac 1 Linac 2 Linac 3
Aramis Undulators
Switch
Yard
C band (36 x 2 m)
27 MV/m, - 20.9 ºC band (16 x 2 m)
27.5 MV/m, 0 º
210 m
2.0 GeV; 2.7 kA
σz= 6 μm (21 fs)
255 m
3.0 GeV
σδ = 0.34 %
εN,proj. = 0.47 μm
498 m
2.1- 5.8 GeV, 2.7 kA
σz= 6.2 μm (21 fs)
σδ = 0.006 %
εN,slice = 0.29 μm
εN,proj. = 0.51 μm
Energy tuning
C band (52 x 2 m)
max 28.5 MV/m, 0 º
12 x 4 m; gap 3.2 – 5.5 mm
λu = 15 mm; K= 1.2; LU= 58 m
THz Pump: FLUTE
S band (54 MeV; 3 nC)
0.1 – 5 THz; > 0.1 mJ
1 (0.8) - 7 Å
5 – 20 fs; 100 Hz
S band
(2 x4 m)
14/16 MV/m
0 / 0 º
Gun
Laser
Heate
r
Booster 1 Booster 2
BC 1
S band
(4x4 m)
16 MV/m
- 17 º
X band
(2 x 0.75 m)
13.3 MV/m
+ 180 º
z = 16 m
E = 130.4 MeV, I = 20 A
σz= 871 μm (2.9 ps)
σδ = 0.15 %
εN,slice = 0.23 μm
εN,proj. = 0.27 μm
63 m
355 MeV, 150 A
σz= 124 μm (413 fs)
S band
100 MV/m
51 º from
0 crossing
R56 = 66.6 mm
Θ = 4.2 º
σδ = 1.07 %
R56 = 20.7 mm
Θ = 2.15 º
σδ = 0.57 %
Energy tuning
C band (8 x 2 m)
max 28.5 MV/m, 0 º
Deflector
Deflector
2.5- 3.4 GeV, 2.7 kA
426 m
Collimation
• Aramis Hard X-Ray Undulator – SASE
• Athos Soft X-Ray Undulator – Self-seeding and SASE
• Two bunch operation is foreseen with 28ns spacing
• Photon energy of Athos and Aramis are decoupled
by a c-band module (1 klystron for 4 cavities) after
the switchyard
• Laser based THz pump source in Athos line
+ SwissFEL + SwissFEL
• Energy gain in s-band Booster 2 shifted from initial 250MeV to
330MeV (limited by RF)
• Laser heater
• No diagnostic section after BC1 – Emittance measured with
“advanced” quad scan.
• BC1 shifted downstream – closer to c-band Linac 1
Considerations about Microbunching
11.04.2012 Bolko Beutner - Paul Scherrer Institute 7
Energy gain of Booster 2 (4 structures
4m each / 2 klystrons) is increased to
about 200MeV.
+ SwissFEL + SwissFEL
Phase I : Electron Source and Diagnostics
Injector Test Facility
11.04.2012 Bolko Beutner - Paul Scherrer Institute 8
Phase II : Two S-band accelerating structures, no BC
Phase III : The full machine
Slit phase space measurements
Phase I: 0.69+- 0.04 mm mrad
(28.5.2010 22h36 240pC 4mm)
Beutner
+ SwissFEL + SwissFEL Bunch Compressor
11.04.2012 Bolko Beutner - Paul Scherrer Institute 9
BC1 during assembly BC1 completed
Movable support with dipole 2 & 3
Dipole 1
Dipole 4
Movable support for dipole 2 & 3
• Bunch Compressor with Movable Girder for the inner Dipoles
• alpha[deg] = 0.0123 * x[mm]
• Dipole Projected Length: LB = 250mm
• Projected length of Drift Arm: L12 = 4375mm
alpha [deg] B[T]
200MeV
R56[mm]
0 0 0
1 0.0466 -2.767
2 0.0931 -11.07
3 0.1397 -24.90
4 0.1861 -44.27
5 0.2326 -69.17
+ SwissFEL + SwissFEL BC Movable Girder
11.04.2012 Bolko Beutner - Paul Scherrer Institute 10
Alignment precision of components after adjustment: 20 m
Vertical deflection of girder reference surface
Courtesy of P. Wiegand & K. Dreyer
Vertical deflection of girder reference surface
Manufacturing and alignment precision of reference surfaces: e vertical < 200 m
+ SwissFEL + SwissFEL Photoinjector Laser System
11.04.2012 Bolko Beutner - Paul Scherrer Institute 11
A. Trisorio et al. Appl. Phys B, 105, 255 (2011).
Output energy
Typical SwissFEL working points for the 266nm TiSa:
Target profile for 200 pC: duration=10 ps, sub-ps rise/fall time
Target profile for 10 pC: duration=3.7 ps, sub-ps rise/all time
Using a Dazzler the target flat top and other shape
can be easily programmed Flat top pulse duration 4.6 ps,
rise time (10-90%) = 0.5 ps
modulation on the plateau <5% rms
Two photon absorption and diffraction efficiency limits the output energy (<35 μJ) Energy not sufficient to generate 200 pC in Cu cathode. The UV Dazzler could be applied to the 10 pC working point for the SwissFEL
Carlo Vicario
+ SwissFEL + SwissFEL Pulse Stacking
11.04.2012 Bolko Beutner - Paul Scherrer Institute 12
• At the SwissFEL injector 5 α-cut BBOs and 10 cm dispersive glass are used to overlap
32 pulses, each 0.6 ps long.
• Total efficiency >70%.
• AR coated α-cut BBO for λ>190 nm with relative low
losses.
• The orthogonal output polarizations makes the
optical temporal diagnostic (which are polarization
sensitive) and attenuation of the beam and the two
pulses operation more complicated
• Poor flexibility, only symmetric shapes
Dispersive glass
L L/2 L/4 L/8
α-BBO α-BBO α-BBO α-BBO
c
LnLnttt
eo
eod
45 deg o e
L
Birefringent
Medium
td
Optical axis
Carlo Vicario
+ SwissFEL + SwissFEL Injector Recent Results
11.04.2012 Bolko Beutner - Paul Scherrer Institute 13
+ SwissFEL + SwissFEL Injector Recent Results
11.04.2012 Bolko Beutner - Paul Scherrer Institute 14
Beam parameters 4/5 April:
• 100 pC beam charge
• Ti:Sapph laser (pulse stacked
mode)
• 100% transmission
• 223.5 MeV
– First S-band cavity only at half
power (requires more
conditioning)
+ SwissFEL + SwissFEL Operation Modes
11.04.2012 15
• Standard operation
• 200 pC
• Maximum FEL pulse energy
• Longest FEL pulse length
• Lowest charge operation
• 10 pC
• Short FEL pulse length
• Single-spike in soft X-ray
• Strong residual energy chirp
• 200 pC
• Large FEL Bandwidth (>1%) for
single short Absorption
spectroscopy.
• Attosecond FEL pulse
• 10 pC
• Strongest compression
• Single-spike in hard X-ray
Charge Wakefield Limited
Diagnostic Limit
Special Cases
Similar FEL Gain length for all standard
modes
=> ~ “constant”
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL Compression Schemes
11.04.2012 16
Linac 1 BC 2 Linac 2+3 Collimator
compression wakes remove chirp double dogleg
(slight decompression)
over-compression wakes add to chirp double dogleg
(slight compression)
compression wakes partially remove chirp chicane
(compression)
Bolko Beutner - Paul Scherrer Institute
Standard modes (200pC – 10pC):
Large Bandwidth mode (200pC):
Attosecond mode(10pC):
+ SwissFEL + SwissFEL Operation Modes Summary
11.04.2012 17
mode V_s
[MV/m]
P_s
[deg]
V_x
[MV/m]
P_x
[deg]
V_c
[MV/m]
P_c
[deg]
200pC 14.13 13.73 17.36 161.94 26.82 21.49
200pC 14.88 23.66 15.50 -176.05 26.45 19.31
lbw 15.22 27.05 15.07 -165.98 26.92 22.01
10pC 14.61 25.57 20.37 -167.74 26.38 19.41
50pC 14.75 27.50 17.71 -166.40 26.05 17.08
100pC 14.40 26.02 16.71 -172.60 26.00 16.61
S X C
Soft limit 14.8 MV/m 25 MV/m 27 MV/m
hard limit 16 MV/m 30 MV/m 27.5 MV/m
E1=330MeV
E2=2.1GeV
Energies of the Chicanes:
after BC2 at Aramis
Bolko Beutner - Paul Scherrer Institute
Profile optimization are obtained by
an iterative semi-analytical
procedure developed by Zagorodnov
and Dohlus: “Semianalytical modelling of multistage bunch
compression with collective effects”
PRSTAB 14,014403 (2011)
+ SwissFEL + SwissFEL Operation Modes Summary
11.04.2012 18
q C1 C2 Z’2 Z’’2 I peak εx0 εy0 I/(ex0 ey0)1/2
200 7 170 0.5 0 3.72 0.320 0.304 1.193e4
200 10 140 0.5 0 2.98 0.307 0.300 0.987e4
200 10 -180 -0.5 0 3.44 0.349 0.289 1.084e4
10 5 300 0 0 1.10 0.136 0.102 0.930e4
50 8 250 0 0 2.29 0.217 0.190 1.124e4
100 10 200 0.2 0 2.76 0.236 0.230 1.181e4
directly after BC2
q C1 C2 Z’2 Z’’2 I peak εx0 εy0 I/(ex0 ey0)1/2
200 7 170 0.5 0 3.60 0.295 0.308 1.195e4
200 10 140 0.5 0 3.00 0.302 0.300 1.012e4
200 10 -180 -0.5 0 3.97 0.344 0.289 1.259e4
10 5 300 0 0 0.83 0.132 0.097 0.733e4
50 8 250 0 0 2.08 0.243 0.190 0.966e4
100 10 200 0.2 0 2.64 0.246 0.238 1.090e4
at Aramis entrance
Current and emittance of central slice are compared
=> similar “gain” parameter of about 1e4
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL Operation Modes – after BC2
11.04.2012 19
10pC
50pC
100pC
200pC 4kA
200pC large bandwidth
200pC 3kA
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL Operation Modes – at Aramis
11.04.2012 20
200pC 4kA
200pC 3kA
200pC large bandwidth
50pC
100pC
10pC
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL FEL Performance 200pC
11.04.2012 21
Sven Reiche
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL Large Bandwidth Mode
11.04.2012 22
head
tail
Long. Phasespace at Aramis
Spectrum of Aramis output pulse
Bolko Beutner - Paul Scherrer Institute
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• Full compression
=> - single FEL Spike
- instable operation
- longitudinal coherence
Attosecond Mode
11.04.2012 23 Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL
Expected Performance
S-Band Phase [deg] 0.018
S-Band Voltage [rel] 1.8 * 1e-004
X-Band Phase [deg] 0.072
X-Band Voltage [rel] 1.8 * 1e-004
Linac 1 Phase [deg] 0.036
Linac 1 Voltage [rel] 1.8 * 1e-004
Linac 2 Phase [deg] 0.0360
Linac 2 Voltage [rel] 1.8 * 1e-004
Linac 3 Phase [deg] 0.0360
Linac 3 Voltage [rel] 1.8 * 1e-004
Charge 1%
initial arrival time [fs] 30
Initial Energy [rel] 1e-004
BC1 angle [rel] 5 * 1e-005
BC2 angle [rel] 5 * 1e-005
• Jitter sensitivities Sj are used to estimate total stability performance σA,
taking into account the expected subsystem stability σj (last slide) and
the number of independent sources N (i.e. Klystrons)
Stability Performance
11.04.2012 24
100pC mode
Bolko Beutner - Paul Scherrer Institute
10pC mode
+ SwissFEL + SwissFEL
• Tolerable Stability goals for the User Community are:
– Arrival time 100fs (20fs)
– Peak Current/Bunch length 50 % (5 %)
– Central Wavelength 0.1 % (0.05 %) (ultimate) stability goals are given in brackets
200pC Modes
11.04.2012 25
200pC 3kA 200pC 4kA large bandwidth
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL Microbunching Studies for SwissFEL
11.04.2012 Bolko Beutner - Paul Scherrer Institute 26
0.7- 7 (30) nm, 100 Hz
> 1 nm: transform limited
Athos Undulators
BC 2Linac 1 Linac 2 Linac 3
Aramis Undulators
Switch
Yard
C band (32 x 2 m)
26.5 MV/m, - 20.9 º
C band (28 x 2 m)
26.5 MV/m, 0 º
C band (44 x 2 m)
26.5 MV/m, 0 º
D’Artagnan
THz Pump
1 (0.8) - 7 Å5 – 20 fs; 100 Hz
S band
(2 x4 m)
14/16 MV/m
0 / 0 º
Gun
Booster 1 Booster 2 BC 1
S band
(4x4 m)
16 MV/m
- 17 º
X band
(2 x 0.75 m)
17 MV/m
+ 180 º
S band
100 MV/m
51 º
Laser
Heate
r
z=16m
I=20A=871 m (2.9 ps)
E=130.4 MeV
σz μ
z=63m
I=150A=124 m (413 fs)
E=355 MeV
z μσ
z=203m
I=2.7kA=6.2 m (21 fs)
E=2.04 GeV
z μσ
z=500m
I=2.7kA=6.2 m (21 fs)
E=2.1 - 5.8 GeV
z μσ
z=271m
E=2.1 or 3.4 GeV
LOW ENERGY HIGH ENERGY
t-tMEAN
(s)
Re
sid
ua
l p
(m
ass u
nits)
= 100 m
-8 -6 -4 -2 0 2 4 6 8
x 10-13
-0.12
-0.1
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0
20
40
60
80
100
120
140
160
180
t-tMEAN
(s)
Re
sid
ua
l p
(m
ass u
nits)
= 20 m
-8 -6 -4 -2 0 2 4 6 8
x 10-13
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.50
50
100
150
200
-8 -6 -4 -2 0 2 4 6 8
x 10-3
0
500
1000
1500
2000
2500
3000
Time (ns)
Inte
nsity (
a.u
.)
Q = 200 pC - x =
y = 0.27 mm
Astra
Starting pulse
-3 -2 -1 0 1 2 3 4
x 10-14
0
2
4
6x 10
-6
Time (s)
No
rma
lize
d
x (m
ra
d) Q = 200 pC
Design
Modified profile
-3 -2 -1 0 1 2 3 4
x 10-14
0
0.5
1x 10
-6
Time (s)
No
rma
lize
d
y (m
ra
d)
Design
Modified profile
START 2 END “REALISTIC PULSE”
Simona Bettoni
+ SwissFEL + SwissFEL
• Different operation modes and compression setups
– Standard mode (200pC – 10pC) with similar peak current allows for a
continuous trade-off between photon pulse length and photon number
– Minimized energy spread for 200pC 3kA mode
• SwissFEL Injector Test Facility is ready to study Beam Dynamics
and Microbunching effects experimentally
• Expected RF stability is sufficient to satisfy user requests
– Main jitter sources are S-band amplitude, X-band phase, and beam
charge
• Microbunching Issues in the Lattice design:
– Laser Heater is mandatory in this design (see Simonas Talk)
– Energy of BC1 was increased from 250MeV to 330-350MeV
– FODO diagnostics section downstream of BC1 was removed
Summary
11.04.2012 27 Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL
11.04.2012 28
Thank You
for Your Attention!
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL Expected Performance from Monte-Carlo
Calculations
11.04.2012 29
• In the simulation runs discussed on the previous slides only single
error sources were changed to determine the sensitivities. And
eventually the expected performance.
• In order to confirm the reliability of the method a set of 100
randomized machine parameter sets were simulated.
MC results
Sensitivity results
goals
arrival time [fs]
7.5 7.8 20
peak current [%]
8.9 9.4 5
beam energy [%]
0.014 0.012 0.05
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL
11.04.2012 30 Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL
• Operation modes
11.04.2012 31
q Z1 Z2 Z2p Z2pp Ipeak ex ey I/sqrt(ex ey)
200 7 170 0.5 0 3.60 0.295 0.308 1.195e4
200 10 -180 -0.5 0 3.97 0.344 0.289 1.259e4
10 6 400 0 0 1.12 0.213 0.100 0.769e4
10 10 500 0.5 0 1.42 0.212 0.100 0.977e4
10 10 500 0 0 1.43 0.214 0.101 0.970e4
50 10 200 0.5 0 1.65 0.199 0.190 0.852e4
50 10 250 0 0 2.09 0.233 0.183 1.012e4
100 10 200 0.5 0 2.65 0.245 0.228 1.121e4
100 10 200 0.2 0 2.64 0.246 0.238 1.090e4
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL Stability Studies
11.04.2012 32
elegant Evaluation Point
for Jitter Astra
Example of jitter analysis done with elegant:
Second order fits are done and if necessary the range
of the fit is adapted manually
First term of this fit is used as
sensitivity Si
Arrival time is numerical resolution
limited to 0.1 fs
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL
• A recent design change of SwissFEL (modifications of Athos line,
decoupling of Aramis and Athos via a c-band module in Athos) the
beam energy at BC2 is fixed to 2.1 GeV compared to 2.04GeV
before.
=> New c-band structures with now 113 cell are required
to increase energy gain per structure
=> Recalculations of wake fields
Design Change
11.04.2012 33 Bolko Beutner - Paul Scherrer Institute
Short-range dipole wakefields in accelerating structures for the NLC
Karl L.F. Bane - SLAC
Formulas from:
+ SwissFEL + SwissFEL Update on RF Stability
11.04.2012 34
S band phase stability 0.018 deg
Voltage stability 1.8 10 -4
0.015 deg
1.2 10 -4
4 kly sband 4 kly sband 2 kly sband
Presented at FLAC 11/2010 Summer 2011 version
Bolko Beutner - Paul Scherrer Institute
System stability expectations are updated by measured data compared to the
initial assumptions and the number of klystrons is reduced from 4 to 2.
+ SwissFEL + SwissFEL Stability Studies
11.04.2012 35
• A little theory of machine jitter
– Sensitivity Sj is the linear correlation between an error source j (with
occurs N times) and the performance goal .
– The jitter of j sj contribute to the total jitter which has to fulfil:
– If j is allowed to use the whole budget for the tolerance is:
– If more sources jitter the tolerances are effectively tighter:
– Since has to be fulfilled on gets for aj:
In this study the sensitivities Sj and tolerances are determined by elegant
simulations. The total jitter using some expected performance values are
compared with the goals. A determination of aj is not done here.
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL X-band vs. C-band Linearization
11.04.2012 36
n – basic harmonic
m – higher harmonic
Voltage of “Linearizer Cavity”:
Simple Considerations:
• Quadratic term in correlated energy spread can
be compensated by an rf field on a higher
harmonic operated at 180 deg (anti-on-crest)
• Voltage of “Lineariser Cavity” depends on the
square of harmonic number ratio
• Between the x-band (4th harmonic) and the c-
band (2nd harmonic) the voltage ration is ¼.
Vlin,X ~ 20MV/m * 2 * 0.75m = 30MV
=> Vlin,C ~ 30MV * (4/2)2 = 120MV
=> 120MV / (4*1.92m) = 15.63MV/m
moderate gradient requirements for one
standard c-band module
120-30MeV = 90MeV are missing – compensation in
S-band booster required!!
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL X-band vs. C-band Linearization
11.04.2012 37
Design for complete SwissFEL compression setup (LiTrack):
BC1: E1 = 330MeV R56 = -55mm
BC2: E2 = 2.1GeV R56 = -22mm
Booster [MV] Linearizer [MV] Linac 1 [MV]
X-band 243.2 24.5 1841.6
C-band 337.2 121.7 1841.5
Current profile and longitudinal phase space after BC2:
Required energy gain per section:
C-band linearization is possible but requires more Voltage !!
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL
• The FEL Process requires a high peak (few kA) while the
slice emittance is sufficiently low (<1 mm mrad)
Why Bunch Compression?
11.04.2012 38
current
slice emittance
Slice emittance is fine in the
central part …
But peak current is too low
=> no SASE
Slice emittance is slightly increased by self-
field effects but still ok in the centre…
Peak current is sufficiently high
=> SASE in the central part of the bunch
compression
If the compression is not uniform only a
small fraction of the particles might
contribute to the FEL!
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL What we would like to have?
11.04.2012 39
current
slice emittance
For good FEL performance we would like to have a large fraction of the
bunch to fulfill the condition of high peak current and low slice emittance.
=> large fraction of particle contribute to lasing
The longitudinal profile should be flat to achieve homogeneous photon
properties along the pulse.
Bolko Beutner - Paul Scherrer Institute
+ SwissFEL + SwissFEL SwissFEL
11.04.2012 Bolko Beutner - Paul Scherrer Institute 40
Linac Undulator
Exp.Hall
Injector
Surface areas not accessible by wild game
+ SwissFEL + SwissFEL First BC Results
11.04.2012 Bolko Beutner - Paul Scherrer Institute 41
head
tail
108deg
“on-crest”
106deg 104deg head
tail lon
gitu
din
al a
xis
energy axis
90deg
First Test of BC:
• only FINSB03 was operational
=> 60MeV => Space Charge “Blow up”
• No X-band
Beutner, Prat, Guetg
“on-crest”
~108deg
+ SwissFEL + SwissFEL
• Objectives long profiles
11.04.2012 Bolko Beutner - Paul Scherrer Institute 42
+ SwissFEL + SwissFEL CDR Setup (manually tuned)
11.04.2012 43
200pC
10pC
Bolko Beutner - Paul Scherrer Institute
head
head
head
head
+ SwissFEL + SwissFEL Semi-analytic Bunch Compression Setup
11.04.2012 44
Initial longitudinal position s0 [m]
Initial longitudinal position s0 [m]
lon
g. P
os. a
fte
r B
C1
s1 [m
] lo
ng
. P
os. a
fte
r B
C2
s2 [m
]
Bunch compression can be
described by the correlation
between initial position and
final position (after each
chicane).
A one sigma region is used to neglect beam tails
Bolko Beutner - Paul Scherrer Institute
In practice these numbers
are obtained by polynomial
fits.
+ SwissFEL + SwissFEL
• First derivative Zn is the inverse compression factor between the
start to the end of BC n.
• Z’n is the position of the current peak after BC n.
• Z’’n is the overall flatness of the current profile after BC n. It can be
increased to suppress “spikes”
Compression Parameterisation
11.04.2012 45 Bolko Beutner - Paul Scherrer Institute
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11.04.2012 Bolko Beutner - Paul Scherrer Institute 46
Multiknob FODO
E. Prat
B. Beutner
Best emittance
measurement with
Nd:YLF laser (Gaussian)
(20 April 2011)
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11.04.2012 Bolko Beutner - Paul Scherrer Institute 47
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11.04.2012 48
Initial longitudinal phase-space:
Energy gain in linac section:
Long. phase-space after acceleration:
Path length effects of the chicanes:
Bolko Beutner - Paul Scherrer Institute
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11.04.2012 49
“requested” compression profile f0:
RF setup of the machine:
“symbolic” tracking of particles – A0 is an representation
of the formulas on the previous slides:
The desired setup of the RF systems is symbolically
written as:
The problem can be split into two:
Setup of main linac after the linearizer cavity to achieve final bunch shape
Setup of injector to achieve correct setup of long. phase-space after
linearizer
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Linac Setup:
• Problem to be solved: What RF setings and initial phase-space
distribution is required to achive the
requested bunch shape?
• Example solution for a two stage compression setup:
Setup of main Linac
11.04.2012 50
As a result we obtain the required phase-space
after the injector α and the RF setup X, Y.
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Injector Setup:
• Problem to be solved: What RF settings in the injector
generate the required
phase-space distribution before the
first chicane?
• Problem can be formulates as:
with the solution:
Injector Setup
11.04.2012 51
initial phase-phase space
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• Idealized machine model:
• “real” machine model:
• RF settings are obtained in an iterative
procedure.
– Machine setup from the idealized formulas are feed into a start-to-end
simulation
– results are compared with the “requested” beam parameters
– Their difference is feed into the idealized formulas to obtain an
correction to the machine settings
Real Machine
11.04.2012 52 Bolko Beutner - Paul Scherrer Institute
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• Convergence after about 10 iterations (each step takes a few
minutes)
• Oscillations of the peak current are mitigated by application of a
fraction of the correction term
Iterative Procedure
11.04.2012 53
longitudinal [m]
Curr
ent
[A]
Peak c
urr
ent
[A]
Iteration step
i.e. x 0.5
Bolko Beutner - Paul Scherrer Institute
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This semi-analytic procedure is used to obtain desired bunch profiles
much more efficient than manual parameter tuning.
It is possible to obtain “similar” profiles while changing parameters of
the linac => optimization of the machine
Compression Setup
11.04.2012 54
C2 Z’2 Z’’2 = 0
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RF Gradient Requirements
11.04.2012 55
S X C
Soft limit 14.8 MV/m 25 MV/m 27 MV/m
hard limit 16 MV/m 30 MV/m 27.5 MV/m
Bolko Beutner - Paul Scherrer Institute
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• With the presented theory of multi-stage compression we can obtain
“similar” bunch profiles with different machine setups.
• For these varying machine setups, which share the same resulting
bunch, the RF stability performance can be compared.
=> parameter Scans
• Especially the distribution of the compression factors between the
two chicanes is relevant here.
Parameter Optimization Strategy
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C2 = 125
Bolko Beutner - Paul Scherrer Institute
C1
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Sven Reiche
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RF designs
mech. design & UP
machining
Assembly & brazing
LL RF measurements
T = 21 deg, P = 10-6
mbar, f = 5713.8 MHz
-60.00
-50.00
-40.00
-30.00
-20.00
-10.00
0.00
5.550E+09 5.600E+09 5.650E+09 5.700E+09 5.750E+09 5.800E+09 5.850E+09
Frequency [Hz]
Re
fle
cti
on
[d
B]
S11
HP RF set-up HP RF processing
since 3.11.11! H. Braun
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C-band Concept
11.04.2012 Bolko Beutner - Paul Scherrer Institute 59
Two bunch energy balance with SLED
48000000
49000000
50000000
51000000
52000000
53000000
54000000
55000000
56000000
57000000
58000000
2300 2350 2400 2450 2500 2550 2600
phase jump
phase mod.
2 Kly.
Longitudinal long range wakes
Transverse long range wakes
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FEL Beam Design Parameters Nominal Operation Mode Special Operation Mode
Long Pulses Short Pulses Large Bandwidth Ultra-Short Pulses
Charge (pC) 200 10 200 10
Energy spread (keV) 350 250 17000 (FW) 1000
Saturation length (m) 47 50 50 50
Saturation pulse energy (µJ) 150 3 100 15
Effective saturation power (GW) 2.8 0.6 2 50
Photon pulse length (fs, rms) 21 2.1 15 0.1
Beam radius (µm) 26.1 17 26 17
Divergence (µrad) 1.9 2 2 2.5
Number of photons (×109) 73 1.7 50 7.5
Spectral Bandwidth, rms (%) 0.05 0.04 3.5 (FW) 0.1
Peak brightness
(# photon/mm2.mrad2.s1.0.1% bandwidth)
7.1032 1.1032 8.1030 1,3.1033
Average brightness
(# photon/mm2.mrad2.s1.0.1% bandwidth)
2,3.1021 5,7.1018 3.1019 7,5.1018
CDR Design Parameters
Optimized Longitudinal Layout is not fully included in these numbers
S. Reiche / R. Ganter