FLASH.Free-Electron
Laserin HamburgLessons from FLASH
FLASH
Upgrade
FLASH II
Lessons
Siegfried SchreiberDESY
FLS 2010SLAC1-6 March 2010
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgFLASH at DESY, Hamburg
FLASH
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgFLASH at DESY in Hamburg
> Single-pass high-gain SASE FEL SASE = self-amplified spontaneous emission
> Photon wavelength range from vacuum ultraviolet to soft x-rays
> Free-electron laser user facility since summer 2005
1st period: Jul 2005 – Mar 2007
2nd period: Nov 2007 – Aug 2009
3rd period: starting late summer 2010
> FLASH is also a test bench for the European XFEL and the International Linear Collider (ILC)
> FLASH is now being upgraded in a shutdown started 21-Sep-2009 to 1.2 GeV to approach the water window
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgFLASH layout – after the upgrade
315 m
Bunch Compressor
Bypass
UndulatorssFLASH
Bunch Compressor
5 MeV 160 MeV 500 MeV 1200 MeV
Accelerating StructuresDiagnostics
FEL Experiments
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgElectron Source: RF-Gun and Laser
>New RF-Gun from PITZ with strongly reduced darkcurrent – by a factor of ~10 (at 3.8 MW)
> Prepared for higher RF power > 5 MW – once a 10 MW klystron is available
> Two fully diode pumped laser systems – replacing the old flash lamp pumped heads
> 10 Hz operation
> Improved low level RF controls of RF Gun and 1st accelerating module
>New synchronization system based on fiber laser reference – phase control over bunch train
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgPITZ – Photo Injector Test Stand at DESY Zeuthen
>Develops electron sources for FLASH and European XFEL
>Has demonstrated key parameters for the European XFEL:
low emittance
high average power operation
10 Hz, 7 MW, 0.7 ms RF pulse length ~50 kW av. power
Talk on PITZ this afternoon, WG5 session
nC) 1 chargebunch -ry (prelimina
mrad mm 010.0681.0%)90(
mrad mm 011.0886.0%)100(
xy
xy
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgExample for smaller bunch charges
> Emittance approaches 0.3 mm mrad for 100 pC
preliminary results
Study of emittance vs.BSA size and chargegun of -6 deg off-crest, booster on-crest
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
BSA size (mm)
Em
it-X
Y (
mm
-mra
d)
1 nC
0.5 nC
0.25 nC
0.1 nC
1 nC results for similar machine conditions (~3 weeks period)
measurements hampered by RF phase stability issues
Laser Spot Size (mm)
Em
itta
nce
(m
m-m
rad
)
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in Hamburg3.9 GHz (3rd harmonic) Module and Module 1
>New 1st accelerating module with better sc cavities, now equipped with Piezo tuners
> 3rd harmonic module with four nine-cell superconducting cavities operated at 3.9 GHz
Built by FNAL in a collaboration with DESY
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgAccelerating Modules
> 7 TESLA type accelerating modules
Superconducting 9-cell Niobium 1.3 GHz cavities operated at 2 K
>Electron beam energy 1.2 GeV
> 7 RF stations
five 5 MW, one 10 MW multibeam klystron, one 3.9 GHz station
Pulse length 1.5 ms
10 Hz
>XFEL type waveguide system on modules 1, 6, and 7
RF power to cavity pairs individually adjusted→ optimization of performance
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in Hamburg7th Accelerating Module
> 7th superconducting accelerating module (XFEL prototype PXFEL1)
> Tested in the module test stand at DESY (CMTB)
> Expected gradient more than 200 MeV – excellent state of the art cavities
>Waveguide distribution system allows gradient optimization
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgFlying modules during installation at FLASH
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgMounting module 7 into the FLASH tunnel
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgsFLASH: Experiment for Seeded FEL Radiation
> Generation of seeded FEL radiation for piloting experiments
> Synchronisation goal for pump probe experiments: 10 fs
> Installed between the collimator and SASE undulators→ new electron beamline with a length of ~ 40 m
> Collaboration of DESY and U Hamburg
> HHG seeding at ~ 35 nm (13 nm as an option)
4 variable gap undulators
In-coupling (seed)
Out-coupling (photons)
Optical replica synthesizer (longitudinal beam diagnostics)
Top-view sFLASH
SASE undulators
FLASH Exp. Hall
Experimental hut
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in Hamburg
sFLASH Section with new Undulators and Mirror Chambers
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgUndulators
> High-gain single-pass SASE FEL
> Fixed gap undulator
6 modules with a total length 27 m
permanent NdFeB magnets
gap 12 mm
> Changing photon wavelength requires a change of the electron beam energy
> Wavelength reach with 1.2 GeV = 5 nm
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgExperimental Hall
Visible Laser
FIR -BeamlinePlane Grating
Monochromator
BL3unfocused (5 -10 mm),
optional multilayer mirror in experiment for few to
sub-μm focus
BL220 μm focus
BL1100 μm focus
PG250 μm focus,
monochromatized
PG1sub-10 μm focus,monochromatized2-stage Raman-
Spectrometer(under commissioning)
> ~ 95 publications on photon science at FLASH in high impact journals
> ~ 50/year on technical developments
http://hasylab.desy.de/facilities/flash/publications/selected_publications
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgPhoton diagnostics upgrades
Experimental hall
Beam distri- bution area
Tunnel
New installations:
> Focusing mirror at BL3
> Fast switching mirror unit
> Split and delay unit as a permanent device in the direct beam lines
> Additional Photon beam position monitors (BPM) with MCP / fluorescence screen monitor
> New online spectrometer based on atomic photoionization
> Micro channel plate (MCP) / fluorescence screen monitor
> and many more
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgOnline Spectrometer
> Online determination of the spectral distribution using ion and electron time-of-flight spectrometer
Gas inlet with ~10-7mbar (rare gases)
Ǿ 22mm apertures at both ends
> Important to tune wavelength and spectral width
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgUser experiments at FLASH
> 4 calls for proposals so far (pilot + 3 user periods)
> Typically ~300 12-h shifts per period scheduled for users
> 3rd user period: 324 shifts for 28 experiment
FLASH Proposals (submitted/approved)
30
4550
75
29 32
18
28
0
10
20
30
40
50
60
70
80
2002 2003 2004 2005 2006 2007 2008 2009
Year
Pro
po
sa
ls
User operation
FLASH Proposals (submitted / approved)
Pilot experiments
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgOrganization of beam time
> Beamtime is scheduled in blocks
> A user block has 4 weeks
> Between user blocks: 1 or 2 study weeks and 1 week user run preparation
FEL physics studies
Improvements of the FLASH facility
Preparation of the next user block (beamlines)
>General accelerator studies weeks
a few blocks per year for general studies, mostly related to the European XFEL or ILC
User period User User period
2005 2006 2007 2008 2009 2010
Periods for upgrade and commissioning
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgOrganization of beam time
>Up to now two periods with user experiments:
1st period: Jul 2005 – Mar 2007
2nd period: Nov 2007 – Aug 2009
3rd period starts late summer 2010
> A total of 14000 hours of user beamtime
> 1st → 2nd period:
Uptime 87% → 93%
45% → 49% of beamtime to users (within user periods)
30% → 33% of total time
> Beam time is overbooked by a factor of ~3
> Experiments form collaborations to work more efficient
> In average one experiment is scheduled for 11.6 12h-shifts
large pressure on experiments and machine to succeed in a short time
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgBeam time distribution during 2nd user period
FEL user experiments 49%
FEL studies + user preparation 30%
Scheduled off 11 %
Accelerator studies 10%
SASE FEL radiation delivery 78 %
Set-up 1 %
Tuning 14 %
Down 7 %up-time during user experiments: 93%
Nov-26, 2007 – Aug-16, 2009
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgSASE Tuning for Experiments
Wavelength changes 55%
Intensity, position, etc. 17 %
After failures 7%
Quality 8% narrow bandwidth, exact
wavelength, etc.
After maintenance 6%
Single, multi, (long), rep.rate
5%
> Wavelength has been changed ~ 140 times
> Tuning time required for wavelength changes is typically ~ 2 hour
Other 2%
10 20 30 400
10
20
30
40
50
60
Hou
rs tu
ning
per
we
ek
User week number
scheduled 48 hours to setup 5th harmonic of 8 nm
Time used for wavelength changes / week
ho
urs
# user week
2nd user period
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgPhoton Wavelengths
10 15 20 25 30 35 400
500
1000
1500
2000
2500
Wavelength delivered to users
Num
ber
of h
ours
Wavelength (nm)
> More than 30 different wavelengths between 6.8 nm and 40.5 nm delivered for users
> Most favorite wavelengths
around 7 nm - as short as possible
around 13.5 nm - availability of multilayer mirrors, best compromise with other users
> Experiments using higher harmonics
3rd harmonic of 7 nm
5th harmonic of 8 nm
3rd harmonic of 40.5 nm
> Shortest wavelength delivered
1.59 nm (5th harmonic of 7.97 nm)
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgSASE performance
Typical user operation parameters
Wavelength range (fundamental) 6.8 – 47 nm Average single pulse energy 10 – 100 µJPulse duration (FWHM) 10 – 70 fs Peak power (from av.) 1 – 5 GWAverage power (example for 500 pulses/sec) ~ 15 mW Spectral width (FWHM) ~ 1 % Peak Brilliance 1029 - 1030 B
B = photons/s/mrad2/mm2/0.1%bw
Multibunch SASE signal (µJ)
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgSummary Upgrade 2009 / 2010
> Upgrade shutdown started September-21, 2009
> Technical commissioning started February-15, 2010
> First beam expected in April, user runs to be started in late summer 2010
upgraded photon diagnostics and
beamlines
new RF gun 7th accelerating module
seeding experiment sFLASH + redesigned electron
beamline
transverse deflecting cavity + spectrometer arm / tuning dump
3rd harmonic module + RF station
exchanged 1st accelerating module
additional RF station + exchanged RF station
exchanged RF stations
optimized llrf controls
new synchronization and feedback systems
improved survey and alignment of accelerator components
(incl. SASE undulators)
upgraded magnet controls
upgraded personnel interlock und radiation safety systems
upgraded and optimized waveguide distribution
new diode pumped photocathode laser; upgraded old laser
system
installation of a second master oscillator (as backup)
new cabling/layout injector llrf electronics
maintenance of infrastructure: water supplies, cryogenics
exchanged injector steerers
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgUpgrade Status
>Upgrade in schedule – technical commissioning started
> First beam to be expected mid April
>Commissioning until summer:
Main goals:
lasing with wavelength below 5 nm
tailor phase space using the 3rd harmonic cavities to improve lasing and to have more flexibility in FEL pulse length
routine operation with long bunch trains and improved synchronization
stable seeding in sFLASH
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgCompression Scheme w/o 3rd Harmonic Cavities
>Non-linearity in the longitudinal phase space leads to a roll-over compression → development of a sharp spike ~ 50 fs with high peak current
> Very sensitive to phase and orbit changes in the collimators
Z (mm)
2 mm1 M
eV
Z (mm)
2 mm
1 M
eV
Ene
rgy
(MeV
)
Z (mm)
2 mm1
MeV
Cur
rent
(A
)
40 A
2 mm
1.5 kA
0.5 mm1 mm
400 A
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgCompression Scheme w/o 3rd Harmonic Cavities
>Non-linearity in the longitudinal phase space leads to a roll-over compression → development of a sharp spike ~ 50 fs with high peak current
> Very sensitive to phase and orbit changes in the collimators
Z (mm)
2 mm1 M
eV
Z (mm)
2 mm
1 M
eV
Ene
rgy
(MeV
)
Z (mm)
2 mm1
MeV
Cur
rent
(A
)
40 A
2 mm
1.5 kA
0.5 mm1 mm
400 A
Measured longitudinal shape of a compressed bunch
Measured by a transverse deflecting cavity placed after the last accelerating module
t [ps]
x [m
m]
0 0.5 1 1.5 2-4
-2
0
2
0 0.5 1 1.5 20
0.5
1
/
max
t [ps]
tspike
65 fs (FWHM) Q
spike 0.12 nC (23 %)
0
50
100
150
200
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in Hamburg
2 mm
2 mm
Compression with and w/o 3rd harmonic cavities
>Non-linearity in the longitudinal phase space leads to a roll-over compression → development of a sharp spike ~ 50 fs with high peak current
> Very sensitive to phase and orbit changes in the collimators
Z (mm)
2 mm1 M
eV
Z (mm)
2 mm
1 M
eV
Ene
rgy
(MeV
)
Z (mm)
2 mm1
MeV
Without 3rd harmonic
cavities
With 3rd harmonic
cavities
50 μm
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgRegular Compression with 3rd Harmonic Cavities
> Flattening of the longitudinal phase space
>More regular compression with high peak current
> About a factor of ~10 more photon energy, longer pulses ~150 fs
50 A
Cur
rent
(A
)C
urre
nt
(A)
S (mm)
200 A
Cur
rent
(A
)
S (mm)
2.4 kA
Cur
rent
(A
)S (mm)
315 m
Bunch Compressor
Bypass
UndulatorssFLASH
Bunch Compressor
5 MeV 160 MeV 500 MeV 1200 MeV
Accelerating StructuresDiagnostics
FEL Experiments
Charge: 1 nC
100 μm
1 mm5 mm
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgExpected Photon Energy and Pulse Length
> Regular compression scheme with 3rd harmonic cavities, charge 1 nC → larger single pulse energy, pulse lengths ~100 fs
> Compression Schemes with lower bunch charge → short pulses down to ~5 to 50 fs
0 5 10 15 20 250
10
20
30
40
50
60
70
80
90
1 nC
0.25 nC
0.02 nC
Radiation pulse width (RMS)
0 5 10 15 2010
-2
100
102
103
0. 25 nC
1 nC
Radiation pulse energy/charge (av.)
0. 02 nC
Undulator length z (m) Undulator length z (m)Pul
se e
nerg
y/C
harg
e (μ
J/nC
)
rms
Pul
se L
engt
h (f
s)
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgSynchronization and Beam Based Feedbacks
> Even with an excellent energy stability of ~1 10-4 the magnetic chicane bunch compressors translates this into arrival time jitter
> Also phase jitter of laser/ RF Gun contributes plus various sources of slow drifts
> jitter and drift along the bunch trains
→ synchronization system based on stable fiber lasers
→ beam picks-ups and other instrumentation at various places along the linac
→ feedbacks using this information
→ successful tests with prototypes ofthese pick-ups (BAMs) (2008)
40 fs rms achieved – goal: 10 fs
2008 data
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgLayout of the Synchronization System
>Most components will be ready for the FLASH start-up
> Synchronization and beam based feedbacks need careful commissioning
> In close cooperation with users, especially with pump-probe experiments
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgOperation with Long Electron Bunch Trains
> FLASH will (again) offer trains of a few hundred pulses at 10 Hz
number of pulses / train depends on the pulse spacing within the train, and on the demands concerning the photon beam parameters
> Lasing with 800 bunches / train (1 MHz bunch spacing, 5 Hz rep. rate) demonstrated in spring 2007, user runs in 2008
> Long train operation has not been possible for a year due to a leak in the dump line
> Successfully repaired in August 2009, new dump line and new diagnostics and loss monitors tested successfully in Sep 2009
> Full beam-loading experiment in Sep-2009
800 bunches at 1 MHz stable, 2400 bunches demonstrated
ILC driven international collaboration
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgLong Bunch Train Run at 7 nm in 2008
> 100 bunches 500 kHz for two experiments in March 2008
>Wavelength: 7.05 ± 0.1 nm
> Average SASE level ~30 μJ (14 mW average power)
Wavelength (nm)
Bunch Number
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgFLASH II – 2nd Undulator Line and Experimental Hall
> Common proposal by DESY and HZB with participation of PSI
> In planning phase, kick-off meeting 28-Jan-2010
FLASH II
FLASH
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgFLASH II layout
>Main features: Seeding and polarized radiation
> Extend user capacity with SASE and HHG/HGHG seeding
> Tunability of FLASH II by moveable undulator gap
>Using existing infrastructure
> Separation FLASH and FLASH II behind last accelerator module
315 m
Bunch Compressor Bypass
UndulatorssFLASH
Bunch Compressor
5 MeV 160 MeV 500 MeV 1200 MeV
Accelerating StructuresDiagnostics
FEL Experiments
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in Hamburg
FLASH
FLASH II
FLASH II EXP HALLPETR
A III
Extraction area
Artist view of FLASH II
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgLessons
The upgrade plans I showed actually reflect many lessons we learnt from 4 years of user operation
FEL experiments – accelerator
> Close cooperation of accelerator and FEL users is essential for success
experimental success often depends on fine adjustment of beam parameters
example: 5th harmonic experiment at 1.59 nm
> Machine upgrades need to be planned and discussed together with users to understand their needs
short wavelength (water window), better synchronization (to fs level) and stability (seeding), fast tuning of wavelength (variable gap), polarization (left and right)
> On the other hand, users need to understand the potential and the limitations of the facility
> Users need to be prepared to take advantage of hundreds or thousands of bunches per second and need to be able to cope with the burst structure
requires new experimental techniques and detectors
> Electron and FEL beam data must be acquired (DAQ) and need to be provided to users – since they are essential for their data analysis
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgLessons
Organization of experiments
> Every experiment has quite different demands on the FEL beam and need to be accounted for
> Flexibility in FEL beam properties required
single pulse energy, number of bunches per sec, distance between bunches, wavelength, spectral width, arrival time stability and so on
frequent changes of beam parameters (from shift to shift, even within shifts)
> Bundling of experiments with similar requirements and good preparation of the run
> Serving a single user at a given time not very efficient (→ FLASH II)
> The often complex experiments need a long preparation phase, but have only a very short running time (11.6 shifts) and a long time spans between experiments
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgLessons
Stability of Beam
> An excellent stability of the beam is essential (sounds trivial…)
> The llrf system turns out to be a key issue for good beam quality: the long rf pulses and high beamloading together with the complicated compression scheme requires tight tolerances in amplitude and phase stability which have to be met
> To complete the llrf system, synchronization to the fs level and beam based feedbacks are important for many experiments
> Climate needs to be taken into account
in Hamburg we observe a large difference between summer and winter runs - especially the summers are quite hot and produce difficulties
> As much non-destructive diagnostics as possible, both for electrons and FEL beam
we need to access the longitudinal phase space (slice parameters) with high precision (fs)
online FEL beam parameters (energy, position, spectrum)
> Operators do have difficulties to learn to run FLASH
efficient operation needs many tools and procedures especially restore procedures,
operator training
Siegfried Schreiber | FLS 2010 - SLAC | 1 Mar 2010
FLASH.Free-Electron Laser
in HamburgSummary
> FLASH finished in August 2009 a very successful 2nd user period
> ~ 95 publications on photon science at FLASH up to now
>Upgrade shutdown started in autumn 2009, beam to be expected in April 2010
>Major modifications of FLASH
energy reach of 1.2 GeV to approach wavelengths below 5 nm
shaping of longitudinal phase space with 3rd harmonic module
synchronization to 10 fs level with new system based on fiber lasers
sFLASH: test of seeding option
>One aim is it to provide routinely long bunch trains to users
> FLASH II in sight: seeding and polarization
Second undulator beamline + new experimental hall (FLASH II) in the planning phase