flash. free-electron laser in hamburg lessons from flash flash upgrade flash ii lessons siegfried...

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



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



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



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



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



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

)



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



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



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



in HamburgFlying modules during installation at FLASH



in HamburgMounting module 7 into the FLASH tunnel



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



in Hamburg

sFLASH Section with new Undulators and Mirror Chambers



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



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



in HamburgPhoton diagnostics upgrades

Experimental hall

Beam distribution 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



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



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



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



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



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



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



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)



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)



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



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



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



in HamburgCompression Scheme w/o 3rd Harmonic Cavities



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



in Hamburg

2 mm

2 mm

Compression with and w/o 3rd harmonic cavities



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



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



FEL Experiments

Charge: 1 nC

100 μm

1 mm5 mm



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)



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



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



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



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



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



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



FEL Experiments



in Hamburg

FLASH

FLASH II

FLASH II EXP HALLPETR

A III

Extraction area

Artist view of FLASH II



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



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



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



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

flash. free-electron laser in hamburg lessons from flash flash upgrade flash ii lessons siegfried...

Documents

flash flash upgrade

hamburg flash slide

hamburg flash layout

siegfried schreiber

hamburg electron source

laser systems

old flash lamp

laser new rfgun