FIRST

C. E

Abstract The first

from the MAThe 380 Menm Ti:Sapphthe 1st to 6thbeen performharmonic in

Qualitativelaser energy

Under the was initiatedHelmholtz Zknowledge olasers. It walinac injectora photo cathtwo undulatequipment wby MAX-lab

TThe facilit

an upgraded the beam tracompressionwell as two udepicted in F

Accelerato

________________________*This work has bee

PP" an EU co-fund

T RESUL

N. Čutić, FErny, A. L’H

J.

generation oAX-lab test FeV electron bhire laser and h harmonic 6 med in lineacircular polarie measuremenand settings o

INTROEuropean pro

d between MZentrum Berlion seeding asas agreed thatr in operation hode gun andtors and a m

was installed ab and BESSY i

THE MAX-ty is utilising t

operation of ansport system. A new laserundulators and

Figure 1.

or and Trans

____________________ en partially supported

ded project under FP7

LTS OF C

F. Lindau, SHuillier, E. MBahrdt, K.

of coherent hEL has receneam has beencoherent enh(263 – 45 nmar mode andization mode nts have been of the microbu

ODUCTIONoject EUROF

MAX-lab and in) to study, s a techniquet MAX-lab sat the lab and

d seeding. BEmagnetic chiat MAX-lab ain collaboratio

-LAB TESTthe MAX-lab

f the photo cam with a mar system for gd chicane hav

sport

Fi

d by the EU Commiss

7 (Grant Agreement 2

OHERENMAX-L

S. Thorin, SMansten, DHolldack, H

harmonic radintly been achin seeded by ahanced radiatim) has successd the 1st toof the radiatormade variatin

unching chican

N EL a collaborBESSY (nowdevelop and

e for free eleshould providd a laser systemESSY provideicane systemand commission.

T FEL injector linac

athode RF gungnetic chican

gun and seedinve been install

igure 1: Layo

sion in the sixth fram

211285)

NT HARMLAB TEST

S. Werin, Maep. of Atom

Helmholtz Z

iation ieved. a 263 ion in sfully o 4th r.

ng the ne.

ration w the build

ectron de the m for d the

m. All ioned

c with n and ne for ng as led as

Thand BaOas a MAXwithextraexit

Thstruchaveand totalrecirthen up toopticenoucompcurreof 25

RF Th

thermadaploweintroCharloweloweelect

Th

ut of the MAX

mework program, Con

MONIC GT FEL *

ax-lab, Lunmic Physics,Zentrum Be

he acceleratora beam transp

O cathode surfthermionic g

X I, MAX II h a 10 ps, 26acted for injecis around 1.7 he main accelctures each pe passed bothpass through beam energy

rculator is reatransported t

o the locationcs in the recugh first and spressing the bent electrons n5-40 pC is typ

Gun Systemhe photo cathmionic gun fpted to also oering the temoducing the rges up to 1 ner emittance ering the lastron energy is his pulse is

X-lab test FEL

ntract no. MEST-CT-

GENERA

d University, Lund Univrlin, Germa

r system [1] coport system. Tface that prevgun for inject

and MAX II63 nm laser pction into the FMeV. The rep

leration is donroviding 95 M

h linacs they athe linacs on

y of around 38alized in a chithrough a trann of the FEL circulator, chisecond order mbeam and prodneeded for thepically achieve

m hode RF gunfor storage rioperate as a pmperature ofgun laser

nC have beenthe extracte

ser energy to1.7 MeV at thvia the lin

L.

2005-020356, the Sw

ATION AT

y, Sweden, versity, Sweany

onsists of a RFThe gun is equviously has betion into the sII. By illuminpulse, photo FEL. The enerpetition rate isne in two 5.2 MeV. When are bent by a

ne more time.80 MeV. The icane and the nslating achro

undulators. Ticane and domomentum coducing a short e FEL interacted inthe FEL.

n is normalling injection.photo cathodf the BaO system descrn extracted, bed charge is owards 25 μhe gun exit.

nac and tran

wedish Research Coun

T THE

eden,

F gun, a linacuipped with aeen used onlystorage rings;

nating the gunelectrons arergy at the guns 2 Hz.

m long linacthe electrons

a recirculator, This gives aexit from theelectrons are

omatic doglegThe magneticogleg provideompaction forspike of high

tion. A charge

ly used as a It has beene gun [2] bycathode andribed above.

but to reach areduced by

μJ/pulse. The

sport system

ncil and IRUVX-

c a y ; n e n

c s , a e e g c e r h e

a n y d . a y e

m

WEOA4 Proceedings of FEL2010, Malmö, Sweden

340 Seeding and Seeded FELs

accelerate to 375 MeV and compressed below 1 ps.

Magnet -System The main component of the test facility is the magnet

system [3] which was provided by HZB/BESSY and consists of a modulator undulator (planar type) and a radiator undulator which is an APPLE II type plus an intermediate magnetic chicane. Table 1 lists the properties of both undulators and the intermediate magnetic chicane.

Laser System The laser system is a combined system which provides

both the RF gun pulse and the seed laser pulse for the harmonic generation. The two parts are placed almost 100 m apart and synchronised via a fibre link.

A laser oscillator (Femtolasers Synergy, 93.71 MHz, 790 nm central wavelength, bandwidth 13 nm FWHM) is placed in the gun laser hutch and locked to the 3 GHz signal generated for the RF system (gun, linacs) with a time jitter of 200-500 fs. This jitter level has been achieved by an improved RF generator.

Table 1: Parameters of the undulator section when tuning the radiator to the 3rd harmonic (88 nm) of the seed laser. In parenthesis, the properties for the 5th harmonic (53 nm) are also given.

Modulator Period length 48 mm No. of periods 30 K 2.34 Chicane (4 mag.) Length of magnets 12 cm Length of drifts 40 cm Magnetic flux density 12(8) mT Radiator Period length 56 mm No. of periods 30 K 1.05 (0.49) The pulses of the oscillator are stretched and split in

two branches. In the gun laser branch the pulses are shaped in a Dazzler, amplified, compressed and tripled to 263 nm giving up to 500 μJ in a 10 ps pulse.

The other branch is sent through a bow-tie polarization-maintaining optical fiber 90 meters to the seed laser where it is amplified, compressed and tripled to 263 nm in a pulse of 350 fs and ~100 μJ energy. A beam transport system delivers the seed laser pulse into the accelerator system.

Diagnostics and Measurement Systems The diagnostics system in the transportline of the

system consists mainly of screens and current monitors. In the test-FEL itself beam positions are measured by YAG screens. Standard current transformers provide shot-to-shot charge readback. These are not able to resolve the short pulses in time but by calibrating the integrated signal to a Faraday block measurement a correct reading can be achieved. The temporal overlap was originally done in two steps. First a rough measurement based on photo diodes where both the direct hit of the electrons and the light from the seed laser were recorded. The second step is based on an Electro Optical system [4]. After first achievement of CHG the EO system can be used directly.

At the end of the electron beamline the electron beam is bent to a beam dump with a YAG screen placed where dispersion is present to allow for energy spread measurements. Unfortunately it has proven difficult to transport the electrons without significant losses to the last YAG screen while retaining the CHG signal, and thus online measurements have been difficult. We have also utilised a THz system close to the beam dump to collect signals proportional to bunch lengths and probing induced microbunching.

Finally, a photon beamline with a horizontally focusing collection mirror and a spectrometer (2400 l/mm grating) with a liquid nitrogen cooled CCD array is being used to record the CHG signal.

RESULTS

Operation Coherent Harmonic Generation (CHG) was set up in a

multi-step process. The spontaneous radiation from the modulator undulator and radiator undulator was recorded to assure the proper gap settings calibrated to the seed laser wavelength. This was necessary as a precise electron beam energy calibration was not at hand. The electron beam orbit was also optimised for best spectrometer

Figure 2: The two undulators ( U48, the modulator, right and UE56, the elliptical radiator, left) in the MAX-lab test FEL.

Proceedings of FEL2010, Malmö, Sweden WEOA4

Seeding and Seeded FELs 341

signal. This wseed laser waYAG screenundulator. Thlight from spectrometerin the chican

the Electro Osignal wa

temporal ovewas followedadjusting thsystem has aminute perioEO signal pdrifts betweewhich maketuning.

Coherent HCHG has

harmonic at mode (see f(133 nm & mode (figurradiation bacthe harmonicundulator w133 nm wherequalled the

The spontusing SPECTwhere fitted

Figure 3. Cocircular modin circular m

was followed as placed on tns placed behis was repeathe seed la

r, despite an ane magnet. Tem

Optical systemas sought werlap by use od by an optimhe transversea tendency to

od. A temporalpartly cures then the RF gues prolonged

Harmonic Gbeen record

263 nm) to thfigures 3 & 466 nm) have

re 3). The sckground and c of the seed

was put to are the 2nd an4th and 6th hartaneous unduTRA [5] wheto achieve th

oherent 4th harde with fitted

mode (red solid

by transversetop of the elec

efore and aftated a few timaser leaking aperture blockmporal overla

m (EO). After twith small adof the seed lasmisation of the overlap. Uo drift out of l feed-back syhe problem [4

un and the linoperation tro

Generation ded from thehe 6th harmoni4). The 2nd a

e also been rspectra show the CHG peak

d laser. In figa fundamentad 3rd harmonirmonic of the ulator radiatioere the gap anhe recorded sp

rmonic signal spontaneous u

d line).

e overlap wherctron beam onter the modu

mes to reduce through to

king the laser ap was adjuste

this the CHG djustments toser delay line.he CHG signUnfortunately,overlap over

ystem based o4]. Relative p

nac remain thooublesome wi

e fundamentalic (45nm) in land 4th harmecorded in ci

the spontank placed at ex

gure 4 the radal wavelengtic of the unduseed.

on was calcund opening anpontaneous si

in both lineaundulator radi

re the n two ulator stray

o the light

ed via

o the . This

nal by , the a 10

on the phase ough, ithout

l (1st linear onics irular neous xactly diator th of ulator

ulated ngles ignal.

Thusthat per pto 1.

A and (133a larbe eonlyincre

PulsTh

showestimdecomakiThis(FWassummigh

ar and iation

Figumod

Figufitted131 radia

s the CHG fluin the 4th harmpulse (at 25 p1 pJ/pulse. modulator unthe resultin

nm) was recorger range thanexplained thaty works on a eased linewidt

se Length he pulse lengws an electronmate for theonvoluting theing the assum gives a low

WHM), far shomption has twht well consis

ure 5. Coherendulator gap.

ure 4: Linear cd spontaneounm and the

ator waveleng

ux could be camonic (66 nm)pC in circular

ndulator gap g CHG signorded. The CHn the full undt the modulat

shorter part th.

gth measuremn beam pulsee photon pue spectral wid

mption that thewer limit on thorter than the wo immediatet of several co

nt 2nd harmo

coherent 4th anus undulator r

harmonics argth).

alculated. The) we have 390mode) which

scan was manal at the 2HG signal is pdulator linewidtion is efficieof the undul

ment with thee length arounulse has beedth of the CHe pulse is transhe pulse lengelectron pulsee shortcomingoherent sub re

nic signal as

nd 6th harmonradiation. (Rare thus 2nd an

e results show0.000 photonsh corresponds

ade (figure 5)2nd harmonicpresent withindth which canent even if itlator, thus an

e EO systemnd 1 ps. Anen made byHG pulse andsform limited.gth of 200 fse length. Thisgs. The pulseegions, where

a function of

nic signal withadiator set tond 3rd of the

w s s

) c n n t n

m n y d . s s e e

f

h o e

WEOA4 Proceedings of FEL2010, Malmö, Sweden

342 Seeding and Seeded FELs

the indicatedFurther, the which limitslinewidth to t

Laser EnerThe laser

strength werein the CHGadjusted by aa large energnatural energinduced enerwill be quickbunching wisetting shouloutput. Howmakes these

In figure 6are shown. higher CHGThe signal thwhich is a sig

A lower cenergy to miintense enoug

The intermresults, but o

There is nmore laser eenergy sprea(133 nm).

Stability The stab

shortcomingsinstability osystem givintemporal vardrift mainly f

Figure 6: Scdifferent exc

d length thespectrometer

s the possibilthe lower harm

rgy and Mor energy ande scanned. Th

G process. Ta rotatable polgy spread by gy spread in thrgy spread theker and a lowill occur quicld be a sensit

wever instabilkind of optim6 the qualitatiA stronger c

G signal whenhen drops whegn of overbunchicane settinicrobunch the gh to over bunmediate chica

only qualitativo definite sign

energy. This iad is not a lim

ility of thes (figure 7).

originating mng energy ariations. Therfrom temperat

can of the laseitations of the

en only referr resolution ility to resolvemonics (longe

dulation d the chicanhis influences The seed laselariser. It is fathe seed lasehe electron bee microbuncher strength is ckly. Theoretitive knob to olities and dr

misations difficive results of chicane (3 An the laser enen the laser isnching. ng (1.3 A) re

electrons, bunch the systemane settings ely. n of a higher is an indicatio

miting factor a

e system haThere is a

mainly from and thus posre is also a loture effects.

er energy (in e microbunchi

rs to one reis around 0.3e the CHG ser wavelength

e magnet sythe microbuncer energy caavourable to iner compared team. With a l

hing in the chneeded. Alsoically the choptimise the ift in the sycult. this kind of s

A) quickly reanergy is incres further incre

equires more ut the laser wam. give interme

CHG signal uon that the naat the 2nd harm

as a coupleclear shot-tothe klystron/

sition as weong term (10

the undulatoring chicane.

egion. 3 nm, signal

hs).

ystem ching

an be nduce to the larger icane over icane CHG

ystem

scans aches

eased. eased,

laser as not

ediate

using atural monic

e of o-shot /linac

ell as min)

Inbe se

Thstabito thlaseropticprojecompsyste

Thhas MAXlinacin thharmachieradiaacce

Thsompurpoperfor a

[1]

[2]

[3]

[4][5]

r) for

Figupulse

figure 7 the een with 25 rehe shot-to-shoilising the klyhe grid 50 Hzr timing [5]. cal fibre wasect, but to rpensate for them was not in

he collaboratisuccessfully bX-lab for Cohc system has bhe 1-6th harm

monic (133 aneved. We beation at 66 nlerator sourcehe main goalse features ev

poses of the ration, diagnosa future FEL f

S.Werin et aInjector for Switzerland 2S. Thorin et a291 J. Bahrdt et FEL at MAX2006. N. Cutic et alT. Tanaka 8(2001)1221

ure 7. Stabilites (wavelengt

result of the ecorded spectrot instabilitiesystron systemz and by a fee

The long tes a factor creduce the bhe drifts usingtended for rou

SUMMAion between Mbuilt and comherent Harmonbeen upgradedmonic (263-4nd 66 nm) inelieve that cinm has nevere before. s of the system

ven beyond thfacility wa

stics and FELfacility within

REFEREal., ``Commis

MAX-lab'', 2004.. al., Nucl. Instr

al., ``UndulatX-lab'', EPAC

, THOA4, theand H. Kit

ty of 133 nmth vs. sweep n

shot-to-shot vra at 133 nm. s have been , locking the

edback systemerm drift indonsidered ini

budget it wasg cheaper meutine user ope

ARY MAX-lab and

mmissioned thnic Generationd and CHG in42 nm) and n circular moircular polarir been obser

m have been he goals. Ones to gain e

L technology tothe MAX IV

NCES ssioning of th

EPAC 200

r. and Meth. A

tors for a See2006. Edinb

ese proceedingtamura, J. S

m CHG signnumber)

variations can

addressed bytrigger phase

m for the seedduced by theitially in thes decided to

eans since theration.

d HZB/Bessyhe test FEL atn. An existingn linear mode(2nd and 4th

ode has beenised coherentrved from an

achieved ande of the mainexperience ofo build a baseproject.

he 500 MeV04, Luzerne,

A, 606 (2009)

eded HGHG-urg, Scotland

gs. Synchr. Rad.

nal. 25 single

n

y e d e e o e

y t g e h n t n

d n f e

V ,

)

-d

.

e

Proceedings of FEL2010, Malmö, Sweden WEOA4

Seeding and Seeded FELs 343