generation of high quality beam - the european x-ray laser...

K. Floettmann STI Meeting, June 23, 2004

DESY

STI Meeting June 23, 2004

Klaus Floettmann

Generation of High Quality Beam


DESYSchematic overview of the TESLA XFEL Injector

Injektor II

Injektor I

Booster

3rd Harm.

BunchCompressor

Injector I Bunch compressor

section

Injector II

3rd harm. section

500 MeV100 MeV

4 TESLA Modules


DESY

Injektor II

Schematic overview of the TESLA XFEL Injector

RF Gun TESLA Modulediagnostics

section

commissioning dump

8 cavities~ 12 MV/m

5 MeV ~100 MeV


DESYDevelopment of the transverse Emittance

– 1nC charge

– uniform transverse distribution

– longitudinal flat-top with 2 ps rise time

– incl. thermal emittance

n = 0.9 µm e


DESYSlice Emittance at the Injector exit

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

-4.00 -3.00 -2.00 -1.00 0.00 1.00 2.00 3.00 4.00

longitudinal position [mm]

slic

e em

ittan

ce [m

rad

mm

]emittance in longitudinal slices of the bunch



0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

-4.00 -3.00 -2.00 -1.00 0.00 1.00 2.00 3.00 4.00


slic

e em

ittan

ce [m

rad

mm

]

w.o. thermal emittance



0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

-4.00 -3.00 -2.00 -1.00 0.00 1.00 2.00 3.00 4.00


slic

e em

ittan

ce [m

rad

mm

]

w.o. thermal emittance0 ps rise time


DESYThe 3rd harmonic section


DESYCorrelated distortion of the longitudinal phase space


DESYThe longitudinal phase space

Longitudinal phase space in front of the bunch compressor with (red) and without (blue) the 3rd harmonic system. The remaining curvature of the phase space is matched to the second order compression factor of the bunch compressor.

Eacc = 20 MV

ϕ = 183.5 °


DESY

Longitudinal particle distribution behind bunch compressor with and without the 3rd

harmonic system.

The longitudinal phase space


DESYThe old bunch compressor concept

ACC1 ACC2 ACC3 ACC4 ACC5RF-GUN BC1

0.0 m 12.0 m

ASTRA with Space Charge

To the end of linac : ELEGANT with CSRwith geometric wake fields without space charge

31.0 MV/m-60 degree

30.0 MV/m-74 degree

AC

C39

ACC6BC2

σz = 1.96 mm 313 µm 71 µm

BC3

nACC7 ACC8 ACC57

UNDULATOR, 200 mσz = 71 µm 25 µm

1655 m


DESYThe new bunch compressor concept

ACC1 ACC2 ACC4 ACC5RF-GUN

0.0 m 12.0 m

ASTRA with Space Charge

ACC39ACC6ACC3 BC1

σz = 2.0 mm 112 µm 22 µm

nACC7 ACC8 ACC57

UNDULATOR, 200 mσz = 20 µm

1545 m

BC2

ACC9

To the end of linac : ELEGANT with CSRwith geometric wake fields without space charge


DESYLongitudinal phase space at the end of the Linac

old layout new layout



2.5 kA



1.4 µm


DESYParameters of the injector

charge 1nC

εx,y 1.4 µm

σz ~20 µm (80 fs)

σE, uncorr < 2.5 MeV


DESYInjector R&D in the TESLA Collaboration

• Cathode development at INFN Milano.• Simulation code development at DESY and

FNAL.• 3rd harmonic cavities at FNAL.• Experimental investigations at the A0 Photo

injector at FNAL.• Injector operation at TTF I and TTF II.• Experimental investigations at the Photo injector

Test stand in Zeuthen PITZ.


DESYThe Photo Injector Test stand in Zeuthen PITZ


DESYRF Gun for the TESLA XFEL


DESYPITZ Results: high duty cycle operation

40 MV/m at the cathode (~ 3 MW),

10 Hz, 800 µs

duty cycle: 0.9 %,

average rf power: 27 kW

no rf trips !!

(results limited by conditioning time)

0.2

0.3

0.4

0.5

0.6

0.7

800 1000 1200 1400 1600 1800 2000 2200

t / µsec

a.u. Forward power

Reflected power

800 µs


DESYPITZ Results: beam dynamics

0

1

2

3

4

5

-150-100-50SP Phase / deg

MeV

/c

Pmean measuredPmean simulated

0

50

100

150

200

keV

/cPrms measuredPrms simulated

Energy and Energy spread measurements

(0.5-1nC)


DESYPITZ Results: beam dynamics

Example of bunch length measurements


DESYSimulation Results on transverse Emittance

Expected lowest transverse emittance for the present parameters of gradient and laser at PITZ:

n µm2.0 e ≤


DESYPITZ Results: transverse emittance

Best measured transverse Emittance


DESYThe new Injector at TTF II

RF gun

4 MeV 150 MeV

bunch compressor

ACC1 (M2*)

ACC2(M1*) ACC3(M3*)

Laser

3rd

harmonic cavity diagnostic section

beam dump

12 MV/m 20 MV/m

Ø gun from PITZ

Ø upgraded laser (tested at PITZ), but still short laser pulses!

Ø 3rd harmonic section not yet installed


DESYCommissioning results at TTF II

Ø injector concept validated

Ø stable rf operation with long pulses and high rep rate

Ø improved stability

Ø transverse emittance (preliminary) ~3 µm


DESYFrom TTF II to the XFEL

TTF II parameters have been achieved at PITZ.In order to reach the XFEL parameters we have to:• increase the gradient on the cathode from 40 MV/m to

60 MV/m – this is scheduled for the next running period at PITZ.

• improve the transverse and longitudinal laser profile further – ongoing

generation of high quality beam - the european x-ray laser...

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