K. Floettmann STI Meeting, June 23, 2004
DESY
STI Meeting June 23, 2004
Klaus Floettmann
Generation of High Quality Beam
K. Floettmann STI Meeting, June 23, 2004
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
K. Floettmann STI Meeting, June 23, 2004
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
K. Floettmann STI Meeting, June 23, 2004
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
K. Floettmann STI Meeting, June 23, 2004
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
K. Floettmann STI Meeting, June 23, 2004
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
]
w.o. thermal emittance
K. Floettmann STI Meeting, June 23, 2004
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
]
w.o. thermal emittance0 ps rise time
K. Floettmann STI Meeting, June 23, 2004
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 °
K. Floettmann STI Meeting, June 23, 2004
DESY
Longitudinal particle distribution behind bunch compressor with and without the 3rd
harmonic system.
The longitudinal phase space
K. Floettmann STI Meeting, June 23, 2004
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
K. Floettmann STI Meeting, June 23, 2004
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
K. Floettmann STI Meeting, June 23, 2004
DESYLongitudinal phase space at the end of the Linac
old layout new layout
K. Floettmann STI Meeting, June 23, 2004
DESYParameters of the injector
charge 1nC
εx,y 1.4 µm
σz ~20 µm (80 fs)
σE, uncorr < 2.5 MeV
K. Floettmann STI Meeting, June 23, 2004
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.
K. Floettmann STI Meeting, June 23, 2004
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
K. Floettmann STI Meeting, June 23, 2004
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)
K. Floettmann STI Meeting, June 23, 2004
DESYPITZ Results: beam dynamics
Example of bunch length measurements
K. Floettmann STI Meeting, June 23, 2004
DESYSimulation Results on transverse Emittance
Expected lowest transverse emittance for the present parameters of gradient and laser at PITZ:
n µm2.0 e ≤
K. Floettmann STI Meeting, June 23, 2004
DESYPITZ Results: transverse emittance
Best measured transverse Emittance
K. Floettmann STI Meeting, June 23, 2004
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
K. Floettmann STI Meeting, June 23, 2004
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
K. Floettmann STI Meeting, June 23, 2004
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