What did we learn from TTF1 FEL?

1
What did we learn from TTF1 FEL?
P. Castro
2
Stability of the electron beam
P. Castro
3
PITZ 1 RF Commissioning Results
in March 2003 we obtained
e.g. 800 µs

• rf pulse length 900 µs
• repetition rate 10 Hz
• gradient 40 MV/m at the cathode ( 3 MW)
• ? duty cylcle 0.9 , average rf
  power 27 kW (results
  limited by conditioning time)

fullfills TTF2 RF parameter requirements
F. Stephan
4
Momentum Measurement

• 41.5 MV/m
• 15 keV/c _at_ 1 nC

F. Stephan, K. Floettmann
5
dark current PITZ A0
Indication of contribution of secondary emission
to the dark current of Cs2Te Cathode. Simulations
are on the way.
Measurements by W. Hartung et. al. The dark
current spike at very low gradient is caused by
multipacting in the gun.
K. Floettmann
6
TTF II, what is required

• We need a long flat-top laser pulse, upgrade of
  the laser is planned, developments are on the
  way, but we dont know what we will have when we
  start the commissioning of the TTF II injector.
• We will start without the 3rd harmonic cavity
• we need to be prepared for different parameter
  sets

K. Floettmann
7
TTF-II Starting Scenario (l30nm, no 3rd harmonic)
Transverse emittance, current, energy spread
along the bunch and longitudinal phase space at
entry of undulator (including space charge
effects in upstream drift)
T. Limberg
8
Status

• S2E with ASTRA, TraFiC4 and elegant done for
• X-FEL (old integrated scheme)
• TTF2 design case with 3rd harmonic RF
• S2E for realistic start up phase of TTF2
• Elegant input decks done (Nina)
• S2E with ASTRA and elegant under way (J.P.
  Carneiro)
• GPT set up for TTF2 tracking (F. Stulle)
• TraFiC4 problem with self consistent tracking of
  very short sub-bunches seems fixed (necessary for
  modelling of extremely spiked longitudinal beam
  profiles)
• Phase space manipulating codes to hand the beam
  back and forth between the codes have to be
  revived (and improved)

T. Limberg
9
Bunch Length Measurement Methods
Profile
Streak camera 250 fs / 80 µm
Transverse-deflecting cavity (LOLA) 330 fs / 100 µm ?
Electro-optical sampling 300 fs / 90 µm
Coherent radiation in principlethe shorter, the easier
direct
indirect
O. Grimm
10
Diagnostics with Coherent Undulator Radiation

• Use specially designed undulator to produce
  desired infrared radiation

I (A)
E (µJ)
? (µm)
t (ps)
O. Grimm
11
TTF1/TTF2/XFEL/LC stability/reliability
Beam uptime and operational uptime (users or
acc.studies)
How much is really available for study/users
(missing pulses)?

• What is the reason for tuning
• Different machine-setting
• Drift of the machine

More accurate specification of machine status
Modes of operation

• Gun/Injector/Analysis/Linac mode (BIS)
• Down/off/user/study/tuning mode (DOOCS panel)

Information availability

• All relevant information available for each mode
  (history and correlations)
• Statistics is kept for logbook
• Leaving a mode stores changes of relevant
  parameters and plots in logbook

B. Faatz
12
Conclusion

• Many lessons can be drawn from TTF1
• Slice parameters
• Stability

Injector is better understood but needs
improvement
S2E simulations are approaching in some aspects
experimental results
More (slice) beam diagnostics needed
More accurate knowledge of machine status
needed .. ..