XFEL Beam Line Internal Review - Injector

22.10.2006 14:00-17:00

The injector starts at the gun and stops at the entrance of the linac1 (which is downstream of the dog-leg and upstream of the bunch compressor 1).

Topics / Speakers
Introduction Injector / K. Flöttmann
Injector Simulations / M. Krasilnikov
Dark Current / J.H. Han
Optic / W. Decking
Diagnostic 1 / D. Nölle
PITZ TCAV / S. Korepanov
Diagnostic 2 / H. Schlarb
Dump / M. Schmitz
Magnets / B. Krause
Vacuum / K. Zapfe

Comments:

Injector Simulations:

  • Velocity bunching has been studied both experimentally and numerically for TTF-1 and did not provide encouraging results. First experimental proof of velocity bunching is expected from Frascati within the next 2 month.
  • The space between gun and module is increased by 0.7 m in case of the 60 MV/m optimization. In case of the shifted 2nd solenoid the space is even increased to 1.6 m (but some space (0.2 to 0.3 m) will be lost due to the necessary redesign of the gun input coupler).

Dark Current:

  • Size of the collimators: 10 mm aperture, 10% energy bandwidth
  • It is agreed that further energy collimation in the dogleg has to be considered

Standard Diagnostics:

  • Add SR port in injector dump line
  • Provide sufficient measurement capabilities to measure the absolute position of the beam within the first module

Transverse Deflection Structure for PITZ

  • Simulations show limited energy resolution due to bunch distortions caused by the cavity field nonlinearities
  • Field is most linear for 1.3 GHz
  • TDS should be ready within approximately 1 year

Special Diagnostics

  • Compared to the present FLASH diagnostic section layout 2 additional OTR stations at 18 and 108 deg phase advance (from first OTR) are needed
  • The vertical TDS has to be placed 36 deg upstream of the first OTR
  • 2 kickers in the diagnostic section have to be foreseen
  • Dark current removal in the time domain should be foreseen either directly after the cavity or better in front of the cavity
  • The laser heater has to be placed in front of the TDS to provide control over the laser-beam interaction
  • The laser heater needs perfect overlap between laser and electron beam and thus special optics matching
  • In view of the limited energy resolution of the TDS due to the internal fields (see previous talk), the TDS philosophy has to be reevaluated
  • The issue of the planned 25 MHz laser versus the existing 27 MHz laser was raised

Beam Dumps

  • The dump arm design should ensure a proper beam size or sweeping on the dump face
  • Beam position may be interlocked with aperture and beam loss monitor

Magnets

  • Magnets should be build for the foreseen energy range
  • A SR port has to be included in the bending magnets

Vacuum

  • Alignment of components