• S. Krinsky
  BNL, Upton, Long Island, New York

Funding: Work supported by DOE contract number DE-AC02-98CH10886.

We consider three definitions of the number of temporal modes in SASE output. These are defined in terms of: (1) the number of minimum area phase space cells occupied by the radiation; (2) the pulse energy fluctuation; and (3) the Wigner function. The conditions under which these definitions are equivalent is discussed.

• J.R. Roensch, J. Rossbach
  Uni HH, Hamburg
• K. Abrahamyan, G. Asova, J.W. Baehr, G. Dimitrov, H.-J. Grabosch, J.H. Han, S. Khodyachykh, M. Krasilnikov, S. Liu, V. Miltchev, A. Oppelt, B. Petrosyan, S. Riemann, L. Staykov, F. Stephan
  DESY Zeuthen, Zeuthen
• M.V. Hartrott, D. Lipka
  BESSY GmbH, Berlin

Funding: This work has partly been supported by the European Community, contract numbers RII3-CT-2004-506008 and 011935, and by the 'Impuls- und Vernetzungsfonds' of the Helmholtz Association, contract number VH-FZ-005.

The main goal of the Photo Injector Test facility at DESY Zeuthen (PITZ) is to test and to optimize photo injectors for Free-Electron Lasers (FELs). The demands on such a photo injector are small transverse emittances, short bunches and a high bunch charge. A FEL is driven by an accelerator which consists of a rf gun followed by an acceleration section and a magnetic bunch compressor. For the effective bunch compression detailed studies of the longitudinal phase space have to be performed. The correlation between the positions of the particles in the bunch and their longitudinal momenta has to be understood and the non-linearities of the longitudinal phase space have to be analysed. A special apparatus for longitudinal phase space tomography at 5 MeV using a dipole, a Cherenkov radiator, an optical transmission line and a streak camera was developed. Results of longitudinal phase space measurements are presented and compared with simulations.

• V. Miltchev
  DESY Zeuthen, Zeuthen

Funding: This work has partly been supported by the European Community, contract numbers RII3-CT-2004-506008 and 011935, and by the 'Impuls- und Vernetzungsfonds' of the Helmholtz Assciation, contract number VH-FZ-005

The high electron beam quality needed for SASE FEL processes requires considerable effort in characterisation and improvement of the electron source. The Photo Injector Test Facility at Zeuthen (PITZ) was built to study the production of minimum transverse emittance electron beams for Free Electron Lasers. In this work we present a study on the detailed reconstruction of the transverse phase space density distribution of electron beams at various operating conditions at PITZ. Transverse emittance values containing only a certain fraction of all particles in the distribution (core emittance) will be estimated for different operating conditions and the results will be compared with simulations.

• H. Zen, T. Fukui, T. Kii, K. Kusukame, K. Masuda, Y. Nakai, H. Ohgaki, T. Yamazaki, K. Yoshikawa
  Kyoto IAE, Kyoto

Transverse phase space tomography [1] using a quadrupole magnet and a beam profile monitor is very useful for emittance measurements especially for non-Gaussian beams, since this method directly gives transverse phase space distributions. We have tried to apply the method to measure the beam emittance of our FEL driver Linac [2]. We found, however, this method suffers from both the energy spread of the beam and the reconstruction noise which deeply depends on the reconstruction algorithm. To obtain reliable results, numerical evaluation using PARMELA which simulates the beam profile in each rotation angle has been carried out. Several image reconstruction method, such as FBP method, ART method, and Ordered Subsets - Expectation Maximization (OS-EM) algorithm [3], have been applied to reconstruct the phase space distribution. We also have introduced a noise cut procedure, and evaluation of a tolerable energy spread where this method can be applied.

[1] C.B. McKee, et al., NIM A 358 (1995) 264. [2] K. Masuda, et al., Proceedings of the 2004 FEL Conference 450. [3] H.M. Hudson and R.S. Larkin, IEEE Trans. Med. Imaging, 13:601 (1994).

• H. Loos, D. Dowell
  SLAC, Menlo Park, California
• M. Boscolo, M. Ferrario, C. Vicario
  INFN/LNF, Frascati (Roma)
• M. Petrarca
  INFN-Roma, Roma
• L. Serafini
  INFN-Milano, Milano
• B. Sheehy, Y. Shen, T. Tsang, X.J. Wang
  BNL, Upton, Long Island, New York

Funding: Work supported by DOE contracts DE-AC02-76SF00515 and DE-AC02-98CH10886

The photoinjectors for future short wavelength high brightness accelerator driven light sources need to produce an electron beam with ultra-low emittance. At the DUV-FEL facility at BNL, we studied the effect of longitudinally shaping the photocathode laser pulses on the electron beam dynamics. We report on measurements of transverse and longitudinal electron beam emittance and comparisons of the experimental results with simulations.

• S. Zhang, S.V. Benson, D. Douglas, D. Hardy, C. Hernandez-Garcia, K. Jordan, G. Neil, M.D. Shinn
  Jefferson Lab, Newport News, Virginia

Funding: This work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Army Night Vision Laboratory, the Air Force Research Laboratory, and by DOE Contract DE-AC05-84ER40150.

The design and construction of an optical transport that brings synchrotron radiation from electron bunches to a fast streak camera in a remote area has become a useful tool for online observation of bunch length and stability. This paper will report on the temporal measurements we have done, comparison with simulations, and the on-going work for another imaging optical transport system that will make possible the direct measurement of the longitudinal phase space by measuring the bunch length as a function of energy.