• M.A. Khojoyan, G. Asova, J.W. Bähr, H.-J. Grabosch, L. Hakobyan, M. Hänel, Ye. Ivanisenko, M. Krasilnikov, M. Mahgoub, M. Otevrel, B. Petrosyan, S. Rimjaem, A. Shapovalov, R. Spesyvtsev, L. Staykov, F. Stephan, G. Vashchenko
  DESY Zeuthen, Zeuthen
• G. Klemz
  MBI, Berlin
• S. Lederer
  DESY, Hamburg
• B.D. O'Shea
  UCLA, Los Angeles, California
• D. Richter
  HZB, Berlin
• J. Rönsch-Schulenburg
  Uni HH, Hamburg

The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops and optimizes electron sources for Free Electron Lasers (FEL’s) such as FLASH and European XFEL. The electrons are generated by the photo effect using a cesium telluride (Cs2Te) cathode and are accelerated in an 1.6-cell L-band RF-gun cavity with about 60MV/m maximum accelerating field at the cathode. The upgraded laser system at PITZ produces flat-top and Gaussian laser pulses of different time durations. Emittance measurements have been done for short Gaussian laser temporal profile ~2ps FWHM and for 6.6 MeV electron beam energy. The transverse projected emittance was measured for various transverse laser spot sizes at the cathode and different low bunch charges to find an optimum condition for thermal emittance measurements. ASTRA simulations were performed for various measurement conditions to estimate the space charge contribution to the emittance. The comparison of emittance measurement results and simulations is presented and discussed in this contribution.

• S. Rimjaem, G. Asova, J.W. Bähr, H.-J. Grabosch, L. Hakobyan, M. Hänel, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, M. Mahgoub, M. Otevrel, B. Petrosyan, A. Shapovalov, R. Spesyvtsev, L. Staykov, F. Stephan
  DESY Zeuthen, Zeuthen
• S. Lederer
  DESY, Hamburg
• M.A. Nozdrin
  JINR, Dubna, Moscow Region
• B.D. O'Shea
  UCLA, Los Angeles, California
• D. Richter
  HZB, Berlin
• J. Rönsch-Schulenburg
  Uni HH, Hamburg

Transverse projected emittance optimization is one of the main research activities at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). The emittance measurement program in the 2009 run period concentrated on projected emittance measurements using a single sit scan technique. The photocathode laser profile has been optimized yielding small emittance. The flat-top temporal profile has been used in the standard projected emittance measurements. The small emittance values down to less than 1 mm-mrad have been measured for the nominal 1 nC bunch charge. Emittance optimizations for lower bunch charges have also been conducted using the same measurement setup and procedure as for the case of 1 nC. Numerical simulations have been carried out to compare the results with the measurements. Measurement and simulation results of the transverse emittance for the bunch charges of 0.1, 0.25, 0.5 and 1 nC will be reported and discussed in this contribution.