• Y.A. Kot
  DESY, Hamburg

The three stage bunch compression system proposed for the European XFEL will be able to achieve overall compression of about 100. This would lead to the reduction of the bunch length up to 2.5 10-5 m for the designed bunch charge of 1nC. It is anticipated that the final compression would be limited here mainly by rf tolerances (jitter) which are determined by technical specifications of the manufacturer. For a large variety of experiments it could be however desirable to go to shorter bunches even on cost of less radiation power. A good possibility to achieve this might be to operate the injector at lower than 1nC bunch charge. In this paper the possibility of the operation of the injector with low charge bunches was investigated. On this issue simulations with ASTRA code have been done in order to find suitable working points for the low charge regimes and to figure out the dependence of the bunch parameters on the initial bunch charge at the cathode. The results of these simulations for the injectors at FLASH and XFEL as well as the discussion about possible problems are presented.