• P.K. Skowronski, S. Bettoni, R. Corsini, S. Döbert, F. Tecker
  CERN, Geneva
• D. Alesini, C. Biscari
  INFN/LNF, Frascati (Roma)
• Y.-C. Chao
  TRIUMF, Vancouver

The objective of the CLIC Test Facility CTF3 is to demonstrate the feasibility issues of the CLIC two-beam technology. CTF3 consists of an electron linac followed by a delay loop, a combiner ring and a two-beam test area. One issue studied in CTF3 is the efficient generation of a very high current drive beam, used in CLIC as the power source to accelerate the main beam to multi-TeV energies. The beam current is first doubled in the delay loop and then multiplied by a factor four in the combiner ring by interleaving bunches using transverse deflecting rf cavities. The combiner ring and the connecting transfer line have been put into operation in 2007. In this paper we give the status of the commissioning, present the results of the combination tests and illustrate in some detail the beam optics measurements, including response matrix analysis, dispersion measurement and applied orbit correction algorithms. We discuss as well the observation of a vertical beam break-up instability which is due to the vertical transverse mode in the horizontal rf deflectors used for beam injection and combination. We outline the attempted methods to mitigate the instability and their effectiveness.

• A.E. Dabrowski, S. Bettoni, H.-H. Braun, E. Bravin, R. Corsini, S. Döbert, C. Dutriat, T. Lefèvre, M. Olvegård, P.K. Skowronski, F. Tecker
  CERN, Geneva

In the CLIC Test Facility 3 (CTF3), the strong coupling between the beam and the accelerating cavities (full beam loading) induces transient effects such that the head of the pulse is accelerated almost twice as much as the steady-state part of the pulse. The beam optics in the machine is tailored for the steady-state and not for the higher energy electrons, which are gradually lost. This can lead to inefficiency and contributes to the activation of the machine. A beam loading compensation scheme has been proposed to minimize this effect. By delaying appropriately the arrival time of rf pulse in accelerating cavities with respect to the beam, the transient energy can be brought close (to within a few percent) of the steady-state one. This paper presents the measurements done on CTF3 using time resolved energy measurements.

• A.E. Dabrowski, S. Bettoni, H.-H. Braun, R. Corsini, S. Döbert, T. Lefèvre, H. Shaker, P.K. Skowronski, F. Tecker
  CERN, Geneva
• J.J. Jacobson, M. Velasco
  NU, Evanston

The CLIC Test Facility CTF3, being built at CERN by an international collaboration, should demonstrate the feasibility of the CLIC two-beam technology by 2010. One of the issues addressed is the control of the electron bunch length in the whole complex. A bunch length measurement system with good resolution is therefore paramount. Two different systems are presently used in CTF3, based on microwave spectroscopy and on transverse rf deflectors, respectively. In the paper we describe the two systems, we discuss the different experimental methods used and present the results of the latest measurement campaigns.