• D. Egger
  EPFL, Lausanne
• A.E. Dabrowski, S. Döbert, D. Egger, T. Lefèvre, O. Mete
  CERN, Geneva

To improve the quality of the CLIC Test Facility 3 drive beam, it has been proposed that a photo injector replaces the actual thermionic gun. This would produce a lower emittance beam and minimize beam losses in the injector since the RF bunching and sub‐harmonic bunching systems would not be needed anymore. Such a photo injector, named PHIN, is currently being developed at CERN. One of the difficulties is to provide a high intensity beam (3.5A) with a stable (0.1%) beam energy over 1.5us as well as a relative energy spread less than 1%. A 90° spectrometer line featuring a segmented dump and an Optical Transition Radiation screen has been constructed and commissioned in order to study the time evolution of the beam energy along the pulse duration. In the following paper, we present the design as well as the results from the previous two PHIN runs.

• M. Petrarca, E. Chevallay, A.E. Dabrowski, M. Divall Csatari, S. Döbert, D. Egger, V. Fedosseev, T. Lefèvre, R. Losito, O. Mete
  CERN, Geneva

The high charge PHIN photo injector is studied at CERN as an electron source for the CLIC Test Facility (CTF3) drive beam as an alternative to the present thermionic gun. The objective of PHIN is to demonstrate the feasibility of a laser-based electron source for CLIC. The photo injector operates with a 2.5 cell, 3 GHz RF gun using a Cs2Te photocathode illuminated by UV laser pulses generated by amplifying and frequency quadrupling the signal from a Nd:YLF oscillator running at 1.5GHz. The challenge is to generate a beam structure of 1908μbunches with 2.33nC perμbunch at 1.5GHz leading to a high integrated train charge of 4446nC and nominal beam energy of 5.5MeV with current stability below 1%. In the present test stand, a segmented beam dump has been implemented allowing a time resolved measurement of the energy and energy spread of the electron beam. In this paper we report and discuss the measured transverse and longitudinal beam parameters for both the full and time gated train of bunches, and the obtained photocathode quantum efficiency. Laser pointing and amplitude stability results are discussed taking into account correlation between laser and electron beam.

• A.E. Dabrowski, S. Bettoni, E. Bravin, R. Corsini, S. Döbert, T. Lefèvre, A. Rabiller, P.K. Skowronski, L. Søby, F. Tecker
  CERN, Geneva
• D. Egger
  EPFL, Lausanne
• A. Ferrari
  Uppsala University, Uppsala
• C.P. Welsch
  The University of Liverpool, Liverpool

The CTF3 facility is being built and commissioned by an international collaboration in order to test the feasibility of the proposed CLIC drive beam generation scheme. Central to this scheme is the use of RF deflectors to inject bunches into a Delay Loop and a Combiner Ring, in order to transform the initial bunch spacing of 1.5 GHz from the linac to a final bunch spacing of 12 GHz. The optimization procedure relies on several steps. The active length of each ring is carefully adjusted to within a few millimeters accuracy using a two‐period undulator. The transverse optics of the machine must be set-up in a way so as to ensure the beam isochronicity. Diagnostics based on optical streak cameras and RF power measurements have been designed to measure the longitudinal behaviour of the beam during the combination. This paper presents their performance and highlights recent measurements.