• M. Olvegård, A.E. Dabrowski, S. Döbert, T. Lefèvre
  CERN, Geneva
• E. Adli
  University of Oslo, Oslo

The CTF3 provides high current (28A) high frequency (12GHz) electron beams, which are used to generate high power radiofrequency pulses at 12GHz by decelerating the electrons in resonant structures. A Test Beam Line (TBL) is currently being built in order to prove the efficiency and the reliability of the RF power production with the lowest level of particle losses. As the beam propagates along the line, its energy spread grows up to 60%. For instrumentation, this unusual characteristic implies the developments of new and innovative techniques. One of the most important tasks is to measure the beam energy spread with a fast time resolution. The detector must be able to detect the energy transient due to beam loading in the decelerating structures (nanosecond) but should also be capable to measure bunch to bunch fluctuations (12GHz). This paper presents the design of the spectrometer line detectors.