• R.T. Jongma, A.C.N. Engels, R.W. Lof, F.J.P. Wijnen, G.F.A.J. Wulterkens, V. Zhaunerchyk, P.A.W. van Dael, A.J.A. van Roij, A.P. van Vliet, W.J. van der Zande
  Radboud University, Nijmegen
• K. Dunkel, C. Piel
  RI Research Instruments GmbH, Bergisch Gladbach
• U. Lehnert, P. Michel, W. Seidel, R. Wünsch
  FZD, Dresden
• A.F.G. van der Meer
  FOM Rijnhuizen, Nieuwegein

The Radboud University in Nijmegen received funding to realize a narrow-band THz laser system and a 45 T hybrid magnet system. Based on results of predesign studies [1], all review committees agreed to continue the project and enter the realization phase. In this paper we present the technical solutions for realization of the main system components. We present the details of the RI Research Instruments GmbH (a former ACCEL Instruments GmbH activity) LINAC system. Operation of the full system (including the electron source) at 3 GHz is desirable and deemed feasible after first experimental studies. As the Nijmegen FEL will operate at wavelength up to 1.5 mm, the cavity will be fully waveguided, complicating the incorporation of an intra-cavity Fox-Smith interferometer required to induce coherence between micropulses and a Michelson interferometer as most ideal outcoupler. The optical distribution system comprises 150 m of vacuum tubing with 25 cm effective diameter (planar and refocusing) mirrors. A robust yet cost efficient realization taking boundary conditions on optical beam parameters at diagnostics station and user stations into account is foreseen.

[1] Design of the Nijmegen high-resolution THz-FEL, R.T. Jongma_, et al. Proc. FEL-08.

• G. Berden, A.F.G. van der Meer
  FOM Rijnhuizen, Nieuwegein
• W.A. Gillespie, P.J. Phillips
  University of Dundee, Nethergate, Dundee, Scotland
• S.P. Jamison
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• A. MacLeod
  UAD, Dundee

Longitudinal electro-optic electron bunch diagnostics has been successfully applied at several accelerators. The electro-optic effect can be seen as an upconversion of the Coulomb field of the relativistic electron bunch (THz radiation) to the visible spectral range, where a variety of standard diagnostic tools are available. Standard techniques to characterise femtosecond optical laser pulses (auto- and cross-correlators) have led to the schemes that can measure electron bunch profiles with femtosecond resolution [1]. These techniques require, however, well synchronized femtosecond laser pulses, in order to obtain the desired temporal resolution. Currently, we are exploring other EO variants which require less advanced laser systems. The first results will be presented in our contribution.

[1] Berden et al. Phys. Rev. Lett. 99, 164801 (2007), B. Steffen et al. Phys. Rev. ST - Acc. Beams, 12, 032802 (2009)