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Wiesner, C.

Paper Title Page
THPP091 One Nano-second Bunch Compressor for High Intense Proton Beam 3578
 
  • L. P. Chau, M. Droba, N. S. Joshi, O. Meusel, U. Ratzinger, C. Wiesner
    IAP, Frankfurt am Main
 
  About ten bunches of 2MeV proton rf-linac with an average current of 150mA at 175 MHz will be deflected by kicker on different paths into a magnetic bending system. Passing this optimized geometry they approach each other longitudinaly (βλ = 0.114m) and arrive at the same time at the focus of the dipole system. For longitudinal focussing of the merged bunches a rebuncher cavity is included in the bending system. The motivation and the layout of the whole project, "Frankfurter Neutronen Quelle am Stern-Gerlach Zentrum" (FRANZ), were presented in details in previous conferences*,**. More accurate investigation results in a revision of the preliminary concept. For a theoretical proof of principle one trajectory with the biggest path length of a new geometry is calculated by a multi particle beam dynamics program (LORASR). Preliminary investigations showed, that magnetic fringing fields and bunch-bunch interactions have to be included as detailed as posible in the beam simulations. In this paper the beam dynamics results from LORASR-simulations, the new geometry and the code development for the bunch compressor are discussed in details.

*L. P. Chau et al. Proc. of the Eur. Part. Acc. Conf., Edinburgh (2006), 1690-1692.
**O. Meusel et al. Proc. of the Lin. Acc. Conf., Knoxville (2006), MOPO51, 159-161.

 
THPP111 A 250 kHz Chopper for Low Energy High Intensity Proton Beams 3623
 
  • C. Wiesner, L. P. Chau, M. Droba, O. Meusel, U. Ratzinger
    IAP, Frankfurt am Main
 
  A neutron pulse with 1 ns pulse length and a repetition rate of 250 kHz is needed for the experiments on nuclear astrophysics using the Frankfurter Neutron source at the Stern-Gerlach-Zentrum. The time structure of the neutron flux is given by the primary proton beam witch hits a 7Li target. The creation of the required time structure on an intense proton beam of 200 mA dc with respect to emittance growth and beam losses is demanding. The pulsing of the ion source depends on the rise time of the plasma whereas the pulsing of the extraction voltage leads into high power deposition into the multi aperture extraction system. On the other hand a chopper system downstream of the RFQ results in rf power consumption due to beam loading and the problem of beam dumping at a beam power of several kW. Therefore it is planed to install a chopper as part of a resonant circuit in the LEBT – section consisting of four solenoids. Two different methods, magnetic and electric deflection, will be discussed with respect to emittance growth, beam losses and the influence on space charge compensation processes. Numerical simulations and preliminary results of experiments will be presented and compared.