Author: Boine-Frankenheim, O.
Paper Title Page
TUO1A02
 Status of Collective Effects at GSI  
 
  • O. Boine-Frankenheim
    GSI, Darmstadt, Germany
  
  A profound understanding and control of collective effects in ion beams will be necessary to reach the design intensity and quality in the existing SIS-18 synchrotron and in the projected SIS-100 for the FAIR project. Simulation and experimental studies of collective effects are therefore an integral part of the ongoing SIS-18 intensity upgrade and the SIS-100 design activities at GSI. In both rings collective effects are caused simultaneously by space charge, impedances and secondary particles. They occur in the longitudinal and transverse planes, in coasting beams as well as for different rf bucket forms. After a brief outline of the role of collective effects at GSI this contribution will focus on recent findings related to the interpretation of signals from intense bunches with space charge. The correct processing of these signals will be especially important for beam diagnostics and feedback control.  
slides icon Slides TUO1A02 [1.937 MB]  
 
WEO3C02 Collimation of Ion Beams 461
 
  • I. Strašík, O. Boine-Frankenheim
    GSI, Darmstadt, Germany
  
  The SIS 100 synchrotron as part of the FAIR project at GSI will accelerate various beam species from proton to uranium. An important issue is to minimize uncontrolled beam losses using a collimation system. An application of the two-stage collimation concept, well established for proton accelerators, is considered for the fully-stripped ion beams. The two-stage system consists of a primary collimator (a scattering foil) and secondary collimators (bulky absorbers). The main tasks of this study are:
  1. to specify beam optics of the system,
  2. to calculate dependence of the scattering angle in the foil on the projectile species,
  3. to investigate importance of the inelastic nuclear interaction in the foil and
  4. to calculate dependence of the collimation efficiency on the projectile species.
A concept for the collimation of partially-stripped ions is based on the stripping of remaining electrons and deflecting using a beam optical element towards a dump location. Residual activation and radiation damage issues of collimator materials are also being studied at GSI. Experimental results from irradiation of carbon-based materials by heavy ions are presented. 		 
slides icon Slides WEO3C02 [1.485 MB]  
 
MOP205 Intense Heavy-Ion Bunches in Dual-harmonic RF Systems 51
 
  • M. Mehler, O. Chorniy
    GSI, Darmstadt, Germany
  • O. Boine-Frankenheim
    TEMF, TU Darmstadt, Darmstadt, Germany
  • O.K. Kester
    IAP, Frankfurt am Main, Germany
  
  For the synchrotron's SIS-18 and SIS-100 (FAIR) a dual-harmonic RF system with the harmonic numbers h1=2, h2=4 and h1=10, h2=20 respectively is planned. Such systems flatten the bunch form and increase the bunching factor Bf therefore reducing the transverse space charge force. For high currents cavity beam loading and potential-well distortion will deform the flattened bunch shape and lead to phase shifts. Optimized settings for the difference between the two RF phases and for the synchronous phase of the main RF harmonic are an option to reduce these effects. In this contribution we will analyse further aspects of the matched bunch distribution, possible instabilities of the obtained distribution will be discussed and results of machine experiments in SIS-18 will be presented.  
 
MOP206 Numerical Calculation of Beam Coupling Impedances for the SIS-100 Synchrotron for FAIR 54
 
  • U. Niedermayer, O. Boine-Frankenheim
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  The transverse impedance of kicker magnets is considered to be one of the main beam instability sources in the projected SIS-100 at FAIR and also in the SPS at CERN. The longitudinal impedance can contribute to the heat load, which is especially a concern in the cold sections of SIS-100 and LHC. In the high frequency range, time domain codes are commercially available to calculate the impedance but they become inapplicable at medium and low frequencies. We present the ongoing work of developing a Finite Integration (FIT) solver in frequency domain which is based on the Parallel and Extensible Toolkit for Scientific computing (PETSc) framework in C++. The code is applied to an inductive insert used to compensate the longitudinal space charge impedance in low energy machines. Another application focuses on the impedance contribution of a ferrite kicker with inductively coupled pulse forming network (PFN) and frequency dependent complex material permeability. In future we plan to confirm our simulations with dedicated wire or coil bench measurements.  
 
TUO1C05 Measurements and Interpretation of the Betatron Tune Spectra of High Intensity Bunched Beam at SIS-18 310
 
  • R. Singh, O. Chorniy, P. Forck, R. Haseitl, W. Kaufmann, P. Kowina, K. Lang
    GSI, Darmstadt, Germany
  • O. Boine-Frankenheim, R. Singh, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  The paper presents the status of the transverse tune measurements in the synchrotron SIS18 at GSI. Presently, there are two systems for tune measurements in operation in the SIS18, namely TOPOS (Tune, Orbit and POsition measurement System) and BBQ (Base Band tune measurement system). The first one is a digital system where the BPM signal is digitized and the bunch position is calculated numerically. The second system is an analog system, where the transverse bunch motion is detected using peak detector. Band limited noise and chirp excitations were used to excite the betatron oscillations. Measurements of the betatron tune spectra were done at injection energy at medium and high intensities. In the frequency spectra a number of peaks around the position of betatron tune were seen. The peaks can be attributed to different bunch head-tail modes which were observed in time domain. These modes were dependent on the beam intensity. In this paper we compare the tune spectra measured at high beam intensity with the theoretical model for the space charge affected head-tail modes.  
slides icon Slides TUO1C05 [1.315 MB]