A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z    

Jacob, J.

 
Paper Title Page
TUPCH099 Development of HOM Damped Copper Cavity for the ESRF 1244
 
  • N. Guillotin, J. Jacob, V. Serriere
    ESRF, Grenoble
  
  At the ESRF, HOM driven longitudinal coupled bunch instabilities are currently avoided up to the nominal beam current of 200 mA by precisely controlling the cavity temperatures and thereby the HOM frequencies of the existing five-cell copper cavities. A bunch-by-bunch feedback is presently being commissioned in order to increase the maximum stored current. In parallel, normal conducting strongly HOM damped cavities are under study to possibly replace the five-cell cavities. The design is based on a scaling of the single cell EU cavity*: a pillbox geometry with nose cones and three attached ridged waveguides loaded by ferrites for effective HOM damping. We report on the electromagnetic simulation making use of the 3D codes HFSS and GdfidL. They allowed optimizing the shape of both cavity and dampers, including electromagnetic absorbing material with frequency dependent parameters.

*E. Weihreter et al. A Ridged Circular Waveguide Ferrite Load for Cavity HOM Damping, this conference.

 
WEXPA02 New Developments on RF Power Sources 1842
 
  • J. Jacob
    ESRF, Grenoble
  
  The classical generation of RF power with klystrons and tetrodes is evolving and changing to meet the demands of higher efficiency and simpler maintenance. Developments of IOT tubes for FEL, Energy Recovery Linacs and Storage Rings, together with solid state technology approaches and combination techniques for high power generation are opening new alternatives to the classical ones. An overview of the new concepts, designs and solutions applied to the new accelerators will be presented. Advantages and drawbacks of new versus classical technologies as well as strategies for the selection will be discussed.  
slides icon Transparencies
WEPCH109 Comprehensive Benchmark of Electromagnetic 3D Codes in Time and Frequency Domain 2167
 
  • V. Serriere, N. Guillotin, J. Jacob
    ESRF, Grenoble
  • F. Marhauser, E. Weihreter
    BESSY GmbH, Berlin
  
  A comprehensive benchmark of todays most powerful numerical 3D Eigenmode and Time Domain Solvers has been performed using the input geometry of a HOM-damped cavity and a highly lossy waveguide load developed at BESSY. The paper details the simulations results together with existing experimental data.  
THPCH082 Broadband Bunch by Bunch Feedback for the ESRF using a Single High Resolution and Fast Sampling FPGA DSP 2976
 
  • E. Plouviez, P. Arnoux, F. Epaud, J. Jacob, J.M. Koch, N. Michel, G.A. Naylor, J.-L. Revol, V. Serriere, D. Vial
    ESRF, Grenoble
  
  In order to increase the current in the ESRF storage ring we have developed a set of multibunch feedback systems aimed at fighting longitudinal and transverse coupled bunch instabilities. The longitudinal feedback (LFB) has been the first system installed and tested. It was designed using the scheme developed at SLAC, ALS and INFN Frascati: bunch by bunch processing of a beam phase error signal and correction using a low Q kicker driven by a QPSK modulator. However, we took advantage for this development of the latest available technology for the signal processing electronics with high resolution, high sampling rate ADC and DAC, and FPGA DSP, as well as for the FPGA programming environment. It allowed us to substantially reduce the complexity: the algorithm runs on a single processor, the kicker requires only 200W of RF power to control a 6GeV beam, and the implementation took only about one year. We will describe the main features of our LFB and present the results already achieved in the damping of instabilities driven by our RF cavity HOM. We will also report on the status of the transverse feedback, which is being built up using the same FPGA system as the longitudinal one.  
THPLS011 Operation and Recent Development at the ESRF 3290
 
  • J.-L. Revol, J.C. Biasci, J-F. B. Bouteille, J. Chavanne, P. Elleaume, L. Farvacque, L. Hardy, J. Jacob, G.A. Naylor, E. Plouviez, A. Ropert, K.B. Scheidt
    ESRF, Grenoble
  
  We report on the achieved performance of the ESRF storage ring as well as developments accomplished or underway. A new hybrid filling mode based on groups of bunches and a 4-bunch filling pattern are now delivered to the users. Following the increasing demand of users for beam stability, the fast orbit feedback has been upgraded. The installation of 5 m-long, 8 mm vertical aperture NEG coated aluminum chambers is progressing at a rate of one chamber per shutdown. The increase in current from 200 to 300 mA is being prepared; however, operation in this mode is still impaired by HOM driven longitudinal instabilities. To overcome this difficulty, a longitudinal feedback is being commissioned. HOM damped cavities are also under study to possibly replace the existing five-cell cavities. The policy of preventive maintenance has been continued. However, in 2005 the machine availability was affected by water leaks occurring on front-end absorbers and on one dipole crotch absorber. The crotch absorbers suffer all from the same erosion process that could be delayed by a systematic vertical realignment, leaving time for procurement and replacement of the entire pool.