Author: Hartel, U.
Paper Title Page
WEPME004 A Digital Beam-Phase Control System for a Heavy-Ion Synchrotron with a Double-Harmonic Cavity System 2926
 
  • J. Grieser, D.E.M. Lens
    TU Darmstadt, RTR, Darmstadt, Germany
  • U. Hartel
    TEMF, TU Darmstadt, Darmstadt, Germany
  • H. Klingbeil, U. Laier, K.-P. Ningel, S. Schäfer, B. Zipfel
    GSI, Darmstadt, Germany
  
  Funding: Funded by GSI Helmholtzzentrum für Schwerionenforschung GmbH
For the new Fa­cil­ity for An­tipro­ton and Ion Re­search (FAIR) at GSI Helmholtzzen­trum für Schw­e­ri­o­nen­forschung GmbH, the heavy-ion syn­chro­tron SIS18 will be op­er­ated with a dou­ble-har­monic cav­ity sys­tem*. The sec­ond cav­ity, run­ning at twice the fun­da­men­tal RF fre­quency, is used to lengthen the bucket which in­tro­duces non­lin­ear­i­ties to the con­trol sys­tem. To damp lon­gi­tu­di­nal rigid di­pole os­cil­la­tions a dig­i­tal feed­back sys­tem con­sist­ing of a fil­ter and an in­te­gra­tor is used. For the ex­ist­ing sin­gle-har­monic setup an FIR-fil­ter is im­ple­mented which re­al­izes a mul­ti­ple band­pass fil­ter with the first pass­band close to the syn­chro­tron fre­quency. Both, the feed­back gain and the pass­band fre­quency of the fil­ter de­pend on the ac­tual value of the syn­chro­tron fre­quency**. It was shown by sim­u­la­tions and in an ex­per­i­ment that this setup can be trans­ferred to a dou­ble-har­monic cav­ity sys­tem ob­tain­ing sim­i­lar re­sults for the re­gion of sta­ble feed­back pa­ra­me­ters, if the os­cil­la­tion fre­quency of the bunch barycen­ter*** is con­sid­ered in­stead of the syn­chro­tron fre­quency of a lin­earized bucket. In this con­tri­bu­tion the re­sults of the sim­u­la­tion and the ex­per­i­ment are pre­sented and com­pared.
*Klingbeil et al.: Phys. Rev. Special Topics - Accelerators and Beams 14, 102802, 2011
**Klingbeil et al.: IEEE Trans. on Nucl. Science, Vol. 54, No. 6, 2007
***Grieser et al.: Proc. 3rd IPAC, 2012 		 
 
THPEA003 Use of FPGA-based Configurable Electronics to Calibrate Cavities 3152
 
  • S. Schäfer, A. Klaus, H. Klingbeil, B. Zipfel
    GSI, Darmstadt, Germany
  • U. Hartel, H. Klingbeil
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  At the GSI Helmholzzen­trum für Schw­e­ri­o­nen-forschung GmbH the ac­cu­racy re­quire­ments for syn­chro­tron rf cav­i­ties have strongly in­creased in the last years, es­pe­cially for multi-har­monic op­er­a­tion. For heavy-ion ac­cel­er­a­tion the am­pli­tude and phase have to be well ad­justed over a whole ma­chine cycle. In order to com­pen­sate small de­vi­a­tions in­duced by low-level rf com­po­nents (LLRF) and trans­mis­sion lines in the con­trol paths, a cal­i­bra­tion elec­tronic (CEL) with a char­ac­ter­is­tic map was de­vel­oped. It is a real-time mod­ule which is based on mod­ern FPGA (Field Pro­gram­ma­ble Gate Array) tech­nol­ogy and adapt­able to spe­cial cav­i­ties with var­i­ous phys­i­cal de­pen­den­cies (e.g. at­ten­u­a­tion, dis­per­sion, tem­per­a­ture drift, aging etc.). The hard­ware and soft­ware ar­chi­tec­ture of this CEL mod­ule are pre­sented here.  
 
THPEA004 Precise Verification of Phase and Amplitude Calibration by means of a Debunching Experiment in SIS18 3155
 
  • U. Hartel, H. Klingbeil
    TEMF, TU Darmstadt, Darmstadt, Germany
  • J. Grieser, D.E.M. Lens
    TU Darmstadt, RTR, Darmstadt, Germany
  • H. Klingbeil, U. Laier, K.-P. Ningel, S. Schäfer, B. Zipfel
    GSI, Darmstadt, Germany
  
  Funding: Work supported by the GSI Helmholtzzentrum für Schwerionenforschung GmbH
Sev­eral new rf cav­ity sys­tems have to be re­al­ized for the FAIR syn­chro­trons and for the up­grade of the ex­ist­ing GSI syn­chro­tron SIS18*. For this pur­pose, a com­pletely new low-level rf sys­tem ar­chi­tec­ture** has been de­vel­oped, which is now used in SIS18 op­er­a­tion. Closed-loop con­trol sys­tems sta­bi­lize the am­pli­tude and the phase of the rf gap volt­ages. Due to com­po­nent im­per­fec­tions the trans­mis­sion and the de­tec­tion of the ac­tual val­ues lead to sys­tem­atic er­rors with­out coun­ter­mea­sures. These er­rors pro­hibit the op­er­a­tion of the rf sys­tems over the whole am­pli­tude and fre­quency range within the re­quired ac­cu­racy. To com­pen­sate the in­evitable er­rors, the tar­get val­ues pro­vided by the cen­tral con­trol sys­tem are mod­i­fied by so-called cal­i­bra­tion elec­tron­ics*** mod­ules. The cal­i­bra­tion curves can be mea­sured with­out the beam, but the de­sired beam be­hav­iour has to be ver­i­fied by ex­per­i­ments. For this pur­pose, a de­bunch­ing sce­nario was se­lected as a SIS18 beam ex­per­i­ment that proved to be very sen­si­tive to in­ac­cu­ra­cies. In this con­tri­bu­tion the re­sults of this ex­per­i­ment are pre­sented, show­ing for the first time at GSI by beam ob­ser­va­tion that the ac­cu­racy re­quire­ments are met based on pre­de­fined cal­i­bra­tion curves.
* “FAIR - Baseline Technical Report,” Volume 2, Accelerator and Scientific Infrastructure, (2006).
** Klingbeil et al.: Phys. Rev. ST Accel. Beams 14, 102802, 2011.
*** S. Schaefer et al., “Use of FPGA-based Configurable Electronics to Calibrate Cavities,” THPEA003, these proceedings.