IPAC2013 - List of Authors (Grieser, J.)

Paper	Title	Page
WEPME003	Determination of Optics Transfer between the Kicker and BPMs for Transverse Feedback System	2923
	M. Alhumaidi, A.M. Zoubir TU Darmstadt, Darmstadt, Germany J. Grieser TU Darmstadt, RTR, Darmstadt, Germany
	The knowledge of the transfer optics between the positions of the Kicker and the BPMs is required for the calculation of the correction signal in transverse feedback systems. Therefore, using nominal values of the transfer optics with uncertainties leads to feedback quality degradation, and thus beam disturbances. In this work, we propose a method for measuring the phase advances and amplitude scaling between the positions of the kicker and the BPMs. Directly after applying a kick on the beam by means of the kicker, we record the BPM signals. Consequently, we use the Second-Order Blind Identification (SOBI) algorithm to decompose the noised recorded signals into independent sources mixture. Finally, we determine the required optics parameters by identifying and analyzing the betatron oscillation sourced from the kick based on its mixing and temporal patterns. Results for the heavy ions synchrotron SIS 18 at the GSI are shown.

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

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.

Paper

Title

Page

Determination of Optics Transfer between the Kicker and BPMs for Transverse Feedback System

2923

M. Alhumaidi, A.M. Zoubir
TU Darmstadt, Darmstadt, Germany
J. Grieser
TU Darmstadt, RTR, Darmstadt, Germany

The knowledge of the transfer optics between the positions of the Kicker and the BPMs is required for the calculation of the correction signal in transverse feedback systems. Therefore, using nominal values of the transfer optics with uncertainties leads to feedback quality degradation, and thus beam disturbances. In this work, we propose a method for measuring the phase advances and amplitude scaling between the positions of the kicker and the BPMs. Directly after applying a kick on the beam by means of the kicker, we record the BPM signals. Consequently, we use the Second-Order Blind Identification (SOBI) algorithm to decompose the noised recorded signals into independent sources mixture. Finally, we determine the required optics parameters by identifying and analyzing the betatron oscillation sourced from the kick based on its mixing and temporal patterns. Results for the heavy ions synchrotron SIS 18 at the GSI are shown.

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

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.