| Paper | Title | Page |
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| MOPPR008 | The Beam Loss Monitoring System at ELSA | 786 |
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| A new diagnostic tool to monitor beam loss in the storage ring at the Electron Stretcher Facility ELSA has been set up. It enables the investigation of causes for electron loss in real time, providing an essential tool needed to achieve the planned beam current upgrade from 30 mA to 200 mA. The monitoring system consists of 32 pin-diode based radiation detectors spread around the storage ring. Therefore, individual electron loss can be localized after each quadrupole. The readout system was designed to allow an integration of single loss events within 70 μs in order to be able to correlate these events to machine state changes. The used monitoring hardware and readout system will be detailed. Furthermore first measurements of the beam loss during injection, the fast energy ramp during acceleration and the extraction phase will be presented. | ||
| MOPPR009 | Dynamic Closed Orbit Correction During the Fast Energy Ramp of ELSA | 789 |
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| ELSA is a fast ramping stretcher ring supplying polarized electrons to hadron physics experiments. To preserve the degreee of polarization, it is necessary to continuously correct the vertical orbit when accelerating the beam from 1.2 GeV to 2.4 GeV. Acceleration is performed within 300 ms, thus with a ramping speed of 4 GeV/s. During the acceleration, beam positions are measured at a rate of 1 kHz using 32 beam position monitors, which are mounted close to the quadrupole magnets. The demanding task is to achieve a vertical rms deviation not exceeding 50 μm all along the fast energy ramp. Therefore, dynamic orbit corrections are applied by means of offline feed-forward techniques, driving 32 vertical steerer magnets which can change currents in less than 10 ms. In our contribution, we show the used concepts and the implementation of the precise closed orbit correction system at ELSA. | ||
| MOPPR010 | Simultaneous Measurement of Emittance at the Storage Ring and the External Beamlines of ELSA | 792 |
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Funding: Funded by the DFG within the SFB / TR 16. The Electron Stretcher Facility (ELSA) consists of several accelerator stages, the last one being a storage ring providing a beam of polarized electrons of up to 3.5 GeV. To ensure a high duty cycle, a slow extraction via a third integer resonance is applied at ELSA. The resonance extraction cause a variation of the emittance in the external beamline. A system for simultaneous measurement of emittance in the storage ring and the external beamlines has been installed. First results including a comparison of both emittances will be shown. |
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| MOPPR011 | A New Diagnostic Beamline at ELSA | 795 |
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Funding: Funded by the DFG within the SFB / TR 16. At the Electron Stretcher Facility (ELSA), a new synchrotron light diagnostic Beamline has been installed in order to perform high resolution, transversal and longitudinal beam profile measurements by analyzing the emitted synchrotron light. For this purpose, the main deflecting AL mirror selects a wide range of wavelengths from 200–800 nm out of the whole synchrotron spectrum. The setup of the beamline and its relevant components will be presented. |
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| TUPPC067 | How to Achieve Longitudinally Polarized Electrons using Integer Spin Tune Resonances | 1326 |
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Funding: Bundesministerium für Bildung und Forschung Commonly, strong solenoids are used in circular accelerators to achieve longitudinal polarization. In practice, however, these solenoids cause a phase space coupling, which has to be compensated for by sophisticated decoupling schemes. We suggest to adiabatically ramp into an integer spin tune resonance, while preserving the degree of polarization. When appropriately adjusting the driving horizontal field contributions at the final energy, the resulting polarization is longitudinal at predefined positions in the accelerator. Here, depending on the energy spread, the degree of polarization is conserved for several seconds. The contribution shows the numerical analysis of this scenario being confirmed by first demonstration tests at the ELSA stretcher ring. |
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| WEPPP059 | First Measurements with Multibunch Feedback Systems at the Fast Ramping Stretcher Ring ELSA | 2840 |
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Funding: Supported by German Research Foundation through SFB/TR 16. At the Electron Stretcher Facility ELSA of Bonn University, an upgrade of the maximum stored beam current from 20 mA to 200 mA is planned. The storage ring operates applying a fast energy ramp of 4 GeV/s from 1.2 GeV to 3.5 GeV. The intended upgrade is mainly limited due to the excitation of multibunch instabilities. As a countermeasure, we succesfully commissioned state-of-the-art bunch by bunch feedback systems in the longitudinal and the two transverse dimensions. First results concerning the commissioning of the systems as well as the operation during the fast energy ramp will be presented. In particular, the performance while controlling the motion of every single bunch, especially in controlled bunch cleaning, will be discussed. |
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| THPPD050 | Fast Ramping Arbitrary Waveform Power Supplies for Correction Coils in a Circular Electron Accelerator | 3623 |
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| New fast ramping power supplies working in pulsed bridge technology upgrade the existing Corrector System at ELSA. Current changes of ±0.8 A/msec are achieved. The newly developed CAN-Bus Interface allows linear interpolation of up to 250 support points with minimal time steps of 1msec. The first stage uses 24 power supplies to improve the position of the beam orbit in the horizontal plane using dipole correction coils. It will be extended to include the vertical plane with new corrector coils in the near future. This poster describes the operating principles of the power supply and the interface. | ||