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| TUPMS014 | Commissioning of the Booster Injector Synchrotron for the HIGS Facility at Duke University | 1209 |
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Funding: This work is supported by the US DoE grant #DE-FG02-01ER41175 A booster synchrotron has been built and recently commissioned at Duke University Free Electron Laser Laboratory (DFELL) as part of the High Intensity Gamma-ray Source (HIGS) facility upgrade. HIGS is developed collaboratively by the DFELL and Triangular Universities Nuclear Laboratory (TUNL). The booster will provide top-off injection into the Duke FEL storage ring in the energy range of 0.27 - 1.2 GeV. When operating the Duke storage ring to produce high energy Compton gamma ray beams above 20 MeV, continuous electron beam loss occurs. The lost electrons will be replenished by the booster injector operating in the top-off mode. The compactness of the booster posed a challenge for its development and commissioning. The booster has been successfully commissioned in 2006. This paper reports experience of commissioning and initial operation of the booster. |
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| TUPMS015 | Challenges for the Energy Ramping in a Compact Booster Synchrotron | 1212 |
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Funding: This work is supported by the US DoE grant #DE-FG02-01ER41175 A booster synchrotron has been recently commissioned at Duke University FEL Laboratory as a part of the High Intensity Gamma-ray Source (HIGS) facility. The booster will provide top-off injection into the storage ring in the energy range of 0.27 - 1.2 GeV. In order to minimize the cost of the project, the booster is designed with a very compact footprint. As a result, unconventionally high field bending magnets at 1.76 T are required. A main ramping power supply drives all dipoles and quadrupoles. Quadrupole trims are used to compensate for tune changes caused by the change of relative focusing strength during ramping. Sextupoles compensate for chromatic effects caused by dipole magnet pole saturation. All these compensations have to be performed as a function of beam energy. Above 1.1 GeV, where the magnets are heavily saturated, the reduction of dynamic aperture is compensated by redistribution of strength among the sextupole families. With these compensations, effects of the magnet saturation do not cause any considerable beam loss during energy ramping. |
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| WEPMN100 | RF Design and Processing of a Power Coupler for Third Harmonic Superconducting Cavities | 2265 |
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Funding: U. S. Department of Energy The FLASH user facility providing free electron laser radiation is built based on the TTF project at DESY. Fermilab has the responsibility for the design and processing of a third harmonic, 3.9 GHz, superconducting cavity which is powered via a coaxial power coupler. Six power couplers have been manufactured at CPI after successful design of the power coupler including RF simulation, multipacting calculation, and thermal analysis. The power couplers are being tested and processed with high pulsed power in an elaborate test stand at Fermilab now. This paper presents the RF design and processing work of the power coupler. |
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| WEPMN101 | Coupling Interaction Between the Power Coupler and the Third Harmonic Superconducting Cavity | 2268 |
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Funding: U. S. Department of Energy Fermilab has developed a third harmonic superconducting cavity operating at the frequency of 3.9 GHz to improve the beam performance for the FLASH user facility at DESY. It is interesting to investigate the coupling interaction between the SRF cavity and the power coupler with or without beam loading. The coupling of the power coupler to the cavity needs to be determined to minimize the power consumption and guarantee the best performance for a given beam current. In this paper, we build and analyze an equivalent circuit model containing a series of lumped elements to represent the resonant system. An analytic solution of the required power from the generator as a function of the system parameters has also been given based on a vector diagram. |
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| THPAS038 | Compensation of the Beam Dynamics Effects Caused by the Extraction Lambertson Septum of the HIGS Booster | 3582 |
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Funding: Supported by US DoE grant #DE-FG02-01ER41175 As part of the High Intensity Gamma-Ray Source (HIGS) upgrade, the booster synchrotron has been recently commissioned. The booster ramps the electron beam between 0.27 and 1.2 GeV for top-off injection into the Duke storage ring. It has symmetrical injection/extraction schemes with a bumped orbit. The injection/extraction kickers and corresponding septa are located in the opposite straight sections of the booster ring separated by about 1/4 of the vertical betatron wave. Due to the nonideal properties of the magnetic material, the magnetic field leaks out into the stored beam chamber, which directly results in orbit distortion, tune and chromaticity shifts and change of coupling. These effects caused by the extraction septum have been measured as a function of extraction energy. Based upon the measurements, we have developed a scheme to compensate the dynamics effects mentioned above. |
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| FRPMS039 | Growth Time of Longitudinal Coupled Bunch Mode Instability in the Duke FEL Facility | 4036 |
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| To determine the required power of an RF amplifier for the longitudinal feedback system (LFS), the growth time of the longitudinal coupled bunch mode instability (CBMI) in the Duke storage ring should be known in advance. In 2005, we measured the longitudinal beam instability with four and eight symmetrically filled buckets in the Duke storage ring. By analyzing measured data, the growth time of the longitudinal CBMI can be estimated. At a beam energy of 274 MeV, the projected growth time is about 0.37 ms for a total stored current of 160 mA. To damp harmful longitudinal CBMI with a relative energy deviation of 0.1% (rms) within the growth time, a sufficient RF power of 135 W (rms) should be delivered to an LFS kicker at a central frequency of 758.8375 MHz. In this paper, we describe measurements of the growth time and the estimation of the RF power requirement for the LFS. | ||
| FRPMS040 | BPM signal conditioning for a wide range of single bunch current operation in Duke storage ring | 4042 |
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Funding: Supported by US DoE grant #DE-FG02-01ER41175. The beam position monitor system of the Duke storage ring has been in operation since 1998. Recently, by injecting at higher energy with a booster synchrotron, the single bunch current threshold is much more increased. This makes the BPM system do not work properly and rises the risk to damaged the BPM signal processing modules. To get reliable orbit data and protect the BPM modules, we carefully studied the BPM signal, and then found a way to overcome this problem. This paper will report the study results and the solution method. |
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| FRPMS041 | A Direct Electron Beam Energy Spread Measurement System for Beam Instability and FEL Research | 4045 |
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Funding: Supported by US AFOSR MFEL grant #FA9550-04-01-0086. One of critical beam parameters for the storage ring based light sources is the energy spread of the electron beam. An accurate measurement of the energy spread remains a challenge. It is well known that the electrons with different energies can degrade the spontaneous emission spectrum of a two-wiggler system in an optical-klystron configuration. The reduced modulation in the spectrum can be used to determine the energy spread of the beam. This paper describes our newly developed energy spread measurement system employing a scanning spectrometer and a fast CCD. A fast CCD with a burst mode of operation is used so that dynamical changes of the energy spread from tens of microseconds to tens of milliseconds can be measured. This system will be used in the beam instability research and free-electron laser research. Together with compact wigglers, such a system can be developed as a dedicated beam diagnostic for storage rings and linacs. |
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| FRPMS042 | Electron Beam Diagnostics for Compact 1.2 GeV Booster Synchrotron | 4051 |
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Funding: Supported by US DoE grant #DE-FG02-01ER41175. First operational experience has been gained with the linac and booster diagnostic system during the commissioning of the booster synchrotron at Duke University. Beam charge measurements are provided by Faraday cups, Integrated Current Transformers (ICT) and Modular Parametric Current Transformer (MPCT). Beam position monitoring is based on BPM system delivered from Bergoz company. Betatron tune measurements use synchrotron radiation (SR) and are different for two modes of operation: stored beam and energy ramping. Transverse profile and temporal beam structure monitoring employ insertable screens, CCD cameras, striplines and dissector. The diagnostics provided good understanding of electron beam behavior and allowed to adjust important beam parameters within design specifications. An overview of the diagnostic instrumentation of the Duke linac and booster synchrotron is given along with measurement examples and discussion of operational experience. |
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| FRPMS044 | A Tune Measurement System for Low Current and Energy Ramping Operation of a Booster Synchrotron | 4063 |
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Funding: This work is supported by the US AFOSR MFEL grant #FA9550-04-01-0086 and by U. S. DOE grant DE-FG05-91ER40665. The betatron tune measurement system is one of the most important diagnostics for any circular accelerator. During the commissioning of a booster synchrotron newly developed for top-off injection into the Duke storage ring, a versatile tune measurement system employing a photomultiplier tube (PMT) and a space filter has been developed to provide reliable measurements for low current operation at a few micro-amperes of beam-current. Using the turn-by-turn technique, this tune measurement system is being used as a live tune monitor during the booster energy ramping. This system has also be used to measure chromaticity and other important beam parameters. In this paper, we describe the tune measurement system in detail and report our most recent experimental results using this system. |