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| WEP027 | A Fast and Accurate Method to Shim Undulator Using Multi-Objective GA | undulator, electron, laser, free-electron-laser | 378 |
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Funding: National Natural Science Foundation of China under grant of 11505174, 11505173 and 11605190 GA (Genetic Algorithm) is one of the most excellent methods to search the optimal solution for a problem, which has been applied to solve various problems. It is hard to estimate shim applied on raw undulator precisely. There are many methods have been developed to solve the problem. In this proceeding, we proposed a fast and accurate method to conclude the shim using multi-objective GA. A multi-objective objective function was set, and multi-objective optimization was also implemented. The evolution time is reduced by setting optimal evolution parameters. To demonstrate the method, we also finished some test on a prototype undulator U38. As a result, it can be achieved only by shimming three times that all the parameters of trajectory center deviation, peak-to-peak error and phase error satisfied the requirements. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP027 | ||
| About • | paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019 | ||
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| WEP042 | Observations of Short-Range Wakefield Effects in TESLA-Type Superconducting RF Cavities | HOM, cavity, wakefield, FEL | 412 |
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Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The accelerators for high power X-ray free-electron laser (FEL) facilities such as the European XFEL and planned LCLS-II X-ray FEL are employing TESLA-type SCRF cavities. Beam propagation off axis in these cavities can result in both short-range and long-range transverse wakefields which can lead to emittance dilution within the micropulses and macropulses, respectively. The Fermilab Accelerator Science and Technology (FAST) facility has a unique configuration of a photocathode RF gun beam injecting two TESLA-type single cavities (CC1 and CC2) in series prior to the cryomodule. To investigate short-range wakefield effects, we used a vertical corrector between these two cavities to steer the beam off axis at an angle into CC2. A Hamamatsu synchroscan streak camera viewing a downstream OTR screen provided an image of y-t effects within the micropulses with resolutions of ~10-micron spatial and 2-ps temporal. At 500 pC/b, 50 b, and 4 mrad off-axis steering, we observed an ~100-micron head-tail centroid shift in the streak camera image. This centroid shift is consistent with a calculated short-range wakefield effect. Additional results for kick-angle compensation will be presented. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP042 | ||
| About • | paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019 | ||
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| WEP067 | Development and Commissioning of a Flip Coil System for Measuring Field Integrals | background, software, quadrupole, undulator | 484 |
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Funding: CAPES grant numbers 88881.134183/2016-01; DOE contract DE-AC02-76SF00515 in support of the LCLS-II project; and FAEPEX-UNICAMP grant number 519.292/94550-19. Many techniques for measuring magnetic fields are available for accelerator magnets. In general, methods based upon moving wires are suitable for characterizing field harmonics, and first and second field integrals. The flip coil moving wire technique stands out due to simplicity, speed, precision, and accuracy. We aimed to develop a reliable, fast and precise flip coil system capable of characterizing field integrals in the two transverse axes. The coil was a single turn loop made of insulated beryllium copper wire. The width of the loop was 5 mm. The approach of measuring second field integrals by changing the coil’s width at one of the ends was analyzed and included in the system. High-performance motorized stages performed angular and transverse positioning of the coil, while manual stages were used to stretch the wire, execute fine adjustments in its transverse position, and change coil’s geometry. Initial tests with the Earth’s field and also with a reference magnet of 126 Gauss-centimeter (G.cm) demonstrated that the system achieves repeatability of 0.2 G.cm for a 60-cm long coil. This work was carried out for the LCLS-II project at SLAC. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP067 | ||
| About • | paper received ※ 08 August 2019 paper accepted ※ 26 August 2019 issue date ※ 05 November 2019 | ||
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| WEP097 | Operational Model of the Athos Undulator Beamline | polarization, undulator, operation, background | 538 |
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| Athos, the new Soft X-ray beamline of SwissFEL, operates 16 Apple X undulators and 15 compact chicanes to implement novel lasing schemes. With the data available after the end of the magnetic measurement campaign (middle 2020), a self-consistent set of equations will be used to summarise all the relevant properties of those devices to start their commissioning. The analytical approach planned will be discussed in great detail and tested with the preliminary experimental data available. Finally, the accuracy of this approach will be evaluated and critically compared to the requirements of the new FEL beamline. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP097 | ||
| About • | paper received ※ 27 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019 | ||
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| THP085 | Status of Athos, the Soft X-Ray FEL Line of SwissFEL | FEL, undulator, operation, laser | 753 |
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| The Athos line will cover the photon energy range from 250 to 1900 eV and will operate in parallel to the hard X-ray line Aramis of SwissFEL. The paper will describe the current layout of the Athos FEL line starting from the fast kicker magnet followed by the dogleg transfer line, the small linac and the 16 APPLE undulators. From there the photon beam passes through the photonics front end and the beamline optics before reaching the experimental stations AMO and FURKA. The focus of this contribution will be on the two bunch operation commissioning (two bunches in the same RF macropulse), which started in 2018, and the characterization of the major components like the APPLE X undulator UE38, the CHIC chicane and the dechirper. The Athos installation inside the tunnel is alternating with Aramis FEL user operation and the first lasing is planned for winter 2019 / 2020. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP085 | ||
| About • | paper received ※ 30 July 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019 | ||
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