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| MOPIK065 | Status of the Development of a BE-Model-Based Program for Orbit Correction at the Electron Storage Ring DELTA | 673 |
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| A new program for orbit correction is currently being developed at the electron storage ring DELTA. Based upon the standard approach of utilizing the linear response of a closed orbit to dipole-field-strength variations, proposed features include a live-updated orbit-response-matrix model and the integration of the Closed-Orbit-Bilinear-Exponential-Analysis algorithm (COBEA) to clean measured orbit-response matrices from noise. This work focuses on the current status of development of the aforementioned program. After an assessment of the situation at DELTA, first measurements are shown along with numerical convergence studies. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK065 | |
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| MOPIK066 | COBEA - Optical Parameters From Response Matrices without Knowledge of Magnet Strengths | 676 |
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| This paper presents some results of Closed-Orbit Bilinear-Exponential Analysis (COBEA), an algorithm designed to decompose (coupled) response matrices into betatron tunes and other optical parameters at beam position monitor and corrector positions. The only additional information strictly required by the algorithm is the ordering of monitors and correctors along the storage ring beam path. The presented method is largely lattice-independent, as no magnet strengths or dimensions are needed, and converges in a reasonable time interval due to usage of gradient-based optimization. After describing key features of the algorithm, a set of COBEA results is compared to LOCO results for the storage rings of MLS and BESSY II. The paper is concluded by a brief discussion of further applications, limits and further development of the COBEA algorithm. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK066 | |
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| WEPAB009 | Pilot Experiments and New Developments at the DELTA Short-Pulse Facility | 2578 |
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Funding: BMBF 05K16PEA, BMBF 05K16PEB, Mercur Pr-2014-0047 At the 1.5-GeV synchrotron light source DELTA operated by the TU Dortmund University, ultrashort radiation pulses in the vacuum ultraviolet (VUV) and terahertz (THz) regime are routinely generated by the interaction of electron bunches with femtosecond laser pulses. A laser-induced energy modulation is converted into a density modulation (microbunching) by a magnetic chicane, leading to coherent emission at harmonics of the initial laser wavelength (coherent harmonic generation, CHG). Path length differences of the energy-modulated electrons along the magnetic lattice lead to a dip in the longitudinal charge distribution, which gives rise to the coherent emission of THz radiation. In first pump-probe photoemission experiments, the spatial and temporal overlap of laser pump and CHG probe pulse on the sample was demonstrated. Furthermore, the effect of two temporally separated seed pulses was studied in the VUV and (sub-)THz regime. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB009 | |
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| WEPAB010 | Progress Towards an EEHG-Based Short-Pulse Source at DELTA | 2582 |
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Funding: Work supported by the accelerator initiative (ARD) of the Helmholtz society, BMBF 05K13PE3, BMBF 05K16PEA. The short-pulse source at the 1.5-GeV synchrotron light source DELTA, operated by the TU Dortmund University, enables the generation of sub-ps radiation pulses in the VUV regime based on coherent harmonic generation (CHG). As an upgrade, the employment of echo-enabled harmonic generation (EEHG) is planned which allows to produce shorter wavelengths. Recent developments and measurements regarding the twofold energy modulation required for EEHG are presented. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB010 | |
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| THPAB011 | Optimization of Multicell Microwave Cavities Using YACS | 3708 |
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Funding: Work supported by the BMBF under contract no. 05K13PEB. YACS is a 2.5D finite element method solver capable of solving for the full 3D eigenfrequency spectra of resonant axisymmetric structures while reducing the computational problem to a 2D rotation plane. The most recent revision of the code introduced arbitrary order basis functions and curved meshes, for both triangular and quadrilateral unstructured meshes. This led to significant increases in convergence rates. However, due to the utilization of curved meshes and the complex coordinate transformations that are involved, spurious modes were introduced when solving the axisymmetric problem. Although workarounds do exist that circumvent these issues by lowering the likelihood and frequency of spurious modes, linear triangular meshes with higher order basis functions were chosen due to their simplicity and spurious free solutions. In order to support the usage of spline cavities as an alternative parameterization to the well known elliptical cavities, parameter space scans were carried out for non-reentrant spline cavities. In addition a new optimization strategy is presented that exploits the arbitrary polynomial order of Bézier curves by utilizing the degree elevation technique. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB011 | |
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