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Title: Application of Genetic Algorithms to Sorting, Swapping and Shimming of the SOLEIL Undulator Magnets

Abstract

Undulators are typically composed of a large number of individual magnets, from tens to many hundreds, depending on undulator type and technology. Characteristics of real magnets often deviate from ideal values, resulting in degradation of the undulator performance. It is known that the imperfections of individual magnets can be mutually compensated, to certain extent, by appropriate sorting of the magnets and/or magnet modules, based on measurements of their individual characteristics, performed before the insertion device (ID) assembly. After the assembly, the quality of the ID magnetic field can be improved by magnet swapping and by shimming, consisting either in small displacements of some of the magnets or in adding small pieces of permanent magnet or soft iron material to appropriate locations of the structure. Mathematically, the magnet sorting, swapping and shimming can be considered as multi-objective constrained optimization problems with large numbers of variables. We show that each of these problems can be efficiently solved by means of Genetic Algorithms with 3D magnetostatics methods and magnetic measurements data used for the fitness calculation. First practical results obtained with three different undulators of the SOLEIL Synchrotron are presented.

Authors:
; ; ; ; ;  [1]
  1. Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 GIF-sur-YVETTE CEDEX (France)
Publication Date:
OSTI Identifier:
21052526
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 879; Journal Issue: 1; Conference: 9. international conference on synchrotron radiation instrumentation, Daegu (Korea, Republic of), 28 May - 2 Jun 2006; Other Information: DOI: 10.1063/1.2436074; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 43 PARTICLE ACCELERATORS; ALGORITHMS; COMPUTER CALCULATIONS; MAGNETIC FIELDS; OPTIMIZATION; PERFORMANCE; PERMANENT MAGNETS; SYNCHROTRON RADIATION; WIGGLER MAGNETS

Citation Formats

Chubar, O., Rudenko, O., Benabderrahmane, C., Marcouille, O., Filhol, J. M., and Couprie, M. E. Application of Genetic Algorithms to Sorting, Swapping and Shimming of the SOLEIL Undulator Magnets. United States: N. p., 2007. Web. doi:10.1063/1.2436074.
Chubar, O., Rudenko, O., Benabderrahmane, C., Marcouille, O., Filhol, J. M., & Couprie, M. E. Application of Genetic Algorithms to Sorting, Swapping and Shimming of the SOLEIL Undulator Magnets. United States. doi:10.1063/1.2436074.
Chubar, O., Rudenko, O., Benabderrahmane, C., Marcouille, O., Filhol, J. M., and Couprie, M. E. Fri . "Application of Genetic Algorithms to Sorting, Swapping and Shimming of the SOLEIL Undulator Magnets". United States. doi:10.1063/1.2436074.
@article{osti_21052526,
title = {Application of Genetic Algorithms to Sorting, Swapping and Shimming of the SOLEIL Undulator Magnets},
author = {Chubar, O. and Rudenko, O. and Benabderrahmane, C. and Marcouille, O. and Filhol, J. M. and Couprie, M. E.},
abstractNote = {Undulators are typically composed of a large number of individual magnets, from tens to many hundreds, depending on undulator type and technology. Characteristics of real magnets often deviate from ideal values, resulting in degradation of the undulator performance. It is known that the imperfections of individual magnets can be mutually compensated, to certain extent, by appropriate sorting of the magnets and/or magnet modules, based on measurements of their individual characteristics, performed before the insertion device (ID) assembly. After the assembly, the quality of the ID magnetic field can be improved by magnet swapping and by shimming, consisting either in small displacements of some of the magnets or in adding small pieces of permanent magnet or soft iron material to appropriate locations of the structure. Mathematically, the magnet sorting, swapping and shimming can be considered as multi-objective constrained optimization problems with large numbers of variables. We show that each of these problems can be efficiently solved by means of Genetic Algorithms with 3D magnetostatics methods and magnetic measurements data used for the fitness calculation. First practical results obtained with three different undulators of the SOLEIL Synchrotron are presented.},
doi = {10.1063/1.2436074},
journal = {AIP Conference Proceedings},
number = 1,
volume = 879,
place = {United States},
year = {Fri Jan 19 00:00:00 EST 2007},
month = {Fri Jan 19 00:00:00 EST 2007}
}
  • DiagOn is a diagnostic tool intended to precisely define the emission axis of an undulator, that has been developed by SOLEIL synchrotron Optics and Detectors groups. It uses the particular structure of monochromatic undulator emission into a narrow hollow cone centered on the axis. One wavelength is selected by a multilayer mirror to produce a characteristic image of the emission cone on scintillator and CCD camera. We review the emission properties of undulator in order to define the best parameters, K value, photon energy and emission angle, for diagnosis. Then the choice of optimal multilayer coating of the mirror ismore » discussed. We finish by some consideration on mirror cooling and mechanical conception for stable operation. The precise localization of the undulator axis will allow an optimal and fast alignment of the elements located before this detector, particularly adjustable aperture from the head of each of the lines.« less
  • A novel electromagnetic Insertion Device (ID) called HU640 (OPHELIE2) has been developed and constructed for the DESIRS beam line at SOLEIL. It is a 10 m-long helical/planar undulator designed to produce any kind of switchable photon polarizations in the range 5 eV - 40 eV. It is composed of three sets of pure air coils mounted in a special arrangment. One set coils is dedicated to generate the horizontal field component. Two other sets, shifted the one from the other by a quarter of period along the ID axis, produce the vertical component with a continuous translation dephasing varying frommore » -180 deg. to +180 deg. . The use of non magnetic material makes the undulator linear with the coil current in terms of peak field and residual integrated field errors. This allows the number of magnetic controls, corrections to be significantly reduced and to ease the on-beam operation. The paper presents the design, the construction and the magnetic measurements of the undulator.« less
  • Short period high field undulators are of interest for X-ray brilliance enhancement in synchrotron radiation applications and for compact Free Electron Lasers. Cryogenic in-vacuum undulators [1] are one of the possible solutions. At SOLEIL, PrFeB magnets were directly chosen, even if still under development at that time. Indeed, they enable to avoid the spin transition reorientation phenomenon which occurs with NdFeB magnets [2] and the magnets can be cooled down directly at 77 K. The first selected grade CR53 from Hitachi presents a remanence of 1.35 T at 293 K and 1.57 T at 77 K, with a coercivity ofmore » 1355 kA/m at 293 K and 6000 kA/m at 77 K. A 2 m long cryogenic undulator of period 18 mm was first built in-house, with a specific Hall probe bench directly installed in the final vacuum chamber. This first cryogenic undulator has been in operation on the storage ring for 4 years [3]. A second U18 cryo-ready undulator using a slightly different magnet grade with a higher coercivity and modules with magnets surrounded by two half poles for easier magnetic optimization is under construction. A third 3 m long cryo-ready undulator U15 with a period of 15 mm is under development. It will be first used for the LUNEX5 FEL [4, 5] project (COXINEL demonstration of FEL amplification with a laser wakefield acceleration [6]). The measurement bench will include a correction of the Hall probe position and angle, the field integrals will be measured with a stretched wire.« less
  • Shimming systems are required to provide sufficient fieldhomogeneity for high resolution NMR. In certain specialized applications,such as rotating-field NMR and portable (ex-situ) NMR, permanentmagnet-based shimming systems can provide considerable advantages. Wepresent a simple two-dimensional shimming method based on harmoniccorrector rings which can provide arbitrary multipole order shimmingcorrections. Results demonstrate, for example, that quadrupolar ordershimming improves the linewidth by up to and order of magnitude. Anadditional order of magnitude reduction is in principle achievable byultilizing this shimming method for z-gradient correction and higherorder xy gradients.
  • In this x-ray/MR hybrid system an x-ray flat panel detector is placed under the patient cradle, close to the MR volume of interest (VOI), where the magnetic field strength is {approx}0.5 T. Immersed in this strong field, several electronic components inside the detector become magnetized and create an additional magnetic field that is superimposed on the original field of the MR scanner. Even after linear shimming, the field homogeneity of the MR scanner remains disrupted by the detector. The authors characterize the field due to the detector with the field of two magnetic dipoles and further show that two setsmore » of permanent magnets (NdFeB) can withstand the main magnetic field and compensate for the nonlinear components of the additional field. The ideal number of magnets and their locations are calculated based on a field map measured with the detector in place. Experimental results demonstrate great promise for this technique, which may be useful in many settings where devices with magnetic components need to be placed inside or close to an MR scanner.« less