02 Synchrotron Light Sources and FELs

T15 Undulators and Wigglers

Paper Title Page
MOZRA02 Trends in the Development of Insertion Devices for a Future Synchrotron Light Source 50
 
  • C.-S. Hwang, C. H. Chang
    NSRRC, Hsinchu
 
 

An in-vacuum undulator with a room-temperature permanent magnet and a superconducting wiggler has become a mature technology and is widely used; it can adopt a short-period length in a medium-energy facility to provide an enhanced photon flux in the hard x-ray region. A cryogenic permanent magnet is applicable for an in-vacuum undulator to enhance the remanence field (Br) and the coercivity force. In future, a cryogenic permanent-magnet undulator and a superconducting wiggler will become mainstream to fulfill a user's requirement of a discrete and a continuous spectrum, respectively, but superconducting technology with HTS wires will have the best potential for the development of insertion devices after the next decade. HTS bulk magnets with magnet flux density 17 T are applicable even for a superconducting undulator; such an undulator can decrease the period length to about 10 mm. A small magnet gap with an extremely- short-period length (about 5 mm) has been studied with a stacked-layer of thin HTS tapes for a superconducting undulator. This report is a review to describe the current and future developments of insertion devices for a medium-energy storage ring and FEL facility.

 

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Slides

 
WEPEA055 General description of IDs initially installed at ALBA 2609
 
  • J. Campmany, D. Einfeld, J. Marcos, V. Massana
    CELLS-ALBA Synchrotron, Cerdanyola del Vallès
 
 

The new 3rd generation synchrotron radiation source ALBA built nearby Barcelona is planned to start operation in 2010 with several different insertion devices installed in the storage ring either from the beginning or within the first year of operation. The list of first insertion devices includes: 2 planar PPM SmCo in-vacuum undulators with the period of 21.6 mm; 2 Apple-II type PPM NdFeB undulators with the periods of 62.36 and 71.36 mm respectively; 1 superconducting planar wiggler with the period of 30 mm and a maximum field of 2.1 T, and a 1 conventional wiggler with the period of 80.0 mm and a maximum field of 1.74 T. The emitted light of these IDs covers wide spectral range extending from hard X-rays to UV. Pre-design of the IDs was done by ALBA, but manufacturing has been outsourced. Production is now finished and they have been tested with magnetic measurements. The paper will present the final as build magnetic designs as well as the main results of magnetic measurements performed on the manufactured devices.

 
WEPD004 Modelling of Elliptically Polarizing Undulators 3087
 
  • L.O. Dallin, D.G. Bilbrough
    CLS, Saskatoon, Saskatchewan
 
 

To investigate the effect of an elliptically polarized undulator (EPU) on the dynamic aperture of storage ring a model is required for use in an optics code. An EPU can be modelled as an array of skew dipole magnets. The skew angle ranges from zero to ninety degrees depending on the degree of polarization. Crudely the EPU can be modelled using alternating skew dipole blocks. A model that better reproduces the sinusoidally varying fields can be achieved by slicing blocks into smaller subsets. Field roll-off produced by the limited transverse dimensions of the magnet blocks can be included as skew multipoles. For example the roll-off of the horizontal field in the vertical undulator mode is very nearly a skew sextupole. The model has the advantage of correctly calculating the path length through the EPU which is important for tracking in six dimensions.

 
WEPD005 Insertion Device Development at the Canadian Lightsource 3090
 
  • M.J. Sigrist, D.G. Bilbrough, S. Chen, L.O. Dallin, W.A. Wurtz
    CLS, Saskatoon, Saskatchewan
 
 

The Canadian Lightsource is a 2.9 GeV 3rd generation lightsource in Saskatoon, Canada. The latest expansion of operations includes adding 4 insertion devices in 2 straight sections. These devices will include a hybrid permanent magnet wiggler, an in-vacuum undulator and 2 APPLE-II type undulators. The 4 m long elliptical APPLE-II IDs will cover overlapping photon energy ranges of 15-200eV and 200-1000eV. These devices will be installed adjacent to one another in the same straight with the magnet arrays mounted on one support structure and a horizontal translation system to allow users to select one device at a time for use on a single beamline. The 2nd straight will include the hybrid wiggler and in-vacuum undulator in a 3 magnet chicane. The wiggler is designed to supply photons for a center beamline and a side beamline accepting radiation 5 mrad off of the centerline of the radiation fan. The critical energy of photons emitted of the sideline are >90% of the critical energy on the centerline. An 8 mrad center chicane magnet separates the photons of the undulator from the wiggler beamlines allowing for 3 beamlines operating with 2 IDs in a single straight section.

 
WEPD006 Cryogenic In-vacuum Undulator at Danfysik 3093
 
  • C.W.O. Ostenfeld, M. Pedersen
    Danfysik A/S, Jyllinge
 
 

Danfysik A/S has built a cryogenic in-vacuum undulator for Diamond Light Source, with a period length of 17.7 mm and an effective K of 1.7 at cryogenic temperatures. The undulator is hybrid-type, with Vanadium Permendur poles and NdFeB poles. In order to verify the performance of the device under cryogenic conditions, an in-vacuum measuring system is required. We present the magnetic measurements at room temperature and under cryogenic in-vacuum conditions. The magnet assembly cannot be baked, due to a choice of high-remanence, low coercivity magnet grade. We discuss the vacuum performance of the undulator.

 
WEPD007 Development of a PrFeB Cryogenic Undulator at SOLEIL 3096
 
  • C. Benabderrahmane, P. Berteaud, N. Béchu, M.-E. Couprie, J.-M. Filhol, C. Herbeaux, C.A. Kitegi, J.L. Marlats, K. Tavakoli, M. Valléau, D. Zerbib
    SOLEIL, Gif-sur-Yvette
 
 

The production of hard X rays at SOLEIL, a 2.75 GeV, requires short period and small gap in-vacuum undulators. For shifting further the radiation toward higher energies, the peak magnetic field of the undulators can be further increased by cooling the permanent magnets at cryogenic temperature below 100 K. A R&D programme for the construction of a 2 m long 18 mm period CPMU is launched: the use of PrFeB enables to increase the peak magnetic field at a cryogenic temperature of 77 K. Praseodymium was chosen instead of Neodymium type magnets, because it prevents the appearance of the Spin Reorientation Transition. The magnetic characterisation of different permanent magnet grades at cryogenic temperatures (NdFeB and PrFeB), and the magnetic and thermal measurements on a small 4 period NdFeB cryogenic undulator are presented. The status on the progress of the CPMU conception is given. The magnetic and mechanical design, including the cooling of the girders at 77K, and the thermal budget are described. The designs of the dedicated magnetic measurement benches, which will be required to check the magnetic performance of the undulator at low temperature, are also reported.

 
WEPD008 Development of a Short Period High field APPLE-II Undulator at SOLEIL 3099
 
  • C.A. Kitegi, F. Briquez, M.-E. Couprie, T.K. El Ajjouri, J.-M. Filhol, K. Tavakoli, J. Vétéran
    SOLEIL, Gif-sur-Yvette
 
 

At SOLEIL, the production of high brilliant photon beams with adjustable polarization is achieved by means of Advanced Planar Polarized Light Emitter-II (APPLE-II) undulators. The HU36 is a short period high field APPLE-II type undulator with 36 mm period and 0.8 T peak field at a minimum gap of 11 mm. The HU36 circularly polarized radiation ranges from 2 keV to 5 keV, while the planar one extends up to 10 keV. High harmonic radiation (up to the 13th) is required to reach such high energy; therefore a small RMS phase error is needed. To enable closing the gap at 11 mm, the HU36 is planned to be installed in a short section where the large horizontal beta function imposes constraining tolerances on the integrated field errors. However at low period and high field, the magnet holders, commonly used at SOLEIL to maintain magnets on the girders, experience mechanical deformation due to the large magnetic forces. This results in the variation of field integrals when the shift between girders is changed. Solutions to minimize these errors are discussed and finally the HU36 magnetic performances are reviewed.

 
WEPD009 Production of High Flux Hard X-ray Photons at SOLEIL 3102
 
  • O. Marcouillé, P. Berteaud, P. Brunelle, N. Béchu, L. Chapuis, M.-E. Couprie, J.-M. Filhol, C. Herbeaux, A. Lestrade, J.L. Marlats, A. Mary, M. Massal, M.-H. Nguyen, K. Tavakoli, M. Valléau, J. Vétéran
    SOLEIL, Gif-sur-Yvette
 
 

The production of high fluxes in the hard X-rays region is a major issue on medium energy storage rings. It requires the installation of Insertion Devices with high magnetic field and a large number of periods. The construction of a superconducting wiggler has been first envisaged but reveals to be maintenance constraining, much more complex and expensive than the permanent magnet technology. A small gap in vacuum wiggler composed of 38 periods of 50 mm has been preferred. The compact magnetic system allows to produce in a limited space a magnetic field of 2.1 T in a small gap of 5.5 mm, whereas an auxiliary counterforce system based on non-magnetic springs compensate the magnetic forces (up to 8.5 Tons) acting between magnet arrays. The gap between jaws and the mechanical deformations have been controlled and corrected. Magic fingers corrections have been also performed to reduce the integrated multipoles and to minimize the 2nd order integrals resulting from the tight width of the wiggler poles. This paper presents the design of the wiggler, the construction, and the results of the measurements after magnetic corrections.

 
WEPD010 Upgrade of the Insertion Devices at the ESRF 3105
 
  • J. Chavanne, L. Goirand, G. Lebec, C. Penel, F. Revol
    ESRF, Grenoble
 
 

An important upgrade of the ESRF is planned from 2009 to 2016. It is mainly driven by the improvement of beamlines performances and capacity. On the storage ring side, the length of the straight sections will be increased from 5 m to 6 m with a possible further extension to 7 m. These long sections will provide a higher photon flux, and it will allow the installation of canted undulators. The length of the insertion devices (ID), such as revolver undulators and in-vacuum undulators, will be modified to fit the first upgraded beamline sections. The resulting implication on the length of new IDs will be presented. The concept of canted undulators is a proposed optional feature. It will rely on novel permanent magnet chicane providing a maximal separation angle of 5.4 mrad while keeping short distance between canted undulators. Magnetic chicane magnets with low fringe field and homogeneous longitudinal field integral have been designed. The developed magnets will be presented.

 
WEPD011 Mini-beta Sections in the Storage Ring BESSY II 3108
 
  • J. Bahrdt, W. Frentrup, A. Gaupp, M. Scheer, F. Schäfers, G. Wüstefeld
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
 
 

At BESSY II photon energies above 2keV can be produced only with bending magnets, a permanent magnet wiggler, superconducting (SC) wavelength shifters and a SC-wiggler. The wiggler brilliance suffers from the depth of field effect and the bending magnets and wavelength shifters produce the X-rays only with a single pole. Experiments such as HIgh Kinetic Energy photoelectron spectroscopy (HIKE) or microspectroscopy on nanostructured materials demand a high brilliance and flux as it is provided by a small period cryogenic undulator. This paper discusses the requirements for the operation of small gap cryogenic devices at BESSY II. A scheme with two adjacent, vertical low beta sections inside of one of the long straight sections is suggested. The straight is divided into two parts by a quadrupole triple in the center. An optic with an increased, vertical beta tune by 0.5 is presently studied. The optics outside of the low beta section and the horizontal tune are kept unchanged.

 
WEPD012 Cryogenic Design of a PrFeB-Based Undulator 3111
 
  • J. Bahrdt, H.-J. Baecker, M. Dirsat, W. Frentrup, A. Gaupp, D. Pflückhahn, M. Scheer, B. Schulz
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
  • F.J. Grüner, R. Weingartner
    LMU, Garching
  • D. Just
    Technische Universität Berlin, Berlin
  • F.H. O'Shea
    UCLA, Los Angeles, California
 
 

In collaboration with the Ludwig-Maximilian-University Munich a cryogenic PrFeB- based undulator has been built. The 20-period device has a period length of 9mm and a fixed gap of 2.5mm. The undulator has recently been installed at the laser plasma accelerator at the Max-Planck-Institute for Quantenoptik. The operation of a small gap device at a high emittance electron beam requires stable magnetic material. A high coercivity is achieved with PrFeB- material which is cooled down to 50K. This temperature is 100K lower as compared to the temperature of a NdFeB-based cryogenic undulator. In this paper we present the mechanic and cryogenic design and compare the predictions with measured data. The results are extrapolated to a 2m-long variable gap undulator.

 
WEPD014 Undulators of the sFLASH Experiment 3114
 
  • H. Delsim-Hashemi, J. Roßbach
    Uni HH, Hamburg
  • U. Englisch, T. Mueller, A. Schöps, M. Tischer, P.V. Vagin
    DESY, Hamburg
  • I. Vasserman
    ANL, Argonne
 
 

A seeded free-electron laser (FEL) experiment at VUV wavelengths, called sFLASH, is being prepared at the existing SASE FEL user facility FLASH. Seed pulses at wavelengths around 35 nm from high harmonic generation (HHG) will interact with the electron beam in sFLASH undulators upstream of the existing SASE undulator section. In this paper the tuning results and performance of the sFLASH undulators are presented.

 
WEPD015 Inductive Shimming of Superconductive Undulators: Preparations for a Realistic Test 3117
 
  • P. Peiffer, A. Bernhard, F. Burkart, S. Ehlers
    KIT, Karlsruhe
  • T. Baumbach, S. Gerstl, A.W. Grau, R. Rossmanith
    Karlsruhe Institute of Technology (KIT), Karlsruhe
  • D. Schoerling, D. Wollmann
    CERN, Geneva
 
 

The monochromaticity and intensity of synchrotron light emitted by undulators strongly depend on the undulator field quality. For the particular case of superconductive undulators it was shown recently that their field quality can be significantly improved by an array of coupled high temperature superconductor loops attached to the surface of the superconductive undulator. Local field errors induce currents in the coupled closed superconducting loops and, as a result, the hereby generated magnetic field minimizes the field errors. In previous papers the concept was described theoretically and a proof-of-principle experiment was reported. This paper reports results of the first quantitative measurement of the phase error reduction in a 12-period short model undulator equipped with a full-scale induction shimming system.

 
WEPD016 Reduction of Dynamic Field Errors in Superconductive Undulators 3120
 
  • P. Peiffer, A. Bernhard, F. Burkart, S. Ehlers, A. Keilmann
    KIT, Karlsruhe
  • T. Baumbach, R. Rossmanith
    Karlsruhe Institute of Technology (KIT), Karlsruhe
  • D. Schoerling
    CERN, Geneva
 
 

In the superconductive undulator SCU14, installed at ANKA, time dependent drifts in the magnetic fields were observed*. Simulations with the software OPERA 3D showed, that the cause of these drifts might be leak and eddy currents in the iron body of the undulator caused by the time-varying currents and fields during current ramps, which slowly decay by ohmic losses. This assumption was crosschecked by measurements at different mockup bodies. This contribution discusses the results of the simulations and measurements and the consequential strategies for avoiding this effect.


* S. Ehlers et. al. "Magnetic field transients in superconductive undulators", in Proceedings of the Particle Accelerator Conference, Vancouver, 2009, to be published.

 
WEPD017 Magnetic Measurements of the 1.5 m Coils of the ANKA Superconducting Undulator 3123
 
  • S. Casalbuoni, T. Baumbach, S. Gerstl, A.W. Grau, M. Hagelstein, D. Saez de Jauregui
    Karlsruhe Institute of Technology (KIT), Karlsruhe
  • C. Boffo, W. Walter
    BNG, Würzburg
 
 

A 1.5 m long superconducting undulator with a period length of 15 mm is planned to be installed in ANKA middle 2010 to be the light source of the new beamline NANO for high resolution X-ray diffraction. The key specifications of the system are an undulator parameter K higher than 2 (for a magnetic gap of 5mm) and a phase error smaller than 3.5 degrees. In order to characterize the magnetic field properties of the superconducting coils local field measurements have been performed by moving a set of Hall probes on a sledge in a liquid helium bath: the results are reported.

 
WEPD018 Status of COLDDIAG: a Cold Vacuum Chamber for Diagnostics 3126
 
  • S. Gerstl, T. Baumbach, S. Casalbuoni, A.W. Grau, M. Hagelstein, D. Saez de Jauregui
    Karlsruhe Institute of Technology (KIT), Karlsruhe
  • V. Baglin
    CERN, Geneva
  • C. Boffo, G. Sikler
    BNG, Würzburg
  • T.W. Bradshaw
    STFC/RAL, Chilton, Didcot, Oxon
  • R. Cimino, M. Commisso, B. Spataro
    INFN/LNF, Frascati (Roma)
  • J.A. Clarke, D.J. Scott
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • M.P. Cox, J.C. Schouten
    Diamond, Oxfordshire
  • R.M. Jones, I.R.R. Shinton
    UMAN, Manchester
  • A. Mostacci
    Rome University La Sapienza, Roma
  • E.J. Wallén
    MAX-lab, Lund
  • R. Weigel
    Max-Planck Institute for Metal Research, Stuttgart
 
 

One of the still open issues for the development of superconducting insertion devices is the understanding of the beam heat load. With the aim of measuring the beam heat load to a cold bore and the hope to gain a deeper understanding in the beam heat load mechanisms, a cold vacuum chamber for diagnostics is under construction. The following diagnostics will be implemented: i) retarding field analyzers to measure the electron flux, ii) temperature sensors to measure the total heat load, iii) pressure gauges, iv) and mass spectrometers to measure the gas content. The inner vacuum chamber will be removable in order to test different geometries and materials. This will allow the installation of the cryostat in different synchrotron light sources. COLDDIAG will be built to fit in a short straight section at ANKA. A first installation at the synchrotron light source DIAMOND is under discussion. Here we describe the technical design report of this device and the planned measurements with beam.

 
WEPD019 Development of Instrumentation for Magnetic Field Measurements of 2m Long Superconducting Undulator Coils 3129
 
  • A.W. Grau, T. Baumbach, S. Casalbuoni, S. Gerstl, M. Hagelstein, D. Saez de Jauregui
    Karlsruhe Institute of Technology (KIT), Karlsruhe
 
 

Precise measurements of the magnetic properties of conventional, i.e., permanent magnet based insertion devices has undergone tremendous improvements over the past 10 to 15 years and initiated a new era in synchrotron light sources worldwide. A similar breakthrough is now necessary in the field of superconducting insertion devices. In this contribution we describe the planned instrumentation to perform magnetic measurements of the local field, the field integrals and the multipole components of superconducting undulator coils in a cold invacuum (cryogen free) environment.

 
WEPD020 Experimental Demonstration of Period Length Switching for Superconducting Insertion Devices 3132
 
  • A.W. Grau, T. Baumbach, S. Casalbuoni, S. Gerstl, M. Hagelstein, D. Saez de Jauregui
    Karlsruhe Institute of Technology (KIT), Karlsruhe
  • C. Boffo, W. Walter
    BNG, Würzburg
 
 

One of the advantages of superconducting insertion devices (IDs) with respect to permanent magnet IDs is the possibility to enlarge the spectral range by changing the period length by reversing the direction of the current in a part of the windings. In this contribution we report the first experimental test of this principle demonstrated on a 70mm NbTi mock-up coil with period tripling, allowing to switch between a 15mm period length undulator and a 45mm wiggler.

 
WEPD021 Fabrication of the New Superconducting Undulator for the ANKA Synchrotron Light Source 3135
 
  • C. Boffo, W. Walter
    BNG, Würzburg
  • T. Baumbach, S. Casalbuoni, A.W. Grau, M. Hagelstein, D. Saez de Jauregui
    Karlsruhe Institute of Technology (KIT), Karlsruhe
 
 

Superconducting insertion devices (IDs) are very attractive for synchrotron light sources since they allow increasing the flux and/or the photon energy with respect to permanent magnet IDs. Babcock Noell GmbH (BNG) completed the fabrication of a 1.5 m long unit for ANKA at KIT. The period length of the device is 15 mm for a total of 100.5 full periods plus an additional matching period at each end. The key specifications of the system are: a K value higher than 2 for a magnetic gap of 5 mm, the capability of withstanding a 4 W beam heat load and a phase error smaller than 3.5 degrees. The field performance of the magnets has been qualified with liquid helium in a vertical dewar. As a result of this test the local correction coils have been installed and the magnets inserted in the final cryostat. During the factory acceptance test, the conduction cooling operation has been qualified and at the moment the undulator is ready to be tested at KIT. This paper describes the main features of the system and the results of the factory acceptance tests.

 
WEPD023 Development of Ultra-High Quality Surface Finish Undulator Vacuum Chambers for the FERMI@Elettra Project 3138
 
  • G. Lanfranco, P. Craievich, D. La Civita, G.L. Loda, A.A. Lutman, F. Pradal, G. Sostero, M. Stefanutti
    ELETTRA, Basovizza
  • M. Canetti, F. Gangini
    RIAL VACUUM S.p.A, Parma
 
 

The FERMI@Elettra project at the ELETTRA Laboratory of Sincrotrone Trieste (ST), currently under construction, will be comprised of a linear accelerator and two Free-Electron-Laser beamlines (FEL1, FEL2). In order to deliver high-intensity VUV and soft X-ray pulses, permanent magnet undulators with 9 mm minimum variable gap will be used. The adopted vacuum chambers will have a 7 by 25 mm2 elliptical internal cross-section. While manufacturing the vacuum chamber in aluminum helps reducing the resistive wall wakefield effects, the chamber inner wall surface quality is strongly correlated to the surface roughness wakefield component. We report on the results of the study to improve the wall surface finish and lower the roughness periodicity. The chamber manufacturing status and its alignment mechanism is also presented.

 
WEPD024 New Scheme of Quasi-Periodic Undulators 3141
 
  • S. Sasaki
    HSRC, Higashi-Hiroshima
 
 

More than a decade has past after the original quasi-periodic undulator (QPU) was proposed.* Until now, much work has been done to improve the QPU performance. One of the first most productive improvements was to introduce the quasi-periodicity in an electron trajectory by partially changing the field strength in a periodic undulator.** Also, a modification of creation theory of one-dimensional quasi-periodicity gave another degree of freedom to build this type of device.*** As the result, many different types of QPUs have been and will be installed in the synchrotron radiation facilities worldwide.**** In this paper, a new scheme of quasi-periodic undulator that has a different magnetic structure is proposed. This new QPU generates a slightly higher intensity radiation with higher harmonics pattern different from those of previous QPUs. This new scheme of QPU is achieved by introducing orthogonal field in each half-period in order to create additional phase delay of electron beam at certain positions predicted by the theory. We discuss about realistic magnetic configurations as well as possibilities and limitations of new-QPUs.


* Hashimoto, Sasaki, NIM A361, 611 (1995)
** Chavanne, et al, Proc EPAC98, p2213, Diviacco, et al, ibid, p2216
*** Sasaki, et al, Proc EPAC98, p2237
**** Steier, et al, Proc EPAC08, p2311

 
WEPD025 Theoretical Examination of Radiation Spectrum from the Quasi-periodic Undulator 3144
 
  • S. Hirata
    Hiroshima University, Faculty of Science, Higashi-Hirosima
  • S. Sasaki
    HSRC, Higashi-Hiroshima
 
 

Different form conventional periodic undulators, the quasi-periodic undulator (QPU) can radiate irrational harmonics instead of rational harmonics. It suits with experiments that need highly monochromatic light after passing through the monochromator. For this reason, the QPU is used in many synchrotron radiation facilities all over the world. Recently, new type QPUs that generate radiation spectra different from those by conventional type QPU were proposed*,**. In principle, the shape of radiation spectrum from a new QPU is determined by magnetic field distribution having different quasi periodic pattern. However, calculated spectra using a realistic magnetic field are often different from those of theoretical expectation. In this paper, a detailed comparative study is conducted to examine why there are these differences, how to correct magnetic field to get predicted spectra that fit to the theory. In addition, a possibility of modifying the basis of theory is investigated. These results, new generation method of new quasi-periodicity, and magnetic field distribution to achieve the best performance are presented at the conference.


* S. Sasaki, Proceedings of PAC09, Vancouver, May, 2009.
** S. Sasaki, Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (in Japanese).

 
WEPD026 In-situ Magnetic Correction for Cryogenic Undulators 3147
 
  • T. Tanaka, H. Kitamura
    RIKEN/SPring-8, Hyogo
  • A. Anghel, M. Bruegger, W. Bulgheroni, B. Jakob, T. Schmidt
    PSI, Villigen
  • A. Kagamihata, T. Seike
    JASRI/SPring-8, Hyogo-ken
 
 

The cryogenic permanent magnet undulator (CPMU) is an insertion device in which permanent magnets are cooled down to cryogenic temperature (CT) to improve the magnetic performances. Although CPMUs are realized by a slight modification of in-vacuum undulators (IVUs), we have several technical challenges to be overcome. Among them, the most important one is how to ensure the magnetic performance, in other words, how to measure the magnetic field at CT, and how to correct it if necessary. A new method of the phase-error correction has been proposed at SPring-8, in which the gap variation is corrected by adjusting mechanically the in-vacuum beam. What is important in this method is that the correction can be done at CT without breaking the vacuum, i.e., an 'in-situ' field correction is possible. The correction method has been tested to check the feasibility using the new CPMU with a magnetic period of 14 mm and a magnetic length of 1.7 m constructed for Swiss Light Source. In this paper, the principle and results are described together with the details of the new measurement system SAFALI (self aligned field analyzer with laser instrumentation) for the field measurement of CPMUs.

 
WEPD027 Tuning of the Fast Local Bump System for Helicity Switching at the Photon Factory 3150
 
  • K. Harada, Y. Kobayashi, T. Miyajima, S. Nagahashi, T. Obina, M. Shimada, R. Takai
    KEK, Ibaraki
  • S. Matsuba
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima
 
 

The fast local bump system for the helicity switching of variably polarizing undulators has been developed at the Photon Factory ring. The system consists of two APPLE-II type variably polarizing undulators and five identical horizontal kicker magnets for local bump with four small corrector magnets to prevent the leakage of the bump. At present, one undulator and the local bump system with corrector magnets are installed. For beam test, the system was operated with frequency up to 50 Hz with feed forward correction. In this presentation, after brief description of the system configuration, the results of the test operation and fine tunings of the fast local bump system are shown.

 
WEPD028 Magnetic Field Adjustment of a Polarizing Undulator (U#16-2) at the Photon Factory 3153
 
  • K. Tsuchiya, T. Aoto
    KEK, Ibaraki
 
 

We have been developing a rapid-polarization-switching source at the B15-16 straight section in the PF 2.5GeV ring. The source consists of tandem two APPLE-II type elliptically polarizing undulators (EPU), namely U#16-1 and U#16-2, and a fast kicker system. These two undulators are designed to obtain the soft x-ray at the energy region from 200eV to 1keV with various polarization states. We have constructed U#16-1 and installed in the PF ring in March 2008. The operation of U#16-1 for the user experiments has been started successfully since April 2008. The construction of the second undulator U#16-2 is underway. U#16-2 will be installed in the PF ring at this summer. We report the result of the magnetic field adjustment of the U#16-2.

 
WEPD029 End Field Termination for Bulk HTSC Staggered Array Undulator 3156
 
  • R. Kinjo, M. A. Bakr, Y.W. Choi, T. Kii, K. Masuda, K. Nagasaki, H. Ohgaki, T. Sonobe, M. Takasaki, K. Yoshida
    Kyoto IAE, Kyoto
 
 

Aiming at realizing a short period undulator with strong magnetic field, we have proposed a Bulk HTSC (high temperature superconductor) Staggered Array Undulator which consists of bulk high temperature superconductor magnets with a staggered array configuration. The experiment with the prototype undulator at 77 K shows this configuration can be applicable to real undulator. We also estimated the magnetic performance of real device by calculations with a loop current model based on Bean model of superconductor. Although end field termination is required for practical use, traditional methods are not applicable for the bulk HTSCs. We found that the end field termination can be realized by controlling the shape and size of bulk HTSCs at the end section by numerical calculation using the loop current model. In the conference, the calculation and experimental result of end field termination will be presented.

 
WEPD030 Elimination of Hall Probe Orientation Error in Measured Magnetic Field of the Edge-focusing Wiggler 3159
 
  • S. Kashiwagi, G. Isoyama, R. Kato
    ISIR, Osaka
  • K. Tsuchiya, S. Yamamoto
    KEK, Ibaraki
 
 

The edge-focusing (EF) wiggler has been fabricated to evaluate its performance rigorously with the magnetic field measurement. It is a 5-period planar wiggler with an edge angle of 2° and a period length of 60 mm. The magnetic field is measured using Hall probes at four different wiggler gaps. It is experimentally confirmed that a high field gradient of 1.0 T/m is realized, as designed, along the beam axis. The magnetic field gradient of the EF wiggler is derived as a function of the magnetic gap. The field gradient decreases with increasing magnet gap more slowly than the peak magnetic field does for the present experimental model. An analytic formula for the field gradient of the EF wiggler is derived and it is shown that the slope of the field gradient with the magnet gap can be changed by varying the magnet width of the EF wiggler. We analyzed the relation between the orientation errors of the measurement system and the measured magnetic field or field gradient using a model magnetic field of the EF wiggle. We corrected the measurement magnetic field based on this analysis and evaluated the performance of the EF wiggler.

 
WEPD031 Observation and Correction of Effects of Variably Polarized Undulator on Electron Beam at SAGA-LS 3162
 
  • T. Kaneyasu, Y. Iwasaki, S. Koda, Y. Takabayashi
    SAGA, Tosu
 
 

An APPLE-II type variably polarized undulator was installed in the SAGA-LS storage ring in 2008. Following the installation, we have investigated influence of the undulator on the electron beam. Based on the measurements, we have developed a feedforward correction system to minimize the effects of the undulator. The correction system successfully compensates for closed orbit distortion (COD), betatron tune shift and a weak change in the betatron coupling. The standard deviation of the COD variation relative to the reference orbit and the tune shift are suppressed to less than 4 micron and 0.001, respectively, when the pole gap is changed at a fixed phase. The observed tune shift is interpreted in terms of a second order focusing effect evaluated by RADIA code. The simulated tune shift fairly agrees with the measurements. To minimize the effects on the betatron coupling, a wire-type skew quadrupole magnet mounted on the undulator duct is utilized. The skew field required for the coupling compensation is consistent with those predicted by field integral measurements. The feedforward correction reduces the effect to a relative change in the vertical beamsize of 5%.

 
WEPD033 Undulator Harmonic Field Enhancement Analysis 3165
 
  • Q.K. Jia
    USTC/NSRL, Hefei, Anhui
 
 

The enhancement of arbitrary odd harmonic field is analyzed for pure permanent magnet undulator. The two dimensional analytical formula of the magnetic field is given for a modified Harbch type undulator, in which the magnet blocks have different size. It is shown that the odd harmonic field can be enhanced by optimal the length ratio of the vertical magnetized magnet blocks and the horizontal magnetized magnet blocks, the 3rd harmonic field can exceeded 20% of the fundamental field and 7th harmonic field can exceeded 3 % of the fundamental field for magnet gap-period ratio equal to 0.1.

 
WEPD034 In-Vacuum Undulator Controller Design for SSRF 3168
 
  • M. Gu, R. Chen, Z.H. Chen, G.-Y. Jiang, R. Wang, Q. Yuan
    SINAP, Shanghai
 
 

The undulator controller based on Siemens S7-300 PLC is mainly consisted of controlling motion of two stepper motor, monitoring real-time gap position of upstream and downstream through position feedback derived from four linear absolute encoders (LAEs) with 0.1μm resolution, monitoring cooling water's temperature and flux (CWTF), monitoring magnet array temperature (MAT), providing remote access for EPICS via Ethernet, as well as MPS and PPS interlock interface to and from upper-level protection system. In addition, the controller is equipped with considerate motion safety protection tactics. As for the gap position protection, besides mechanical hard stop, software limit, photo-interrupter limit and kill switch are available to achieve it. As for the taper protection, software limit is available to achieve it.

 
WEPD038 Insertion Devices for the MAX IV 3 GeV Ring 3171
 
  • E.J. Wallén
    MAX-lab, Lund
 
 

The MAX IV light source, presently under construction at MAX-lab in Lund, Sweden, will consist of two separate storage rings and a linac-driven short-pulse facility. The two storage rings are operated at different energies, 3 GeV and 1.5 GeV, to provide synchrotron radiation of high brightness over a broad spectral range. The 3 GeV linac serves as a full-energy injector for the storage rings as well as the driver of the short-pulse facility delivering intense x-ray pulses. The paper describes a selection of possible insertion devices to be installed at the MAX IV 3 GeV ring and the expected heat loads produced by the insertion devices.

 
WEPD039 First Magnetic Tests of a Superconducting Damping Wiggler for the CLIC Damping Rings 3174
 
  • D. Schoerling, M. Karppinen, R. Maccaferri
    CERN, Geneva
  • A. Ams
    IMFD, Freiberg
  • A. Bernhard, P. Peiffer
    KIT, Karlsruhe
  • R. Rossmanith
    FZK, Karlsruhe
 
 

Two damping rings (e+, e-) are foreseen for the CLIC injection chain. In each damping ring 76 two meter long wigglers will be installed. The short period (40-50 mm), combined with a gap larger than 14 mm and a requested field in the mid-plane BPeak > 2 T requires the usage of superconducting technologies to meet these requirements. To demonstrate the feasibility of this wiggler design a short-model vertical racetrack wiggler (40 mm period; 16 mm gap) was built and successfully tested at CERN. The wiggler carries a current of 730 A and 910 A and reaches a mid-plane peak field of Bpeak = 2 T and Bpeak = 2.5 T at 4.2 K and 1.9 K, respectively. The results show that the wiggler model meets the magnetic requirements of the CLIC damping rings at 1.9 K. The paper will also discuss the improvements we propose to enhance the performance in order to meet the CLIC specifications also at 4.2 K.

 
WEPD040 Spectrum Property Analysis of a Wiggler-like Undulator 3177
 
  • S.D. Chen, T.M. Uen
    NCTU, Hsinchu
  • C.-S. Hwang
    NSRRC, Hsinchu
 
 

A wiggler with the property of low total radiation power and keeping high photon flux in hard x-ray region, 5-20 keV, which is necessary for the special demand of users, was under investigated for reducing the difficulty of the design of optical components in the beam line and decreasing the load of RF cavity power. Such an insertion devise was called wiggler-like undulator. The spectrum of wiggler-like undulater was investigated with a code, of which the algorithm is based on the compromising between photon flux and radiation power of insertion devices for spectrum optimization. The property of the spectrum of the wiggler-like undulator are discussed herein. Furthermore, the brilliance and the power distribution are somehow also discussed.

 
WEPD041 Auto-field Shimming Algorithm for an Elliptically Polarized Undulator 3180
 
  • C.M. Wu, C.-S. Hwang, F.-Y. Lin
    NSRRC, Hsinchu
 
 

Shimming magnetic field error on each pole in the Elliptically Polarized Undulator (EPU) is a time-consuming work and highly based on experience without scientific systematic methods. Therefore, an auto-field shimming program is developed to save time on pole shimming process. The program is including two major steps to analyze where the poles is defective or imperfect. Step one is to clarify the magnetic pole quality. If its quality is far away to user-defined standards, we change the pole instead of processing to balance them relatively for uniform magnetic field. The magnetic pole quality is based on deltaB/Bavg and deltaI/Iavg(half period of integral) percentage. The second step is to build the effective field and once integral model of pole and permanent magnet calculation. If we shim the defective pole by moving vertically and transversely, it would surge intrinsic change of the deltaB/Bavg and deltaI/Iavg at defective and surrounded poles. Auto-field shimming algorithm would assist us to plan shimming strategies to deal with magnetic poles.

 
WEPD042 Design and Development of an Elliptically Polarized Undulator of Length 3.5 m for TPS 3183
 
  • C. H. Chang, C.-H. Chang, H.-H. Chen, J.C. Huang, M.-H. Huang, C.-S. Hwang, F.-Y. Lin, C.M. Wu
    NSRRC, Hsinchu
 
 

An elliptically polarized undulator of length 3.5 m and period length 48 mm (EPU48) is designed to fulfil experiments on spin-polarized PES and inelastic scattering at the Taiwan Photon Source (TPS). EPU48 would be used to produce variously polarized light in the soft X-ray spectral domain 0.4-1.5 keV. To achieve efficient mechanical performance and a high quality of photon source, a new manufacturing method by casting is adopted to fabricate a key component of the carriage of the undulator at National Synchrotron Radiation Research Center (NSRRC). We expect this approach to bestow advantages of decreased assembly error, increased rigidity and highly precise properties. Here we describe details of the design of the magnetic circuit and the mechanical design of the EPU48 based on this new concept of engineering construction.

 
WEPD043 The Development of Gradient Damping Wiggler for ALPHA Storage Ring 3186
 
  • Z.W. Huang, D.J. Huang
    NTHU, Hsinchu
  • S.D. Chen, M.-H. Huang, C.-S. Hwang, C.Y. Kuo, F.-Y. Lin, Y.T. Yu
    NSRRC, Hsinchu
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
 
 

A novel gradient damping wiggler (GDW) was developed for the ALPHA storage ring in Indiana University. The GDW will be used to change the momentum compaction factor and the damping partition at ALPHA storage effectively. There is one middle pole and two outer poles that they have gradient field were assembled together on the same girder to be a full set of GDW magnet system. The dipole and gradient field strength of the middle (outer) pole is 0.67 T (-0.67) and 1.273 T/m (1.273 T/m), respectively. The magnet gap of the middle and outer pole is 40 mm and 35.87 mm, respectively, that the three combined function of dipole magnet can be charged by the same power supply. There is a trim coil on the three magnets to adjust the first and second integral field to zero. The good field region of middle pole and outer pole in transverse x-axis (deltaB/B=0.1%) are ±50mm and ±40mm separately. A prototype GDW magnet was fabricated and a Hall probe measurement system was set up to measure the magnet field to verify the magnet design and the magnet construction performance. The field cross-talk and the fringe field are also discussed herein by different methods.

 
WEPD044 Modelling Synchrotron Radiation from Realistic and Ideal Long Undulator Systems 3189
 
  • D. Newton
    The University of Liverpool, Liverpool
 
 

An analytic description of the synchrotron radiation from electrons with short-period helical trajectories is given by the Kincaid equation. A new code is under development which generates an analytical description of an arbitrary magnetic field, including non-linear and higher-order multipole (fringe field) components. The magnetic field map of a short-period undulator was modelled, using a 3-d finite element solver, and it's analytical field description has been used to compare the synchrotron radiation output from electrons with a 'realistic' trajectory in terms of the ideal analytic equations. The results demonstrate how small numerical inaccuracies in the particle tracking can lead to large inaccuracies in the calculated synchrotron output. The affects of the higher order field modes are studied which give additional insights into the radiation output from long undulator systems.

 
WEPD045 The Rapid Calculation of Synchrotron Radiation Output from Long Undulator Systems 3192
 
  • D. Newton
    The University of Liverpool, Liverpool
 
 

Recent designs for third generation light sources commonly call for undulator systems with a total length of several hundreds of metres. Calculating the synchrotron output from bunches of charged particles traversing such a system using numerical techniques takes an unfeasibly long time even on modern multi-node computer clusters. Analytical formulae (i.e. the Kincaid Equation) provide a more rapid solution for an idealised system but necessarily fail to produce the non-ideal response which is under investigation. A new code is described which generates an analytic description of an arbitrary magnetic field and uses differential algebra and Lie methods to describe the particle dynamics in terms of series of transfer maps. The synchrotron output can then be calculated using arbitrarily large step size with no loss of accuracy in the trajectory. The code is easily adapted to perform parallel calculations on multi-core machines. Examples of the radiation output from several long magnet systems are described and the performance is assessed.

 
WEPD046 Electron Beam Heating Effects in Superconducting Wigglers at Diamond Light Source 3195
 
  • E.C.M. Rial, J.C. Schouten
    Diamond, Oxfordshire
 
 

Diamond Light Source is currently operating with two multipole superconducting wigglers, one with 49 poles at 3.5 T and another with 49 poles at 4.2 T. The cryogenic arrangement is similar in both cases; each cryostat contains a liquid helium bath cooled by four cryocoolers. The design goal was to allow up to six months continuous operation in the storage ring between refilling the liquid helium bath. However, the helium boil-off is much higher than expected, necessitating much more frequent refills. As well as having a cost implication, this also currently poses a restriction on the operating beam current. In this report we present the results of measurements carried out under various beam conditions to try to understand the reason for the higher boil-off in terms of heat load seen by the cryostat and effective cryocooler performance. We also present our plans for dealing with the problem in the near and longer term.

 
WEPD047 Development Status of a Superconducting Undulator for the Advanced Photon Source (APS) 3198
 
  • E.R. Moog, M. Abliz, K.D. Boerste, T.W. Buffington, D. Capatina, R.J. Dejus, C. Doose, Q.B. Hasse, Y. Ivanyushenkov, M.S. Jaski, M. Kasa, S.H. Kim, R. Kustom, E. Trakhtenberg, I. Vasserman, J.Z. Xu
    ANL, Argonne
  • N.A. Mezentsev, V.M. Syrovatin
    BINP SB RAS, Novosibirsk
 
 

A number of prototype magnetic structures for a superconducting undulator have been successfully built and tested. The field quality of a test device was measured in a vertical dewar; the phase errors were 7.1 deg. at the maximum design current with no phase shimming. The Advanced Photon Source (APS) specification for overall trajectory was met using the end compensation coils. Several Hall probes have been calibrated at cryogenic temperatures. The design for a cryostat to hold the undulator for installation in the APS storage ring is nearing completion, and a cryogenic measurement facility to measure the magnetic field of the completed undulator is under development.

 
WEPD048 A Simple Model-based Magnet Sorting Algorithm for Planar Hybrid Undulators 3201
 
  • G. Rakowsky
    BNL, Upton, Long Island, New York
 
 

Various magnet sorting strategies have been used to minimize trajectory and phase errors in undulators, ranging from intuitive pairing of stronger and weaker magnets, to full 3D FEM simulation with actual Helmholtz coil magnet data. We present a simpler approach, first deriving trajectory displacement, kick angle and phase error signatures of each component of magnetization error from a 3D Radia* undulator model. Then, for a given sequence of magnets, the trajectory and phase profiles are computed by cumulatively summing the scaled displacements and phase errors. The rms error is then minimized by swapping magnets according to one's favorite optimization method. A fast, simple magnet swapping algorithm, implemented in Mathematica, is described. 100,000 iterations take only minutes, so dozens of solutions can be compared. This approach was applied recently at NSLS to a short in-vacuum undulator, which required no trajectory or phase shimming. We also obtain trajectory and phase error signatures of some mechanical errors, to guide "virtual shimming" and specifying mechanical tolerances. Finally, multipole signatures of some simple inhomogeneities are modeled.


* O. Chubar, P. Elleaume, J. Chavanne, "A 3D Magnetostatics Computer Code for Insertion Devices", SRI97 Conference August 1997, J. Synchrotron Rad. (1998). 5, 481-484

 
WEPD049 Progress on Insertion Device Related Activities at the NSLS-II and its Future Plans 3204
 
  • T. Tanabe, O.V. Chubar, T.M. Corwin, D.A. Harder, P. He, G. Rakowsky, J. Rank, C.J. Spataro
    BNL, Upton, Long Island, New York
 
 

National Synchrotron Light Source-II (NSLS-II) project is now in the construction stage. A new insertion device (ID) magnetic measurement facility (MMF) is being set up at Brookhaven National Laboratory in order to satisfy the stringent requirement on the magnetic field measurement of IDs. ISO-Class7 temperature stabilized clean room is being constructed for this purpose. A state-of-the-art Hall probe bench and integrated field measurement system will be installed therein. IDs in the project baseline scope include six damping wigglers, two elliptically polarizing undulators (EPUs), three 3.0m long in-vacuum undulators (IVUs) and one 1.5m long IVU. Three-pole wigglers with peak field over 1 Tesla will be utilized to accommodate the users of bending magnet radiation at the NSLS. Future plan includes: 1) an in-vacuum magnetic measurement system, 2) use of PrFeB magnet for improved cryo undulator, 3) development of advanced optimization program for sorting and shimming of IDs, 4) development of a closed loop He gas refrigerator, 5) switchable quasi-periodic EPU. Design features of the baseline devices, IDMMF and the future plans for NSLS-II ID activities are described.

 
WEPD050 Performance Evaluation of Undulator Radiation at CEBAF 3207
 
  • C. Liu
    CASA, newport news
  • G.A. Krafft
    JLAB, Newport News, Virginia
  • G.M. Wang
    BNL, Upton, Long Island, New York
 
 

The possibility of producing sub-ps x-ray by putting undulator in CEBAF machine will be discussed. The performance of undulator radiation at CEBAF will be calculated and compared with storage ring light source.