IPAC2014 - Classification: 02 Synchrotron Light Sources and FELs / T15 Undulators and Wigglers

Paper	Title	Page
WEOAA02	Development of the Very Short Period Undulators	1845
	S. Yamamoto KEK, Ibaraki, Japan
	We have been exploring a method to fabricate very short period undulators, a period length of which is one order-of-magnitude shorter than the ordinary period of several cm. We are developing a plate-type magnet some 100mm long with a period length of 4mm. We selected this period length since we can generate 12-keV radiation with the first harmonic of this undulator in the 2.5-GeV storage ring. A multi-pole magnetizing method was applied to magnetizing this plate: a periodic undulator field (of 4-mm period in this case) was generated by pulsed electro-magnets, and was transcribed into the plate. The magnetization procedure allows the undulator field to be obtained in a very short gap between the pair of opposing plates, which is also one order-of-magnitude shorter than a gap in the ordinary undulators. We report the magnetization method to obtain a very short period and present the test results. The calculated spectrum of the radiation from the measured field compares well with that from an ideal magnetic field in the region of the fundamental radiation in case of 2.5-GeV energy of the electron beam.
	Slides WEOAA02 [5.189 MB]
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WEPRO022	Modal Analysis of Helical Undulator Radiation In Cylindrical Waveguide	1989
	T.L. Vardanyan, M. Ivanyan, V. Sahakyan, A.V. Tsakanian, G.S. Zanyan CANDLE SRI, Yerevan, Armenia
	The coherent radiation of the relativistic electron beam with helical orbit in circular waveguide is studied. The radiation field configuration is obtained using modal expansion technique. For short electron bunches the coherent part of radiation is evaluated. The coherent radiation effects on the bunch performance are analyzed.
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WEPRO023	Preventing Superconducting Wiggler Quench during Beam Loss at the Canadian Light Source	1992
	W.A. Wurtz, L.O. Dallin, M.J. Sigrist, J.M. Vogt, M.S. de Jong CLS, Saskatoon, Saskatchewan, Canada
	The Canadian Light Source utilizes two superconducting wigglers for the production of hard x-rays. These superconducting wigglers often quench during beam loss, even though tracking calculations predict that the beam is lost on an aperture far from the wigglers. We present measurements that suggest the tracking simulations are correct and the electron beam indeed strikes the predicted limiting inboard aperture. By simulating the interaction of the beam with the aperture, we find that some scattered electrons can retain sufficient energy to remain inside the storage ring. The simulations show that some of these scattered electrons strike the wiggler vacuum chamber and deposit energy in the superconducting coils, causing the quench.
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WEPRO024	Simulation of a Long-period EPU Operating in Universal Mode at the Canadian Light Source	1995
	W.A. Wurtz, D. Bertwistle, L.O. Dallin, M.J. Sigrist CLS, Saskatoon, Saskatchewan, Canada
	The Canadian Light Source is implementing an elliptically polarizing undulator (EPU) with period 180 mm for the production of soft x-rays with variable polarization. Two issues arise from implementing such a device. First, a long-period EPU can cause significant loss of dynamic aperture due to strong dynamic focusing. Second, to compensate for polarization effects due to beamline optics, the EPU must be able to produce light with an arbitrary polarization at the source point, which is referred to as universal mode. We present a scheme for operating the EPU in universal mode and discuss the use of BESSY-style current strips in order to compensate for dynamic effects. Tracking simulations suggest that dynamic aperture can be sufficiently recovered for all required operating points in universal mode.
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WEPRO027	W164: A Wiggler Dedicated to the PUMA Beamline and the FEMTOSLICING Project at SOLEIL	1998
	O. Marcouillé, H.B. Abualrob, P. Brunelle, L. Chapuis, M.-E. Couprie, T.K. El Ajjouri, M. Labat, J.L. Marlats, F. Marteau, A. Mary, A. Nadji, K. Tavakoli, M.-A. Tordeux, M. Valléau SOLEIL, Gif-sur-Yvette, France
	The W164 out-vacuum wiggler was designed and built at SOLEIL with the double goal of producing high energy photons for the PUMA beamline (10 keV to 70 keV) and to be used as a modulator for the FEMTOSLICING project. The insertion device requires simultaneously reaching low resonant energy (1.55 eV) and high critical energy of photons (above 10 keV), leading to the choice of high field and large periods. The 3.28 m long wiggler is composed of 20 periods of 164 mm made of NdFeB magnets and vanadium permendur poles. The required effective field for the FEMTOSLICING is 1.53 T and the maximum total field reaches 1.8T at the minimum gap of 14.5 mm. The small transverse size of the poles was optimized to minimize the magnetic forces (8 tons maximum) resulting, together with the large field produced at minimum gap, to a large vertical dynamic field integral (DFI) inside the horizontal physical aperture of the chamber. A dedicated permanent magnet system was designed, constructed and installed at both wiggler ends to cancel the DFI at minimum gap. The construction of the wiggler, the results of the magnetic measurements and the effects on dynamics measured on electron beam are presented.
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WEPRO028	A Robinson Wiggler Proposal for the Metrology Light Source	2001
	T. Goetsch, J. Feikes, M. Ries, G. Wüstefeld HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung and Land Berlin. The Metrology Light Source (MLS), situated in Berlin (Germany) is owned by the Physikalisch-Technische Bundesanstalt and was built / is operated by the Helmholtz-Zentrum Berlin. It is an electron storage ring operating from 10⁵ MeV to 630 MeV. The MLS serves as the national primary source standard from the near infrared to the extreme ultraviolet spectral region . Users of synchrotron radiation demand an improved lifetime which is Touschek dominated at the MLS. A possible solution to meet this demand is to lengthen the electron bunches. By installing a Robinson Wiggler (RW), damping effects can be transferred from the longitudinal to the horizontal plane ,*, thereby increasing the energy spread and reducing the horizontal emittance. By varying the energy spread, the bunch length can be increased and thus the scattering rate decreased, resulting in an improved lifetime. According to preliminary estimations a considerable increase in lifetime seems achievable, while preserving the source size. R. Klein et al., Phys. Rev. ST-AB 11, 110701, 2008 K. W. Robinson, Radiation effects in circular electron accelerators, 1958. * H. Abualrob et al., MOPPP062, IPAC2012, New Orleans, 2012
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WEPRO029	Developing of Advanced Magnet Structures for Cryogenic in Vacuum Permanent Magnet Undulators	2004
	C. Kuhn, J. Bahrdt, A. Gaupp, M. Scheer, B. Schulz HZB, Berlin, Germany
	Cryogenic in vacuum permanent magnet undulators with periods less than 10 mm and correspondingly narrow gaps require tighter geometric and magnetic tolerances and complex pole designs from different materials to achieve the needed high field strengths. We use new mechanic designs and manufacturing technologies for magnet and pole assembly. We develop new precise and UHV-compatible joining methods which are different from the current approaches which are based on mechanical clamping or gluing. . We examine the mechanical and magnetic properties by performing tests and discuss the results.
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WEPRO031	Design and Commissioning of the FLASH2 Undulators	2007
	A. Schöps, O. Bilani, T. Ramm, M. Tischer, S. Tripathi, P. Vagin DESY, Hamburg, Germany
	This paper reports about aspects of design, manufacturing, and commissioning of the 12 FLASH2 variable gap undulator segments. The accuracy of gap drive and encoder systems was tested by magnetic measurements; changes in the phase error proved to be a highly sensitive probe to verify a reproducibility of 1 μm. After magnetic tuning of the IDs, the remaining gap dependence in the field integrals could be successfully compensated by corrector coils. Inconsiderate handling of components during assembling necessitated an elaborate demagnetisation process before the tuning could start.
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WEPRO032	Phase Shifters for the FLASH2 FEL	2010
	M. Tischer, P. Neumann, A. Schöps, P. Vagin DESY, Hamburg, Germany
	The FLASH2 SASE undulator section consists of 12 IDs. Each of them is followed by an intersection component comprising a phase shifter and various parts for diagnostics and beam steering. The phase shifter is a compact and simple electromagnetic chicane and has to assure constructive interference of the radiation of adjacent undulators for all wavelengths. The magnetic performance, field errors and the hysteresis behavior have been investigated and were found to be within the required accuracy. The results are discussed in relation to the undulator conditions. From these data tables for steering the phase shifter current as function of undulator gap were derived and implemented in the control system.
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WEPRO033	Design and Magnetic Measurements on Bi-harmonic Undulators	2013
	G. Sharma, G. Mishra Devi Ahilya University, Indore, India S. Tripathi DESY, Hamburg, Germany
	In recent years there exists interests in harmonic lasing of free electron lasers for short wavelength operation with low energy electron beams. In a planar undulator , the electron radiates at odd harmonics on axis however the harmonic gain of the FEL is much less than that of fundamental. It has been shown in earlier works that it is possible to enhance the harmonic radiation by increasing the harmonic wiggler field to the fundamental by putting high permeability shims inside the undulator. The common material is the vanadium permendur (μ ~800) , which has been used effectively to design the harmonic undulator. In this paper, we report the design and fabrication of seventh and ninth harmonic undulator for free electron laser applications. We use CRGO shims with μ ~ 2-3. The permanent magnet undulator is a four block per period design. The undulator is a variable gap type and consists of NdFeB magnets with six periods, each period is of 5cm length. The undulator has been measured in hall probe and pulsed wire bench. It is shown that the pulsed wire magnetic measurements yields results in close agreement with hall probe results.
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WEPRO034	Magnetic Measurement Developments for Undulators	2016
	P. Vagin, P. Neumann, M. Tischer DESY, Hamburg, Germany
	FLASH2 is an extension of the present VUV-FEL facility at DESY. It includes a separate tunnel with a 12 x 2.5m = 30m long planar hybrid undulator. The undulators have 31.4mm period length and 1T field at a minimum gap of 9mm. The paper presents recent progress in the magnetic measurements of these undulators. Several specific details of the measurement tools will be discussed like peculiarities in the Hall probe calibration and noise, positioning accuracy and synchronization of voltage measurement with probes movement during scan, noise issues of various voltage integrators for stretched wire and search coil measurements.
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WEPRO035	Radiation Damage of Undulators at PETRA III	2019
	P. Vagin, O. Bilani, A. Schöps, M. Tischer, S. Tripathi, T. Vielitz DESY, Hamburg, Germany
	In the new octant of PETRA~III, there are 14 undulator beamlines covering photon energy range from 0.3keV to 150keV. There are also 80m of damping wigglers in order to achieve a low emittance of 1nmrad. Some of these devices, operating at PETRAIII since 2008, accumulated total radiation doses of about 100kGy. Visible corrosion at the magnet structures of some permanent magnet undulators setting in after a few years and a high dose rate measured regularly by thermoluminescent dosimeters (TLDs) gave reason to inspect the magnetic field of all insertion devices in the PETRA tunnel. This paper presents details of the magnetic field degradation caused by radiation damage to the undulator magnets. For some undulators changes in the spectral properties of the generated light were observed. It was measured with different taper settings in order to partly compensate the nonuniform demagnetization along the structure. The results are compared with the data from the sFLASH undulators and measurements of special 3 pole "sacrificial" undulator, installed in FLASH. Its magnetic field is periodically remeasured and shows field amplitude decrease of 1% per 16kGy accumulated dose.
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WEPRO036	Construction and First Magnetic Field Test of a Superconducting Transversal Gradient Undulator for the Laser Wakefield Accelerator in Jena.	2022
	V. Afonso Rodríguez, A. Bernhard, A.W. Grau, P. Peiffer, R. Rossmanith, M. Weber, C. Widmann, A. Will KIT, Karlsruhe, Germany M. Kaluza, M. Nicolai, A. Sävert IOQ, Jena, Germany M. Reuter HIJ, Jena, Germany
	Funding: This work is funded by the German Federal Ministry for Education and Research under contract no. 05K10VK2 and 05K10SJ2. A superconducting transversal gradient undulator (TGU), tailored to the particular beam properties of the laser wakefield accelerator (LWFA) at the University of Jena, has been designed and constructed at KIT. This undulator in combination with a specialized beam transport line will be employed to produce undulator radiation with natural bandwidth despite the relatively large energy spread of the electrons produced by the LWFA. The fabrication of this undulator and first results of the magnetic field measurement are discussed in this paper.
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WEPRO038	Possibility for Quasi-periodic Knot-APPLE Undulator	2026
	S. Sasaki, A. Miyamoto HSRC, Higashi-Hiroshima, Japan N. Kawata, T. Mitsuyasu Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan S. Qiao SIMIT, Shanghai, People's Republic of China
	An intense on-axis radiation power from an undulator is a serious problem especially for a low-photon-energy beamline in a facility with high or medium energy storage ring. This problem may be solved by using a Figure-8, a Pera, or a Knot undulator configuration,. However, these schemes are useless for variably polarizing undulators such as an APPLE undulator and other similar variations since such devices are not capable for reducing on-axis power density in the linear mode. In these circumstances, we have completed a conceptual magnet design of Knot-APPLE udulator which is capable to generate elliptically polarized radiation as well as linearly polarized radiation. This pure permanent magnet device is equipped with a motion mechanism of APPLE undulator. In this paper, we present detailed magnet design feature, magnetic field distributions, and radiation properties including variations of polarization in comparisons with other exotic devices. In addition, a possibility to introduce a quasi-periodicity in this type of undulator is considered in order to achieve further reduction of second and third harmonic radiation intensities. S. Sasaki, "Undulators, wigglers and their applications," p.237-243 (Ed. by H. Onuki and P. Elleaume, Taylor & Francis Inc, New York, 2003). **S. Qiao, et. al, Rev. Sci. Instrum., 80, 085108 (2009).
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WEPRO039	Status of PAL-XFEL Undulator Program	2029
	D.E. Kim, H.-S. Kang, W.W. Lee, K.-H. Park PAL, Pohang, Kyungbuk, Republic of Korea M.-H. Cho, I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea S. Karabekyan, J. Pflüger XFEL. EU, Hamburg, Germany
	Pohang Accelerator Laboratory (PAL) is developing 10 GeV, 0.1 nm SASE based FEL for high power, short pulse X-ray coherent photon sources named PAL-XFEL. At the first stage PAL-XFEL needs two undulator lines for photon source. PAL is developing undulator magnetic structure based on EU-XFEL design. Recently, the hard X-ray undulator changed its minimum magnetic gap to 8.3 mm from the previous 7.2 mm to alleviate the wake field impact, and to increase the allowances for the re alignment. Accordingly, the period is also changed from 24.4 mm to 26.0 mm to generate 0.1 nm at 10 GeV electron energy. In this report, the modification efforts and the progress on the prototyping of hard x-ray undulator system will be presented.
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WEPRO040	Field Measurement Facility for PAL-XFEL Undulators	2032
	K.-H. Park, Y.-G. Jung, D.E. Kim, S.N. Kim, I.S. Ko, B.H. Lee, H.-G. Lee, M.S. Lee, S.B. Lee, H.S. Suh, C.W. Sung PAL, Pohang, Kyungbuk, Republic of Korea
	Pohang Accelerator Laboratory (PAL) is developing the SASE based FEL for X-ray coherent photon sources. The PAL developed the prototype undulator that was 5.0 m magnetic length. The PAL has constructed the undulator field measurement facility to confirm the field qualities of the XFEL undulators in the assembly building. The temperature stability of the measurement rooms was controlled within ±0.1°C. Two field measurement benches that included Hall probe scan, flip coil and stretched wire system were installed and evaluated their performances. The field profile of the prototype undulator was characterized and shimmed using the installed measurement system. This paper described the field measurement facility with the performance test results of the two benches.
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WEPRO041	Undulator Radiation Spectral Broadening Due To Radiation Energy Loss	2035
	N.V. Smolyakov NRC, Moscow, Russia
	A relativistic electron passing through an undulator generates electromagnetic radiation at the expenses of its own kinetic energy. This effect is usually not taken into account if the number of periods of the undulator is relatively small (100 - 200). However, at FEL facilities, long installations have been built, planned or are under construction, where many undulators are installed one after another for a total of several thousand undulator periods. For instance, the SASE1 and SASE2 lines at the European XFEL will consist of 35 undulators with 124 periods each. In this case, because of the electron energy decrease along its trajectory, the radiation from different undulators will drop out of synchronism. As a result, the radiation spectral line will be much wider. In the presented report, this effect was analyzed analytically and numerically. An expression for the critical number of undulator periods, when the effect of electron energy loss should be properly taken into account, is derived. It is found that, for the case of the European XFEL, this number is about 1200 periods.
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WEPRO042	Damping Wiggler with Tapered Period	2038
	K. Karyukina BINP, Novosibirsk, Russia A.V. Bogomyagkov, E.B. Levichev BINP SB RAS, Novosibirsk, Russia
	Strong-field short-period wigglers installed in electron storage ring increase the radiation damping integral I2 and either increase or decrease the I5 integral responsible for quantum excitation. In case of the I5 integral decreasing, the beam emittance can be substantially reduced. In the paper we discuss additional reduction of I5 by applying of the longitudinal modulation of the wiggler period (tapering).
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WEPRO046	Beam Dynamic Effect of Multi-period Robinson Wiggler in Taiwan Photon Source	2044
SUSPSNE013	use link to see paper's listing under its alternate paper code
	C.W. Huang NTHU, Hsinchu, Taiwan C.-S. Hwang NSRRC, Hsinchu, Taiwan S.-Y. Lee IUCEEM, Bloomington, Indiana, USA
	Robinson wiggler is a special insertion device that can be used to decrease natural emittance of the Taiwan Photon Source (TPS) storage ring. There are four poles in one set of Robinson Wiggler and each pole has combined with dipole and quadrupole field strength. The dipole field strength multiply quardupole field strength in each pole should be negative. This Robinson wiggler can change damping partition number and then affect the emittance. This study will evaluate practicability of reducing the emittance of TPS storage ring by muti-period Robinson wiggler and will be installed in the 7 m long-straight section. One period of the traditional Robinson Wiggler include four poles with different field polarity. In the same length, the mult-period Robinson Wiggler have many period in one set of Robinson Wiggler that is different from the traditional Robinson wiggler. Due to the traditional Robinson wiggler can not be effective to improve emittance in TPS storage ring (the efficiency is only 7%). So we adopt to use muti-period Robinson wiggler, the efficiency can be up to 37%, and the linear matching result is better than one period Robinson Wiggler.
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WEPRO047	A New Cooling System for Cryocooled Permanent Magnet Undulators at Diamond Light Source	2047
	E.C. Longhi, A.G. Miller, E.C.M. Rial, A.J. Rose, J.C. Schouten, C.W. Thompson, A. Thomson, J.H. Williams DLS, Oxfordshire, United Kingdom C. Monroe Monroe Brothers Ltd., Moreton-in-Marsh, United Kingdom
	Cryocooled permanent magnet undulators (CPMUs) using NdFeB magnets around 150K were first proposed by Hara. These are cooled by using either GM cryocoolers or circulating sub-cooled liquid nitrogen. Due to the heat load from radiation and wakefield heating from the electron beam, temperature gradients can develop along the length of the magnet girders which could be as large as several degrees for the Diamond Light Source (DLS) storage ring operating parameters. Some grades of the magnetic material (NdxPr1-x)2Fe14B have remanence curves versus temperature which increase significantly for temperatures below 150K with peaks below 80K. This means that the operating temperature of a CPMU using this material can be close to the boiling point of liquid nitrogen. The proposed cooling system for the new DLS CPMU is based on a thermosiphon allowing nitrogen to boil inside the cooling channels without a circulating pump. This has the advantage of absorbing large amounts (>250W) of heat with very small temperature gradients. We report here the results of a prototype magnet beam cooled with a thermosiphon producing a temperature gradient of less than 0.05K along a 2m beam at ~77K. T. Hara et al., Phys Rev Spec Top. Accelerator & Beam, Vol 7, 2004. ** J. Bahrdt et al., AIP Conf. Proc., SRI 2009, Melbourne Australia, vol. 1234, pp. 499-502, 2010.
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WEPRO048	A Concept of a Universal Superconducting Undulator	2050
	Y. Ivanyushenkov ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. Tiny round electron beams of free-electron lasers and relatively new diffraction-limited storage rings make possible utilization of electromagnetic helical undulators based on double-helical windings. It has been understood for a while that a coaxial pair of double-helical windings can generate helical as well as planar magnetic fields. Such a coil structure can potentially be realized with superconducting windings thus forming the concept of a universal superconducting undulator (Universal SCU). An example of a possible universal SCU for the recently suggested Advanced Photon Source multi-bend achromat storage ring is given in this paper. The results of the magnetic simulation together with initial cryogenic considerations are presented. D.F. Alferov, Yu.A. Bashamakov, E. G. Bessonov, Sov. J. Tech. Phys. 21(11), (1976) 1408.
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WEPRO049	Experience of Operating a Superconducting Undulator at the Advanced Photon Source	2053
	Y. Ivanyushenkov, K.C. Harkay ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. A superconducting test undulator SCU0 was installed into the storage ring of the Advanced Photon Source (APS) in December 2012 and has been in user operation since January 2013. The first year's experience of operating such a novel insertion device at the APS is summarized in this paper. The performance of the SCU0 as a photon source is presented. The measured heat load from the electron beam is described together with the observed cryogenic behavior of the device. The effect of the SCU0 on the APS electron beam is also presented.
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WEPRO093	Possibility of Application of THz Wiggler in Low Energy FEL for Measurements of Electron Bunch Longitudinal Structure	2177
	E. Syresin, S.A. Kostromin, R.S. Makarov, N.A. Morozov, D. Petrov JINR, Dubna, Moscow Region, Russia M. Krasilnikov DESY Zeuthen, Zeuthen, Germany
	Funding: The work is funded by HGDF-RFBR Grant HRJRG-400 The infrared undulator constructed at JINR and installed at FLASH in 2007 is used for longitudinal bunch shape measurements in the range of several tenths of μm. The presented below electromagnetic wiggler is applied for a narrow-band THz radiation for measurements of electron bunch longitudinal structure in FEL with electron energy of several tenths of MeV. This is a planar electromagnetic device with 6 regular periods, each of 30 cm long. The K parameter is varied in the range 0.5- 7.12 corresponding to a range B=0.025- 0.356 T of the peak field on axis. The wiggler is simulated for 19.8 MeV/c FEL. The bunch compression scheme allows the whole wavelength range to be covered by super-radiant emission with a sufficient form factor. The wavelength range corresponds to 126 μm - 5.3 mm for the electron beam momentum of 19.8 MeV/c. The 3D Opera simulations of THz wiggler will be discussed.
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WEPME031	Magnetic Design of the First Prototype Pure Permanent Magnet Undulator for the ILSF	2326
	A. Ramezani Moghaddam, J. Rahighi ILSF, Tehran, Iran H. Ghasem IPM, Tehran, Iran M. Lamehi Rashti Nuclear Science & Technology Research Institute, Tehran, Iran A. Ramezani Moghaddam NSTRI, Tehran, Iran
	Iranian light source facility (ILSF) is a 3GeV, 400 mA, 3rd generation light source under design and construction. This paper describes the details of the preliminary magnetic design of the first prototype PPM undulator for the ILSF. In the preliminary design, the undulator period and some other parameters have been determined to reach desired x-ray spectrum to be used for soft x-ray application. A PPM layout and a model undulator with 16 poles is used to calculate the properties of the designs.
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Paper

Title

Page

Development of the Very Short Period Undulators

1845

S. Yamamoto
KEK, Ibaraki, Japan

We have been exploring a method to fabricate very short period undulators, a period length of which is one order-of-magnitude shorter than the ordinary period of several cm. We are developing a plate-type magnet some 100mm long with a period length of 4mm. We selected this period length since we can generate 12-keV radiation with the first harmonic of this undulator in the 2.5-GeV storage ring. A multi-pole magnetizing method was applied to magnetizing this plate: a periodic undulator field (of 4-mm period in this case) was generated by pulsed electro-magnets, and was transcribed into the plate. The magnetization procedure allows the undulator field to be obtained in a very short gap between the pair of opposing plates, which is also one order-of-magnitude shorter than a gap in the ordinary undulators. We report the magnetization method to obtain a very short period and present the test results. The calculated spectrum of the radiation from the measured field compares well with that from an ideal magnetic field in the region of the fundamental radiation in case of 2.5-GeV energy of the electron beam.

Slides WEOAA02 [5.189 MB]

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WEPRO022

Modal Analysis of Helical Undulator Radiation In Cylindrical Waveguide

1989

T.L. Vardanyan, M. Ivanyan, V. Sahakyan, A.V. Tsakanian, G.S. Zanyan
CANDLE SRI, Yerevan, Armenia

The coherent radiation of the relativistic electron beam with helical orbit in circular waveguide is studied. The radiation field configuration is obtained using modal expansion technique. For short electron bunches the coherent part of radiation is evaluated. The coherent radiation effects on the bunch performance are analyzed.

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WEPRO023

Preventing Superconducting Wiggler Quench during Beam Loss at the Canadian Light Source

1992

W.A. Wurtz, L.O. Dallin, M.J. Sigrist, J.M. Vogt, M.S. de Jong
CLS, Saskatoon, Saskatchewan, Canada

The Canadian Light Source utilizes two superconducting wigglers for the production of hard x-rays. These superconducting wigglers often quench during beam loss, even though tracking calculations predict that the beam is lost on an aperture far from the wigglers. We present measurements that suggest the tracking simulations are correct and the electron beam indeed strikes the predicted limiting inboard aperture. By simulating the interaction of the beam with the aperture, we find that some scattered electrons can retain sufficient energy to remain inside the storage ring. The simulations show that some of these scattered electrons strike the wiggler vacuum chamber and deposit energy in the superconducting coils, causing the quench.

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WEPRO024

Simulation of a Long-period EPU Operating in Universal Mode at the Canadian Light Source

1995

W.A. Wurtz, D. Bertwistle, L.O. Dallin, M.J. Sigrist
CLS, Saskatoon, Saskatchewan, Canada

The Canadian Light Source is implementing an elliptically polarizing undulator (EPU) with period 180 mm for the production of soft x-rays with variable polarization. Two issues arise from implementing such a device. First, a long-period EPU can cause significant loss of dynamic aperture due to strong dynamic focusing. Second, to compensate for polarization effects due to beamline optics, the EPU must be able to produce light with an arbitrary polarization at the source point, which is referred to as universal mode. We present a scheme for operating the EPU in universal mode and discuss the use of BESSY-style current strips in order to compensate for dynamic effects. Tracking simulations suggest that dynamic aperture can be sufficiently recovered for all required operating points in universal mode.

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WEPRO027

W164: A Wiggler Dedicated to the PUMA Beamline and the FEMTOSLICING Project at SOLEIL

1998

O. Marcouillé, H.B. Abualrob, P. Brunelle, L. Chapuis, M.-E. Couprie, T.K. El Ajjouri, M. Labat, J.L. Marlats, F. Marteau, A. Mary, A. Nadji, K. Tavakoli, M.-A. Tordeux, M. Valléau
SOLEIL, Gif-sur-Yvette, France

The W164 out-vacuum wiggler was designed and built at SOLEIL with the double goal of producing high energy photons for the PUMA beamline (10 keV to 70 keV) and to be used as a modulator for the FEMTOSLICING project. The insertion device requires simultaneously reaching low resonant energy (1.55 eV) and high critical energy of photons (above 10 keV), leading to the choice of high field and large periods. The 3.28 m long wiggler is composed of 20 periods of 164 mm made of NdFeB magnets and vanadium permendur poles. The required effective field for the FEMTOSLICING is 1.53 T and the maximum total field reaches 1.8T at the minimum gap of 14.5 mm. The small transverse size of the poles was optimized to minimize the magnetic forces (8 tons maximum) resulting, together with the large field produced at minimum gap, to a large vertical dynamic field integral (DFI) inside the horizontal physical aperture of the chamber. A dedicated permanent magnet system was designed, constructed and installed at both wiggler ends to cancel the DFI at minimum gap. The construction of the wiggler, the results of the magnetic measurements and the effects on dynamics measured on electron beam are presented.

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WEPRO028

A Robinson Wiggler Proposal for the Metrology Light Source

2001

T. Goetsch, J. Feikes, M. Ries, G. Wüstefeld
HZB, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung and Land Berlin.
The Metrology Light Source (MLS), situated in Berlin (Germany) is owned by the Physikalisch-Technische Bundesanstalt and was built / is operated by the Helmholtz-Zentrum Berlin. It is an electron storage ring operating from 10⁵ MeV to 630 MeV. The MLS serves as the national primary source standard from the near infrared to the extreme ultraviolet spectral region *. Users of synchrotron radiation demand an improved lifetime which is Touschek dominated at the MLS. A possible solution to meet this demand is to lengthen the electron bunches. By installing a Robinson Wiggler (RW), damping effects can be transferred from the longitudinal to the horizontal plane **,***, thereby increasing the energy spread and reducing the horizontal emittance. By varying the energy spread, the bunch length can be increased and thus the scattering rate decreased, resulting in an improved lifetime. According to preliminary estimations a considerable increase in lifetime seems achievable, while preserving the source size.
* R. Klein et al., Phys. Rev. ST-AB 11, 110701, 2008
** K. W. Robinson, Radiation effects in circular electron accelerators, 1958.
*** H. Abualrob et al., MOPPP062, IPAC2012, New Orleans, 2012

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WEPRO029

Developing of Advanced Magnet Structures for Cryogenic in Vacuum Permanent Magnet Undulators

2004

C. Kuhn, J. Bahrdt, A. Gaupp, M. Scheer, B. Schulz
HZB, Berlin, Germany

Cryogenic in vacuum permanent magnet undulators with periods less than 10 mm and correspondingly narrow gaps require tighter geometric and magnetic tolerances and complex pole designs from different materials to achieve the needed high field strengths. We use new mechanic designs and manufacturing technologies for magnet and pole assembly. We develop new precise and UHV-compatible joining methods which are different from the current approaches which are based on mechanical clamping or gluing. . We examine the mechanical and magnetic properties by performing tests and discuss the results.

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WEPRO031

Design and Commissioning of the FLASH2 Undulators

2007

A. Schöps, O. Bilani, T. Ramm, M. Tischer, S. Tripathi, P. Vagin
DESY, Hamburg, Germany

This paper reports about aspects of design, manufacturing, and commissioning of the 12 FLASH2 variable gap undulator segments. The accuracy of gap drive and encoder systems was tested by magnetic measurements; changes in the phase error proved to be a highly sensitive probe to verify a reproducibility of 1 μm. After magnetic tuning of the IDs, the remaining gap dependence in the field integrals could be successfully compensated by corrector coils. Inconsiderate handling of components during assembling necessitated an elaborate demagnetisation process before the tuning could start.

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WEPRO032

Phase Shifters for the FLASH2 FEL

2010

M. Tischer, P. Neumann, A. Schöps, P. Vagin
DESY, Hamburg, Germany

The FLASH2 SASE undulator section consists of 12 IDs. Each of them is followed by an intersection component comprising a phase shifter and various parts for diagnostics and beam steering. The phase shifter is a compact and simple electromagnetic chicane and has to assure constructive interference of the radiation of adjacent undulators for all wavelengths. The magnetic performance, field errors and the hysteresis behavior have been investigated and were found to be within the required accuracy. The results are discussed in relation to the undulator conditions. From these data tables for steering the phase shifter current as function of undulator gap were derived and implemented in the control system.

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WEPRO033

Design and Magnetic Measurements on Bi-harmonic Undulators

2013

G. Sharma, G. Mishra
Devi Ahilya University, Indore, India
S. Tripathi
DESY, Hamburg, Germany

In recent years there exists interests in harmonic lasing of free electron lasers for short wavelength operation with low energy electron beams. In a planar undulator , the electron radiates at odd harmonics on axis however the harmonic gain of the FEL is much less than that of fundamental. It has been shown in earlier works that it is possible to enhance the harmonic radiation by increasing the harmonic wiggler field to the fundamental by putting high permeability shims inside the undulator. The common material is the vanadium permendur (μ ~800) , which has been used effectively to design the harmonic undulator. In this paper, we report the design and fabrication of seventh and ninth harmonic undulator for free electron laser applications. We use CRGO shims with μ ~ 2-3. The permanent magnet undulator is a four block per period design. The undulator is a variable gap type and consists of NdFeB magnets with six periods, each period is of 5cm length. The undulator has been measured in hall probe and pulsed wire bench. It is shown that the pulsed wire magnetic measurements yields results in close agreement with hall probe results.

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WEPRO034

Magnetic Measurement Developments for Undulators

2016

P. Vagin, P. Neumann, M. Tischer
DESY, Hamburg, Germany

FLASH2 is an extension of the present VUV-FEL facility at DESY. It includes a separate tunnel with a 12 x 2.5m = 30m long planar hybrid undulator. The undulators have 31.4mm period length and 1T field at a minimum gap of 9mm. The paper presents recent progress in the magnetic measurements of these undulators. Several specific details of the measurement tools will be discussed like peculiarities in the Hall probe calibration and noise, positioning accuracy and synchronization of voltage measurement with probes movement during scan, noise issues of various voltage integrators for stretched wire and search coil measurements.

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WEPRO035

Radiation Damage of Undulators at PETRA III

2019

P. Vagin, O. Bilani, A. Schöps, M. Tischer, S. Tripathi, T. Vielitz
DESY, Hamburg, Germany

In the new octant of PETRA~III, there are 14 undulator beamlines covering photon energy range from 0.3keV to 150keV. There are also 80m of damping wigglers in order to achieve a low emittance of 1nmrad. Some of these devices, operating at PETRAIII since 2008, accumulated total radiation doses of about 100kGy. Visible corrosion at the magnet structures of some permanent magnet undulators setting in after a few years and a high dose rate measured regularly by thermoluminescent dosimeters (TLDs) gave reason to inspect the magnetic field of all insertion devices in the PETRA tunnel. This paper presents details of the magnetic field degradation caused by radiation damage to the undulator magnets. For some undulators changes in the spectral properties of the generated light were observed. It was measured with different taper settings in order to partly compensate the nonuniform demagnetization along the structure. The results are compared with the data from the sFLASH undulators and measurements of special 3 pole "sacrificial" undulator, installed in FLASH. Its magnetic field is periodically remeasured and shows field amplitude decrease of 1% per 16kGy accumulated dose.

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WEPRO036

Construction and First Magnetic Field Test of a Superconducting Transversal Gradient Undulator for the Laser Wakefield Accelerator in Jena.

2022

V. Afonso Rodríguez, A. Bernhard, A.W. Grau, P. Peiffer, R. Rossmanith, M. Weber, C. Widmann, A. Will
KIT, Karlsruhe, Germany
M. Kaluza, M. Nicolai, A. Sävert
IOQ, Jena, Germany
M. Reuter
HIJ, Jena, Germany

Funding: This work is funded by the German Federal Ministry for Education and Research under contract no. 05K10VK2 and 05K10SJ2.
A superconducting transversal gradient undulator (TGU), tailored to the particular beam properties of the laser wakefield accelerator (LWFA) at the University of Jena, has been designed and constructed at KIT. This undulator in combination with a specialized beam transport line will be employed to produce undulator radiation with natural bandwidth despite the relatively large energy spread of the electrons produced by the LWFA. The fabrication of this undulator and first results of the magnetic field measurement are discussed in this paper.

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WEPRO038

Possibility for Quasi-periodic Knot-APPLE Undulator

2026

S. Sasaki, A. Miyamoto
HSRC, Higashi-Hiroshima, Japan
N. Kawata, T. Mitsuyasu
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
S. Qiao
SIMIT, Shanghai, People's Republic of China

An intense on-axis radiation power from an undulator is a serious problem especially for a low-photon-energy beamline in a facility with high or medium energy storage ring. This problem may be solved by using a Figure-8, a Pera, or a Knot undulator configuration*,**. However, these schemes are useless for variably polarizing undulators such as an APPLE undulator and other similar variations since such devices are not capable for reducing on-axis power density in the linear mode. In these circumstances, we have completed a conceptual magnet design of Knot-APPLE udulator which is capable to generate elliptically polarized radiation as well as linearly polarized radiation. This pure permanent magnet device is equipped with a motion mechanism of APPLE undulator. In this paper, we present detailed magnet design feature, magnetic field distributions, and radiation properties including variations of polarization in comparisons with other exotic devices. In addition, a possibility to introduce a quasi-periodicity in this type of undulator is considered in order to achieve further reduction of second and third harmonic radiation intensities.
*S. Sasaki, "Undulators, wigglers and their applications," p.237-243 (Ed. by H. Onuki and P. Elleaume, Taylor & Francis Inc, New York, 2003).
**S. Qiao, et. al, Rev. Sci. Instrum., 80, 085108 (2009).

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WEPRO039

Status of PAL-XFEL Undulator Program

2029

D.E. Kim, H.-S. Kang, W.W. Lee, K.-H. Park
PAL, Pohang, Kyungbuk, Republic of Korea
M.-H. Cho, I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea
S. Karabekyan, J. Pflüger
XFEL. EU, Hamburg, Germany

Pohang Accelerator Laboratory (PAL) is developing 10 GeV, 0.1 nm SASE based FEL for high power, short pulse X-ray coherent photon sources named PAL-XFEL. At the first stage PAL-XFEL needs two undulator lines for photon source. PAL is developing undulator magnetic structure based on EU-XFEL design. Recently, the hard X-ray undulator changed its minimum magnetic gap to 8.3 mm from the previous 7.2 mm to alleviate the wake field impact, and to increase the allowances for the re alignment. Accordingly, the period is also changed from 24.4 mm to 26.0 mm to generate 0.1 nm at 10 GeV electron energy. In this report, the modification efforts and the progress on the prototyping of hard x-ray undulator system will be presented.

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WEPRO040

Field Measurement Facility for PAL-XFEL Undulators

2032

K.-H. Park, Y.-G. Jung, D.E. Kim, S.N. Kim, I.S. Ko, B.H. Lee, H.-G. Lee, M.S. Lee, S.B. Lee, H.S. Suh, C.W. Sung
PAL, Pohang, Kyungbuk, Republic of Korea

Pohang Accelerator Laboratory (PAL) is developing the SASE based FEL for X-ray coherent photon sources. The PAL developed the prototype undulator that was 5.0 m magnetic length. The PAL has constructed the undulator field measurement facility to confirm the field qualities of the XFEL undulators in the assembly building. The temperature stability of the measurement rooms was controlled within ±0.1°C. Two field measurement benches that included Hall probe scan, flip coil and stretched wire system were installed and evaluated their performances. The field profile of the prototype undulator was characterized and shimmed using the installed measurement system. This paper described the field measurement facility with the performance test results of the two benches.

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WEPRO041

Undulator Radiation Spectral Broadening Due To Radiation Energy Loss

2035

N.V. Smolyakov
NRC, Moscow, Russia

A relativistic electron passing through an undulator generates electromagnetic radiation at the expenses of its own kinetic energy. This effect is usually not taken into account if the number of periods of the undulator is relatively small (100 - 200). However, at FEL facilities, long installations have been built, planned or are under construction, where many undulators are installed one after another for a total of several thousand undulator periods. For instance, the SASE1 and SASE2 lines at the European XFEL will consist of 35 undulators with 124 periods each. In this case, because of the electron energy decrease along its trajectory, the radiation from different undulators will drop out of synchronism. As a result, the radiation spectral line will be much wider. In the presented report, this effect was analyzed analytically and numerically. An expression for the critical number of undulator periods, when the effect of electron energy loss should be properly taken into account, is derived. It is found that, for the case of the European XFEL, this number is about 1200 periods.

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WEPRO042

Damping Wiggler with Tapered Period

2038

K. Karyukina
BINP, Novosibirsk, Russia
A.V. Bogomyagkov, E.B. Levichev
BINP SB RAS, Novosibirsk, Russia

Strong-field short-period wigglers installed in electron storage ring increase the radiation damping integral I2 and either increase or decrease the I5 integral responsible for quantum excitation. In case of the I5 integral decreasing, the beam emittance can be substantially reduced. In the paper we discuss additional reduction of I5 by applying of the longitudinal modulation of the wiggler period (tapering).

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WEPRO046

Beam Dynamic Effect of Multi-period Robinson Wiggler in Taiwan Photon Source

2044

SUSPSNE013

use link to see paper's listing under its alternate paper code

C.W. Huang
NTHU, Hsinchu, Taiwan
C.-S. Hwang
NSRRC, Hsinchu, Taiwan
S.-Y. Lee
IUCEEM, Bloomington, Indiana, USA

Robinson wiggler is a special insertion device that can be used to decrease natural emittance of the Taiwan Photon Source (TPS) storage ring. There are four poles in one set of Robinson Wiggler and each pole has combined with dipole and quadrupole field strength. The dipole field strength multiply quardupole field strength in each pole should be negative. This Robinson wiggler can change damping partition number and then affect the emittance. This study will evaluate practicability of reducing the emittance of TPS storage ring by muti-period Robinson wiggler and will be installed in the 7 m long-straight section. One period of the traditional Robinson Wiggler include four poles with different field polarity. In the same length, the mult-period Robinson Wiggler have many period in one set of Robinson Wiggler that is different from the traditional Robinson wiggler. Due to the traditional Robinson wiggler can not be effective to improve emittance in TPS storage ring (the efficiency is only 7%). So we adopt to use muti-period Robinson wiggler, the efficiency can be up to 37%, and the linear matching result is better than one period Robinson Wiggler.

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WEPRO047

A New Cooling System for Cryocooled Permanent Magnet Undulators at Diamond Light Source

2047

E.C. Longhi, A.G. Miller, E.C.M. Rial, A.J. Rose, J.C. Schouten, C.W. Thompson, A. Thomson, J.H. Williams
DLS, Oxfordshire, United Kingdom
C. Monroe
Monroe Brothers Ltd., Moreton-in-Marsh, United Kingdom

Cryocooled permanent magnet undulators (CPMUs) using NdFeB magnets around 150K were first proposed by Hara*. These are cooled by using either GM cryocoolers or circulating sub-cooled liquid nitrogen. Due to the heat load from radiation and wakefield heating from the electron beam, temperature gradients can develop along the length of the magnet girders which could be as large as several degrees for the Diamond Light Source (DLS) storage ring operating parameters. Some grades of the magnetic material (NdxPr1-x)2Fe14B have remanence curves versus temperature which increase significantly for temperatures below 150K with peaks below 80K**. This means that the operating temperature of a CPMU using this material can be close to the boiling point of liquid nitrogen. The proposed cooling system for the new DLS CPMU is based on a thermosiphon allowing nitrogen to boil inside the cooling channels without a circulating pump. This has the advantage of absorbing large amounts (>250W) of heat with very small temperature gradients. We report here the results of a prototype magnet beam cooled with a thermosiphon producing a temperature gradient of less than 0.05K along a 2m beam at ~77K.
* T. Hara et al., Phys Rev Spec Top. Accelerator & Beam, Vol 7, 2004.
** J. Bahrdt et al., AIP Conf. Proc., SRI 2009, Melbourne Australia, vol. 1234, pp. 499-502, 2010.

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WEPRO048

A Concept of a Universal Superconducting Undulator

2050

Y. Ivanyushenkov
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
Tiny round electron beams of free-electron lasers and relatively new diffraction-limited storage rings make possible utilization of electromagnetic helical undulators based on double-helical windings. It has been understood for a while that a coaxial pair of double-helical windings can generate helical as well as planar magnetic fields*. Such a coil structure can potentially be realized with superconducting windings thus forming the concept of a universal superconducting undulator (Universal SCU). An example of a possible universal SCU for the recently suggested Advanced Photon Source multi-bend achromat storage ring is given in this paper. The results of the magnetic simulation together with initial cryogenic considerations are presented.
* D.F. Alferov, Yu.A. Bashamakov, E. G. Bessonov, Sov. J. Tech. Phys. 21(11), (1976) 1408.

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WEPRO049

Experience of Operating a Superconducting Undulator at the Advanced Photon Source

2053

Y. Ivanyushenkov, K.C. Harkay
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
A superconducting test undulator SCU0 was installed into the storage ring of the Advanced Photon Source (APS) in December 2012 and has been in user operation since January 2013. The first year's experience of operating such a novel insertion device at the APS is summarized in this paper. The performance of the SCU0 as a photon source is presented. The measured heat load from the electron beam is described together with the observed cryogenic behavior of the device. The effect of the SCU0 on the APS electron beam is also presented.

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WEPRO093

Possibility of Application of THz Wiggler in Low Energy FEL for Measurements of Electron Bunch Longitudinal Structure

2177

E. Syresin, S.A. Kostromin, R.S. Makarov, N.A. Morozov, D. Petrov
JINR, Dubna, Moscow Region, Russia
M. Krasilnikov
DESY Zeuthen, Zeuthen, Germany

Funding: The work is funded by HGDF-RFBR Grant HRJRG-400
The infrared undulator constructed at JINR and installed at FLASH in 2007 is used for longitudinal bunch shape measurements in the range of several tenths of μm. The presented below electromagnetic wiggler is applied for a narrow-band THz radiation for measurements of electron bunch longitudinal structure in FEL with electron energy of several tenths of MeV. This is a planar electromagnetic device with 6 regular periods, each of 30 cm long. The K parameter is varied in the range 0.5- 7.12 corresponding to a range B=0.025- 0.356 T of the peak field on axis. The wiggler is simulated for 19.8 MeV/c FEL. The bunch compression scheme allows the whole wavelength range to be covered by super-radiant emission with a sufficient form factor. The wavelength range corresponds to 126 μm - 5.3 mm for the electron beam momentum of 19.8 MeV/c. The 3D Opera simulations of THz wiggler will be discussed.

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WEPME031

Magnetic Design of the First Prototype Pure Permanent Magnet Undulator for the ILSF

2326

A. Ramezani Moghaddam, J. Rahighi
ILSF, Tehran, Iran
H. Ghasem
IPM, Tehran, Iran
M. Lamehi Rashti
Nuclear Science & Technology Research Institute, Tehran, Iran
A. Ramezani Moghaddam
NSTRI, Tehran, Iran

Iranian light source facility (ILSF) is a 3GeV, 400 mA, 3rd generation light source under design and construction. This paper describes the details of the preliminary magnetic design of the first prototype PPM undulator for the ILSF. In the preliminary design, the undulator period and some other parameters have been determined to reach desired x-ray spectrum to be used for soft x-ray application. A PPM layout and a model undulator with 16 poles is used to calculate the properties of the designs.

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