Two 3.4 m long wigglers are being designed and constructed at Lawrence Berkeley Laboratory&apos;s (LBL) Advanced Light Source (ALS). A 19 period planar wiggler with 16.0 cm period length is designed to provide photons up to 12.4 keV for protein crystallography. This device features a hybrid permanent magnet structure with tapered poles and designed to achieve 2.0 T at a 1.4 cm magnetic gap. An elliptical wiggler is being designed to provide circularly polarized photons in the energy range of 50 eV to 10 keV for magnetic circular dichroism spectroscopy. This device features vertical and horizontal magnetic structures of 14 and 14  1  /2 periods respectively of 20 cm period length. The vertical magnetic structure is a 2.0 T hybrid permanent magnet configuration. The horizontal  structure is an iron core electromagnetic design, shifted longitudinally  1  /4 period with respect to the vertical magnetic structure. A maximum horizontal peak field of 0.1 T at an oscillating frequency up to 1 Hz wi..

D. Humphries

D. Plate

E. Hoyer

G. Portmann

J. Akre

P. Pipersky

R. Schlueter

S. Marks

T. Jackson

Y. Minamihara

Hoyer, E.

Akre, J.

Humphries, D.

Jackson, T.

Marks, S.

Minamihara, Y.

Pipersky, Paul

Plate, D.

Portmann, Gregory J.

Schlueter, R.D.

eScholarship - University of California

Lawrence Berkeley National LaboratoryRecent WorkTitleWigglers at the Advanced Light SourcePermalinkhttps://escholarship.org/uc/item/6048w6p1AuthorsHoyer, E.Akre, J.Humphries, D.et al.Publication Date1995-04-14eScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaLBL-37106 UC-414 Lawrence Berkeley Laboratory UNIVERSITY OF CALIFORNIA Accelerator & Fusion Research Division Presented at the Particle Accelerator Conference, Dallas, TX, May 1-5, 1995, and to be published in the Proceedings Wigglers at the Advanced Light Source E. Hoyer, J. Akre, D. Humphries, T. Jackson, S. Marks, Y. Minamihara, P. Pipersky, D. Plate, G. Portmann, R. Schlueter April1995 Prepared for the U.S. Department of Energy under Contract Number DE-AC03-76SF00098 :::0 ITI ("') , -'· C 1T1 -s 0 :::0 0 Ill ITI s:: en z ...... ("') DJZITI r+O mr+n 0 ""0 OJ -< ...... o.---10 I I OJ -'· I ti ("') I -s 0 w Ill "'0 ....... -s '< ..... '< IS} • ..... m DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California. ,, (! Wigglers at the Advanced Light Source LBL-37106 UC-414 E. Hoyer, J. Akre, D. Humphries, T. Jackson, S. Marks, Y. Minamihara, P. Pipersky, D. Plate, G. Portmann, R. Schlueter Accelerator and Fusion Research Division Lawrence Berkeley Laboratory University of California Berkeley, California 94720 I April1995 This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. Wigglers at the Advanced Light Source E. Hoyer, J. Akre, D. Humphries, T. Jackson, S. Marks, Y. Minamihara, P. Pipersky, D. Plate, G. Portmann, R. Schlueter*, Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720 USA ABSTRACI' Two 3.4 m long wigglers are being designed and cons-tructed at Lawrence Berkeley Laboratory's (LBL) Advanced Light Source (ALS). A 19 period planar wiggler with 16.0 em period length is designed to provide photons up to 12.4 keV for. protein crystallography. This device' features a hybrid permanent magnet structure with tapered poles and designed to achieve 2.0 T at a 1.4 em magnetic gap. An elliptical wiggler is being designed to provide circularly polarized photons in the energy range of SO eV to 10 keV for magnetic circular dichroism spec-uoscopy. This device features vertical and horizontal magnetic sttuctures of 14 and 14 112 periods respectively of 20 em period length. The vertical magnetic sttucture is a 2.0 T hybrid permanent magnet configuration. The horizon-tal sttucture is an iron core electtomagnetic design, shifted longitudinally lf4 period with respect to the vertical magnetic structure. A maximum horizontal peak field of 0.1 T at an oscillating frequency up to 1 Hz will be achieved by excitation of the horizontal poles with a trape-zoidal current waveform. ·· I. IN1RODUCTION The ALS, a third generation synchrotron light source, is now in routine operation with three 4.6 m long undula-tors. Two of these devices have 5.0 em period lengths (IDA-U5.0 and IDB-US.O) and the third device has an 8.0 em period length (IDC-US.O), which, at 1.5 GeV ALS operation, produce high brightness in the SO to 1500 e V and 15 to 1000 eV ranges respectively.[l] A fourth 4.6 m long undulator, with a 10.0 em period length (IDG-U10.0), is nearing completion and is slated for installation lafer this year and will produce high brightness radiation, in the 5 to 900 eV range when the ALS operates at 1.5 GeV.[2] Currently, two 3.4 m long wigglers are being designed and constructed. One is a 19 period planar wiggler with 16.0 em period length (IDD-W16.0) designed to provide photons up to 12.4 keV for protein crystallography.[3] The other is a 14 period, 20 em period length cross-field elliptical wiggler (IDH-EW20.0) being designed to provide circularly polarized photons in the energy range of 50 eV to 10 keV with chirality switching up to 1Hz for magnetic circular dichroism spectroscopy.[4) The principal parame-ters for the wigglers are tabulated in Table I. ll. W16.0 WIGGLER The planar wiggler, W16.0 Wiggler, includes a mag -netic structure, support/drive system, control system and vacuum system and is shown in Fig.1:· Table I Wiggler Parameters Parameter (units) W16.0 ·EW20,0 Min. Vert. Mag. Gap (em) 1.4 1.4 Horizontal Magnetic Gap (em) 7:1. Peak Vertical Field {'I) 2.0 2.0 Peak Horizontal Field {'I) 0.095 Max. Hor. Field Freq. (Hz) 1.0 Period Length (em) 16.0 20.0 No. of Periods 19 14 V, 14 1/2 H Entrance/Exit Sequence 0,-1/4,3/4, -1, 1.. Vertical End Cor. Range (G-em) 4000 5000 MIM Range (G-em) +/- 3000 +/- 3000 The variable gap, hybrid-permanent magnet magnetic sttucture design and construction are different from those of the ALS undulators. To achieve the 2.0 T peak field, the design requires that the vanadium permendur poles be tapered in the poletip region in both the longitudinal and transverse directions to reduce saturation. To null the dipole field integral through the device, water cooled coils in the end structures with bipolar power supplies are used. To meet the higher order field integral requirements, in the 1.0 em by 6.0 em aperture, block sorting to minimize the effects of the minor components is planned and multiple trim magnets will be used for final tuning.[5,6] The basic building block of the magnetic sttucture is the half-period pole assembly. This unit consists of an aluminum keeper, a pole that is pinned in the keeper and 12 Nd-Fe-B blocks, 6 on each side of the pole, that are bonded to both the pole and keeper. The 25 kg half-period pole assemblies, are individually mounted on two backing beams and the pole surfaces are aligned to within 25 microns with respect to each other on each backing beam. The support/drive system, which provides the frame-work for holding the magnetic structures and the drive system that opens and closes the vertical magnetic sttucture gap, is very similar to that of the ALS undulators, but shorter. 3.5 m in length and wider, 1.5 m in width. Gap motion is achieved with a stepper-motor/gear box/roller chain drive with coupled left-hand and right-hand 2 mm pitch Transrol roller screws that are attached to the upper and lower backing beams. The control system, a Compumotor system, is identical to those used on the ALS undulators. The vacuum system is also similar to those of the ALS undulators, but only 3.8 m in length. *This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. If Fig. 1 W16.0 Wiggler end sectional and elevation views . ~cted spectral output of the W16.0 Wiggler, when inserted m the ALS operating at 1.5 and 1.9 GeV- 400 rnA, is shown in Figure 2. Design of W16.0 Wiggler is nearly completed and fabrication . is well along. Completion is slated for the end of this year. ill. EW20.0 ElLIPTICAL WIGGLER The mechanical configuration of the Hybrid-El~tromagnet ~lliptical.Wiggler is shown in Fig. 3. The verti~ magnetic field IS. generated with a variable gap hybrid-pennanent magnetic sttucture; the horizontal mag-netic field comes fro~ an iron core electromagnetic struc-ture. The support structure/drive and control systems are identical to the Wl6.0 Wiggler. The vacuum chamber configuration features a beam tube with multiple pumping ports that are connected to a pumping chamber. . The vertical. magnetic. field structure consists of a peri-odic structure With 14 penods. To achieve the 2.0 T peak field, the vanadium pecmendur poles are tapered in both the transverse and longitudinal directions near the pole tip. The design requires that the Nd-Fe-B matenal be retracted from the midplane to allow the horizontal magnetic field sttucture to be brought as close to the vacuum chamber as possible. The entrance and exit vertical magnetic structures are configured so that the central electron beam omit is on-axis for all field values. To achieve this, the normalized pole potential sequence for the entrance/exit is 0 (field clamp), 1/4, -3/4, 1, -1... The appropriate pole potentials are achie~ed by m~g the amount of permanent magnet ~ and adJusbng with electromagnetic coils. Except for ~od length and pole configuration, design and con-~~on of the EW20.0 vertical magnetic structure is very Similar to the W16.0 Wiggler. The horizon~ magnetic structure has the same period length as the vertical magnetic structure but is longitudi-nally phase shifted lf4 period relative to the vertical magnetic structure. The poles and coils of the horizontal magnetic field structure are tucked between the upper and .. -. 1e+1&~-------------'-----.. 1e+l5 le+13 1e+12 ~---==~_..._._"""':':"~---.......~_.....-... ........ -.~..---.J 0 11000 10000 111000 20000 PIIOIOn EMrvY I•VJ Fig. 2. Estimated flux from W16.0 Wiggler at ALS storage ring energies of 1.5 and 1.9 Ge V. lower vertical magnetic field structures. The magnetic field distribution includes 14 1(1. periods and the ends are modified to achieve the same normalized potential structure as ~ose for the vertical field. At both wiggler en~, the honzon tal structure extends lj4 period past the vertical structure so as to avoid linear polarization contamination of the circularly polarized photon beam. The horizontal structure cores are laminated from 0.64 mm thick M-36 electrical steel. They are powered by water cooled electrical coils. A system of struts are used for support and adjustment of the horizontal magnetic structure. Coil excitation is with a bipolar, regulated power supply that will provide a trapezoidal wave form for frequencies from DC up to 1 Hz. . The elliptical wiggler vacuum chamber is a welded stainless steel assembly that includes a beam chamber 18 puinpout tubes and a pump tube. The beam cttarr:ber aperture, with internal dimensions of 1.0 em by 6.1 em, is adequate for dynamic aperture requirements. With this beam aperture, a minimum vertical gap of 1.4 em and a horizontal magnetic gap of 7.2 em are achieveable. The ., II y z::. -~ 1( 110 meter Fi~. 3 Side sectional and elevation views of the EW20.0 Elliptical Wiggler chamber has a rectangular water cooling channel on the side where the synchrotron light from the upstream bend magnet strikes; this reduces thermal distortions. With ALS opemtion at 1.9 GeV and 400 rnA. the maximum chamber temperature rise is 4 °C. To achieve good vacuum, 18 dis-tributed pump-out ports are located along the length of the beam chamber. To further reduce photon induced desorbtion, a photon stop is located upstream of the chamber to block some of the beam that would otherwise impinge on the chamber. The pump-out ports are con-nected to the pump blbe to which ion pumps and titanium sublimation pumps are attached. The pump-out ports are slotted to provide satisfactory impedance to the electron beam along the length of the beam chamber. The vacuum chamber configuration and planned pumping should provide an average gas pressure of less than 10 -9 Torr after 40 A hr of beam operation in the ALS. , ... ,5....------------------, 100 1000 Photon Ene19Y [eV) Fig. 4 Polarization figure of merit for the EW20.0 Elliptical Wiggler Supporting and adjusting the vacuum chamber in the elliptical wiggler is accomplished with a system of struts. This arrangement allows the chamber-pumptube assembly to be lowered in the wiggler and then removed from the device for UHV processing after completion of the magnetic measurements. Spectral calculations, shown in Fig. 4, indicate that the device will produce a· figure of merit. defmed as flux times de~ee of circular polarization squared, of greater than 10 4 photons/sec/0.1% BW at photon energies up to 5 keV and greater than 1013 photons/sec/0.1% BW for photon energies between 5-10 keV, for a 5 mrad hori-zontal fan with the ALS operating at 1.5 GeV and 400 mA.[7] Status of the elliptical wiggler is that the conceptual design is complete and design and fabrication has started. The project is currently on hold. IV. REFERENCES [1] E. Hoyer, et al.,"Undulators at the ALS, 5th Inter-national Conf. on Syn. Rad. Inst. ", [LBL-35844], Rev .Sci. Inst 66 (2), 1898 (February 1995). [2] "U10.0 Undulator Conceptual Design Report", LBL PUB-5390 (June 1994). [3] "W16.0 Wiggler Conceptual Design Report", LBL PUB-5288 (Feb. 1991). [4] "EW20.0 Elliptical Wiggler Conceptual Design Report", LBL-PUB -5400 (March 1995). [5] D. Humphries, et al., "A Multiple Objective Magnet Sorting Algorithm for the ALS Insertion Devices". 5th International Conf. on Syn. Rad. Inst. ", [LBL-35535], Rev. Sci. Inst 66 (2), 1904 (February 1995). [6] E. Hoyer, et al.," Multiple Trim Magnet. or "Magic Fingers", for insertion device field integral correction, 5th International Conf. on Syn. Rad. lnSL", [LBL-35865], Rev. Sci. Inst 66 (2), 1901 (February 1995). [7] S. Marks, et al, "Optimization Design Study for an el-liptical wiggler at the ALS", 5th International Conf. on Syn. Rad. lost.", [LBL-35510], Rev. Sci. lost 66 (2), 1940 (February 1995). LAWRENCE BERKELEY LA BORA TORY UNIVERSITY OF CALIFORNIA TECHNICAL AND ELECTRONIC INFORMATION DEPARTMENT BERKELEY, CALIFORNIA 94720 ·- -- ..-"CCJ 

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Wigglers at the Advanced Light Source

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Wigglers at the Advanced Light Source

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