Akre, J.

Chin, J.

Gath, B.

Hassenzahl, W.V.

Hoyer, E.

Humphries, D.

Kincaid, B.

Marks, S.

Plate, D.

Portmann, Gregory J.

Schlueter, R.D.

eScholarship - University of California

Lawrence Berkeley National LaboratoryRecent WorkTitleFirst Undulators for the Advanced Light SourcePermalinkhttps://escholarship.org/uc/item/6rf395r8AuthorsHoyer, E.Akre, J.Chin, J.et al.Publication Date1993eScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaLBL-33197 UC-410 Lawrence Berkeley Laboratory UNIVERSITY OF CALIFORNIA Accelerator & Fusion Research Division Presented at the IEEE Particle Accelerator Conference, Washington, D.C., May 17-20, 1993, and to be published in the Proceedings First Undulators for the Advanced Light Source E. Hoyer, J. Alae, J. Chin, B. Gath, D. Humphries, B. Kincaid, S. Marks, P. Pipersky, D. Plate, G. Portmann, R. Schlueter, and W.V. Hassenzahl May 1993 Prepared for the U.S. Department of Energy under Contract Number DE-AC03-76SF00098 ::c I'TI (") ., -'·Om "10::c orom S::IIIZ ...... (") Ill ZITI t+O lllt+(") 0 ~ ~ 0.---tQ r CD r (") I 0 w "0 w '< ...... ID ...... ........ 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. LBL-33197 UC-410 LSGN-103 FIRST UNDULATORS FOR THE ADVANCED LIGHT SOURCE E. HOYER, J. AKRE, J. CHIN, B. OATH, D. HUMPHRIES, B. KINCAID, S. MARKS, P. PIPERSKY, D. PLATE, G. PORTMANN, and R. SCHLUETER ACCELERATOR and FUSION RESEARCH DIVISION Lawrence Berkeley Laboratory University of California Berkeley, CA 94720 and W.V. HASSENZAHL Lawrence Livermore National Laboratory University of California Livermore, CA 94550 MAY 1993 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. First Undulators For The Advanced Light Source E. Hoyer, J. Akre, J. Chin, B. Gath, D. Humphries, B. Kincaid, S. Marks, P. Pipersky, D. Plate, G. Portmann, and R. Schlueter Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720 W. V. Hassenzahl Lawrence Livermore National Laboratory, University of California, Livermore, California 94551 Abstract . The first three undulators, each 4.6 m in length, for the Advanced Light Source (ALS) at Lawrence Berkeley Laboratory (LBL), are near completion and are undergoing qualification tests before installation into the storage ring. Two devices have 5.0-cm period lengths, 89 periods , and achieve an effective field of 0.85 T at the 14 mm minimum magnetic gap. The other device has a period length of 8.0 em, 55 periods, and an effective field of 1.2 T at the minimum 14 mm gap. Measurements on the first 5 em period device show the uncorrelated field errors to be 0.23%, which is less than the required 0.25 %. Measurements of gap control show reproducibility of ± 5 microns or better. The first vacuum chamber, 5.0 m long, is flat to within 0.53 mm over the 4.6 m magnetic structure section and a 4 x w-11 Torr pressure was achieved during vacuum tests . Device description, fabrication, and measurements are presented. I. INTRODUCTION The ALS, a third-generation synchrotron radiation source is currently being commissioned at LBL. Concurrently, the first ALS undulators are nearing completion, undergoing qualification testing, and are to be installed soon in the low-emittance 1.5 Ge V storage ring to produce high brightness beams in the UV to soft x-ray range. Two devices have 5.0-cm period lengths (IDA-U5.0 and IDB-U5.0), and the third device has an 8.0-cm period length (IDC-U8.0), which will produce high brightness in the 50 to I500 e V and 6 to I 000 e V ranges respectively. The undulator specifications and design have been reported elsewhere[l , 2, and 3]; the first U5.0 Undulator near completion is shown in Figure I. II. MAGNETIC STRUCTURE As seen in Figure 1, the magnetic structure includes two large backing beams, each has five assembly sections and two end pole structures attached. Six low-reluctance flux shunts connect the two backing beams magnetically. A U5 .0 assem-bly section, Figure 2, consists of 35 half-period pole assem-blies, each bolted to a pole mount. The basic building block of the magnetic structure is the half period pole assembly which consists of an aluminum keeper, a Vanadium Permendur pole and six Nd-Fe-B magne-tized blocks. Manufacture of these assemblies is as follows : - Nd-Fe-B blocks are ordered with stringent specifications which include He~ I0400 Oe[4]. -1-- Blocks are inspected for defects, mechanical dimensions , magnetic imperfections and measured using an automated Helmholtz coil system { 5}. Results show that the 4,582 U5.0 blocks have average easy axis magnetization of 1.1137 T (cr =· O.OIIO T) and average minor axis magneti-zation components of 0 .0031 T (cr = 0.0044 T) and O.OOII T (cr = 0.0043 T)[6]. Figure 1 U5.0 Undulator Figure 2. U5 .0 Undulator Assembly Section - Blocks are sorted into the six-block arrays. The sorting al-gorithm, code INSORT, minimizes pole excitation errors, reduces direct field effects at the electron beam., and gen-erates assembly diagrams showing where each block goes in each half-period pol~ assembly. - The Vanadium Permendur poles are machined, heat treated in a hydrogen furnace at 875 degrees C for four hours and then finish machined. Each pole is pinned to its keeper with four stainless pins. - The Nd-Fe-B blocks are positioned with a bonding fixture and bonded into the pole-keeper assembly with a room temperature curing epoxy (Technicol8260/8261) [7]. Assembly section fabrication utilizes a milling machine and a pole assembly holding fixture to place and bolt the half-period pole assemblies to the pole mount. To achieve the 25 Jlm vertical and 50 !liD longitudinal pole tip positional tol-erances, the half-period pole assemblies are aligned using an automated coordinate measurement machine, , statisti-cally-based error reference planes, and shimming techniques. The aligned assemblysections are installed on the back-ing beams and aligned relative to each other using optical tool-ing and laser interferometric techniques[8]. The longitudinal positions of the assembly sections are measured using a sim-ple linear interferometer and associated optics. Because of the differential expansion coefficient between the aluminum as-sc:mbly section and the steel backing beam, a bi-linear temper-ature compensation function is applied to the position data to predict periodicity errors at a pre-determined operating tem-perature which in general differs from measurement tempera-tures. The vertical alignment of the assembly section reference planes, to within a 12 Jlm tolerance, are obtained by using an angular interferometer, and performing an integrated angle calculation on the data . .Repeatability error for these measure-ments is typically less than 3 Jlm. The magnetic structure is terminated with end structures that contain Nd-Fe-B rotor assemblies to null the undulator dipole field. These rotors are driven through linkages from the backing beams and can be positioned to within 1 degree[9 and 10]. Each end structure is outfitted with a multiple trim mag-net cartridge that corrects higher order magnetic field errors in the undulator. A cartridge contains up to nine transversely lo-cated permanent magnets (Nd-Fe-B) that are vertically ori-ented and adjustable to correct for both vertical and horizontal undulator field integral errors[11]. The backing beams are of low carbon steel construction and stress-relieved at 600--700 degrees C for four hours. The Ni-Fe flux shunts connecting the upper and lower backing beams reduce the effect of environmental magnetic fields on the undulator magnetic field[12]. III. SUPPORT/DRIVE /CONTROL SYSTEMS A generic support/drive/ control system is used for the ALS undulators. The support and drive system, shown in Figure 1, includes the support structure that provides the framework for holding the magnetic structure and the drive system that opens and closes the magnetic gap. Gap motion is achieved with a stepper-motor/gear box/roller chain drive with coupled left-hand & right-hand 2 mm pitch Transrol roller screws attached to the upper and lower backing beams [ 13]. Adjustment of the magnetic gap can be as fine as 5 J..Lm. through the use of offset keys in the roller screw shaft cou-plings. Compensating springs match the gap dependent mag-netic load to within 20%. Magnetic field taper can be provided manually by stepping one of the main roller chain sprocket's teeth with respect to the chain in increments of 87 Jlmlsprocket tooth (AFJE = 0.96% at 1.4 em gap). A Compumotor system, Indexer Model No. 500-Driver Model PK130M-Absolute Rotary Encoder Model ARC, is used to drive and control the magnetic gap. This stepper motor and absolute rotary encoder system is designed such that each motor step and encoder step corresponds to 0.067 Jlm and 0.106Jlm motion of the gap respectively. The motor control system also alloyvs for velocity profiling during a move. Results of sui?pcirt, drive, and control system tests are given in Table I. Table I Suooortldrive/control svstem test results Test Magnetic structure alignment (upper-to-lower structure) Gap range Gap opening-closing time Reproducibility Backlash (encoder to gap) Scan rate Performance Gap parallelism within 5 J..Lm; transverse within 250 Jlm; longitudinal within 150 JliD 14 mm to 210 mm 1 minute :::::; ±5 J..Lm; ±20% for 1 Jlm steps :::::; 10 JliD 3.33 mm/sec max. A gage block and a laser interferometer is used to cali-brate the absolute encoder to the gap position. Figure 3 shows the deviation from linearity with and without compensating springs (three hysteresis loops each). The backlash of the sys-tem has gap dependence, and the character of the upper hys-teresis curve is due to the compensating springs not exactly canceling the force of the magnetic field. Nonlinearities are removed with calibration. Each undulator is outfitted with a transparent enclosure for safety, and for maintaining uniform temperature through-out the insertion device. Tests show that the gap sensitivity coefficient, due to a vertical temperature gradient in a backing beam, is 6 Jlm/0.1 degree C and that the temperature gradient is eliminated when fans circulate air within the enclosure. IV. VACUUM SYSTEM The 5.1 m long IDA-U5.0 commissioning vacuum cham-ber, shown in Figure 1, is machined from two 5083-H321 aluminum plates and welded together[14]. Pockets machined into the chamber accommodate the poles of the magnetic structure for small magnetic gap operation. Mechanical mea--2-surements taken at the completion of final assembly, after UHV conditioning and under vacuum, are given in Table IT. 50 0 ······· . ~ -50 ... c. c; -100 ······· s· k ... .,. 8 -150 ....... . Iii -200 ...... . 0 ' Measured Gap Position (mm) Figure 3. Hysteresis Loops with and without compensating for IDB-U5.0. Table II ALS Commissioning Vacuum Chambers Measurements Measurement IDA-U5.0 IDB-U5.0 IDC-U8.0 Vertical aperture 18.9Tmm 18.83 mm In progress Min. v.c. gap 21.64. mm 21.77 mm In progress V.C. flatness 0.53 mm 0.74mrn In progress Hor. straightness 0.08mm 0.05mm In progress The pumping· system of each vacuum chamber incll}des three combination 60 1/s ion/ 600 1/s titanium sublimation pumps, a 2400 1/s ALS absorber tsp pump, and 4800 1/s of non-evaporable getter (Saes-type ST707/CTAM/30D strip). Chamber ultra-high vacuum conditioning is at 140 qe-grees C, for a minimum of 48 hours[15]. The base pressure achieved after conditioning is 3.7 x 10-11 Torr for the IDA-U5.0 chamber and 7.0 x lQ-11 Torr for the IDB-U5.0 cham-ber. V. MAGNETIC MEASUREMENTS A high speed, precision magnetic measurement system has been designed and built for detailed magnetic characteri-zation of ALS insertion devices[16]. Primary magnetic field information, integral and local data, are derived from Hall probe measurements. A 5.5 m long integral coil is also used to measure field integrals. The rms harmonic residual, defined as the rms value of the deviation of the measured fidd on axis from the ideal field, provides an indication of spectral performance[17]. For IDA - U5.0, the specified rms harmonic residual is 0.25%; magnetic measurements show a value of 0.23%. Field integrals through IDA are close to specified toler-ances and very acceptable for ALS operations. VI. ACKNOWLEDGMENT 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. ' VII. REFERENCES [1] "U5.0 Undulator Conceptual Design Report," LBL PUB-5256 (Nov. 1989). [2) "U8.0 Undulator Conceptual Design Report," LBL PUB-5276 (May 1990). [3) E. Hoyer, et. al., "The U5.0 Undulator for the ALS, 4th International Conf. on Sync. Rad. Inst.," [LBL-30459], Rev., Sci. Instrum. 63 (1), 359 (January 1992). [4) E. Hoyer, "U5.0 Magnetic Structure Magnetized Nd-Fe-B Blocks," LBL Spec. M734D (Apr. 1989) [5] S. Marks, et. al., "ALS Insertion Device Block Measurement and Inspection," [LBL-29955], IEEE PAC. 91CH3038-7, 2739 (May 1991). [6] S. Marks, "Measurement & Characterization of U5.0 Permanent Magnet Blocks," LBL Eng. Note M7225 (Oct. 1991). [7] D. Humphries, "Block Bonding Procedure for IDAIIDB/IDC," LBLEng. Note M7121 (Feb. 1991) [8] B. Gath, "Magnetic Structure Installation and Alignment into Backing Beam," LBL Eng. Note M7265 (Mar. 19~2). [9] D. Humphries, et al, "Modeling and Measurement of the ALS U5.0 Undula:tor End Magnetic Structure," IEEE PAC (May 1993). [10] P. Pipersky, "U5.0 End Module Assembly & Installation," LBL Eng. Note M7277A (April1992). [11] E. Hoyer, "Multiple Trim Magnets," LBL Eng. Note · M7354 (May 1993). [12] E. Hoyer, et. al, "Flux Shunts for Undulators," IEEE PAC (May 1993). [13] J. Chin, "IDA, IDB, IDC Support & Drive System .Assembly and Alignment Notes," LBL Eng. Note M7349 (July 1992). [14] D. Plate, "Fabrication Procedure & Production Inspection Record for Vacuum Chambers, LBL Eng. Note M7292A(Aug. 1992). [15] D. Plate, "Insertion Device Vacuum Chamber Bakeout Procedure," LBL Eng. Note M7304 (Sept. 92). [16] S. Marks, et al, "ALS Insertion Device Magnetic Measurements," IEEE PAC (May 1993). [17] C. Wang, et. al, "Calculated Radiation Spectrum of ALS U5.0 Undulator ·Based Upon Magnetic Measurements," IEEE PAC (May 1993). -3-LA~NCEBERKELEYLABORATORY UNIVERSITY OF CALIFORNIA TECHNICAL INFORMATION DEPARTMENT BERKELEY, CALIFORNIA 94720 ~._.._ ..,. 

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First Undulators for the Advanced Light Source

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First Undulators for the Advanced Light Source

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